Poor Idle / Rovergauge Help
Discussion
Hi all,
I am trying to get to the bottom of poor / uneven idle on my Chimaera and I have purchased the excellent RoverGauge from Mark and Blitz and it works a treat.
The results confirm my suspicions that I might have an air leak after the AFM as when at maximum vacuum (idle) both lambdas continuously show +100% short-term trim and will only reduce or go negative and cycle nicely lean / rich if I lift the revs to say 2000RPM, where I guess the vacuum is less and any leak would be less pronounced so the mixture can be made to go rich.
I’ve checked the obvious – plenum to servo and carbon canister, fuel regulator to stepper motor housing, pipes on the nearside of engine and vacuum advance. All look good.
I also note the target is idle is very low. What causes this? When the engine RPM drops below this value I do see the idle bypass increase which makes sense.
No signs of hissing, so I am at a real loss. Is it plenum off time or worth checking anything else first?
It’s driving me bonkers!
Nick
I am trying to get to the bottom of poor / uneven idle on my Chimaera and I have purchased the excellent RoverGauge from Mark and Blitz and it works a treat.
The results confirm my suspicions that I might have an air leak after the AFM as when at maximum vacuum (idle) both lambdas continuously show +100% short-term trim and will only reduce or go negative and cycle nicely lean / rich if I lift the revs to say 2000RPM, where I guess the vacuum is less and any leak would be less pronounced so the mixture can be made to go rich.
I’ve checked the obvious – plenum to servo and carbon canister, fuel regulator to stepper motor housing, pipes on the nearside of engine and vacuum advance. All look good.
I also note the target is idle is very low. What causes this? When the engine RPM drops below this value I do see the idle bypass increase which makes sense.
No signs of hissing, so I am at a real loss. Is it plenum off time or worth checking anything else first?
It’s driving me bonkers!
Nick
Thanks Bob,
Have tried an alternative genuine stepper but stiil the same.
The stepper goes to max when I stop it and the revs shoot to 2k RPM when I first start-up and then drop, so it is working.
The thing is, the cars smells as though it is running rich and I note that the lambda cables have been hacked and looking thru the history, it has had the occasional emission 'issues' in the past.
What would the effect be if the lambda probes had been connected opposite sides? Looks physically feasible as the cables are presently running on top of the rockers since the re-work by others.
Cheers
Nick
Have tried an alternative genuine stepper but stiil the same.
The stepper goes to max when I stop it and the revs shoot to 2k RPM when I first start-up and then drop, so it is working.
The thing is, the cars smells as though it is running rich and I note that the lambda cables have been hacked and looking thru the history, it has had the occasional emission 'issues' in the past.
What would the effect be if the lambda probes had been connected opposite sides? Looks physically feasible as the cables are presently running on top of the rockers since the re-work by others.
Cheers
Nick
If it smells rich then I'd follow that lead but the poor idle high idle issue sounds more like an air leak as you're suggesting. If it were me under that bonnet I'd be tempted to turn the manual air bleed down say one turn and look again at the rovergauge readings. The reason for poor idle level is possibly because the stepper is at full stroke so can't balance it out. Lowering manual bypass air may bring thd stepper back into play
Thanks Guys,
I managed to clamp the air bleed and set the base idle to 550-650 RPM, which surprised me as I didn't think it would run at this low RPM.
Removed the clamp and I managed to get a positive idle correction to the stepper.
But both lambdas still reading + 100%. Will have another look later today.
I am regularly resetting the ECU by disconnecting the battery when I am away from the car
I managed to clamp the air bleed and set the base idle to 550-650 RPM, which surprised me as I didn't think it would run at this low RPM.
Removed the clamp and I managed to get a positive idle correction to the stepper.
But both lambdas still reading + 100%. Will have another look later today.
I am regularly resetting the ECU by disconnecting the battery when I am away from the car
Interesting this topic
I have a very similar issue,runs fine but idle is suspect and also has the tendency of cutting out when stationery,but starts straight away with no issue
Fuel smell is also present especially the longer the engine is turning over
Had her booked in with Jools to sort but unfortunately I bust 2 disks in my back and had to cancel😡😭😭
I have a very similar issue,runs fine but idle is suspect and also has the tendency of cutting out when stationery,but starts straight away with no issue
Fuel smell is also present especially the longer the engine is turning over
Had her booked in with Jools to sort but unfortunately I bust 2 disks in my back and had to cancel😡😭😭
Edited by CHIMV8 500 on Saturday 29th April 13:04
chimV8 Sticking stepper, gets slightly out of sync. When you say it starts straight away, is this after tuning ign off, if so Ecu pulls stepper back in so in essence resetting itself to zero or fully retracted position so idles ok then stepper starts to fall out of position, Ecu can't read this it just reads lambda's so carrys on trying to make fuelling adjustments, steppers out of position and Ecu goes round in circles tyring to correct air fuel ratio.
Turn it all off. Stepper resets and for awhile it works again.
I never had Rover gauge but after a while I could watch the the numbers on ECUMATE and the stepper operation, when it all worked ok those numbers were consistent everytime, and around 130 if my memory is correct, when it stuck for a few seconds it then read higher numbers and never recovered back to those lower numbers. Re set Ecu, off you go again with good numbers and idle, sometimes for a day or two perfect, then rough idle, eucmate plugged in and higher numbers recorded. Operating the stepper manually then confirmed, sometimes it would pulse out ok, it then wouldn't pull it back, a number of pulses then it would start to move, Ecu now reads its position wrong as it's assumed the stepper has moved in congunction with its pulses which it obviously has not.
That's my take on it.
Turn it all off. Stepper resets and for awhile it works again.
I never had Rover gauge but after a while I could watch the the numbers on ECUMATE and the stepper operation, when it all worked ok those numbers were consistent everytime, and around 130 if my memory is correct, when it stuck for a few seconds it then read higher numbers and never recovered back to those lower numbers. Re set Ecu, off you go again with good numbers and idle, sometimes for a day or two perfect, then rough idle, eucmate plugged in and higher numbers recorded. Operating the stepper manually then confirmed, sometimes it would pulse out ok, it then wouldn't pull it back, a number of pulses then it would start to move, Ecu now reads its position wrong as it's assumed the stepper has moved in congunction with its pulses which it obviously has not.
That's my take on it.
ClassicChimaera said:
A new stepper motor but that's fraught with risk as the one I paid £70 didn't work any better.
Get rid of the lot but that's really rather expensive.
Do you have ECUMATE or Rover gauge, you should be able to effect the steppers operation to confirm if it sticks or not.
Replaced the stepper previous and was a good improvement, have rovergauge how do you effect stepper?Get rid of the lot but that's really rather expensive.
Do you have ECUMATE or Rover gauge, you should be able to effect the steppers operation to confirm if it sticks or not.
For vacuum leaks check all fittings around trumpet base drivers side are tight. I had a slightly loose power steering bottle bracket bolt that screw to the base, tightened it and it fixed my vacuum leak.
I've seen eBay folk put smoke through the intake and watch to see if any smoke escapes and that's your leak.
Process of elimination I'm afraid, try not to throw good money after bad......
I've seen eBay folk put smoke through the intake and watch to see if any smoke escapes and that's your leak.
Process of elimination I'm afraid, try not to throw good money after bad......
CHIMV8 500 said:
Replaced the stepper previous and was a good improvement, have rovergauge how do you effect stepper?
There should be a facility to adjust the stepper position manually on Rover gauge surely! Blitz racing is at the Kitcar show this weekend. Unless someone else has Rovergauge and can elaborate he might be along sometime next week to help you out.
Have you got something that shows the stepper motors position on your screen shots, it might have a manual adjustment button there.
Your 100% values and things like throttle pot position are all indicators. It says 8% throttle opening, I'm sure this should be below 5% at idle but I might be wrong so hopefully someone who has used Rovergauge can point you in the right direction.
ClassicChimaera said:
There should be a facility to adjust the stepper position manually on Rover gauge surely!
Yes there is, I used it to prove that TVR Parts had sold me a faulty stepper. I cant recall the precise function but I didn't have to look very hard to find it. It strokes the plug back and forward so that the measured limits can be tested against TVR specs. I don't know if it allows mid stroke testing^^^ this
The stepper is an electrically controlled signal and the Ecu reads it by assuming when ign is turned off stepper should over retract via electrical pulses drawing the arm in to a set zero. When you fire the car again the Ecu just reads the steppers position via how many pulses it takes to get out to an even idle in conguunction with lambda and AFM temp readings etc
If the stepper doesn't react to these electrical impulses correctly and gets out of position it's then effecting mixture. It should retract fully the next time you stop and turn off. If it doesn't the Ecu will step it out via the correct amount of pulses but it's not in the correct position.
I think there's upto about 300 pulse positions available but the stepper only requires upto about 200,, im sure mine when working correct fluctuated at around 130 so when you turn ignition off the stepper should over pulse to ensure it's fully in for the next time. Each time the Ecu counts from zero out and controls its position thus on start up. It's why some days mine was fine, other days it was out and caused the usual problems at start up.
Other days it started fine then after some driving or a blip of the throttle it would stick and off we do again.
Dodgy temp sensor is another one but if your Ecu is reading steady temps via Rovergauge then I'd not suspect that.
Someone who has watched normal stepper operation via diagnostics should tell straight away if the numbers or whatever Rovergauge uses are where they should be. Once you record all these good positions and numbers etc you can read a fault much easier and quicker.
My symptoms could be low or no idle, or high idle 1500 revs, the steppers position reflected that problem in it's incorrect positioning.
Most people who have long time reliable steppers don't often moan of idle issues.
The stepper is an electrically controlled signal and the Ecu reads it by assuming when ign is turned off stepper should over retract via electrical pulses drawing the arm in to a set zero. When you fire the car again the Ecu just reads the steppers position via how many pulses it takes to get out to an even idle in conguunction with lambda and AFM temp readings etc
If the stepper doesn't react to these electrical impulses correctly and gets out of position it's then effecting mixture. It should retract fully the next time you stop and turn off. If it doesn't the Ecu will step it out via the correct amount of pulses but it's not in the correct position.
I think there's upto about 300 pulse positions available but the stepper only requires upto about 200,, im sure mine when working correct fluctuated at around 130 so when you turn ignition off the stepper should over pulse to ensure it's fully in for the next time. Each time the Ecu counts from zero out and controls its position thus on start up. It's why some days mine was fine, other days it was out and caused the usual problems at start up.
Other days it started fine then after some driving or a blip of the throttle it would stick and off we do again.
Dodgy temp sensor is another one but if your Ecu is reading steady temps via Rovergauge then I'd not suspect that.
Someone who has watched normal stepper operation via diagnostics should tell straight away if the numbers or whatever Rovergauge uses are where they should be. Once you record all these good positions and numbers etc you can read a fault much easier and quicker.
My symptoms could be low or no idle, or high idle 1500 revs, the steppers position reflected that problem in it's incorrect positioning.
Most people who have long time reliable steppers don't often moan of idle issues.
Edited by ClassicChimaera on Monday 1st May 12:42
I like the note below
I only ever effected its operation when engine was running when I knew it to already be out of step, excuse the pun, sometimes worked other times just made it worse. What I was able to do was hold the stepper in my hand and feel and watch the pulses move it With the manual operation and clearly see it sticking. Fecked!
Be careful here- all this ECU resetting clears the long term fuel trim down- so the ECU has to re learn the setting. This takes at least 2.5 mins at plus 90'c at a fixed idle. So put it on long term trim, and let the car idle, and you should see the long term trim slowly move bit by bit. Assuming it sets at less than 100%, the short term should then start to cycle around the mid point again. If you just reset ECU without letting it learn or the engine is not hot enough you will get the symptoms you describe.
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