quick help needed

[Larry Larson]

Hi,
My'95 Bonneille SSEi broke down on the road last night. All the classic symptoms of clogged fuel filter so I just replaced it. But it still won't rev above 4K. While parked when I rev at about 3500RPM it just fluctuates between 3500 and 4000. Last night on the highway it would buck under load, then died completely. I let it sit for 10 minutes, then it started right up and ran fine in town. Any ideas?

[sonoma_zr2]

Could be as simple as plugs and wires. Try unplugging the maf sensor, the car will run without it, just not as efficiently. Could be a throttle position sensor. Also sounds like a plugged catalytic converter. Any codes?

[RJolly87]

Are you just free revving in park? If so, rev limiter. If not, you may wish to start checking fuel pressure, spark plugs, etc. It could even be a clogged catalytic converter. You will need to start troubleshooting the issue, otherwise, if you want to start just throwing money at it, you could start by cleaning the MAF sensor.

[2002BonnevilleSE]

I'm thinking catalytic converter could be the problem too. When they get plugged there is no power.
It will run all day long till you drive it.
I had one do that in a Ranger.......pulled one end of the exhaust off of it....rammed a bar through the center of it....hasn't acted up now in 4 yrs.
Of course where I live in Pa we don't have emmison testing either.
If thats the case you can get a Magnaflow one for around $65

[Larry Larson]

Thanks. Yes, I was free revving in Park. I did manage to make it home just now-- 100 miles. I kept it at 65. When I tried to go up to 70, it started bucking again, and I barely made it home. The plugs and wires were recently replaced. The check engine light is not coming on. No way to check codes unless I take it to the mechanic.

[00Beast]

Unbolt the exhaust before the cat, tie it up and go for a drive. That will eliminate the cat. It will be loud, though.

[Larry Larson]

I'm thinking the cat is the next thing to try. I'll unbolt it and see what happens. The problem with that is that yesterday it ran fine, revved normally and never bogged down on the highway. Intermittent problems are the hardest ones to solve. SInce my SSEi has dual exhaust, does that mean it has 2 cat converters?
And, hypothetically of course, if one were to replace bad cats with straight pipes, would this mess anything up since cats usually have O2 sensors?

[sonoma_zr2]

It has dual outlets from the muffler. There is only 1 cat and pipe to the muffler.

[Larry Larson]

I should add that for a couple months before this problem started, I would notice that the boost gage seemed to be reading on the high end even under low load conditions. Plus, at idle, the boost gage would be moving around a lot.

[Billha]

Sounds like it could also be a bad coil pack. In my experience, the only symptom when one fails is that the engine will bog down/stumble under load.

[willwren]

There is a 4k rev limiter in park and neutral, and one of the worst things you can do to your car is test it. No-load revving will damage your motor.

Get your fuel pressure checked (you can rent a tester at most auto parts stores) and check the cat.

[Larry Larson]

mystery solved-- it was the PCU. I took it to a shop and it was throwing codes in a pretty crazy way. Now everything works fine, and I was even able to get my electronic compass to work.

Thanks for all the help.

[Larry Larson]

OOPS, I spoke too soon. It has crapped out again. First time was in town, 96 degrees outside, while running errands I left it parked and running so my friend could stay cool in the AC. Afterwards it starting running bad, and then quit completely. Then it started right up and ran fine. Then on a long trip yesterday it ran just fine at 75 MPH for 2 hours, then started missing. I exited and it ran real bad until I shut it off at the gas station. Then I started it and it ran just fine-- another hour at 75 MPH, then it crapped out when I exited and drove home in town. I just took it back to the shop that replaced the PCU last week. It was not showing any codes and they don't have a clue what's wrong with it. They said I'd have to bring it back when it's running bad. Any ideas? The mechanic said if it was the catalytic converter, it would have thrown a code and it would not run at all.

[willwren]

The cat will NOT throw a code, as there was no post-catalytic oxygen sensor until 1996. So no, it wouldn't throw a code. Get the cat checked for backpressure.

In addition, start thinking crank sensor, as they don't always throw a code, and they can fail thermally.

[Larry Larson]

I had the cat replaced today, so we'll see if that solves the problem.

[hammerheart]

Have you checked the fuel pressure yet?
Would a failing fuel pump cause this as the car heats up or as the disparity between the pressure it can supply and what is demanded grows too sizable for the engine to run?

I'd say rent a fuel pressure gauge from an auto store and check the fuel pressure. It's cheaper than throwing money at it.

[1oldman]

The "gearheads" that have posted know a lot, actually tons, more than I do, plus I know nothing about S/C engines. When my NA '92 acts like that when it's heat soaked, it's almost always the ICM/Coil Pack causing the trouble. Just a thought. - BC

[Krenzy]

Hoping to hear if the cat was the problem..

[Larry Larson]

If the problem was the coil pack, wouldn't that have thrown a code? I had a new computer put on, the car did it's missing/bucking thing a day later, but when they checked for codes after that, there were none. They said I'd have to bring it in while it's running bad.

[willwren]

No, coils won't throw a code. The PCM can't even see them.

If you have consecutive misfires on one cylinder, it will throw a code.
If you have random multiple misfires it will throw a code.

You seem to be throwing a ton of money at the problem without proper troubleshooting. Have you CHECKED the coils per Techinfo?
Have you checked the fuel pressure?
Have you pulled any spark plugs to inspect them?
Have you been very carefully watching your coolant levels?
Does your mechanic even have the ability to read the codes in a hybrid 94/95 PCM?


Can you give us a better VERY detailed description of the problem?