I have recently bought a 90 chevy silverado z71 350 motor it has a few problems i cant figure out what it is. When it cranks it has a rough idle and to the point of almost dying even in reverse then when i get down the road after being on the gas the rpms kick in and doesnt do it again until i come to a stop or when idling in park. I have changed the oil and oil filter, spark plugs, transmission fluid change, oil treatment added and also gas system treatment has been added and the ignition burner coils have been bought but not replaced yet but one of the old ones that was taken out has oil on it. Also my turn signals were working fine and last night all of a sudden they stopped working all together inside and out but my flashers headlights and brake lights still come on. This is my only transportation can anyone help me figure out what this could be?

SOURCE: 1995 Chevy silverado with a

I have experienced this problem on similar vehicles. You should try and replace the coolant temp sensor. If it is not reading the correct temp to the ecm, it will not get the right fuel map. Also, the cts will not always throw a code.

SOURCE: 1989 cavalier z24 dies at stops and transmission kicks!

I had the same problem with my 1989 Chevy Cavalier Z24 with the Automatic transmission. There is an electric lock up clutch within the torque converter that engages at roughly 35mph. It's designed to give the car better highway mileage. If that circuit fails, the clutch will remain in the "locked" position when hot, and stalls the car unless neutral is engaged and the car comes to a complete stop. I remember the car making all sorts of odd noise with this malfunction. I took mine to the dealership and they had it repaired in an hour.

My daughter had a similar problem with her 1988 Cavalier Z24 with the manual 4-speed transmission. There is a speed sensor on the top of the transmission that I replaced which solved the problem for her.

Marvin

• 85242 Answers
• Posted on Apr 07, 2009

SOURCE: 1993 olds cutlass supreme 3.1 multi port loading up at idle

Here are some of the causes of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

SOURCE: Rough idle and acceleration on 1998 Chevrolet Silverado 5.0

Bad EGR valve comes to mind here. Assuming the plugs are good, the EGR valve woiuld be what I'd look at.

SOURCE: 1999 pontiac grand am 4 cylinder rough idle, rpms fluxuates

Most likely your throttle position sensor is faulty. You could have a vacuum leak as well. Most probable cause is a bad sensor. Is your check engine light on? Have you checked your engine codes? You can go to autozone.com and register for full free online repair manual.

Testimonial: "the check engine light had been on but we unplugged the battery yesterday for a couple of hours and put it back in and the light isn't on anymore. "