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
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
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