E36 M3 Evo rough idle problem SOLVED
Discussion
Some of you folk probably know about the problems I've been having with my Evo the rough idle problem that no-one could solve. It rocked the car on it's suspension and shunted the drive train when crawling on a closed throttle. No good at all.
I've typed up the whole story in hope that it will be useful to anyone with a dodgy idle on their car.
It started one day when I popped out of work at lunch time to pick something up. I'm careful not to rev or use the car hard before the oil is at least to 80 degrees, and this trip was no different. As I pulled back into the works car park and dipped the clutch it started running rough. I revved it to try and clear the problem to no avail.
After booking the car in for a check-up a few days later, my mechanic BMW specialist chap tested a few things and replaced a few perished hoses. It was a touch better, but he drew a blank.
So, to the dealership then. I booked the car in and had to wait a week for a slot, in the meantime the car was awful to drive, and I took to keeping the throttle open at junctions so I could slip the clutch a bit, this stopped the driveline shunt, and the car stalling, as it would do. This made commuting a real chore. The day the car was booked in it stalled at a junction. I restarted and gave it a hefty boot out of the corner, which unfortunately exposed a very thin line of cord on the outside edge of the rear tyre. They had done plenty of miles and needed replacing, but this just finished them off!
I explained the idle problem to the technician who reassured me that they'd sort the problem. A week later and I arrived to pick up the car. They assured me that they'd fixed the problem having re-timed the exhaust cam which was 'way out', but hadn't road tested it due to the rear tyre. The cost was £690. Great I thought, sorted, and the car was brought round for me, rocking on it's suspension just as it had when I brought it in. The technician came out and said that the car had been fine in the workshop the previous day. I took the car to work and it was exactly as before. I had some new pilot sports fitted and dropped the car back at the dealership under the same job. Later they rung and said that I needed a new Vanos unit at £2500 fitted, and would I like to go ahead. I decided to cut my losses and parked the car up whilst I recouped my funds a bit.
I was using my Dad's Honda Beat in the meantime which was great through the summer with the roof down and the little 650cc 3 cylinder thrumming away, but as autumn approached I took an intermittent loan from work and bought a Panda 100hp which is great.
I set about researching rough idle and vanos fixes and after much reading decided to eliminate all possibilities.
1. Clean the air flow meter in the induction pipework with oil free electrical spray
2. Take apart the induction right down to the throttle bodies so that I could clean the idle control valve that is mounded below
3. Change the vanos 'o'ring seals and gaskets
4. If these measures didn't work I'd replace the vanos solenoids before admitting defeat!
After picking up my parts from BMW, I set about taking the vanos covers off. Exhaust side first, I found only just tight exhaust cover bolts, one bolt head snapped off, a torx headed bolt, and another so rusted and gunged up that I couldn't get the allen key in. No oil leaks through thankfully. This cover provides a surface for the solenoids to push against. If it is loose, the vanos solenoids don't seal properly, hence reports of lost oil when a cover bolt sheers.* After removing the cover, I eased the solenoids out with a cloth and pliers, and replaced the perished and split o rings, inspected the solenoid sockets for any rubber debris, and refitted with fresh gaskets and bolts. Starting the car up, it was still rough, so left it for another day.
Over the next couple of Saturdays I removed the airbox and all of the connecting hoses so that I could get to the Idle Control Valve, a cyclindrical Lucas part that can just be seen below the induction trumpets (see below). This was a swine as all of the hoses to the airbox have jubilee clips out of range of screwdrivers! With that de-gunged and everything replaced and tightened, I turned my attention to the intake vanos solenoid seals. These were no perished like the exhaust ones were, but had worn flush with the solenoid body, so these were replaced. Next to the air flow meter, which I sprayed liberally with an oil free electrical cleaner. I then gently swabbed away at the surfaces with kitchen towel wound around some small pliers. I put everything back together and jump started the M3 from the Panda. Immediately it was sounding better and dropped into a smooth idle with virtually zero vanos noise.
I was delighted and left the car to warm it's fluids whilst I tidied the garage up. After around 20 minutes with the occasional blip of throttle it was still steady as a rock.
I'll be insuring and using the car daily before selling. The car now runs very smoothly indeed which is in keeping with its clean bodywork and overall great condition.
So my conclusions are
- If you have a the inclination, try the above which, in addition to time will cost around £40 (new vanos £1500 plus fitting)
- Vanos woes are largely due to BMW not servicing the units - they didn't even spot a loose cover and headless bolt on the critical vanos cover, and the perished orings weren't sealing which may well have compounded the timing/idle problem
- With the above work carried out I don't know which part it was that sorted the idle problem, it may have been one, it may have been all of them.
I've typed up the whole story in hope that it will be useful to anyone with a dodgy idle on their car.
It started one day when I popped out of work at lunch time to pick something up. I'm careful not to rev or use the car hard before the oil is at least to 80 degrees, and this trip was no different. As I pulled back into the works car park and dipped the clutch it started running rough. I revved it to try and clear the problem to no avail.
After booking the car in for a check-up a few days later, my mechanic BMW specialist chap tested a few things and replaced a few perished hoses. It was a touch better, but he drew a blank.
So, to the dealership then. I booked the car in and had to wait a week for a slot, in the meantime the car was awful to drive, and I took to keeping the throttle open at junctions so I could slip the clutch a bit, this stopped the driveline shunt, and the car stalling, as it would do. This made commuting a real chore. The day the car was booked in it stalled at a junction. I restarted and gave it a hefty boot out of the corner, which unfortunately exposed a very thin line of cord on the outside edge of the rear tyre. They had done plenty of miles and needed replacing, but this just finished them off!
I explained the idle problem to the technician who reassured me that they'd sort the problem. A week later and I arrived to pick up the car. They assured me that they'd fixed the problem having re-timed the exhaust cam which was 'way out', but hadn't road tested it due to the rear tyre. The cost was £690. Great I thought, sorted, and the car was brought round for me, rocking on it's suspension just as it had when I brought it in. The technician came out and said that the car had been fine in the workshop the previous day. I took the car to work and it was exactly as before. I had some new pilot sports fitted and dropped the car back at the dealership under the same job. Later they rung and said that I needed a new Vanos unit at £2500 fitted, and would I like to go ahead. I decided to cut my losses and parked the car up whilst I recouped my funds a bit.
I was using my Dad's Honda Beat in the meantime which was great through the summer with the roof down and the little 650cc 3 cylinder thrumming away, but as autumn approached I took an intermittent loan from work and bought a Panda 100hp which is great.
I set about researching rough idle and vanos fixes and after much reading decided to eliminate all possibilities.
1. Clean the air flow meter in the induction pipework with oil free electrical spray
2. Take apart the induction right down to the throttle bodies so that I could clean the idle control valve that is mounded below
3. Change the vanos 'o'ring seals and gaskets
4. If these measures didn't work I'd replace the vanos solenoids before admitting defeat!
After picking up my parts from BMW, I set about taking the vanos covers off. Exhaust side first, I found only just tight exhaust cover bolts, one bolt head snapped off, a torx headed bolt, and another so rusted and gunged up that I couldn't get the allen key in. No oil leaks through thankfully. This cover provides a surface for the solenoids to push against. If it is loose, the vanos solenoids don't seal properly, hence reports of lost oil when a cover bolt sheers.* After removing the cover, I eased the solenoids out with a cloth and pliers, and replaced the perished and split o rings, inspected the solenoid sockets for any rubber debris, and refitted with fresh gaskets and bolts. Starting the car up, it was still rough, so left it for another day.
Over the next couple of Saturdays I removed the airbox and all of the connecting hoses so that I could get to the Idle Control Valve, a cyclindrical Lucas part that can just be seen below the induction trumpets (see below). This was a swine as all of the hoses to the airbox have jubilee clips out of range of screwdrivers! With that de-gunged and everything replaced and tightened, I turned my attention to the intake vanos solenoid seals. These were no perished like the exhaust ones were, but had worn flush with the solenoid body, so these were replaced. Next to the air flow meter, which I sprayed liberally with an oil free electrical cleaner. I then gently swabbed away at the surfaces with kitchen towel wound around some small pliers. I put everything back together and jump started the M3 from the Panda. Immediately it was sounding better and dropped into a smooth idle with virtually zero vanos noise.
I was delighted and left the car to warm it's fluids whilst I tidied the garage up. After around 20 minutes with the occasional blip of throttle it was still steady as a rock.
I'll be insuring and using the car daily before selling. The car now runs very smoothly indeed which is in keeping with its clean bodywork and overall great condition.
So my conclusions are
- If you have a the inclination, try the above which, in addition to time will cost around £40 (new vanos £1500 plus fitting)
- Vanos woes are largely due to BMW not servicing the units - they didn't even spot a loose cover and headless bolt on the critical vanos cover, and the perished orings weren't sealing which may well have compounded the timing/idle problem
- With the above work carried out I don't know which part it was that sorted the idle problem, it may have been one, it may have been all of them.
- The fact that I lost no oil despite having a loose cover could show faulty exhaust solenoids
Edited by joesnow on Saturday 15th November 15:43
Hi Joe. I have exactly the same problem with my E36-M3-Evo. I've done the same as you re. Idle Control Valve (I also checked it by applying voltage). I also had perished Crankcase Breather Hoses and a perished rubber cap on a t-piece on the 'Fuel preparation circuit'. I also replaced the Fuel Filter and Spark Plugs.
All these didn't fix the problem. I eventually took it for a diagnostic and found 2 fault codes.
1. Code 24 :- Ignition Coil Cylinder 3
2. Code 22 Advance Valve, VANOS exhaust.
I changed the coil pack and did a heck of a lot of reading up about the Vanos.
I haven't got round to checking the exhaust solenoid yet, but will do that very soon, my thoughts are that the exhaust solenoids have either failed electrically (I'll do an impedance check, and maybe apply 12 volts and see if they click), or the o-rings have worn and need replacing. I hope there's no physical damage to the solenoid plungers, but I've never had the solenoid cover come loose, so hopefully they won't be damaged.
If the solenoids seem ok, I can only think that the Vanos piston seals have gone. The Vanos pistons have a dual seal arrangement consisting of a teflon outer seal, with a nitrile o-ring 'packer' underneath. The formulation of the nitrile o-ring is such that it shrinks with heat/age and the pistons fail to seal properly resulting in reduced performance. Modified seal kits are available from http://www.beisansystems.com/ Or an overhauled and improved vanos is available from www.DrVanos.com .
NOTE!!!! Anyone reading this who wants to replace the piston seals please note that the European M3 Evo has a totally different Vanos unit than the American model, and Rajaie, who is the founder of beisansystems does not currently have a repair procedure for the European M3 Evo (S50 double vanos), as he lives in America and hasn't had access to a european car in order to document the repair procedure. Dr.Vanos supplies a reconditioned Vanos unit for the european car, so I am gonna contact them for a repair procedure for that model, they don't have a repair procedure pdf for that model on their website (only the single vanos E36 and the E39 M5 and E46 M3 double vanos)
Joe, I have to ask you, when you replaced the solenoid o-rings on the exhaust solenoids and you say you started the car and it was still lumpy, how long did you let it run for? If it was only a short period, then there wouldn't have been time for the vanos unit to fill with oil and get up to a high enough oil pressure to move the exhaust vanos piston. I'm thinking if this is the case, it was indeed the o-ring repair that fixed the problem of the rough idle on your car. Could you report back on this, because this might help me to clarify if this is indeed the problem with mine.
I will have a look at mine within the next week (just waiting for a 32mm spanner I've ordered, to take off the fan) and I'll report back, for anyone else who's interested.
regards everyone,
Dan.
All these didn't fix the problem. I eventually took it for a diagnostic and found 2 fault codes.
1. Code 24 :- Ignition Coil Cylinder 3
2. Code 22 Advance Valve, VANOS exhaust.
I changed the coil pack and did a heck of a lot of reading up about the Vanos.
I haven't got round to checking the exhaust solenoid yet, but will do that very soon, my thoughts are that the exhaust solenoids have either failed electrically (I'll do an impedance check, and maybe apply 12 volts and see if they click), or the o-rings have worn and need replacing. I hope there's no physical damage to the solenoid plungers, but I've never had the solenoid cover come loose, so hopefully they won't be damaged.
If the solenoids seem ok, I can only think that the Vanos piston seals have gone. The Vanos pistons have a dual seal arrangement consisting of a teflon outer seal, with a nitrile o-ring 'packer' underneath. The formulation of the nitrile o-ring is such that it shrinks with heat/age and the pistons fail to seal properly resulting in reduced performance. Modified seal kits are available from http://www.beisansystems.com/ Or an overhauled and improved vanos is available from www.DrVanos.com .
NOTE!!!! Anyone reading this who wants to replace the piston seals please note that the European M3 Evo has a totally different Vanos unit than the American model, and Rajaie, who is the founder of beisansystems does not currently have a repair procedure for the European M3 Evo (S50 double vanos), as he lives in America and hasn't had access to a european car in order to document the repair procedure. Dr.Vanos supplies a reconditioned Vanos unit for the european car, so I am gonna contact them for a repair procedure for that model, they don't have a repair procedure pdf for that model on their website (only the single vanos E36 and the E39 M5 and E46 M3 double vanos)
Joe, I have to ask you, when you replaced the solenoid o-rings on the exhaust solenoids and you say you started the car and it was still lumpy, how long did you let it run for? If it was only a short period, then there wouldn't have been time for the vanos unit to fill with oil and get up to a high enough oil pressure to move the exhaust vanos piston. I'm thinking if this is the case, it was indeed the o-ring repair that fixed the problem of the rough idle on your car. Could you report back on this, because this might help me to clarify if this is indeed the problem with mine.
I will have a look at mine within the next week (just waiting for a 32mm spanner I've ordered, to take off the fan) and I'll report back, for anyone else who's interested.
regards everyone,
Dan.
Right...... I've just fixed it! Woohoo!
It turned out to be a wire had come off the Exhaust Advance Solenoid. I checked impedance across the 3-pin plug for the Exhaust Solenoids and there was 4 Ohms from centre to one side, and Infinity from centre to the other. I popped the solenoids off, and, sure enough, the green wire had come off the top solenoid.
There was some evidence of oil leaking from around the bottom solenoid, so I'm gonna get a full set of O-rings and gaskets for the covers. I may put some shims between the back of the solenoids and the inside of the cover, because there's also evidence of the solenoids 'skewing' slightly. There's wear marks near where the 2 o-rings are.
That's it. After 3-months trying to cure a rough idle problem, it came down to 1 wire! At least I've changed a few other bits that were knackered along the way.
It turned out to be a wire had come off the Exhaust Advance Solenoid. I checked impedance across the 3-pin plug for the Exhaust Solenoids and there was 4 Ohms from centre to one side, and Infinity from centre to the other. I popped the solenoids off, and, sure enough, the green wire had come off the top solenoid.
There was some evidence of oil leaking from around the bottom solenoid, so I'm gonna get a full set of O-rings and gaskets for the covers. I may put some shims between the back of the solenoids and the inside of the cover, because there's also evidence of the solenoids 'skewing' slightly. There's wear marks near where the 2 o-rings are.
That's it. After 3-months trying to cure a rough idle problem, it came down to 1 wire! At least I've changed a few other bits that were knackered along the way.
Dan, so glad you have it fixed. Turning that key and hearing the car settle down is a great moment after the inconvinience and dare I say heartache of the car not running right.
I think I ran the car for around a minute after refitting the exhaust solenoids, but it was still rough. A couple of weeks later after cleaning the other things, the car started easily and settled straight away which would indicate vanos seals plus something else. I have a DaveF K&N cone fitted, so a mucky AFM may have compounded the problem.
Although the idle is good now, I may look at testing the vanos exhaust solenoids to make sure they are working correctly, dependant on how the performance of the car feels.
On the re-inbursment, I'm just happy that I didn't go down the new vanos route. When I went to pick the car up, I haggled back labour costs, and on that same day went to buy the Fiat, managing a £1500 discount, so all in all, just happy the car is running ok, allowing me to sell it. I'll enjoy getting back behind the wheel to make sure it is 100% before it goes though. It's very clean with excellent paint, wheels and rare suede interior, and has the added bonus of bilstein PSS9 adjustables, thicker eibach antiroll bars, yellowstuff brake pads and new BMW disks, titanium gearknob that improves change feel, and new pilot sports on the rear. With the recent work I've done should run very well now.
I think I ran the car for around a minute after refitting the exhaust solenoids, but it was still rough. A couple of weeks later after cleaning the other things, the car started easily and settled straight away which would indicate vanos seals plus something else. I have a DaveF K&N cone fitted, so a mucky AFM may have compounded the problem.
Although the idle is good now, I may look at testing the vanos exhaust solenoids to make sure they are working correctly, dependant on how the performance of the car feels.
On the re-inbursment, I'm just happy that I didn't go down the new vanos route. When I went to pick the car up, I haggled back labour costs, and on that same day went to buy the Fiat, managing a £1500 discount, so all in all, just happy the car is running ok, allowing me to sell it. I'll enjoy getting back behind the wheel to make sure it is 100% before it goes though. It's very clean with excellent paint, wheels and rare suede interior, and has the added bonus of bilstein PSS9 adjustables, thicker eibach antiroll bars, yellowstuff brake pads and new BMW disks, titanium gearknob that improves change feel, and new pilot sports on the rear. With the recent work I've done should run very well now.
Edited by joesnow on Monday 24th November 11:24
Hi Joe, if the car idles smoothly, the exhaust advance solenoid is definitely working. It's easy to do a check though. Just measure the impedance across the 3-pin plug for the solenoids. From centre pin to each outer pin should be approx. 4 Ohms.
I've changed all the o-rings for my exhaust and inlet solenoids now. Complete with new gaskets and bolts for the solenoid covers, total price of parts from BMW, £31.
I've also put shims between the back of the solenoids and the inside of the solenoid covers to stop the solenoids moving around as much, thus reducing wear and vibration of the solenoids. (mine all had evidence of 'skewing').
I've changed all the o-rings for my exhaust and inlet solenoids now. Complete with new gaskets and bolts for the solenoid covers, total price of parts from BMW, £31.
I've also put shims between the back of the solenoids and the inside of the solenoid covers to stop the solenoids moving around as much, thus reducing wear and vibration of the solenoids. (mine all had evidence of 'skewing').
BennyBoy
High idling can also be caused by an air leak somewhere between your Mass Airflow Sensor, and the throttle bodies. Although, with an Idle Control valve (ICV), a modern engine's revs would probably 'hunt' up and down, rather than run fast.
You could try spraying easy start, or carb cleaner around the intake piping while your engine is running and if there is a further increase in revs, you've found a leak.
Be careful!! This stuff is extremely flammable. I would only recommend doing this when your car is only slightly warm, ie. a couple of minutes after you've started it from stone cold. Also don't spray near the exhaust manifold, and do it outside, or in a well-ventilated area.
I found my Crankcase Breather hose had completely perished on my car (90,000 miles). It's a pig to get at 'cause it's under the air box/plenum chamber. But if you're inspecting your ICV, you'll already have that stuff off, so have a look.
Maybe have a look at your 'Throttle position sensor'. Mounted on the radiator end of the throttle linkage. Unplug the connector (press the wire clip in and pull off) It's 3 pins, measure the resistance from centre to either outer pin while moving the throttle with your hand (engine off!). I can't remember the values, but for one side, the resistance should be high, and fall as you open the throttle, and the other side resistance should be low and rise as you open the throttle.
Good luck!
High idling can also be caused by an air leak somewhere between your Mass Airflow Sensor, and the throttle bodies. Although, with an Idle Control valve (ICV), a modern engine's revs would probably 'hunt' up and down, rather than run fast.
You could try spraying easy start, or carb cleaner around the intake piping while your engine is running and if there is a further increase in revs, you've found a leak.
Be careful!! This stuff is extremely flammable. I would only recommend doing this when your car is only slightly warm, ie. a couple of minutes after you've started it from stone cold. Also don't spray near the exhaust manifold, and do it outside, or in a well-ventilated area.
I found my Crankcase Breather hose had completely perished on my car (90,000 miles). It's a pig to get at 'cause it's under the air box/plenum chamber. But if you're inspecting your ICV, you'll already have that stuff off, so have a look.
Maybe have a look at your 'Throttle position sensor'. Mounted on the radiator end of the throttle linkage. Unplug the connector (press the wire clip in and pull off) It's 3 pins, measure the resistance from centre to either outer pin while moving the throttle with your hand (engine off!). I can't remember the values, but for one side, the resistance should be high, and fall as you open the throttle, and the other side resistance should be low and rise as you open the throttle.
Good luck!
Edited by DanB99 on Friday 9th January 21:22
Well done for DIYing the issue. Another 'common' cause for a dodgy idle on the E36 M3 is the weak flexi section from the exhaust manifold. They are prone to cracking and even a small split will cause a lumpy idle and a loss in power. If it gets bad enough the car will frequently stall and have starting issues. A replacement part from the stealers is in the region of £700 + fitting but many opt for the cheaper option of having a section welded in. When done in situ it can be prone to fail but you'll pay for labour to have the manifold removed to have it done more extensively.
If you have a rough idle and a lack of pull low down the revs it's well worth checking this out.
If you have a rough idle and a lack of pull low down the revs it's well worth checking this out.
Cheers for the extra advice chaps.
I will get around to looking at this next weekend as I spent this weekend under an M5 - fixing a diff leak. New diff seals all round!
I don't think it will be the flexi joint on the manifold as we had these out not long ago and after a good inspection they were fine.
It is not a rough idle, just sits at about 1K rpm so it could be the throttle position sensor or the ICV I think - leaky pipes would be a bit 'lumpier' wouldn't they?
I will get around to looking at this next weekend as I spent this weekend under an M5 - fixing a diff leak. New diff seals all round!
I don't think it will be the flexi joint on the manifold as we had these out not long ago and after a good inspection they were fine.
It is not a rough idle, just sits at about 1K rpm so it could be the throttle position sensor or the ICV I think - leaky pipes would be a bit 'lumpier' wouldn't they?
Ben! I was about to email you a link to this page with regards to the high idle. I deffo agree about attacking it with carb cleaner or similar to check air leaks - Willis is an old hand at this. If we do that and take a look at the ICV we should be able to sort something.
Have you double checked the throttle cable to engine connection is correct with the new engine?
Have you double checked the throttle cable to engine connection is correct with the new engine?
Hi BennyBoyEvo,
Did you ever find a solution to this problem (idling at 1000rpm)?
My Evo has exactly the same symptoms, it's not a rough idle, occasional miss but otherwise its steady, just stuck at 1000rpm? I've just refurbished the vanos, hoping that that would resolve the problem- but it hasn't.
Any tips? Thanks in advance!
Did you ever find a solution to this problem (idling at 1000rpm)?
My Evo has exactly the same symptoms, it's not a rough idle, occasional miss but otherwise its steady, just stuck at 1000rpm? I've just refurbished the vanos, hoping that that would resolve the problem- but it hasn't.
Any tips? Thanks in advance!
What a fantastic write up. I have certainly benefited from it.
I recently got my M3 back from the bodyshop,and it starts to idle really rough. It shakes from left to right and rpm is really low at around 500. I can't think of any reason cause it just MOTed a few days before I got it back. I am no mechanic so I was just going to send the car to CPC performance in Amersham,but then I came across your article and I thought I will give it a go first. Following your steps, clean the air box ,the air flow meter ,pipeworks and put them back together and wow the problem solved! The car doesn't shakes and cough anymore. Obviously the problem was cause by the dust in the bodyshop which must have somehow got into the air intake system and affect the AFM.Now it's idling as it should no hesitation and just purr.
Thank you Joe
I recently got my M3 back from the bodyshop,and it starts to idle really rough. It shakes from left to right and rpm is really low at around 500. I can't think of any reason cause it just MOTed a few days before I got it back. I am no mechanic so I was just going to send the car to CPC performance in Amersham,but then I came across your article and I thought I will give it a go first. Following your steps, clean the air box ,the air flow meter ,pipeworks and put them back together and wow the problem solved! The car doesn't shakes and cough anymore. Obviously the problem was cause by the dust in the bodyshop which must have somehow got into the air intake system and affect the AFM.Now it's idling as it should no hesitation and just purr.
Thank you Joe
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