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This truck came to me from another shop. The owner has unleashed the parts cannon. When I got it the truck would barely idle and drive into the shop. Both long and short fuel trims were maxed out on the positive side. I found the driver's side pcv hose not seated onto the pcv. fixed that and it idles good in closed loop and runs good but is still at 30% positive fuel trim long term and about 15% short term both banks. o2 sensors are now switching and look good. The Owner has done the following: All plugs and coil packs, intake gasket, Mass air flow meter, fuel filter, PCM, Bank 2 sensor 1 o2 sensor, Fuel pump drive module, injector cleaning.
I took it for a drive and the truck has plenty of power and find that under WOT the o2s stay full rich, Fuel pressure tests good and injectors pass a balance test all within 1 lb of drop. So problably no a fuel delivery problem.
The fuel trims remain pretty constant throughout the rpm range so it doesn't indicate a vacuum leak.
I have reset the KAM and it comes back to the same trims.
There are no cam timing codes which I expected with this milage on this motor. When you start it cold it is rough in open loop and then smooths out as soon as closed loop begins. I have tested the purge valve for leaks and blocked off the brake booster. no change. I have smoke tested it and used water to identify vacuum leaks and I find none.
The temp sensors seem accurate.
There is a decent sized exhaust manifold leak on Bank 2 cylinder 5, this makes sense why this bank indicates lean on bank 2 sensor 1 and the bank 2 sensor 2 shows a bit rich due to the exhaust leak I believe.
Still, this whole truck is very lean and I am thinking I have more then one exhaust leak here. Tomorrow I will scope the cam and crank sensors and see what I get.
Am I wasting my time chasing this until the the exhaust manifold leak is fixed? Your thoughts would be greatly appreciated. Thank you!
Is that air intake stock and is the MAF g/s correct at hot, unloaded idle for this engine size, which is at least 5.4 grams per second? Also yes, you should fix that exhaust leak or else computer's fighting a false lean condition.
The grams per second would vary from 3 (low) to 8 at idle at different times but the idle would also vary some (cause or effect?), I monitored the power and grounds to the MAF while this was happening and they looked good. I tried another MAF sensor I had from another truck and no change. I checked the fuel pressure twice on a mechanical gauge, well within spec and would increase as you gave it fuel. I did a fuel injector balance test and they were all within 1.5 lbs. I scoped all the injectors both for voltage and current and it all looked good. I did an in cylinder pressure waveform and that looked good.
The Bank 1 sensor 1 seemed lazy, it would stick at idle to lean .02 ish. but would come up and switch fine when ever you gave it fuel or were driving down the road.
This is not a flex fuel vehicle. I did reset the Kam and check a fuel sample. All good.
I removed and plugged every vacuum line and pinched off the brake booster and pcv system- no change.
There is an aftermarket cold air intake on this. I suggested to the owner that we put the stock intake back on, fix the exhaust leak and see what we have and the owner declined the work and took the truck. So I may never know for sure what was causing this lean condition. A combination of factors I think. I am pretty disappointed I couldn't prove it.
