MISFIRE! At idle!

[camslambam]

Hey guys.
Wondering if anyone could help me out.

Car has been misfiring for quite some time now. We went ahead changed the oil and spark plugs and seemed to fix it just fine. Then 2-3 days later started up again. This time the car would shut off when I would put it under low rpm load (reverse to 1k rpm) it would drop dramatically and shut off.


Changed the battery out and it was fine! Seemed to be perfect. Idle at 800, thing ran great. Next day (yesterday) misfire returned in the afternoon! Took it in to make sure battery and alternator were fine (battery voltage moves with rpm). At idle it sits right around 500, a little above, and moves like from 550-500. Like mentioned before battery voltage also jumps around. Temps are fine. Oil pressure fine. Everything is fine. The AC then stops being cold at idle. But when I begin to drive the car works perfect. RPM goes back to 800. Only when I stop for more than 2-3 minutes does it begin to misfire again! :dontknow:

Things got me going crazy trying to figure it out! Seems like after some driving car acts fine but if I stop it for any period of time it goes back to being moody and misfiring....

Where should I start? Injectors? Fuel filter? Maybe bad fuel?:dontknow::dontknow:

 

[Slitherbeast]

IAC Idle air controller Have you done anything with the throttlebody lately?

 

[ICPREY]

How old are the spark plug wires?

 

[VENOMOUS1 RACING]

I agree I would start with cleaning the throttle body and IAC pintle. It seems like it's an idle control problem. Check all wiring! Throttle Position Sensor can wreak havoc with troubleshooting as well. NO codes? See if you can hook up a scanner and read what voltages different sensors output and you'll likely be able to see the problem.:burnout:

 

[camslambam]

Done nothing to throttle body.

Car came with the spark plug wires. Bought the truck used at 45k miles.

No codes. What exactly can I do to the TPS and the IAC to try to fix this?

Sorry here is a better question. Where exactly is the IAC? I read into it more and could be that it's dirty or sticky. Going to spray it down with carb cleaner and see if it works, but not sure where it is exactly.

 

[VENOMOUS1 RACING]

It is on the throttle body! There is the TPS sensor and IAC MOTOR on the throttle body. The IAC is the bigger of the two and on the passenger side of the throttle body. Usually two screws torx bit style hold it on there.

 

[camslambam]

Thanks! Going to take it off and clean it later today see if it fixes it!!

 

[Slitherbeast]

Don't be scared to pull on the IAC . Make sure it moves in and out fairly easily. The computer allows air through to get the idle perfect. If it pops off just put it back in. Rockauto has them for $200 ! Pricey!! Try to get it to work first. Next option is to replace it

 

[BADBLACKSRT10]

Try hooking a scanner up to it and see if it throws out any codes related to the misfire. Could be something simple.

 

[yellowfever#154]

Describe the battery voltage fluctuation a little further. How low does the voltage drop while idling?

 

[camslambam]

Well the problem seems to have gone away alone. 3 days now and I have had no misfire.

The voltage would fluctuate between 12.89-12.95 when idle in D, instead of being a constant 13.

I pushed in a bunch of spark plug wires and plugs and it seems to have fixed the problem. Idling now at 800rpm although the other day when I would rev it a bit would stick at 1.2-1.3k.... Meaning it's more than likely a IAC issue.