I joined a few weeks ago and read around on this before I decided to post. Basically the car wants to stall the harder you press the gas, if you feather it gently and increase rpms.. it's fine, but if you attempt to evne rev it slightly, it falls on its face... Here's what I've done so far:

After reading, most people were saying to check o2 sensors, filter, the MAF, fuel filter, fuel pump, and alternator...

Had a diagnostic done at a garage, threw 3 codes: 2 refering to the o2 sensor reading too lean, one refering to the MAF possibly being bad.

so I checked the o2 sensors.... the upstream o2 wasn't even connected, the plug had broken, and the plug to the o2 sensor itself was pretty much melted on the cat... so purhased a new one, fixed the plug, installed, runs better but still hesitates

Cleaned the MAF using non chlorinated air intake cleaner thast safe for MAfs... annndddd that did a whole lot of nothing (I really hoped this was the smoking gun as I read some people with K&N had oil build up in the MAF from the filter oil, and I had just cleaned and oiled it, but no love.)

The alternator was tested and is fine.

THe fuel filter was replaced in the last 3 years, plus I always run 93 and add a descent injector cleaner every other tank.

now here's the find... unplugging the MAF... car runs and idles fine... for the frist few seconds may want to stall.. but after that... it's OK. but when at WOT... still feels like there is something missing, not sure if this is due to there being no reading coming fromt he MAF, or if something else may be wrong... (I read about the 2 modules behind the battery.. is there anyway to check or clean those?)

any ideas? Thanks (sorry for the long post, but wanted to make sure I explained everything )

 

have you rounded up the usual suspects? Plugs, wires, fuel filter, module?

 

The plugs, wires, and distributer cap were all replaced about 600 miles ago, and I just cleaned and oiled the K&N last week.... Where would I get those modules at? (I believe one is the burn-off and there's another, right behind the battery)

 

It will be of some value here if you let everyone know the year of your vette and is it a stick or auto.

 

I was referring to the ignition module.

 

http://www.corvettefever.com/techart...maf_codes.html

 

1987 Greenwood edition Auto trans, TPI

 

The engine will sound like an outboard with the exhaust under water when you try to accelerate.

You have injectors that are fouled. Cleaning may help, but more than likely, they will need to be replaced.
Aaron

 

If he suspects that, why not take it out and have them tested before throwing parts at it?

 

I see no mention of checking fuel pressure. If it checks out ok static with no appreciable leak down, tape the gauge to the windshield with vac line disconnected and plugged to see if pressure holds during a short WOT burst. If not check 1) the filter and 2) the pump.

Also check base timing with a light.

After you cleared the stored codes does it throw any new codes?

 

I ended up getting an Actron code scanner (the one that makes the check engine light blink the codes, $29 at Advance Auto)... here's what I have (I wrote exactly what it says in the book that came with it)...

22 - Throttle Position Sensor (TPS) - signal voltage is low during engine idle OR Fuel cutoff relay circuit open or shorted to ground.

33 - Mass air flow (MAF) sensor - signal voltage or frequency is high during engine eidle. OR Manifold absolute pressure (MAP) sensor - signal voltage is high during idle. (Note: Engine mis-fire or unstable idle may cause this code)

34 - Mass air flow (MAF) sensor - signal voltage or frequency is low during engine cruise. OR Manifold absolute preasure (MAP) sensor - signal voltage is low during ignition on. OR Pressure sensor circuit - signal voltage too high or low (carburetor engines).

36 - Mass air flow (MAF) sensor - burn-off circuit problem. OR Transmission shift problem (electronically controlled transmissions only). OR Direct ignition system (DIS) fault - loss of 24x signal or extra or missing pulses in electronic spark timing (EST) signal. OR Ignition system fault - loss of High Resolution Pulse signal.

Since they are farely inexpensive, I ordered both the power-on and burn-off MAF relays (on sale for $12.98 each), they will be in tomorrow morning... any ideas? maybe just a bad MAF? ignition module? Thanks again...

 

I also put a can of "SeaFoam" in with about 4 gallons of gas... and I'll be honest.... it's farely normal now.. I know it's throwing all those codes, but a lot of the hesitation is gone, from accelerating from a stop to just WOT.....

 

Before you buy an MAF sensor, check for current. I don't know what spec is (unless it's just a 12V signal), but Mr. agent 86 can probably find that one...

 

The 2 relays came in... installed and cleared the codes.... and it runs like a beast.... no stutter.. no hesitation... no check engine light and no codes. Thanks to all for the information.