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1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 02-03-2009, 12:55 AM   #1
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Default Running lean after overhaul


So, after three months of on and off, I got my 3.8 NA '99 Bonne SLE put back together.

The problem began after the car blew out a radiator hose and then started misfiring and kicking out white smoke.

I was unsure if it was blown head gasket or LIM/UIM, but at the advice here, I started off on a voyage to replace the LIM/UIM. Here'* what was replaced...

Fuel regulator, PVC valve, MAP, LIM/UIM gaskets, Dorman upper intake manifold with ZZP HV3 insert, ZZP stage 1 throttle body and sensors, air filter, ECT, water pump, radiator hoses, coolant elbows, serpentine belt, front and rear transmission mounts, fuel filter, spark plugs, spark plug wires, front and rear O2 sensors, oil filter, oil, antifreeze (non-dex Prestone mix-with-anything), tranny filter, tranny fluid, engine oil pan gasket, tie rod end and a starter.

The starter, serp belt and radiator hoses were actually replaced right before the misfire started. The car had gone a LONG time without a full tuneup, as I was unable to get the spark plug wires and fuel filter off. The spark plugs had 193K on them, and looked brand new. The O2 sensors also had 193K on them... but they were toast, even though they still functioned. Many of the other parts (water pump, MAP, ECT) were replaced proactively, as I was right there. The oil and pan needed removal since I dumped a pint of coolant into the pan while removing the intake. My oil pan gasket was toast, anyway.

During the overhaul, I discovered fuel in the fuel regulator vacuum line, which is what I suspected was causing the misfires... in any case, it was obvious that the fuel regulator had to go.

During the overhaul, my old intake and throttle body were completely gummed up. Seeking a little upgrade, I got the ZZP HV3 intake insert and a stage 1 throttle body, which is hogged out slightly... and more importantly, was not full of tar. While replacing the LIM/UIM, I blocked off the throttle body intake passages with plugs and JB Weld.

Due to the HUGE pile of parts coming and going, I did bonehead a thing or two... I forgot to replace the EGR stovepipe... but I am not too worried about this at this point, since I blocked off the coolant. I also neglected to use the included fuel injector sleeves and O rings. These must have slipped under the box flaps, so I bought my own O-rings and reused the sleeves. I also didn't replace the rear vacuum port (to the power brakes) on the UIM, reusing the old.

So, once starting the car, I immediately got a P0336 and a CEL. Also, the car wouldn't idle below 800 rpm. I thought these were related, so I traced the wires from the crank sensor to the ICM and finally found I had accidentally crushed a pin in a connector. Once fixed, the CEL went away... but the car still stalls below 800 rpm. While idling the car, I got a P0171 pending... but it hasn't triggered the CEL yet. I did notice the fuel trim being highish.

This has led me to suspect a vacuum leak... but using propane to search for a leak came up with nothing... so I'm stumped. I thought the HV3 or stage 1 throttle body might have something to do with it, but they aren't introducing more unmetered air, so I can't imagine they are the problem.

Otherwise, the car runs nice. It'* a LOT more responsive... and I would say that there is a 5-8% power increase using the seat-of-your-pants dyno. It idles once the car warms up, and I suppose it will idle once it gets warmer (it has been fairly cold at the Jersey Shore). It'* almost as if the choke was broken... _if_ the car had a choke.

I would normally accept this kind of behavior from a '74 Nova... but not a fuel injected '99 Bonne.

Any ideas would be appreciated.

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Old 02-03-2009, 01:42 AM   #2
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Hmm... brain fart. I think I got the APN UIM, not the Dorman. I have the Dorman PVC kit and several other minor parts.

Second brain fart... I also replaced the thermostat with a HD drilled 180 degree one from ZZP, as well.


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Old 02-03-2009, 06:32 AM   #3

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From what I see it should all be good.

You wrote that up very well. In total agreement with you about plugging the coolant ports and no longer needing to worry about which stovepipe is in there. Any other codes like evap etc coming up?

I've personally put the vacuum hoses on the evap switch incorrectly and caused a flow during non flow vacuum leak. Looking at the switch one of the nipples is labled "CAN". Make sure that line traces back to the canister. If it goes to the TB, there'* a possible problem.

Next up, instead of propane try using carb cleaner or TB cleaner to spray around the motor. I'd suspect the O ring on the vacuum port that snaps intot he back of the intake. There should have been a new ring or piece in the kit you got. Pretty much any ring that fits decently will do the job.

Double check the pcv valve. There should be a ring under the valve and on the cap that covers the valve.

And last of all, ensure there are no plug wires touching the O2 sensor or it'* wiring.

Those are the typical culprits. Give them a try and see if that helps out.
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