1985 vette no cold high idle tried everything.
03-15-2018, 09:11 PM
#41
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great, now that we can finally rule it out with data
here is my question:
you said you did the minimum idle adjustment...
and you say u just need to rest the weight of the foot on the pedal which both cracks the tb blade and moves the tps.
im going to suggest you try and make that adjustment mechanically.
both tb and tps.
I believe that your issue is really simple, a matter of not enough air hetting in the with where you have seated the tb blades.
i can qualitatively corraberate your claims of a slow acting iac. mine was the same on my 85. I did the minimum idle adjustment probably 30 times.
my symptoms were not exactly the same but close.
on the 85 one of the things i couldnt stand was how slow the iac was to react to putting air conditioning on.
in my case, i ended up doing a complete headgasket job, and in the process, i replaced the prom to an elm 3200 as i mentioned up the thread. Im not sure exactly what the issue was but all i can say is after all parts were cleaned and reinstalled, replaced the iac and cleaned tb, the car ran better. ut still not as good as my 87. my &7 responds to idle control and ac drag quickly and idle has never been an issue.
IT WAS NOT UNTIL i purchased the ipdated prom, from the very end of 85 /early 86, that my 85 suddenly ran like my 87. Absolutely perfectly. i never ever hear about the elm 3200 chip. For me, it completely changed the way the car functioned in a very positive way.
i can tell you are fristrated and ive been there. good luck.
here is my question:
you said you did the minimum idle adjustment...
and you say u just need to rest the weight of the foot on the pedal which both cracks the tb blade and moves the tps.
im going to suggest you try and make that adjustment mechanically.
both tb and tps.
I believe that your issue is really simple, a matter of not enough air hetting in the with where you have seated the tb blades.
i can qualitatively corraberate your claims of a slow acting iac. mine was the same on my 85. I did the minimum idle adjustment probably 30 times.
my symptoms were not exactly the same but close.
on the 85 one of the things i couldnt stand was how slow the iac was to react to putting air conditioning on.
in my case, i ended up doing a complete headgasket job, and in the process, i replaced the prom to an elm 3200 as i mentioned up the thread. Im not sure exactly what the issue was but all i can say is after all parts were cleaned and reinstalled, replaced the iac and cleaned tb, the car ran better. ut still not as good as my 87. my &7 responds to idle control and ac drag quickly and idle has never been an issue.
IT WAS NOT UNTIL i purchased the ipdated prom, from the very end of 85 /early 86, that my 85 suddenly ran like my 87. Absolutely perfectly. i never ever hear about the elm 3200 chip. For me, it completely changed the way the car functioned in a very positive way.
i can tell you are fristrated and ive been there. good luck.
03-15-2018, 09:24 PM
#42
yes i meant hlh sorry.
you have to look on the prom chip in the computer and read the numbers behind it.
i can relate to the desire to solve the puzzle. its what keeps me in the hobby
have you tried changing the module in the dizzy yet
you have to look on the prom chip in the computer and read the numbers behind it.
i can relate to the desire to solve the puzzle. its what keeps me in the hobby
have you tried changing the module in the dizzy yet
03-15-2018, 09:29 PM
#43
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I haven't tried that. I didn't think it would have anything to do with it since the car ran and responded to the throttle ok. ill check the proms tomorrow. any clue on why it didn't go into hold 1k mode? may be part of my underlying iac control issue
03-15-2018, 09:48 PM
#44
Le Mans Master
Cut and form a paper clip into a "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' sockets. Turn on the ignition, but DON'T start the engine. This will force the ECM into its diagnostic mode. Wait 30 seconds to allow the IAC pintle to fully extend. With the ignition still on, go under the hood, remove the electrical connector from the IAC, then turn off the ignition and remove the paper clip jumper from the ALDL. With the IAC pintle fully extended (closed) all idle air will be controlled by the position of the throttle plates. Some manuals indicate that the EST bypass connector should be disconnected for this procedure, while some make no mention of it. While timing is a factor in idle speed, the EST should only operate as a function of engine RPM, temperature, and detonation sensor inputs. To remove all doubt, disconnect the EST bypass connector is your car is so equipped. Some TBI and V-6 engines do not have this bypass connector, and therefore must be set with no regard to the EST system. The EST can be bypassed on some cars by grounding the diagnostic terminal at the ALDL and continuing with the procedure, but the fuel mixture will be skewed to the rich side, affecting idle speed as well. In any event, the minimum air position idle speed range is wide enough to allow for some variations. As always, it is best to consult your service manual for the exact procedure for your system.
03-15-2018, 09:52 PM
#45
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03-15-2018, 09:54 PM
#46
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There is alot...and I mean a LOT of WAG'ing going on in this thread.
OP, you were off to a good start, but ya gotta get that thing on a scan tool. You need to have "eyes" to see what the ECM is commanding, vs. what is actually happening....and what the ECM is even seeing. Bad (new) sensors? You used two, to eliminate that possibility, which is smart...but for the price of the extra sensors, you could have bought a top-of-the-line scan tool that would prove what the sensors are doing and the ECM is seeing. Get a good, high-end SCAN TOOL
I have one exactly like that and it does a lot; custom data stream, DTC's, diagnostic flow charts, actuate electronic controls, system tests (on Fords), Freeze frame or "snap shots".....the thing is awesome. Spend $75...get this car fixed and you'll have a great tool for the rest of your life. As a mechanic, you "get that".
OP, you were off to a good start, but ya gotta get that thing on a scan tool. You need to have "eyes" to see what the ECM is commanding, vs. what is actually happening....and what the ECM is even seeing. Bad (new) sensors? You used two, to eliminate that possibility, which is smart...but for the price of the extra sensors, you could have bought a top-of-the-line scan tool that would prove what the sensors are doing and the ECM is seeing. Get a good, high-end SCAN TOOL
I have one exactly like that and it does a lot; custom data stream, DTC's, diagnostic flow charts, actuate electronic controls, system tests (on Fords), Freeze frame or "snap shots".....the thing is awesome. Spend $75...get this car fixed and you'll have a great tool for the rest of your life. As a mechanic, you "get that".
03-15-2018, 09:58 PM
#47
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There is alot...and I mean a LOT of WAG'ing going on in this thread.
OP, you were off to a good start, but ya gotta get that thing on a scan tool. You need to have "eyes" to see what the ECM is commanding, vs. what is actually happening....and what the ECM is even seeing. Bad (new) sensors? You used two, to eliminate that possibility, which is smart...but for the price of the extra sensors, you could have bought a top-of-the-line scan tool that would prove what the sensors are doing and the ECM is seeing. Get a good, high-end SCAN TOOL
I have one exactly like that and it does a lot; custom data stream, DTC's, diagnostic flow charts, actuate electronic controls, system tests (on Fords), Freeze frame or "snap shots".....the thing is awesome. Spend $75...get this car fixed and you'll have a great tool for the rest of your life. As a mechanic, you "get that".
OP, you were off to a good start, but ya gotta get that thing on a scan tool. You need to have "eyes" to see what the ECM is commanding, vs. what is actually happening....and what the ECM is even seeing. Bad (new) sensors? You used two, to eliminate that possibility, which is smart...but for the price of the extra sensors, you could have bought a top-of-the-line scan tool that would prove what the sensors are doing and the ECM is seeing. Get a good, high-end SCAN TOOL
I have one exactly like that and it does a lot; custom data stream, DTC's, diagnostic flow charts, actuate electronic controls, system tests (on Fords), Freeze frame or "snap shots".....the thing is awesome. Spend $75...get this car fixed and you'll have a great tool for the rest of your life. As a mechanic, you "get that".
03-15-2018, 10:01 PM
#48
Le Mans Master
It still sounds like a screwy IAC problem, the factory manual indicates that if the pintle is extended beyond 28mm it can get damaged and stop working correctly. Have you tested each harness pin to the IAC to see if you're getting a signal at it?
03-15-2018, 10:02 PM
#49
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There is alot...and I mean a LOT of WAG'ing going on in this thread.
OP, you were off to a good start, but ya gotta get that thing on a scan tool. You need to have "eyes" to see what the ECM is commanding, vs. what is actually happening....and what the ECM is even seeing. Bad (new) sensors? You used two, to eliminate that possibility, which is smart...but for the price of the extra sensors, you could have bought a top-of-the-line scan tool that would prove what the sensors are doing and the ECM is seeing. Get a good, high-end SCAN TOOL
I have one exactly like that and it does a lot; custom data stream, DTC's, diagnostic flow charts, actuate electronic controls, system tests (on Fords), Freeze frame or "snap shots".....the thing is awesome. Spend $75...get this car fixed and you'll have a great tool for the rest of your life. As a mechanic, you "get that".
OP, you were off to a good start, but ya gotta get that thing on a scan tool. You need to have "eyes" to see what the ECM is commanding, vs. what is actually happening....and what the ECM is even seeing. Bad (new) sensors? You used two, to eliminate that possibility, which is smart...but for the price of the extra sensors, you could have bought a top-of-the-line scan tool that would prove what the sensors are doing and the ECM is seeing. Get a good, high-end SCAN TOOL
I have one exactly like that and it does a lot; custom data stream, DTC's, diagnostic flow charts, actuate electronic controls, system tests (on Fords), Freeze frame or "snap shots".....the thing is awesome. Spend $75...get this car fixed and you'll have a great tool for the rest of your life. As a mechanic, you "get that".
03-15-2018, 10:07 PM
#50
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I have no specs as to what I would be looking for at what pins.of the connector
03-15-2018, 10:21 PM
#51
and as for this issue a few have said to get a scanner but no one has said exactly what one to get that will do this. I know I need a scanner and 75 bucks I can spend to get this moving along but not 500 like some of these other ones. what do you got and where do I get one.
sry bud. u lost me. i mentioned aldl canle and tunerpro rt.
furthermore, not tough to use google and see which scanners can be used on the 85.
i think u r in over your head.
good bye.
03-15-2018, 10:23 PM
#52
Team Owner
Pro Mechanic
^Right? 
Sounds good. Best of luck to you.
.
.
Last edited by Tom400CFI; 03-15-2018 at 10:24 PM.
03-15-2018, 11:26 PM
#53
Le Mans Master
Turn the key to on but don't start up the car so it's in diagnostic mode. Use a test light to ground each pin the light should either flash or go solid.
If the light flashes or is steady for each circuit the problem is likely with the IAC valve if one of the circuits doesn't trigger your test light, check it for continuity.
If all the circuits test good, check for resistance between coils on the terminal between a and b then c and d resistance should be greater than 20 ohms, if it's ok, faulty ecm connection or ecm if it's not the manual says to replace IAC valve and ecm.
This is almost exactly the instructions from an '85 manual for testing the IAC valve.
04-07-2018, 09:34 PM
#54
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ok well I figured I would pop over here and give you guys the update. so I did the injectors with new 24lbs did a full tune up and all new upper intake gaskets it does run considerably smoother with more power which I knew it would but it did not solve the start stall on cold morning start up. and I do have the 3200 prom in both of the computers I was trying. the owner took the car back today and is ok for now dealing with putting his foot on the gas to get it going in the morning easier only take maybe 15 seconds of holding the gas at 12-1500 and then it wil idle fine after that. so an improvement for sure but never really got to solve that iac issue. it may be back at the end of the season to try again but for now its run the best it has since he bought it so any improvement is good.