Just can't get my Chimaera to run properly

[Fenderer]

I've had a long and enduring battle trying to get my Chimaera 4.0HC running smoothly over the last few years. I thought I was making good progress but there is always a consistent misfire problem which keeps coming back and I just can't resolve it. If the car is left idling for too long it seems to foul its own plugs, and when you pull away I lose 4 cylinders and get a very strong smell of fuel. Sometimes they come back, but there is nearly always the feeling of one being down. To remedy I have to take out all the plugs clean them, refit and start again but the same cycle repeats. I've always been convinced it's just poor ignition so I've replaced just about every part of the ignition system plus some likely contenders.


This is the list of everything I've replaced:
- rotor arm
- distributor cap
- temperature sender
- HT leads (AC Delco OE)
- NGK BPR6ES plugs
- lambda probes
- coil NGK
- Ignition amplifier
- Bosch Omega V6 injectors
- New MAF

Plug extenders removed, and leads fitted with heat socks.

RoverGauge shows everything as normal although Lambda fuel trim on the 'odd' bank is -100. Short term looks normal.

Checking with an infra red thermometer shows cylinder 8 is running much colder than the others, 100 deg+ colder which leads me to believe it's not firing properly at all. I swapped the HT lead on this cylinder but no improvement.

I've run right around in circles on it now and not sure where to go next..

Any ideas how to methodically pin this fault down?

[Mbwa-kali]

I get your frustration as that's a pretty expensive list of parts! I don't have experience of a similar fault but seems you have fuel and most likely spark so wonder if there is anything going on in the plenum or with the air supply which is causing a loss of combustion on one bank and a specific cylinder? I assume you have ruled out an EMU fault and compression is good/stable?

[blaze_away]

After a long period with similar issues and similar rovergauge I finally tracked my problem down to vacuum leaks on various parts of the plenum and manifold.
I fixed those and it now runs the best ever.

Have a look here https://www.pistonheads.com/gassing/topic.asp?h=0&...

[Fenderer]

Hi ,Yes it's true to say I've developed a rather enduring love/ hate relationship with this car!

I've ruled out anything cylinder/ compression related for the main reason that the fault is intermittent. It will run OK for a while with a clean set of plugs but as soon as there is a period of bad running it becomes a vicious circle and will never run properly after that until I go through the same spark plug clean routine. The plugs come out black, although since fitting the new injectors they are at least keeping a bit cleaner on the electrode and the soot is confined to the insulator. As you can imagine continually getting those plugs out and refitting every 20 miles or so has become a real bind!! The fact it doesn't seem to be able to burn off the deposits itself suggests to me I'm still struggling with a weak spark? But I'm just guessing without any kind of HT diagnostic equipment.

[Fenderer]

blaze_away said:

After a long period with similar issues and similar rovergauge I finally tracked my problem down to vacuum leaks on various parts of the plenum and manifold.
I fixed those and it now runs the best ever.

Have a look here https://www.pistonheads.com/gassing/topic.asp?h=0&...

Thanks that certainly sounds possible, will check through those.

[981Boxess]

I see you have temp sender on your list but is that the one for the dash gauge?

It sounds like you have the car running with the "choke" on.

[Fenderer]

981Boxess said:

I see you have temp sender on your list but is that the one for the gauge?

No it's the other one in the inlet manifold, the one that commonly fails.

[981Boxess]

Fenderer said:

Checking with an infra red thermometer shows cylinder 8 is running much colder than the others, 100 deg+ colder which leads me to believe it's not firing properly at all. I swapped the HT lead on this cylinder but no improvement.

If it fouls and stops firing then the temp will drop, you will always get one that gives in before the others, it might have slightly lower compression than the rest.

[blitzracing]

The problem is only on one bank, and a misfiring plug shows as lean, not rich. RoverGauge clearly shows a massive over fuelling on one bank and has hit the stops on the amount of adjustment available on the failing bank. Your plugs say the same thing. The injectors are fired in blocks of 4 at the same time on each bank, so you have limited options-

1) The failing bank has an intermittent short in the loom that is grounding the switched side of the injectors- this will hold all 4 open and severely flood that bank. It has happened on TVR ECU looms that have rubbed through.
2) ECU has a failing switching transistor to ground on that will do the same thing
3) Its possible you have a very lazy lambda sensor on the failing side- swap them over and see if the fault moves.

Unfortunately the ECU wont throw an error code unless the lambda stops switching for some time, so wont pick up slow switching probes. If a probe output is stuck high (ie a short on the loom) it will try and remove fuel- but Im assuming your short term is actually cycling on the failing bank? Interestingly the long term is set at idle so the ECU has picked up the fault at idle apart from any running issues you have had.

It wont be ignition related as you have found already. Its unlikely to be an ECU sensor like temp or AFM as affects only one bank. Go and buy a set of Noid lights and plug on top of an injector on each bank and observe the flash pattern of the LED. Both banks should flash in a very similar fashion on a working engine. Id expect to see the failing bank lamp to come on permanently if the loom grounds out or transistor goes short circuit.

Edited by blitzracing on Monday 11th October 17:59

[Fenderer]

Thanks Blitzracing this is really helpful. Will work on this...

[981Boxess]

Fenderer said:

The plugs come out black ..............

Do all 8 look the same?

[blitzracing]

This - good point I was assuming 4 on one side fouling?

[hot metal]

I get this problem, sort of, but is quite rare & only on 2 & 4.

[Fenderer]

981Boxess said:

o all 8 look the same?

Yes all 8 are identical.

[Fenderer]

blitzracing said:

This - good point I was assuming 4 on one side fouling?

No all the plugs are fouled...and the cold cylinder is on the no. 8 on the even bank which isn't the one that is showing -100 on long term lamdba on Rover Gauge, so it's really confusing....

Edited by Fenderer on Monday 11th October 19:13

[blaze_away]

Have you had any work done involving the valley gasket ?

I had a cold cylinder last year that ran cold, turned out the valley gasket was bent over on that inlet.

[981Boxess]

Fenderer said:

981Boxess said:

Do all 8 look the same?

Yes all 8 are identical.

So are we talking black smoke out the exhaust and corresponding diabolical fuel consumption then?

[spitfire4v8]

Fenderer said:

No all the plugs are fouled...and the cold cylinder is on the no. 8 on the even bank which isn't the one that is showing -100 on long term lamdba on Rover Gauge, so it's really confusing....

Edited by Fenderer on Monday 11th October 19:13

theres an issue with rg in that it shows the wrong side lambda on the versions ive got ie odd bank on screen is even bank on car ...

[Steve_D]

I little sluthing implies you are local to me.
Why not borrow my spare ECU to eliminate that.

Steve
Southways automotive
Fareham
But live in Cowplain.

[davep]

spitfire4v8 said:

theres an issue with rg in that it shows the wrong side lambda on the versions ive got ie odd bank on screen is even bank on car ...

Dan and Colin did use the left and right bank convention for the earlier releases of RoverGauge, but later brought in odd and even so as to avoid confusion. There could have been an oversight during the 'search and replace' when the change for the revised RoverGauge software was introduced. Perhaps contact Colin and flag the issue.