Idle is jumping ... what can it be!

I have a 1990 Cavalier Z24 3.1

I have new plug and wires, , new exhaust, new cat, new IAC Motor, new PVC Valve, new H2O sensor, cleaned the throttle plate and so ready to scream. Ive been to 2 mechanics just to get a diagnostic cuz I dont get it.....and they get no codes nothing on diagnostics....Ive even passed emmissions....Ive put in fuel inj cleaners, octane boosters....what next. Ive done all the work myself and Im not giving up....now that i changed the O2 sensor its worse. It idles choppy like its gonna stall and its stalled a few times at lights.....anyone got any ideas?

Have the fuel pump checked to ensure adequate fuel is being delivered to the engine. Also check the fuel filter. If your car is surging, the throttle position sensor should be checked and the connector cleaned and reseated. The sensor itself can be checked with a multimeter while disconnected. Any meter in the right hands can easily do that for you. Lastly, check the air intake plumbing for obstructions. You may have hit a bad batch of gas; whereas some gas line anti-freeze might help saving you the cost of having a fuel purge.

Just a few shots in the dark mind you.

Tookie

ps: scrap the gas line anti-freeze idea. The FIC treatment should have corrected that solution.

Tookie

I am not familiar with the throttle position sensor. I am takingi t to another mechanic tommorrow...what should I tell him to do so they dont do a typical diagnositic again....I wish this was something I could check...is it? Cuz I have a test light. Where exactly is it and how do I check it? You'd think I'd know since I can make harnesses....golly..this is insane

I'm surprised your car didn't produce any codes! It's quite possible the last mech used some other device other than a code reader able to retrieve and "store" codes for interpretation, and missed an output of one or more.
The TPS works like a Potentiometer in most cars. It's very much like an expensive turn volume control button on a radio. You'd need a multimeter capable of reading resistance (ohms); or voltage in some cases. The output from the TPS tells the computer what position the throttle is in and the computer adjusts the running procedure accordingly. Sometimes the TPS will output very erratic signals and the computer just can't manage them because the vary so widely and quickly. By rights a default routine should engage, and the car should go into "limp mode". It's the computer's way of saying "just get me home" or to a mech. I expect you know what a clean/tight harness oughta look like?
The best advice I could offer is to find another mech; or spend some time getting to know the engine's workings more completely so you can t-shoot the prob and determine whether you are capable of doing the repair/replacement yourself. Knowledge is critical here.

Tookie

Im noticing that and since Im a woman the mechanics are not talking to me with, lets just say they think im dumb, Im not I did all the work myself. The codes only came up O2 sensor and I changed that but anything else they said would require a fuel pressure test of some sort and to check the injectors....Im trying ot get the right info by coming here I appriciate anything you can give me to resolve my problem...thanks :)

I certainly didn't wish to imply you're being a woman had anything to do with t-shooting and fixing the problem. I'm guessing the fact you posted a reply to my last, that you recieved no implication as such. If you did feel so, I do sincerely offer my apologies, and will choose my words more carefully in the future.
Now on to the problem. The pressure test you mention might be to indicate some malfunction in the fuel delivery system. The fuel pump could be performing lees than par. There are specs available that would allow you to ascertain as to whether fuel is being delivered in sufficient quantity under normal running. They shold look something like X=amt over T=time. Eg: 100ml per minute. Less than spec should mean either a blockage, a deteriorating fuel pump, or a leak in the fuel delivery system.
Next, I suggest you check the air intake. I once had a prob with a car producing a code for "lean mixture". Cause: Mech left a small piece of wipe rag near the air intake plumbing, and the rag was ingested during a start. Thus the sensor indicated lean whereas the prob was lack of sufficient air intake=too much fuel/not enough air!
Just to be sure, check for cracks in the coil paks. It's a common recurring prob with some chevs. Look for micro fissures near the corners of each pak where spark might leak to grnd.
Make sure your air filter is allowing plenty of air. Remove it and retry a drive.
Do you get a stong gasoline odor when you open bonnet; or when you run the heater fan? If so, check for leaking at the injectors where they plug into the engine. Some Cavs are notorious for that problem. Easy fix.

Keep us posted.

hth

Tookie

I just had the same thing with my sunfire let me guess it don't show up on your diagnostics test I was so pissed with mine I thought it was the EGR velve and changed it but it was somthing wrong with the computer in my car it under the driverside front wheel well and why GM puts them there I'll never know why lol why would you put a computer outside? any that might be it good luck keep me posted

wow...that sounds like whats going on here. The thing that is getting to me is that is costs to get every test done and Im broke but I still need my car. I am glad for all the feedback...too bad I couldnt get a step by step....oh well....

well they shouldn't of charged you for the diagnostics test because it didn't do anything if anything they should of carged you for like 5 mins work lol anyway go to really good garage go in and tell them your boyfriend or dad said they think it might be somthing to do with the ECM and you would like them to test it ( I think people at garages don't take women as serious as they should) but I hope you find out the problem good luck keep me posted with what it was because I'm curious now lol