I have a 1990 chevy pickup 1500, 2wd. auto. the problem os that it idels ok. while in park you can give it halg throttle it runs fine, but as soon as i put it in drive and drive it down the road it starts to cuts out, stytters misses, but not back threw the tbi, it does this at about 20mph, and up. any help would be great, thanks paul

You 1st need to read the fault codes, you can do this without any special tools and just a paper clip to jumper the diagnostic connector under the dash on drivers side. Follow the link

FAQ How to read older GM codes for free

You only give it air when pushing the gas pedal. Clean the throttle body and idle air control motor.

Ok. Ideal is idle. Again clean the throttle body, inside. Check or replace the air filter.

is the check engine light on? check for mas air flow sensor

if you can find away to read the codes you will probably find that it has a bad throttle position sensor

1990 Chevy 4.3 l engine runs rough at idle half the time-- sometimes it's OK, other days it's rough and can smell raw gas, as tho it's running rich... any ideas?

fuel filter,or egr dirty or not working right

ICM idle control module, loc throttle body, it may be dirty, remove clean or replace, its easy..

Pumping the accelerator on a fuel injected car is usually a worthless exercise--the technique works on carbureted cars with accelerator pumps. But in your case, it may be helping a bad throttle position sensor make some idle contacts come together. the throttle position sensor has a variable resistor to tell the engine computer where the throttle opening is--and a switch to tell the computer if the throttle is open or closed as at idle. This sensor isn't cheap so I would buy a Haynes manual to help you check it out before replacing it. Some auto parts stores will "read your diagnostic trouble codes or DTC's" for free. Even if your check engine light is not on, some transitory codes can get latched in memory and help you solve the problem.

Short the test terminal, and read blinking engine light blinks, count them they will be fast and pause and be fast again each code is 2 digits long. This will help me to solve your problem. Thanks