I have a '91 Formula 350. The problem is somewhat intermittent. Sometimes when the engine RPM is between approximately 1500-2000 RPM, the engine begines to hesitate and stumble. The car will hesitate then accelerate then hesitate...etc. If I push the accerator pedel down enough to cause the transmission to downshift and the RPM's increase to above 2500 the car runs excellent. What should I look for? I tried cleaning the IAC valve recently to fix the problem, but no luck. Any information would be greatly appreciated. Thanks

Chris

 

Does it do this always at that RPM and different speeds, or does it seem to be speed related to?

How about throttle position? Does it always seem like your foot is at the same position when it does it?

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'97 Bonneville SSE

 

I will have to try and check these things out and post the results. Thanks

 

Also check for bad spark plugs or plug wires. I just finished fixing a similar problem on my car. I was changing the spark plugs and noticed a wire was on a header and was cracking.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER, NO CAT
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
160* Stat
2:73 GEARS
Rebuilt 700R4, with manual valve body
B&M Megashifter, 5" Autometer Tach w/shift lite
Soon to be installed
3:73 Richmond Gears and 3" Hooker Aero Chamber
Corvette Servo & .500 boost valve
15.61@ 95.2mph G-Teched, 1-2 shift slippage
"There is nothing more addicting than speed"

 

Chris, I have been fighting the same problem. It can be a real driveability issue sometime. 88GTA 350. GM Tech had a good idea. Is your foot usually always in the same spot, for TPS. Hey if you get tackled, post results or give me an e-mail.


g

 

I finally got a chance to try some things. It would appear that my foot or at least the engine RPM is always in the same spot. It started doing it in OD so I slowed and put it in Drive, it did the same stumbling at about the same RPM. Second wasn't as noticeable, but I though I felt it. Also if it helps, the car is real jerky when its cold. It feels like it accelerates in "steps". You push the gas down and it will accelerate real hard, then hesitate, then accelerate...etc. Hope this helps. Thanks for the help so far.

Chris