LUMP Chimera help required

[chrispitman]

Have got the beast back on the road at last passed the MOT with out a problem.

BUT

I have a running problem, when I give it a little throttle the engine dies the springs back into life then dose this again and agian until the revs pick up shunt down the road. Above 2200rpm its fine I can take my foot off the power then re apply and all is OK. But at low speed its really badly shunting, its feels like someone is pulling the coil on and off.

I have set the AFM to 1.8 volts and adjusted the throttle pot to sit around 0.33 - 0.35. They were on 1.87 and 0.387.

Also the Guy at the MOT station said that the CO value was zero said it was running on fresh air. the print out says fast idel 0.20 and idle 0.3 he said that it needed more fuel.

Any ideas anybody.

Edited by chrispitman on Wednesday 28th November 21:43

Edited by chrispitman on Wednesday 28th November 21:46

[spend]

Get the fuel pressure checked, make sure th pump is running (Peters hot wire advocacy is a quick'n'easy check)

Dave

[Bensonv8]

Have you tried re-setting the ECU.
Maybe lambda sensors ??

[Altrezia]

Mine does it too - this is as far as we've got:

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[That Daddy]

Bensonv8 said:

Have you tried re-setting the ECU.
Maybe lambda sensors ??

Yes, when i reset my tps/afm it run like crap till the ECU was reset,and would not relearn until the hard reset.

[blitzracing]

If its still running really lean, it could also to be an airleak in the plenum area so check all the rubber pipes that attach to it and its sealing to the trumpet base. Also check for air leaks in the pipe between the plenum and AFM. The ECU should provide enough fuel based on the AFM output,(amongst other things) but if a leak occurs the AFM voltage drops as not all the air is being metered, so the fuel is limited. The water temperature thermistor also has a big influence if its wrong. The problem "Altrezia" refers to is very specific, in so much the idle mixture is OK, but at about 1500 rpm the car snatches under light load. This is due to lack of airflow through the AFM with the cam TVR use at low RPM plus the ECU mpping is causing it to run lean. Its only a problem on some cars, as its marginal if the ECU can maintain lambda 1, and even a dirty connector is enough to change the airflow reading in or out of range. I should have an easy fix for this one shortly without a rechip or remap.

Mark

[dwgriffith]

Also the Guy at the MOT station said that the CO value was zero said it was running on fresh air. the print out says fast idel 0.20 and idle 0.3 he said that it needed more fuel.

Any ideas anybody.
For a cat car if the CO had been much higher it would fail the MOT? CO measurements in isolation are an indicator only, what were the values of HC and O2 at the same time and was the lambda value above or below 1.

[chrispitman]

Think I have made a mistake on reading the MOT printout.

Fast Idel test
Speed - manual
CO - 0.00 %vol
HC - 5 ppm
Lambda - 1.00

Idel test

speed - manual
CO - 0.00 %vol

Summary results

Fast idel - pass
speed (2500-3000) - pass
CO (0.02) - pass
HC (200) - pass
Lamb (0.97-1.30) - pass

idel - pass
spedd (450-1500) - pass
CO (0.30) - pass

I think what I have done is put down the test results specs the actual CO reading was 0.00 %vol, but with this reading should I be able to still achive a lambda of 1.

New to this stuff have just go my head around building the engine, now its another big learning curve on tuning and setup. Dose anyone have any links to a guide that I could read and understand this more.

[blitzracing]

As I understand it, but dont quote me:

Lambda Value, based on the unused oxygen in the exhaust. Too little the engine is running rich and all oxygen is used up. To lean and the remaining oxygen goes up as there is insufficent fuel. Lambda 1 is purely a value devised as a mid point for power, emissions, and fuel consumption, based on excess oxygen only

CO value. Carbon monoxide value. This also goes up with more fuel, as there is less oxygen around to turn Carbon monoxide into carbon dioxide.

Hydrocarbons. Basically unburnt fuel. This is a measure how effcient the burn is. I think the hydrocarbons go up if not all the fuel is burnt due to lack of air (rich) but it may occur on very lean mixtures where the flame front cannot be maintained.

Whatever the chemistry, all these values are closely interlinked dependent on engine efficency and mixture settings. The 14CUX should maintain the mixture around 14.7:1 (lambda 1), and if it cant it will generate fault codes (you need a reader to access these.) Having said I dont know how far out of range and for how long, before the ECU flags the fault. On the cars Ive looked at that run lean at a narrow rev range, there was no sign of the ECU being in fault mode.

Im doing a bit here, but have loads more to add soon. There is a graph of the various parameters

http://www.g33.co.uk/fuel_injection.htm

Mark

[spend]

Do note that the MOT readings are taken after the cats, rather than after the engine which your lambda sensors measure, when you are comparing theoretical engine efficiency vs tail pipe measurements. If you have cats that it is

Dave