94 Buick Lesabre 3.8 Upon RPM increase car stumbles and bumbles, no power at all.

94 Buick Lesabre 3.8 VIN L.

The symptoms are the following:

1. Car starts and idles as normal each and every time.
2. Upon RPM increase car stumbles and bumbles, no power at all.
3. Spark plug inspection reveals raw gas smell and light carbon buildup indicating fuel rich condition and/or weak spark.
4. Spark visual indicates weak spark voltage as indicated by yellowish spark (although this is inconclusive)


Symptom occurred overnight…Ok after long drive home, began first thing next morning.

ODB1 computer show no codes pertaining to engine.

Crank sensor is new.
Fuel pump and filter are new.
Plugs are new.
Intake manifold new 3 months ago.


Car and engine mechanicals in good order as car is well maintained.

Throttle Pos. Sensor checks OK.
fuel pressure checks OK.
fuel pressure regulator check OK.
All sensors and wiring pass visual inspection(although pin out voltage testing has not occurred)
Exhaust back pressure test. OK
Vacuum lines check OK



That’s all I can think of for now. Have spent lots of time and money to no avail. If you have some ideas or would like to take a crack at this let me know.

Thank you,

How about the MAF, have you disconnected it to see how it runs?

Have disconnected MAF, Temp sensor, o2 sensor and others, with engine running, with no change.

thank you for reply.

All sensors and wiring pass visual inspection(although pin out voltage testing has not occurred)If you don't have a scanner capable of reading live data on the 94, checking voltage input/output of the sensors should be one of the first things on the agenda. Of course, a scanner makes this a lot easier. Before replacing any more needless parts, you may want to call a few shops and ask if they have a live data scanner (not a code reader) that will retrieve data on an 94-95 GM OBDI PCM with an OBDII connector, otherwise we can only speculate as what parts to change next!

try maf or could be your not getting good spark and yellow spark would be coil because should be blue spark. 3.8-3800 are good for having these problems.

You should really check/change the bad coil pack. When I first got my car one of the coil packs was bad (orange spark) but it idle smooth and drove with no problems for almost a whole year. Then one day out of the blue at a stop light the car just stumbled and the check engine light came on. Mostly same symptoms as you stumbling on acceleration, high rpms but no acceleration. Took it to get scanned at the dealership, The said bad "clogged" EGR valve. I did some investigating and changed out the coil pack as I did not have the "arm" the dealership wanted to charge for the EGR valve. The problem went away the next day out of the blue just as it came. My hypothesis is that over time the lack of complete combustion burn from the bad coil had clogged up the EGR valve and caused the stumbling problem and when I changed out the bad coil pack it allowed the engine the clear itself. Hope this can help.

I have a 1992 Buick Lesabre, and right now we are believing (about 60/40) that the infamous intake manifold gasket is mimicking a blown head gasket. There is no fudge around anything, yet the intake manifold gasket was diagnosed shortly before it started to bumble. AFter it was driven awhile, the mechanic said that it "cleaned it selfout" for now. Now it drives like a charm, yet we only drove it a few blocks home. We are seriously looking into having the intake gasket replaced (about $400 dollars.) It is a dicey operation. We are praying that that is all it is. Peace be to you concerning your vehicle.

I have a 1992 Buick Lesabre, and right now we are believing (about 60/40) that the infamous intake manifold gasket is mimicking a blown head gasket. There is no fudge around anything, yet the intake manifold gasket was diagnosed shortly before it started to bumble. AFter it was driven awhile, the mechanic said that it "cleaned it selfout" for now. Now it drives like a charm, yet we only drove it a few blocks home. We are seriously looking into having the intake gasket replaced (about $400 dollars.) It is a dicey operation. We are praying that that is all it is. Peace be to you concerning your vehicle.

92s are not susceptible to the famous 3800 intake manifold gasket problem because the intake is all metal, not plastic like in 93 and forward (they may have gone back to metal at some point, but I don't know.) Nonetheless, this is not to say that your intake gasket could not be bad, because it could. What are your symptoms? (Start a new post and you'll get some good advice.)