94 Buick RoadMaster Estate Wagon LT 1 issues

[kur4o]

I bet you have a cracked exhaust manifold. Much cheaper to change than trying to diagnose.
Don`t go to the daunted mistery alient wire strategy. It is pure waste of time and effort.
The only time I have seen topped blms were when there is alot of fresh air in the exhaust or there is heavy gasket failure with coolant in the cylinders leading to flase readings..

[Bentwings]

I really appreciate all the advise. The info on the idle air passages is of particular note. Somewhere I asked how the and where the idle air passage was. I have never seen a picture of the right side of the intake. I’ve been blown off when questioning the idle air function and how it evenly distributes the air. When the idle air goes through the metered controller then is directed to each port in the proper amount is quite amazing. The usual comment is that if the scanner says the idle air is within limits,it’s ok. But above indicates that it’s possible, maybe likely that these manifold passages are blocked or restricted. I sure would like to see the bare manifold. We’re i doing the work it would be boiled clean or otherwise carefully cleaned. Transmission shops have great cleaning machines. Our boiling tank was banned by the EPA many years ago.

Since I’ve moved to the boat and marina I simply can not do my own work on cars. I do service my boat myself. To side track a moment, I’ve installed a new AC unit, repaired the anchor winch, replaced the sliding cabin door tracks and rollers and added a support roller, repaired nav lights, built a step for the transom exit doorway, built a swim platform riser so it’s flush with the dock, added new dock lines including splicing the loops., cleaned and repaired the water system, built a new cabin table, changed oil and filters on both motors and vee drive transmissions, pumped the bottom of the fuel tank free of water, and winterized the entire boat last year. This year I won’t have to as I’m living on it, currently I’m installing a winter heater. So I’m not opposed to getting my hands dirty. My boat is my shop now.

We have looked for a cracked exhaust manifold. We looked from the top and from underneath on the hoist for this early on. I would think you could hear it, as quiet as the motor runs. The pipe that holds the O2 sensor has been replaced on both sides. We have removed them twice looking for leaks but they are clean and tight.

Vilefly, I’d gladly pay you to look at this car. As big as this town is and as many hotrodders there are, there really are not many really good shops that can get right into the nitty gritty of a problem like this. I’ve been blown off so many times that I just don’t even care to deal with them. I’m not the easiest customer to deal with but I do require straight up work. I will not be part of a “shop project car” that sits for months on end with nothing done. I require a finish date. But when the work is completed and the result is not fixed then we need discussion about where to proceed. He has been very good about this and not charged for a lot of testing and diagnostics.

We are going to revisit the exhaust manifolds if the intake cleaning does not fix it. A good many connectors will be separated so possibly something might show up there.

[vilefly]

For now, it's just me and one other guy at the shop, and we are trying to keep up with demand. Basically, it's full-on resurrection season in the fall season, and ......it's fall. My boss is the other set of brains for the shop, and he has been away from the shop trying to fix sell his deceased father's house. Not sure if he'll ever get it done, being a perfectionist and all. I have lots of people dropping off cars as if we have a layaway plan or something. I get it done, they take forever to pay for it or pick it up. I could take a look at it, but I cannot dedicate myself to it completely. I tend to put these kind of "somebody else's diagnostic failure" cars in a rotation pattern in between the straight up "turnkey" vehicles which pay the bills. I try to get the straight jobs done in a decent amount of time, then I allow some diagnostic time for the mystery vehicle in between jobs. So, promising a solution to a mystery problem in a certain scheduled time and date won't happen. It contains too many variables at this time.

We are located in south kansas city, mo. Not sure if you are hundreds of miles away or not.

Here's one thing I never heard throughout this discussion. Has the computer's powers and grounds been checked out electrically, under load conditions, at the computer connector? Does this guy have access to schematics, and know how to test for these things?

As to the changing of the entire harness to fix one wire.....the answer is NO. Don't do it. Not worth the new problems you will introduce......like the other hole in your wallet.

Granted, you still claim to have a low vacuum reading, which still indicates a mechanical problem, but I am starting to wonder about the mechanic in question.

[Bentwings]

Today I stopped by the shop to see progress. He had the manifold off and soaking in cleaner. We looked at the gaskets. These are thin steel with something between. Very smooth. There was a slight sign of maybe leaking on two adjcent ports. Just a slight discoloration. Otherwise they looked ok. You could see the intake surface machine pattern but not really feel it. The chins wall sealer simply fell off with some leakage ther. Otherwise the motor looked pretty clean inside. The head ports looked ok even with flashlight shining not much carbon. We looked at the throttle body where the IAC is and you could see the entrance to what must be the IAC spider. They are not very big but there was some carbon build up. He said he would clean that up on assembly.

I sure hope this fixes it .....but I have my doubts.

So maybe that’s the issue. Hopefully he will have it done Monday. He is very busy with winters prep things on cars.

[vilefly]

Hook up a vacuum gauge when you are done to see if it returned to normal (18-20" of Hg).

Had a 94 firebird come in with the opposite symptom yours had. It kept adjusting lean in closed loop on one side until it started missing out, because the BAD o2 sensor stayed stuck at .56V, and it RELENTLESSLY believed the o2 sensor without setting any code for it. Replaced the sensor, and cured it. I seriously wonder about your O2 sensor wiring, but we still had a bad vacuum reading, which trumps the electrical with a physical problem. A shorted-to-ground O2 sensor harness may be your other problem. There should be a .45V reference sent from the computer to the O2 sensor's output signal. Unplug the O2 sensor and look for that exact voltage +/- .05V. If it is out of range, begin the hunt for a bad ground or short to ground or open circuit.

The latest beta version of EEHACK 4.8.2 lets you reset the fuel trims, which is a great tool for finding the truth about O2 sensors. Reset, and see if it smoothes out.

[vilefly]

Reviewing post #12......."There is low manifold vacuum. It measures in metric by the scanner and I recall about 10-11 inches by conversion. Also vacuum gage."

I am wondering if this was a MAP sensor reading instead of a vacuum gauge reading, for they are opposites. Map sensor reading = Barometric pressure - vacuum reading. So if I assume this has been posted wrong...... baro pressure (29.89) - 10" MAP = 19.89" Hg vacuum reading. Which would be a normal vacuum reading. 10-8" Hg of MAP pressure is normal.

The statement "also vacuum gauge" might not hold any weight. This is disturbing. I suggest you clarify.