350 TPI Idling at 1500 RPM

Lasic1 · 06-28-2009, 08:16 PM

Hi, My 87 GTA with 350 TPI and AT will not idle at the normal 575 RPM but fairly constantly races up to 13 to 1500 rpm. This condition normally occurs after the motor is up to operating temperature can be intermitent. I no longer believe the codes since 13,14,22,33 & 34 since I've replaced most of the sensors. The IAC, TPS, coolant sensor, oxygen sensor and fan relay switch have all been replaced. Still codes 13 & 14 continue to come on. I've checked the throttle body butterflies and they are closed when the idle is up to 1500. I've changed PROMS twice and this made no difference. I have not changed the ECM since the current was tested by TPI and didn't show any defects. I think the MAF is ok since I cleaned it with a spray and codes 33 & 34 disappeared.
At this point I'm out of fresh ideas and I'm wondering if I have a short in the ECM harness or air is finding it's way into the engine from either an intake leak or an external source.
Any ideas?

Thanks,
Laser

EnfuegoZ28 · 06-30-2009, 08:22 PM

Check all the plastic tubing between the MAF and the throttle body for cracks. Check for cracks in any of the rubber vacuum lines. sounds like it may be something simple that you are overlooking.

JessyB_96 · 07-05-2009, 06:01 PM

my 89 iroc tpi was doing the same thing ocassionally and if i taped the gas it would usually stop it was cause my butterfly was gettin just a little stuck sometimes i just wd40'd it and it stopped doing it but when i went to inspect the butterfly the first few times it looked fine o just try that regardless

06 SS · 07-05-2009, 06:39 PM

symptoms scream vacuum leak. Since it seems to only happen after warming up, I would check the EGR lines first. Followed by any thermal vacuum switches you can find.