Thread: '98 P38 Overfuelling

RangerFelix, I should stress I am not a mechanic, so I may be on a wrong tangent with the diagnosis. The good news (well sort of good news) is that you have traced the problem back to the motor and eliminated transmission, brakes bearings etc...The fact that all the plugs carbon up after 1500k, to me, indicates that the problem is global to all cylinders and is not unique to one bank of the motor. There are 2 Cat converters one for each exhaust manifold, so I'm inclined to think it improbable (not impossible) for both cat converters to collapse at the same time.
Maybe start with a few less invasive tests first? I was thinking firstly checking the air intake of the air filter box. Also check that the throttle physically opens when the accelerator is pressed. Are there any modifications to the intake system that have been carried out by a previous owner?
Failing finding any blockages or restrictions I would be looking to get the car hooked up to a Nanocom or similar to see what fault codes come up.

Good luck

Gary

Originally Posted by glenhendry

I have tried O2s, MAF and new inlet ducting. My last suspicion is inlet manifold.
High Long Term Fuel Trims - why?

Good luck!

Glen

I picked up a vacuum gauge for 26 bucks from ebay and am going to use it to check the inlet system for leaks, they can also tell you about other engine issues, worth the investment

Steve

HI

As others have said, reading fault codes is the way to go, cheapest is a wifi elm327 adaptor and an app which will tell you a lot about your ECU.

Much better is a nanocom, faultmate or hawkeye but they are not a necessity.

Steve

I feel kinda dumb now. The lack of power was due to a (very) maladjusted throttle. Readjusted that and voila...power is back.

Car is still over fuelling. I will try new o2 sensors next.

There are no stored faults in the ECU.

Don't you just love finding out that it was cheap and easy fix? Amazing how we fear the worst though on a p38

Gary

The ECU might re-learn the fueling settings now you've fixed the problem!

You should have a fault code via the OBDII connector if the O2 sensors are causing the engine ECU to default to runnung rich. Worth checking before you buy new Lambda's.

Originally Posted by davidsonsm

You should have a fault code via the OBDII connector if the O2 sensors are causing the engine ECU to default to runnung rich. Worth checking before you buy new Lambda's.

I read the fault codes. There were none.



Just a little status update: drove 1000k's since I adjusted the throttle. Now power is back. Fuel consumption is still not good.



19.4l/100km on dirt at 80-90kph cruise control (Parachilna to Coober Pedy).



Do faulty lambdas always throw a fault code?



Just to sum up here is what I've done:

New air filter

New MAF

New spark plugs

New ht leads

Read fault codes - none found



When I start the car I can smell that it is over fuelling. Exhaust is coming out of the pipe - not black though. So it doesn't seem like the cats or muffler are blocked.



Thanks for any help