Bouncing tach

[SonicRiot]

I have a post somewhere about code 13, but I don't know if this has to do with it. Everytime my car is in neutral at normal temp, the engine "surges" and bounces from 1000 RPM to 1500 RPM every second. When in gear or giving it gas, it doesn't happen. The car does not feel like it has lost power, though. If I floor it, while stopped, it will dissapear. I am going to run codes now, so I'll tell you what I get.

But any ideas of a diagnosis for now? I need to use this car a lot during the next two weeks.

 

[SonicRiot]

ok...frustrated now. madflame
I can't get the car to throw 13 (IAB), but now it is throwing 24 - Intake Air Temperature (IAT) or Vane Air Temperature (VAT) sensor out of range. I figured it was doing this because it is below freezing ( shrug ?) and the car wasn't warmed up.

HOWEVER, when I did the *goose* test, the car almost stalled (stayed at 400 RPM for almost 3 seconds) and I just kept my floored on the gas until the engine leaped to 6000 RPM in a matter of a second. eek!

Do I just have dirty injectors? I don't know if the bouncing is caused by the IAB, but the car will not throw that code. In fact the last time it threw 13 (IAB), it also threw 11, which is all systems check OK. Plus, I have no drop in performance (that I can see). Also, in cold weather, the car idles at about 1800 RPM and drops over the next minute to a more regular idle. It ONLY bounces when at normal temp in neutral (moving OR stationary). If I stop and give it hard gas for a second and tach up the engine, it goes away. So, WTF?!?! rant

HELP! and thanks.

 

[projectSHO89]

Once again, ignore the 24 code if it is below 50F

Once again, it is the IAC's responsibility to control idle speed by bypassing air around the throttle place.

Check for a binding or unhooked cruise cable. Mine tends to come loose and interferes with the throttle return position.

Steve

 

[SonicRiot]

I don't have cruise control...

and I understand about the IAC, but the car wont throw those codes... is it still possible that is what it is? my symptoms sound different than some of the other when I did a search...that is why I posted here.

Thanks

 

[Anthony1238]

My iab valve was bad and it didn't throw a code...

 

[SonicRiot]

wow... slap

I am an idiot...
I DO have cruise control! I just found this out today when I looked at my steeing wheel! That's how little I ever even think about using it...

Oh, wait... I have NEVER used it!


Anyway...My car now has close to 90k on it. Should I bother cleaning the IAB or just replace it? Will just resetting the idle do anything?

 

[billyshoe]

Could it be the #1 plug wire intermittently misfiring? I was having a simular problem I did plug well gaskets & switched out wires and I no longer have this bouncing needle problem.