bouncing idle
 

After months of trying and failing ive finally got my fc to turn over but now my idle bounces up and down at about 1500 rpms and then eventually smooths out at about 1000 and then surges and smooths out. I have a hole in my exhaust not sure if that would cause it and also low fuel but its never happened in my 86 gxl so i have no idea whats causing it. I also checked for vac leaks but havent found any. Any suggestions?

check your tps and your afm, exelerated warm up? what all have you done to your car, is it completley stock?

the cars completely stock it had been sitting 10 years prior to me buying it ive given it a complete tune up and rebuilt the fuel system the one thing though when putting in the new injectors they didnt come with the lower grommets but before i changed my injectors they didnt have them either so it seemed ok to put em in. my afm is fine i swapped it out and put it in my 86 gxl to see if it worked or not and the gxl ran fine still. it could possibly be the excelerated warm up because it bounces a 1500 then smooths out at 1000 but when i rev the engine above 45k i have to catch the rpms to make sure it doesnt stall out then slowly pump the gas until it goes down to 1000 and then it will idle some what ok

check your tps.

i have the same problem i undid my tps but didnt unplug it only unbolted it and i just changed my spark plugs but when it starts the idle keeps bouncing and when i hit the gas it wont go over 3000 rpms it just bounces with the throttle all the way idk whats wrong with it it was just running fine right before i did that i have no leaks at all and didnt unplug anything

mine does similar it bounces till it get warm then runs good after that.. any ideas ?

Check your Idle Air Control... Had the same problem on my FC and it ended up being the valve. GL

i cleaner it out but it didnt change still does it do i need a new one or could it be something else??

On the bottom of the valve there's a hose that leads from the intake if I'm not mistaking you should have it too.

Clamp the hose with the engine on if the idle becomes steady then yes your valve needs replacing.

So, if the TPS or IAC valve are bad, those are $400+ parts... Is there any way around this issue aside from buying a piece from a car someone is parting out?

Replaced my tps and the idle is no longer bouncing but whenever I rev it to 4k and up when I let off the gas the car almost stall and I have to catch the rpms or it will stall or idle low and then go back to 1000

'Bouncing' or 'hunting'?
 

I've heard that depending upon ambient temperature, the starting rpm may jump to a high rev as a function of assumed pollution; then drop down. But even after this it will 'hunt' for a while, only smoothing out after a few minutes. Though I've had mine for many years, the family always asks, "Wassa matter with your car?"

maybe mine will always do it then ha im from canada so we got a little colder weather hahaha

Changed my tps but now I put my foot to the floor and it struggles to rev to 5k and won't go over. Instead of trying to find out what it is can anyone tell me everything to replace that has to deal with idle except for the maf bcuz mine is fine

You may well have changed the TPS, but is that TPS correctly adjusted/calibrated?

A couple of suggestions...

• You haven't mentioned whether you have checked for vacuum leaks or replaced all the vacuum hoses.
• Loose connections / leaks in the intake between the MAF and the throttle body or loose funnel connection at the throttle body.
• There are several unused vacuum ports that just have caps, which can split and leak.
• Power brake booster, if equipped, can be a potential vacuum leak.
• Oxidized contacts / loose connectos for all idle-related sensors (MAF, boost pressure, water temp, air temp) could lead to erratic input to the ECU.
• Ditto connectors for the BAC & other solenoids.
• Last not least, there is a ground point connector for many of these sensors on the top of the engine under the throttle body. Need to remove upper intak to get to it, though.

check out so.. vac lines & spark plugs

Mine was doing the same thing after removing / replacing the UIM. It was because I put the metal throttle body gasket in backwards. It's indented on one side, and I didn't notice the upper corners are different, so the indentation was facing the wrong way (DOH!). It allowed too much air to get past the ISC passage in the throttle body, so when the ISC was working the idle bounced around. Unplugging the ISC cable would stop the hunting but it wasn't an issue with the ISC solenoid, just the gasket backwards. Just something else to think about if you replaced the throttle body gasket and then the issue starts.