Random super high idle

[Cparkes foo]

Hi my car is a 94 3100 gp most of the time it runs great as it has just under 50k but recently it has started reving to 2500 to 3000 rpm, i have replaced iac,tps,map,ats,ecu,plugs wires throttle body gasket,and rubber grommets for pcv, problem has not changed. It has got a 50/50 chance if it runs right or not any suggestions no engine codes plz help

[Cparkes foo]

On a different note ive learned when in nuetral or park i no longer have a rev limiter and at about 4500rpm my doors lock even in park

[Galaxie500XL]

Sounds like a wiring issue, to be honest.  Ground wires would be the first place I'd check.

[55trucker]

Try disconnecting the IAC harness AFTER you shut down the engine (shutting off the engine bottoms out the IAC pintle).

 

Leave the harness off the IAC & try to restart the engine, it should not fire seeing as the IAC is closed, if the engine does fire your sucking air in from somewhere else or the IAC is not closed.

 

Pull off your intake snorkel and peek into the throttle body, the blade should be completely closed, if it not then adjust the throttle stop screw so it is just closed all the way but does not bind.

 

Let us know what happens after you're tried these measures.

 

 

Not setting a code is odd, if the idle is out of range (300 rpm) for more than 50 secs the PCM will set a code.

[Cparkes foo]

Will try all these things and report back thank you btw clean white grand prixs are sick nice car

[Cparkes foo]

Unplugged iac wont run and throttle body is closed still have to check grounds at a glance they all look fine(no crust) and my engine light has started coming on but no codes, scanner does not registar that its even hooked up so i guess wire chasing is what needs to be done unless there is anyone who has had this and has a fix

[Cparkes foo]

I just tried to do the jumper wire on the obd 1 access point and no flashing codes either

[Imp558]

Still sounds like a ground

[Galaxie500XL]

I just tried to do the jumper wire on the obd 1 access point and no flashing codes either

With a jumper, you ought to at a minimum get the flashing *1 *2 of the check engine light, indicating the ECM is at least operating.  Are you positive the ECM is getting 12 volts?

[55trucker]

The vehicle is a '94, it's OBD1.5, the paperclip/jumper will not function. You're going to find that not every scanner will access the PCM as the necessary software/cable is required.

 

There is another thread on a similar issue with another 94 model.

[55trucker]

Unplugged iac wont run and throttle body is closed still have to check grounds at a glance they all look fine(no crust) and my engine light has started coming on but no codes, scanner does not registar that its even hooked up so i guess wire chasing is what needs to be done unless there is anyone who has had this and has a fix

The PCM has set a code because the IAC was disconnected while the ignition was on, that is normal, seeing as the car is an OBD 1.5 you're going to need a scanner that can read this particular series of electronics. The IAC code should be a DTC-35.

[Cparkes foo]

It goes to our local gm dealer they say they will scan it for me on tuesday i did a little digging on this obd1.5 wow what a nightmare for the diy on a budget guy if i would have known about this i would have hunted a 92 or93 when i was lookin for my car lol

[Cparkes foo]

And thanks for directing me to the other posts they were very helpfull

[Cparkes foo]

So its fixed it was a bad brand new tps talk about bs

[94 olds vert]

I should have posted. My L67 in my 2000 GTP had a similar issue when the TPS was going out. After replacing it, that solved the issue.

[55trucker]

So its fixed it was a bad brand new tps talk about bs

Curious:

 

what was the brand of the faulty TPS?

[Garrett Powered]

this does not seem like proof it was the TPS. the problem was there before u put in that one. 

[Garrett Powered]

If it does it again in a while you may have to do the crank sensor.  That's what I was thinking lol

[wlkstout]

Not sure but does the 94 3.1's have the same issues with the lower intake manifold gasket leaking?

Sounds very similar to what my 91 Olds Cutlass Supreme 3.1 was doing before i replaced the LIM gasket. Mine never threw codes either.

Did you also look at the EGR?

[mfewtrail]

this does not seem like proof it was the TPS. the problem was there before u put in that one. 

 

He said he was taking it to a dealer, so the TPS diagnosis is probably correct. It's not that uncommon for them to cause rpm surges intermittently when they start to fail.

 

@ Cparkes Foo - The OBD 1.5 thing isn't that big of a deal, there are plenty of old scan tools floating for a reasonable price that will read it. If you need suggestions for one, let me know.