Rover V8 power loss at high load - Help please!
Discussion
I've failed whilst trawling various car forums trying to find a solution to my engine problem, I can’t seem to come up with the right search string to enter and PH looks to be the most promising, especially since the core members seem to be TVR owners, who are intimate with and knowledgeable about their power plants. That's not a dig, BTW! I'm after a Griff if I ever move this one one!
Firstly, I have to apologise for the lengthy post, but I want to get as much information in as possible on the first go to maximise the potential for an early solution. I have a list of things to check/change, but I'm hoping I may be able to shortcut to something the collective can point out as the definitive cause....
The unit in question is a 4.0 in a pre-production MG RV8. It'll idle smoothly and rev quite happily at standstill, but when any load is applied, it stutters at around 3,000rpm (it seems ok up to then) and my initial thought was that it felt like fuel or air starvation, vacuum leak or spark failure. The fault is less prominent when the engine's cold (I know I shouldn't give it the beans without it being warmed, but this is only to test for the fault), but as soon as it gets warmer, the fault gets worse. I can get 100yds up the road to the roundabout without the fault manifesting (about 30 seconds after starting), but after that, it gets progressively more obvious. After more than five minutes it won't take more than 20% throttle, especially in the higher gears, but runs fine on part throttle below 3000. Until you get on the gas with some load (eg: high gear), you wouldn’t know there was an issue.
This first showed up on a trip to Pendine for the VHRA weekend as I pulled away from the Severn Toll, but wasn’t noticeable until then (I’d done about 30 miles since the MOT without noticing anything amiss) and got worse on the return journey.
It used to be a race car before it was repurposed as a road car (ie: I ran out of money) but the engine ran completely standard throughout that time. It had a +040 rebuild by John Eales about a decade (and less than a thousand miles) ago, but has stood unused since then (money, time and health problems), and was only recently revived. It showed good emissions performance at the MOT last month ('super clean' apparently). Temp ranges from normal to hot, but it was always like that when racing too. The fan cuts in ok and brings temp down. I’ve put new oil in the engine, gearbox and rear axle, drained and renewed the coolant (and bled the system), fully rebuilt the braking system, plus the other changes listed below as a result of trying to fix the fault.
My list of possible causes is/was:
Fuel pressure low - faulty regulator/knackered pump/blocked filters/crap in tank blocking inlet
Intake or vacuum leaks
Vac advance failure on dizzy
Rotor arm fault
Cracked dizzy cap
Blocked air filter
Intake pipe between AF sensor and throttle body collapsing under strong vacuum (this is what I imagine it feels most like)
Duff plugs/leads/coil
Sensor fault - AF sensor (it's the hot wire one)/Throttle pot/ Fuel temp/Coolant temp
Thermostat failure leading to incorrect temp reading by ECU
Blocked/dirty injectors
Collapsed cat cores/silencer
And the biggie, ECU fault.
(Feel free to add others....)
I haven't got round to changing the plugs or leads yet, and the electrical tests on components/sensors are slightly daunting (I’m definitely a mechanical person, not electrically-minded at all!), and I don’t know what the readings should be or even where I can find the info and how to test each item (which colour leads, pins, procedure etc). I do possess a multimeter, but it doesn’t get much use…
Things that have made no difference so far (all mechanical tasks, you notice):
I've changed the fuel filters (and put an extra see-through one in too), the idle fuel pressure's ok (2.9bar), it's got a new coil, there's no vacuum leaks that I can find, the dizzy vac feed is in the right place (not the Japanese position), the idle control valve controls the idle ok (is there any other way to test this part?), I've cleaned the K&N air filter, and the AF sensor (used contact cleaner for that one), checked the exhaust and cats (they’re fine).
I've checked all hoses on the inlet side except for vac collapse. I’m pretty sure it’s not an individual plug or plug lead failure as it’s the whole engine shutting off, not one or two cylinders, but could it be the King lead breaking down under load?
Next on the list of things to do is removing and cleaning out the tank before I chuck in a can of injector cleaner, and strap a camera under the bonnet to look at the inlet hose when I give it some gas.
I’ve come across rovergauge, which looks great and might give me more info, but I’m not sure if it’s compatible with my ECU. How do I know/check? Will it help in this situation? Anyone else familiar with it?
My last issue is that as it’s a pre-production vehicle, its spec might not be as intended, and I'm not fully sure which bits are away from spec.
Thanks very much for your patience and for taking the time to read this. I’d be very grateful for any other suggestions, and all advice on what and how to test or check.
Here’s hoping for an easy win…
Firstly, I have to apologise for the lengthy post, but I want to get as much information in as possible on the first go to maximise the potential for an early solution. I have a list of things to check/change, but I'm hoping I may be able to shortcut to something the collective can point out as the definitive cause....
The unit in question is a 4.0 in a pre-production MG RV8. It'll idle smoothly and rev quite happily at standstill, but when any load is applied, it stutters at around 3,000rpm (it seems ok up to then) and my initial thought was that it felt like fuel or air starvation, vacuum leak or spark failure. The fault is less prominent when the engine's cold (I know I shouldn't give it the beans without it being warmed, but this is only to test for the fault), but as soon as it gets warmer, the fault gets worse. I can get 100yds up the road to the roundabout without the fault manifesting (about 30 seconds after starting), but after that, it gets progressively more obvious. After more than five minutes it won't take more than 20% throttle, especially in the higher gears, but runs fine on part throttle below 3000. Until you get on the gas with some load (eg: high gear), you wouldn’t know there was an issue.
This first showed up on a trip to Pendine for the VHRA weekend as I pulled away from the Severn Toll, but wasn’t noticeable until then (I’d done about 30 miles since the MOT without noticing anything amiss) and got worse on the return journey.
It used to be a race car before it was repurposed as a road car (ie: I ran out of money) but the engine ran completely standard throughout that time. It had a +040 rebuild by John Eales about a decade (and less than a thousand miles) ago, but has stood unused since then (money, time and health problems), and was only recently revived. It showed good emissions performance at the MOT last month ('super clean' apparently). Temp ranges from normal to hot, but it was always like that when racing too. The fan cuts in ok and brings temp down. I’ve put new oil in the engine, gearbox and rear axle, drained and renewed the coolant (and bled the system), fully rebuilt the braking system, plus the other changes listed below as a result of trying to fix the fault.
My list of possible causes is/was:
Fuel pressure low - faulty regulator/knackered pump/blocked filters/crap in tank blocking inlet
Intake or vacuum leaks
Vac advance failure on dizzy
Rotor arm fault
Cracked dizzy cap
Blocked air filter
Intake pipe between AF sensor and throttle body collapsing under strong vacuum (this is what I imagine it feels most like)
Duff plugs/leads/coil
Sensor fault - AF sensor (it's the hot wire one)/Throttle pot/ Fuel temp/Coolant temp
Thermostat failure leading to incorrect temp reading by ECU
Blocked/dirty injectors
Collapsed cat cores/silencer
And the biggie, ECU fault.
(Feel free to add others....)
I haven't got round to changing the plugs or leads yet, and the electrical tests on components/sensors are slightly daunting (I’m definitely a mechanical person, not electrically-minded at all!), and I don’t know what the readings should be or even where I can find the info and how to test each item (which colour leads, pins, procedure etc). I do possess a multimeter, but it doesn’t get much use…
Things that have made no difference so far (all mechanical tasks, you notice):
I've changed the fuel filters (and put an extra see-through one in too), the idle fuel pressure's ok (2.9bar), it's got a new coil, there's no vacuum leaks that I can find, the dizzy vac feed is in the right place (not the Japanese position), the idle control valve controls the idle ok (is there any other way to test this part?), I've cleaned the K&N air filter, and the AF sensor (used contact cleaner for that one), checked the exhaust and cats (they’re fine).
I've checked all hoses on the inlet side except for vac collapse. I’m pretty sure it’s not an individual plug or plug lead failure as it’s the whole engine shutting off, not one or two cylinders, but could it be the King lead breaking down under load?
Next on the list of things to do is removing and cleaning out the tank before I chuck in a can of injector cleaner, and strap a camera under the bonnet to look at the inlet hose when I give it some gas.
I’ve come across rovergauge, which looks great and might give me more info, but I’m not sure if it’s compatible with my ECU. How do I know/check? Will it help in this situation? Anyone else familiar with it?
My last issue is that as it’s a pre-production vehicle, its spec might not be as intended, and I'm not fully sure which bits are away from spec.
Thanks very much for your patience and for taking the time to read this. I’d be very grateful for any other suggestions, and all advice on what and how to test or check.
Here’s hoping for an easy win…
You sound like you've done a ton of work....and not changed the plugs ??
WOW.
Change the plugs, do a compression test while they are out, ensure leads are good etc.
You mention fuel pressure....if in doubt, test it.
All other speculation etc....just test for them all. There are many possibilities.
And your post isnt clear....has this engine ever ran correctly ?
WOW.
Change the plugs, do a compression test while they are out, ensure leads are good etc.
You mention fuel pressure....if in doubt, test it.
All other speculation etc....just test for them all. There are many possibilities.
And your post isnt clear....has this engine ever ran correctly ?
Many thanks for your replies.
@stevieturbo: I had the fuel filters already, and I've concentrated on the MOT and cost-free items so far (apart from my time). Picking up plugs today, and Magnecor leads on order (payday - yay!) and I checked the fuel pressure at idle with a borrowed (calibrated) gauge, but not dynamic fuel pressure. I notice there is a vacuum port on the regulator, but I haven't checked it's effect yet.
Yes, it has run correctly, before the lay-up, and for a short time (maybe an hour total driving time) afterwards too.
@E-bmw: Standard ECU, as far as I know, and the 'clean' comment was from the MOT tester. the engine isn't tesed under load anyway, if I recall correctly. I haven't yet checked to see if the timing or vac advance on the dizzy is ok.
@paintman: Thanks for that, I'll get on with ID tonight.
I'll fit plugs and leads and check compression and timing, and report back....
@stevieturbo: I had the fuel filters already, and I've concentrated on the MOT and cost-free items so far (apart from my time). Picking up plugs today, and Magnecor leads on order (payday - yay!) and I checked the fuel pressure at idle with a borrowed (calibrated) gauge, but not dynamic fuel pressure. I notice there is a vacuum port on the regulator, but I haven't checked it's effect yet.
Yes, it has run correctly, before the lay-up, and for a short time (maybe an hour total driving time) afterwards too.
@E-bmw: Standard ECU, as far as I know, and the 'clean' comment was from the MOT tester. the engine isn't tesed under load anyway, if I recall correctly. I haven't yet checked to see if the timing or vac advance on the dizzy is ok.
@paintman: Thanks for that, I'll get on with ID tonight.
I'll fit plugs and leads and check compression and timing, and report back....
bjd7326 said:
Have you changed the little black box on four or three wires remotely mounted from the dizzy?
Do you mean the ignition amplifier?The later ones mounted on the side of the dizzy did suffer from heat issues & LR came up with a kit to remotely mount them.
http://www.rangerovers.net/repairdetails/classic/e...
The MGR used the 14CUX ecu with lambda sensors. You can split the diagnostics into to parts.
1) Ignition. Just start with a strobe and make sure the base timing is correct and you get full advance at about 3500 rpm. Assuming the strobe triggers reliably the the HT, ignition amp and coil are probably OK
2) Fuel / ECU. There is the diagnostic "RoverGauge" (runs on a laptop) and diagnostic cables to connect to the ECU OBD port on Ebay for £35. This will give you any fault codes and full ECU sensor data. The car will be fitted with Lambda probes, and you can use these to check full load fuelling with a test meter on the black and and white wires on long leads so you can read it in the cabin. You should get a 0 to 1.2 volt cycling signal below 3400 rpm, but above that it should be at least 1.2 volts. If it drops to zero its running out of fuel. Guess work is a very bad way of diagnosing engine faults.
Ive done lots here:
http://www.g33.co.uk/fuel_injection.htm
BTW Magnecores are nothing but trouble on the RV8, you are far better with OEM leads. Unless you buy the black ones the core resistance is too low and it causes excessive ringing voltages in the coil primary that can glitch the rev counter.
1) Ignition. Just start with a strobe and make sure the base timing is correct and you get full advance at about 3500 rpm. Assuming the strobe triggers reliably the the HT, ignition amp and coil are probably OK
2) Fuel / ECU. There is the diagnostic "RoverGauge" (runs on a laptop) and diagnostic cables to connect to the ECU OBD port on Ebay for £35. This will give you any fault codes and full ECU sensor data. The car will be fitted with Lambda probes, and you can use these to check full load fuelling with a test meter on the black and and white wires on long leads so you can read it in the cabin. You should get a 0 to 1.2 volt cycling signal below 3400 rpm, but above that it should be at least 1.2 volts. If it drops to zero its running out of fuel. Guess work is a very bad way of diagnosing engine faults.
Ive done lots here:
http://www.g33.co.uk/fuel_injection.htm
BTW Magnecores are nothing but trouble on the RV8, you are far better with OEM leads. Unless you buy the black ones the core resistance is too low and it causes excessive ringing voltages in the coil primary that can glitch the rev counter.
Edited by blitzracing on Tuesday 23 August 15:44
Thanks for all your input, folks. I appreciate your time and knowledge.
Magnecor leads returned, OEM ones on.
Ok, so in between major landscaping, I've discovered that it's not:
Vac advance failure on dizzy
Rotor arm fault
Cracked dizzy cap
Intake pipe between AF sensor and throttle body collapsing under strong vacuum
Duff plugs/leads/coil.
I also checked compression yesterday while changing plugs, all good, 170 psi +/- 2%.
I also read that you should "make sure plug leads 5 and 7 don’t run next to each other (5 and 7 are adjacent in the firing order and cross firing can occur)" - any truth in that?
I also vaguely remember seeing something about old Range Rovers having a mode where if the speed or acceleration is significantly different from expected, then the ECU does something to put a dampener on your fun. I'm running 50 profile tyres (std was 65) - would that make a difference? The speed sensor is in the speedo cable before it goes through the bulkhead.
See-thru filter ok to 7 bar.
Mark@blitz, many thanks for that link, loads of good info. I'll also get hold of a strobe gun to check timing.
Next task (as it's a no-cost one) is to drop the tank and clean it out. Any tips? The most amusing one for de-rusting I read about is to remove the pickup and sender, chuck some vinegar, nuts and bolts in and gaffertape it to the front of a concrete mixer (got one of those) for a couple of hours! That'll please the neighbours!
Magnecor leads returned, OEM ones on.
Ok, so in between major landscaping, I've discovered that it's not:
Vac advance failure on dizzy
Rotor arm fault
Cracked dizzy cap
Intake pipe between AF sensor and throttle body collapsing under strong vacuum
Duff plugs/leads/coil.
I also checked compression yesterday while changing plugs, all good, 170 psi +/- 2%.
I also read that you should "make sure plug leads 5 and 7 don’t run next to each other (5 and 7 are adjacent in the firing order and cross firing can occur)" - any truth in that?
I also vaguely remember seeing something about old Range Rovers having a mode where if the speed or acceleration is significantly different from expected, then the ECU does something to put a dampener on your fun. I'm running 50 profile tyres (std was 65) - would that make a difference? The speed sensor is in the speedo cable before it goes through the bulkhead.
See-thru filter ok to 7 bar.
Mark@blitz, many thanks for that link, loads of good info. I'll also get hold of a strobe gun to check timing.
Next task (as it's a no-cost one) is to drop the tank and clean it out. Any tips? The most amusing one for de-rusting I read about is to remove the pickup and sender, chuck some vinegar, nuts and bolts in and gaffertape it to the front of a concrete mixer (got one of those) for a couple of hours! That'll please the neighbours!
Many, many summers ago I had a fault remarkably similar to yours on a race Imp that I used on the road. Stationary, it would rev happiliy, but all of a sudden (after filling up with fuel I later worked out) all power was lost on acceleration, worse when going up hill.................
The Imp tank was in the front obviously............ on draining and cleaning the tank a rubber grommet, free, courtesy of Esso was retrieved from the tank. It was blocking the fuel pickup under load after being sucked towards and over the exit from the tank. Going up hill made it worse as gravity helped the situation.
A lot of head scratching time was spent on that one, so I hope it has the potential to help here.
The Imp tank was in the front obviously............ on draining and cleaning the tank a rubber grommet, free, courtesy of Esso was retrieved from the tank. It was blocking the fuel pickup under load after being sucked towards and over the exit from the tank. Going up hill made it worse as gravity helped the situation.
A lot of head scratching time was spent on that one, so I hope it has the potential to help here.
You are still making life very difficult for yourself- this could well be limp home mode due to a faulty sensor but without a diagnostic you have no idea. If the MGR is the same as the RangeRover, the management warning light is not enabled in the firmware Eprom chip on the ECU, so if the ECU is in limp home mode you simply dont know. Another diagnostic tool is ECUmate that can read the sensors and fault codes, but I believe its no longer in production. Ask someone nicely on the TVR Chimeara or Griff forum if someone can lend you one or RoverGauge if you dont want to fork out.
Plug leads should be spaced apart and in a the correct position to prevent "cross firing" where a spark can be introduced across plug leads leading to a misfire. I doubt thats your issue however- seen loads of TVR HT leads packed together and misfiring does not seem to be an issue.
|http://thumbsnap.com/k26XwcXQ[/url]
There is only a speed limit on the software for the 4x4 tunes due to off road tyres, I doubt that will be the case on the MGR. Apart from that the speed input just tells the ECU if the car is stationary so it lowers the tick over, nothing more. Where are you geographically?
Plug leads should be spaced apart and in a the correct position to prevent "cross firing" where a spark can be introduced across plug leads leading to a misfire. I doubt thats your issue however- seen loads of TVR HT leads packed together and misfiring does not seem to be an issue.
|http://thumbsnap.com/k26XwcXQ[/url]There is only a speed limit on the software for the 4x4 tunes due to off road tyres, I doubt that will be the case on the MGR. Apart from that the speed input just tells the ECU if the car is stationary so it lowers the tick over, nothing more. Where are you geographically?
Edited by blitzracing on Tuesday 30th August 20:00
blitz: many thanks for the info. The link you provided has given me loads of food for thought, and I appreciate the testing advice included there, I'm going to give it a good go.
BTW, I'm about 10 miles south of Oxford.
I've also had a lead made up by a mate who works in electronics (got the instructions from the rovergauge site - that's some great work by the Bourassa lads!), so I'll try over the next week or so to get rovergauge involved now, that's my next step. I like your idea of monitoring lambda readings from the cockpit. If I can get the right connectors for my multimeter leads, I might have a crack at that too....
My main problem is that I'm currently very limited on the time I can allocate to physically sort the problem (the work listed above has taken the best part of 2 years, it's been MOT'd since April and it took me nearly a fortnight to find time to fit plugs and leads), so although actual progress is slow, PH's super helpful membership has been a great resource for info gathering, and an encouraging, supportive boost to get things done. Thank you folks.
As soon as I have progress to report or readings from rovergauge, I'll be back here....
BTW, I'm about 10 miles south of Oxford.
I've also had a lead made up by a mate who works in electronics (got the instructions from the rovergauge site - that's some great work by the Bourassa lads!), so I'll try over the next week or so to get rovergauge involved now, that's my next step. I like your idea of monitoring lambda readings from the cockpit. If I can get the right connectors for my multimeter leads, I might have a crack at that too....
My main problem is that I'm currently very limited on the time I can allocate to physically sort the problem (the work listed above has taken the best part of 2 years, it's been MOT'd since April and it took me nearly a fortnight to find time to fit plugs and leads), so although actual progress is slow, PH's super helpful membership has been a great resource for info gathering, and an encouraging, supportive boost to get things done. Thank you folks.
As soon as I have progress to report or readings from rovergauge, I'll be back here....
The MGR uses a unique connector and you cant get the plugs anyway, so you need to make a plug up from scratch, or put pins onto the USB lead and slide them into the OBD connector. It also needs a dropper resistor in the connector, plus the receive signal has to be inverted by programming the USB device. Let me know if you get stuck- Im 8 miles southfrom wantage , so pretty near to you.
Thanks Mark.
I got one of these: http://www.ebay.co.uk/itm/131239350240?_trksid=p20...
Is it correct before I go and plug it in?
Looking at the photo here, it looks similar..... https://github.com/colinbourassa/libcomm14cux/blob...
I got one of these: http://www.ebay.co.uk/itm/131239350240?_trksid=p20...
Is it correct before I go and plug it in?
Looking at the photo here, it looks similar..... https://github.com/colinbourassa/libcomm14cux/blob...
Not sure if you've solved this yet, but when I was running a '93 Discovery with a 3.5 rover v8 I had a remarkably similar issue to you and went through pretty much everything you list in OP trying to rectify the issue. Got worse and worse over about six months while I nor anybody else could figure it out. Turned out to be an issue with lambda sensors causing one bank of the engine to be reading cold so running too rich once it was actually warm.
Hope this helps - I remember the pain well!
Hope this helps - I remember the pain well!
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