Myron

so i some how lost my ac idle up valve screw. Went to the Stealer ship..picked one up and put it on today. The idle was pretty high so i tightened the screw to a nice idle and then a little more adjusting when i turned on the AC.

Now when it gets a little hot, that damn thing wont stop surging.
if i am driving and let of the gas..after a few seconds...feels like i my truck has turned off . i think it just surges....

i checked all the lines, and could not find anything. I marked the lines before i took of the old idle up valve...

any ideas

thanks in advance.
I also read about the long thread on surging, but i dont seem to have that big of a problem..

thook

Give me a little bit and I can help you out more. Then again, by that time, someone else may have already chimed in. But, I will check back with you.

thook

Does your truck have the vacuum switching valve on the rocker arm/valve cover? It will have two vac lines coming from the idle up valve to it. It should also have an electrical connector....two wires.

abecedarian

TPS adjustment?

thook

Yeah....that's what is sounds like. More so than the a/c valves.

abecedarian

Hmmm.... I was re-reading and this struck me as odd:
The idle screw should only affect idle when the a/c is on. Maybe double check the vacuum hoses again and again?

Myron

when the ac is off and when i play around with the idle screw...my idle goes up and when i tighten it..the idle goes down.
i will check the lines again.. and i there is no electric connectors on this idle up valve

thook

No....not on the idle up valve. Look on top of the valve cover. There should be a switching valve that has two hoses hooked up to it that are coming from the idle up valve. The switching valve has an electrical connector.

Myron

got a fsm pic? lol..
i can go take a look again

Yopar

iTrader: (2)

Sounds like the TPS could be in need of re-adjustment. The idle will jump up after a certain point, when the TPS sends a specific voltage to the computer to advance the timing. You could be right in the area where the voltage is on the edge of this adjustment, back and forth, causing the surging. Anyone else agree? I'd read the service manual's method on adjusting the TPS, and check some of the threads here for tips on doing it.

abecedarian

I hear what your saying, and you're almost correct.
What happens is the TPS is sending a signal that the throttle is slightly open (based on the TPS 'variable' signal for throttle position), but there is a second circuit in the TPS that signals that the throttle is so close to being closed that the ECU should consider it closed. That second circuit is the IDL signal to the ECU.
If the throttle is technically closed, but the ECU doesn't get the IDL signal from the TPS, it will continue to look at the O2 sensor for feedback about the fuel mixture, and since the O2 sensor (and the ECU circuitry to deal with it) doesn't respond particulary quickly, the idle speed will 'hunt' or fluctuate.
When the ECU is given the IDL signal, it falls into a 'lean' state, which ignores the O2 sensor and is meant to optimize fuel economy and the transition to on-throttle response.

abecedarian

Is this the culprit?

thook

That's the idle up valve. This is the vacuum switching valve I'm talking about.....



Regardless, I really don't think it's the surging problem. If that thing was leaking, more than likely he would just have a high idle. But, it would affect things if the a/c was on and the switching valve was either not hooked up or not operational. To a lesser degree than the TPS, though.

Myron

okay...so after driving around today and tonight...my surging problem seemed to be gone, but now..i just have a really high idle..and the ac idle up screw is all the way down...

thook

You could have a vacuum leak somewhere.

Or, maybe the TPS isn't set correctly. Maybe set past the IDL setting?

Have you checked your timing?

abecedarian

If it's just idling high, then yeah, vacuum leaks or possibly the timing is set to far advanced- be sure to jumper the E1 TE1 terminals in the diagnostic plug when setting the timing. Also check that the throttle isn't getting held open by the dashpot or other issue. Then go off to the TPS if nothing else is apparent.

thook

Dashpot is such a funny word.....<<giggles>>


And, for that matter, so is giggles.....<<chuckles>>

And, well.....so is .....

Who the hell comes up with these words, anyway?

abecedarian

Clowns?

thook

Clowns huffing on balloons, maybe....