Chimaera overfueling and won t sit in idle mode
Discussion
Hello,
I have a 1993 Chimaera 4.3. I have just got into rovergauge so I can check all is working as it should. It’s overfuelling I believe for some reason which I need to investigate, but what I want to know is why the “idle mode” light doesn’t come on and let the ecu start trying to alter the idle. Should this light (on the rovergauge screen) light up green when it’s trying to idle the engine rpm?
I have a 1993 Chimaera 4.3. I have just got into rovergauge so I can check all is working as it should. It’s overfuelling I believe for some reason which I need to investigate, but what I want to know is why the “idle mode” light doesn’t come on and let the ecu start trying to alter the idle. Should this light (on the rovergauge screen) light up green when it’s trying to idle the engine rpm?
You are on corrected throttle position reading and is is showing a value (9%?), the ECU will only go into idle strategy when TPS is at zero.
Do you have any throttle motion active?
What does the uncorrected throttle value read?
My understanding is that the ECU will set 0% (uncorrected) to whatever the lowest reading it has seen so it seems like your system has previously seen a lower reading.
The 'self correct' may only work down to a specific value, I'd have to look at the code. It may only work on later code versions too.
Those short term trims don't look good either. What do long term look like?
Do you have any throttle motion active?
What does the uncorrected throttle value read?
My understanding is that the ECU will set 0% (uncorrected) to whatever the lowest reading it has seen so it seems like your system has previously seen a lower reading.
The 'self correct' may only work down to a specific value, I'd have to look at the code. It may only work on later code versions too.
Those short term trims don't look good either. What do long term look like?
Edited by CGCobra on Wednesday 12th August 21:34
I have fitted the ACT adapted TPS as the original failed and would only show 99% permanently. This new TPS, I have rotated it all the way round and the minimum throttle it shows is 10% corrected/ 20% absolute. I was led to believe you had to look at the corrected setting!? Either way not sure how I can reduce this.
First though I now need to sort out a misfire on two cylinders, 4 and 6. These cylinders are not firing for some reason. I have fitted new plugs and made no difference, still no firing. Swapped around the HT leads to see if a lead had failed but no change. Removed the extenders for the plugs and put the leads straight onto the plug, no difference. When I lift the lead straight off the distributor there is a spark jumping I can visually see. What do you think could be the next check?
Thanks for the replies, I appreciate the help. New to the TVR scene.
Sam
First though I now need to sort out a misfire on two cylinders, 4 and 6. These cylinders are not firing for some reason. I have fitted new plugs and made no difference, still no firing. Swapped around the HT leads to see if a lead had failed but no change. Removed the extenders for the plugs and put the leads straight onto the plug, no difference. When I lift the lead straight off the distributor there is a spark jumping I can visually see. What do you think could be the next check?
Thanks for the replies, I appreciate the help. New to the TVR scene.
Sam
Info on tps.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
You need to sort out the misfires first as these will affect your readings.
If you pull the lead off the plug does the spark jump the gap?
These cars will foul spark plugs quickly at frequent cold starts sat on the drive so try to avoid that, I would inspect/clean them.
https://www.pistonheads.com/gassing/topic.asp?h=0&...
You need to sort out the misfires first as these will affect your readings.
If you pull the lead off the plug does the spark jump the gap?
These cars will foul spark plugs quickly at frequent cold starts sat on the drive so try to avoid that, I would inspect/clean them.
It’s odd regarding the TPS, when the sensor is wound back until it stops it’s only at 10% in rovergauge. That’s with it unbolted, the sensor will not travel any further. Will look into that more once I can sort the misfiring.
So the engine was running ok, but over fueling still, but then it dropped a cylinder (number 2) and would not run at all on that cylinder. Next day cylinder 4 joined in and currently cylinder 2 and 4 will not run at all.
I have swapped the plugs and fitted new ones. Started it up and exactly the same, didn’t even try to run on those cylinders. I’ve since swapped the HT leads to see if that makes a difference but doesn’t. Removed the spark plug extenders and no difference. I’ve held a screw driver to the injectors and all are ticking. Took the distributor cap off, noticed sanding marks from before, did have some discolouration on some contacts so sanded them and this made no difference either. Think I will order a new distributor cap? Can these get worn and over sanded? Condition looks fine on the outside.
What’s the next steps do you think?
Thanks Sam
So the engine was running ok, but over fueling still, but then it dropped a cylinder (number 2) and would not run at all on that cylinder. Next day cylinder 4 joined in and currently cylinder 2 and 4 will not run at all.
I have swapped the plugs and fitted new ones. Started it up and exactly the same, didn’t even try to run on those cylinders. I’ve since swapped the HT leads to see if that makes a difference but doesn’t. Removed the spark plug extenders and no difference. I’ve held a screw driver to the injectors and all are ticking. Took the distributor cap off, noticed sanding marks from before, did have some discolouration on some contacts so sanded them and this made no difference either. Think I will order a new distributor cap? Can these get worn and over sanded? Condition looks fine on the outside.
What’s the next steps do you think?
Thanks Sam
I've only looked at the program code in my own PROM which is the last generation (R3652 IIRC) I see yours is earlier, R2967, this may work differently, I seem to recall reading that and older TPS potentiometers were slotted which would be consistent with this.
If I've understood correctly older tunes required the potentiometer to be rotated to achieve a specific voltage with the TPS against it's (non-adjustable) stop. On the later versions the program has additional code in the TPS reading area which monitors the lowest reading 'seen' and adjusts it's calculated percentages by that, obviously in normal use this variation should be very slight.
This has the benefit that the TPS does not need to be accurately set (within limits) and so does not need the slotted screw holes. Also if the engine was started with some pressure already on the throttle it will not throw a fault and will correct itself once the pedal is released.
I'm pretty sure there is a minimum reading for the TPS (78mV rings a bell) and it's possible that there is a maximum limit too, I'd have to go back and have a look. Not something I've ever had an issue with so not looked in detail.
This value can be seen in the battery backed RAM values which you can read in RG by the way. Maybe an idea to get a screen grab of that.
With RG, when you read Corrected TPS value this is with respect to the minimum value hence should read zero for closed throttle which is probably why you've been advised to read that way, I'd agree with that too.
You are seeing 9%, presumably with a closed throttle so either:
1-Your tune is not performing the minimum TPS calculation/setting possibly due to its generation.
2-There may be a maximum value above which the calculation isn't performed.
3-At some point your system has monitored a lower value - The BB-RAM value is maintained over a normal power down so could have occurred some time back if your ECU has not had the full time power removed.
By coincidence I'm currently working with another RG user who also has an ACT plenum on the car and it also seems to be part of the issue or at least not helping.
It seems that on these engines there is no idle bypass circuit and instead the throttle plates have an adjustable stop screw so you set the base idle by adjusting this which opens the throttle plates to let air in via that route. Please correct me if not the case.
If you are only firing on 6 cylinders this will presumably have been set high to get enough air through to allow the working cylinders to give idle speed. This will no help your TPS value as this will now give a higher reading.
I'd say your more important issue is the none running cylinders, sort this and you may sort or at least help the TPS issue. Sounds like you've replace plugs and leads, would it be worth swapping leads from other, working, cylinders so known good? Have you checked if spark is actually reaching the plugs?
If it is then you may have injector issues (they are fired as a bank so if 2 & 8 are working than 4 & 6 must be switched too). May be worth removing the injectors and testing for flow and/or swapping with other cylinders to see if the problem moves. Also worth checking the wires to the injector and/or the signal from the plug.
If you eliminate spark and fuel issue then you probably want to check compression and maybe valve operation.
If you still have TPS issue after that you might want to check out if the tune you have is adjusting the zero position. If you get a copy of the program from RG and post it up I may be able to find the TPS routine and see if that code is present. If this is not present then you may want to switch to a tune which does have it or find a way to modify your TPS attachment to allow that. I'd say that a plenum which needs the base idle to be set from the throttle plates probably also needs this function.
By the way I'd also recommend reading the MAF output as Linear rather than Direct, the readings make more sense that way.
If I've understood correctly older tunes required the potentiometer to be rotated to achieve a specific voltage with the TPS against it's (non-adjustable) stop. On the later versions the program has additional code in the TPS reading area which monitors the lowest reading 'seen' and adjusts it's calculated percentages by that, obviously in normal use this variation should be very slight.
This has the benefit that the TPS does not need to be accurately set (within limits) and so does not need the slotted screw holes. Also if the engine was started with some pressure already on the throttle it will not throw a fault and will correct itself once the pedal is released.
I'm pretty sure there is a minimum reading for the TPS (78mV rings a bell) and it's possible that there is a maximum limit too, I'd have to go back and have a look. Not something I've ever had an issue with so not looked in detail.
This value can be seen in the battery backed RAM values which you can read in RG by the way. Maybe an idea to get a screen grab of that.
With RG, when you read Corrected TPS value this is with respect to the minimum value hence should read zero for closed throttle which is probably why you've been advised to read that way, I'd agree with that too.
You are seeing 9%, presumably with a closed throttle so either:
1-Your tune is not performing the minimum TPS calculation/setting possibly due to its generation.
2-There may be a maximum value above which the calculation isn't performed.
3-At some point your system has monitored a lower value - The BB-RAM value is maintained over a normal power down so could have occurred some time back if your ECU has not had the full time power removed.
By coincidence I'm currently working with another RG user who also has an ACT plenum on the car and it also seems to be part of the issue or at least not helping.
It seems that on these engines there is no idle bypass circuit and instead the throttle plates have an adjustable stop screw so you set the base idle by adjusting this which opens the throttle plates to let air in via that route. Please correct me if not the case.
If you are only firing on 6 cylinders this will presumably have been set high to get enough air through to allow the working cylinders to give idle speed. This will no help your TPS value as this will now give a higher reading.
I'd say your more important issue is the none running cylinders, sort this and you may sort or at least help the TPS issue. Sounds like you've replace plugs and leads, would it be worth swapping leads from other, working, cylinders so known good? Have you checked if spark is actually reaching the plugs?
If it is then you may have injector issues (they are fired as a bank so if 2 & 8 are working than 4 & 6 must be switched too). May be worth removing the injectors and testing for flow and/or swapping with other cylinders to see if the problem moves. Also worth checking the wires to the injector and/or the signal from the plug.
If you eliminate spark and fuel issue then you probably want to check compression and maybe valve operation.
If you still have TPS issue after that you might want to check out if the tune you have is adjusting the zero position. If you get a copy of the program from RG and post it up I may be able to find the TPS routine and see if that code is present. If this is not present then you may want to switch to a tune which does have it or find a way to modify your TPS attachment to allow that. I'd say that a plenum which needs the base idle to be set from the throttle plates probably also needs this function.
By the way I'd also recommend reading the MAF output as Linear rather than Direct, the readings make more sense that way.
Thanks so much for taking the time to reply - invaluable info there. What you say all makes sense- I shall sort the non running cylinder issues first.
When I bought the car it had new magnecor leads fitted, so as you said I’ve swapped the known working leads across with no success. I will double check again at the plug it’s sparking - was last time I checked I’m sure. Are the injectors easy enough to remove and swap cylinders?
Thanks again, I really appreciate everyone’s help.
When I bought the car it had new magnecor leads fitted, so as you said I’ve swapped the known working leads across with no success. I will double check again at the plug it’s sparking - was last time I checked I’m sure. Are the injectors easy enough to remove and swap cylinders?
Thanks again, I really appreciate everyone’s help.
samcourtney86 said:
Thanks so much for taking the time to reply
No problem, happy to help.samcourtney86 said:
When I bought the car it had new magnecor leads fitted, so as you said I ve swapped the known working leads across with no success. I will double check again at the plug it s sparking - was last time I checked I m sure.
I agree with @Belle427Belle427 said:
Magnecor leads are seen as junk by those who know, would expect new leads to be ok though.
What colour are they as some are for racing only applications, not saying that's the issue but just something to check.
I think the only people who rated Magncor leads were RPI and they rated anything they were selling!What colour are they as some are for racing only applications, not saying that's the issue but just something to check.
However if you've changed to a lead from a cylinder which was firing then that should be sufficient to prove that the lead is not the problem. For now at least!
Out of interest, how long have you had the car and has it been working OK up until now?
samcourtney86 said:
Are the injectors easy enough to remove and swap cylinders?
Thanks again, I really appreciate everyone s help.
The injectors are easy enough to remove and swap but it does require a bit of work, it will be slightly different in your case as you don't have the standard plenum and I have no idea what else is non-standard to achieve that, but the work required is typically:Thanks again, I really appreciate everyone s help.
Remove plenum
Remove trumpet base
Unplug electrical connectors to injectors
Remove fuel rail, injectors presumably attached as they are clipped to the rail - It may be necessary to disconnect the fuel hoses to the rail, depends on the installation.
You may be able to test the injectors by simply applying voltage to them to check if they click and, if the fuel rail has pressure, if any fuel is expelled.
I have a cheap injector tester which will pulse the injectors similar to how they work in reality. Alternatively swapping them and seeing if the problem moves could also prove one way or the other.
Just to look at the longer term issue, one other thing I notice is that on your original RG screen grab it shows that the STLT are both very high -ve values, odd bank is maxed out. This is removing fuel so the engine would be running very rich if closed loop was not in operation. That would suggest some underlying issue. It could be due to your none firing cylinders but, from what you've said, they are both on the even side so I'd only expect to see trim on that side, in fact that has the lower (-ve) value. Is it possible that the rich mixture is causing/contributing to the non-firing?
Has your ECU been unplugged recently? If so the long term trims will have been reset and I think these only get reset after an adaptation procedure which involves getting the engine to temperature (quite a high temperature I believe) and letting it idle for a while, about 10 min's I believe. I'm not too au-fait with this as my car runs open loop so never done it myself.
A screen-grab of your battery backed RAM settings should help see if this has been done.
Hello,
Yes just the TPS sensor has been changed.
I have had the car a year, it’s not ideal as the car is not on the road so only gets a small run and otherswise is idle running most of the time, which I hear isn’t great for the plugs, especially when overfuelling as it is. I have swapped the plugs and cleaned them etc many times to see if this is causing the issue but never makes the cylinders fire.
They are magnecor blue leads, and yes have swapped the leads to rule out etc.
The car was running ok, then started not running on 1 of the cylinders, but now both.
Hoping this weekend to compression test the cylinders and if I get chance swap the injectors around. We keep updated. I will upload some pictures too.
Thanks Sam
Yes just the TPS sensor has been changed.
I have had the car a year, it’s not ideal as the car is not on the road so only gets a small run and otherswise is idle running most of the time, which I hear isn’t great for the plugs, especially when overfuelling as it is. I have swapped the plugs and cleaned them etc many times to see if this is causing the issue but never makes the cylinders fire.
They are magnecor blue leads, and yes have swapped the leads to rule out etc.
The car was running ok, then started not running on 1 of the cylinders, but now both.
Hoping this weekend to compression test the cylinders and if I get chance swap the injectors around. We keep updated. I will upload some pictures too.
Thanks Sam
Haven’t had much time over the weekend unfortunately to look into this. However, new distributor cap and rotor arm from Motoclan turned up today so popped it on, made no difference. On fitting it I’ve notice it has way more play in it that the original, is this ok- see video
https://youtube.com/shorts/SF9poBPbf7c?is=-o0mkdm_...
Secondly after running it to see, still wasn’t running on the 2 cylinders, I popped the plugs out of those to find the were dry and look as new (they are new as put them in last week). Shouldn’t they have a bit of fuel on them at least?
Thanks Sam
https://youtube.com/shorts/SF9poBPbf7c?is=-o0mkdm_...
Secondly after running it to see, still wasn’t running on the 2 cylinders, I popped the plugs out of those to find the were dry and look as new (they are new as put them in last week). Shouldn’t they have a bit of fuel on them at least?
Thanks Sam
Aftermarket parts even from the likes of motoclan can be complete junk to be honest, quality spares are no longer available.
I would expect to smell some fuel on the plugs, maybe this is a clue its not your spark that`s missing.
Pull the suspect cylinder plug out and hold it to the block whilst cranking to see if its sparking.
I would expect to smell some fuel on the plugs, maybe this is a clue its not your spark that`s missing.
Pull the suspect cylinder plug out and hold it to the block whilst cranking to see if its sparking.
No fuel on the plugs suggests injectors not working You need a set of these to check that pulses are reaching the injectors:
https://www.ebay.co.uk/itm/324364505756?var=0&...
Also available on Amazon
https://www.ebay.co.uk/itm/324364505756?var=0&...
Also available on Amazon
Agreed, plugs should not be dry so that would indicate no fuel getting through. If there's sufficient slack in the cables you may be able to swap injector leads with adjacent cylinder see is problem moves.
The injectors have a live feed to them which gets switched to ground in the ECU to fire, you could check if you have a live to the problem injectors. You could also check continuity to a working cylinder on the same bank, the injectors are all grouped together (batch fire), no continuity would indicate wire fault.
The injectors have a live feed to them which gets switched to ground in the ECU to fire, you could check if you have a live to the problem injectors. You could also check continuity to a working cylinder on the same bank, the injectors are all grouped together (batch fire), no continuity would indicate wire fault.
Belle427 said:
Aftermarket parts even from the likes of motoclan can be complete junk to be honest, quality spares are no longer available.
I would expect to smell some fuel on the plugs, maybe this is a clue its not your spark that`s missing.
Pull the suspect cylinder plug out and hold it to the block whilst cranking to see if its sparking.
Unfortunately, as with most products, I think we've had peak car part a good while back. That's the price we pay for wanting everything to be cheap!I would expect to smell some fuel on the plugs, maybe this is a clue its not your spark that`s missing.
Pull the suspect cylinder plug out and hold it to the block whilst cranking to see if its sparking.
It's very disappointing when you've lived through times where, as products evolved, they typically improved but then they started getting worse.
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