Slight miss maybe...

jeepgclwj · #1 08-10-2007, 06:37 PM

Well I have recently noticed a slight stutter or miss or whatever it could be. I have not gotten any check engine light or anything. I though it could have been for the real hot last couple days here. 102 degrees out but today was only 88 and I think it was worse now. lol. I hope its nothing serious...

Any thoughts on how I can figure out what it is...

richtazz · #2 08-10-2007, 09:45 PM

A little more info would help. At what point does it stutter, when cold/warm, at highway cruising speed, during hard acceleration, light acceleration etc...?

jeepgclwj · #3 08-10-2007, 09:54 PM

I only notice it a idle, and the car runs fine other than the slight studder. Other than that I really dont know much more than that. I'm going to check my plugs and wires tomorrow....

tblake · #4 08-11-2007, 12:06 AM

Ha, My gtp does the same thing. A slight miss at idle. Above idle its just fine and whe im in drive its just fine. I've replaced the plugs/wires/fuel filter/air filter/ran fuel system cleaner through it. I just can seem to get it to go away. I believe mine may be a failing IAC motor. I've had mine off a couple times, both times it was almost siezed solid. So i cleaned it and oiled it and put it back in. Seemed to run and idle better, but a week later it seems like its got its slight misfire back. I wish i had a scan tool to read sensor values. Good luck with it, let me know what you find out!

jeepgclwj · #5 08-11-2007, 04:30 AM

Excuse my ignorance but what is an IAC motor?

richtazz · #6 08-11-2007, 05:52 AM

IAC= Idle Air Control

It's an electronic stepper motor that varies the amount of air allowed into the engine at idle and part throttle. When they go bad, it can cause heistation, hard starting, start/stalls etc... It's basically the electronic equivalent of a choke on a carburetor.

BNaylor · #7 08-11-2007, 12:10 PM

I seriously doubt an IAC will cause a miss on one or two cylinders at idle. However, still a good idea to clean it (pintle only) and the throttle body to include where IAC mounts (orifice) with TB spray cleaner. Start with spark plugs and ignition wires. Run some good fuel injection system cleaner through 1 tank of gas. Injectors will get clogged with poor quality non top tier gas and cause an idle misfire or roughness.

Also, remove the front 02 sensor and clean with TB spray cleaner. Make sure you see light through the directional vanes and all carbon is removed. A front 02 sensor will cause a poor idle in the closed loop mode which is when engine is fully warmed up and the sensor is being used to keep the fuel injection system air/fuel mixture ratio at the ideal 14.7:1.

richtazz · #8 08-11-2007, 01:27 PM

I was reading the original question as the car was stumbling off idle, not mis-firing, as I agree with you Bob that an IAC rarely (if ever) causes a miss.

BNaylor · #9 08-11-2007, 01:52 PM

Quote:

Originally Posted by richtazz

I was reading the original question as the car was stumbling off idle, not mis-firing, as I agree with you Bob that an IAC rarely (if ever) causes a miss.

I see no problems with your reply Rich so don't worry about it.

You weren't the first to raise the IAC issue. What I do know based on a prior past testing is a bad IAC will really raise hell. The idle shoots up, the engine runs very rough overall (rocks back n forth), and it sounds like the engine has a massive vacuum leak. Another unique symptom is the high uncontrolled idle above 1K rpm without the additional symptoms above.

tblake · #10 08-12-2007, 10:10 AM

So what would you guys suspect is my problem? O2 sensor. Again, slight miss at idle, but above idle or in gear its smooths right out.

What you state about the engine rocking back and forth is kind of accurate.

I didnt know that you could clean o2 sensors with carb spray. Maybe Ill just replace it, it has 80,000 on the original one.

Burtnette · #11 08-12-2007, 04:20 PM

I think I have the same problem as you guys lol. But mine only does it mainly when it's in neutral and sometimes park but never drive. Weird.

richtazz · #12 08-13-2007, 06:02 AM

we're not qualified to help with your problems Tblake,

, oh....you meant your car!

I'd start with checking for a vacuum leak, or possibly a fuel pressure test to rule out a failing FPR. Also, a MAF will cause off idle issues but not trip a CEL, as well as a TPS with a slight flat spot.

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