1985 vette no cold high idle tried everything.
03-15-2018, 09:23 AM
#21
Le Mans Master
Back probe the iac when cold and see if it's getting power. If it's not the ecm isn't seeing something if continuity is good. At that point go on win aldl make the cheap cable that works with the obd1 port, download the free software and read the data streams. Otherwise you're just shooting from the hip not knowing what the ecm is and isn't seeing.
When my cousins multitecs went bad he had all sorts of weird issues. The injectors are easy enough to ohm check if you haven't already. I don't remember the spec.
When my cousins multitecs went bad he had all sorts of weird issues. The injectors are easy enough to ohm check if you haven't already. I don't remember the spec.
03-15-2018, 09:28 AM
#22
Race Director
no worries about the wording I got through it. ok so here it is point blank and simple its NOT fuel. sorry to be so direct but the issue is that the car is not commanding the iac to open on its own when cold. like I said I can get the car to start and run fine if I just rest my foot on the pedal to open it a hair. so like I said its not fuel or fuel pressure related this is strictly and electrical issue and I have done the minimum idle thing a few times raising it a hair and I have played with it all over and no matter where i put it still no start when cold without cracking the throttle blades open. right now its set so when the car is fully warmed up I have about a 600rpm in gear and 800 in neutral that's as high as I would want it. as for the hlh 3200 I don't think that's my issue either as I have had 2 different computers with 2 different proms and neither made a difference. I understand that the 3200 has a higher base idle but the fact is that the car in the morning is trying to start on an iac in the position it would be in if the car was fully warmed up and I do not know why it isn't getting the command to re open
I'm going to tell you something right now, your never going to solve this problem with such a closed mind.
How do you know its not so rich at startup that only an open throttle will allow for a flammable fuel/air mixture ?
Your closed mindedness is what is screwing you. Stop thinking in terms of the absolute. You already admitted you don't know what's wrong.
Last edited by PatternDayTrader; 03-15-2018 at 09:31 AM.
03-15-2018, 09:38 AM
#23
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Ah .. How do you know the iac is not being commanded open without a scanner ? How exactly do you know its NOT fuel again ?
I'm going to tell you something right now, your never going to solve this problem with such a closed mind.
How do you know its not so rich at startup that only an open throttle will allow for a flammable fuel/air mixture ?
Your closed mindedness is what is screwing you. Stop thinking in terms of the absolute. You already admitted you don't know what's wrong.
I'm going to tell you something right now, your never going to solve this problem with such a closed mind.
How do you know its not so rich at startup that only an open throttle will allow for a flammable fuel/air mixture ?
Your closed mindedness is what is screwing you. Stop thinking in terms of the absolute. You already admitted you don't know what's wrong.
03-15-2018, 09:49 AM
#24
Race Director
as I have said before when the car is sold I can remove the iac and turn the key on to see if it reacts which it doesn't. then at that point if I turn the pintle in reinsert it and then start the car it starts fine and idle comes down as it should as the car warms. so I am a pretty convinced that the root issue is after the car has gone through a full warm up and returns to ice cold over night that the iac is not opening again. yes I need to be able to scan the car and would love some actual advice on how to do that I don't have a spare od lap top to put **** but may be able to find one if there is actual free software I can download to watch the data. I do agree it would help if I can have some actual sensor readings to start a base line at.
I gotta tell ya, if I were you I would be getting the car nice and warm, then putting a fuel pressure gauge on it and measuring how long it takes to leak down.
It sounds to me like you have a bunch of injectors leaking fuel into the intake ports and so you have an overly rich condition at startup.
Like it or not, if the car idles properly when warm, in gear and in neutral, ac on or off then the iac system and circuitry is probably functioning properly.
03-15-2018, 09:58 AM
#25
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and I don't have to crack the throttle open full all I have to do is rest my foot on the gas to open it a hair so trust me its not flooded I get it to start on its own but it idles at a whopping 500 but is barely staying alive like that so believe me its not a fuel issue.
03-15-2018, 10:04 AM
#26
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Back probe the iac when cold and see if it's getting power. If it's not the ecm isn't seeing something if continuity is good. At that point go on win aldl make the cheap cable that works with the obd1 port, download the free software and read the data streams. Otherwise you're just shooting from the hip not knowing what the ecm is and isn't seeing.
When my cousins multitecs went bad he had all sorts of weird issues. The injectors are easy enough to ohm check if you haven't already. I don't remember the spec.
When my cousins multitecs went bad he had all sorts of weird issues. The injectors are easy enough to ohm check if you haven't already. I don't remember the spec.
03-15-2018, 10:05 AM
#27
Race Director
and I don't have to crack the throttle open full all I have to do is rest my foot on the gas to open it a hair so trust me its not flooded I get it to start on its own but it idles at a whopping 500 but is barely staying alive like that so believe me its not a fuel issue.
Come back in a few days when your mind is off tilt, and your ready to fix the car.
Last edited by PatternDayTrader; 03-15-2018 at 10:10 AM.
03-15-2018, 10:10 AM
#28
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dude I am not getting into this crap with you on here. I have been wrenching for years and no I am not a tpi expert or a vette expert but I know what a car is like when too rich. I have no black smoke and no miss fires and I don't have to open the throttle all the way to clear it. listen to what I am saying, just because most cars have bad injectors doesn't mean that's my issue so instead of force feeding this fuel issue down my throat how about throwing some actual electrical advice my way so I can rule that out if you think its not my issue. then if you prove its my issue is not electrical which I doubt you will then you can start sending me in other directions.
But until then prove me wrong
But until then prove me wrong
Last edited by bigrigpardo; 03-15-2018 at 10:11 AM.
03-15-2018, 10:17 AM
#29
Safety Car
Try disconnecting the Cold Start Injector and then it's temperature switch and see what happens. I know that you don't believe that it has anything to do with it but just give it a try.
I replaced my cold start injector and when going thru the pile of them I had one just stay wide open which would cause havoc with your idle.
Have you verified that the Temperature readings coming from the sensors? A bad temperature sensor can give you a bunch of problems all by itself. A lot of cold start issues we deal with here have something to do with the temperature sensors. When they go bad the engine is not seeing the correct temperature and will either assume that the engine is very cold or possibly very hot. On my 1988 C4 I have two temperature sensors, one for the ECM and the other for the dashboard gauge. If the engine sensor fails there is no indicator or warning that the engine is seeing the incorrect temperatures. These sensors fail regularly. Another reason for sensor failure is that they don't have a good connector or even a faulty source of voltage or a bad ground. My dashboard gauge temperature sensor's connector dried out and became very brittle and crumbled when handled.
As mentioned earlier you should really check your vacuum hoses to be sure that they are all connected properly. Check for any vacuum leaks near the brake pedal inside of car, then check near Cruise Control and finally the EGR and the solenoid where the EGR gets it's vacuum source.
A faulty EGR can cause strange idle characteristics. You might be sure it is operating properly. These EGR's require vacuum to work on the L98 engine.
Many years ago I bought a set from Mid-America that has several tools that make setting up your fuel injection and diagnosing problems MUCH easier. They are short plugs that go in between the harness and the device you are testing.
In my understanding the O2 sensor has to get fully warmed up to allow the car to run in the "Closed Loop". Have you verified that your O2 sensor is plugged in and working properly? When you first start the car what are the readings that the O2 sensor is sending you? Unless this car has been retrofitted with a heated O2 sensor it is unlikely to go into the Closed Loop mode within a couple minutes.
I wish you the very best in solving this issues with this Corvette that you are working on!
I replaced my cold start injector and when going thru the pile of them I had one just stay wide open which would cause havoc with your idle.
Have you verified that the Temperature readings coming from the sensors? A bad temperature sensor can give you a bunch of problems all by itself. A lot of cold start issues we deal with here have something to do with the temperature sensors. When they go bad the engine is not seeing the correct temperature and will either assume that the engine is very cold or possibly very hot. On my 1988 C4 I have two temperature sensors, one for the ECM and the other for the dashboard gauge. If the engine sensor fails there is no indicator or warning that the engine is seeing the incorrect temperatures. These sensors fail regularly. Another reason for sensor failure is that they don't have a good connector or even a faulty source of voltage or a bad ground. My dashboard gauge temperature sensor's connector dried out and became very brittle and crumbled when handled.
As mentioned earlier you should really check your vacuum hoses to be sure that they are all connected properly. Check for any vacuum leaks near the brake pedal inside of car, then check near Cruise Control and finally the EGR and the solenoid where the EGR gets it's vacuum source.
A faulty EGR can cause strange idle characteristics. You might be sure it is operating properly. These EGR's require vacuum to work on the L98 engine.
Many years ago I bought a set from Mid-America that has several tools that make setting up your fuel injection and diagnosing problems MUCH easier. They are short plugs that go in between the harness and the device you are testing.
In my understanding the O2 sensor has to get fully warmed up to allow the car to run in the "Closed Loop". Have you verified that your O2 sensor is plugged in and working properly? When you first start the car what are the readings that the O2 sensor is sending you? Unless this car has been retrofitted with a heated O2 sensor it is unlikely to go into the Closed Loop mode within a couple minutes.
I wish you the very best in solving this issues with this Corvette that you are working on!
03-15-2018, 10:18 AM
#30
Race Director
dude I am not getting into this crap with you on here. I have been wrenching for years and no I am not a tpi expert or a vette expert but I know what a car is like when too rich. I have no black smoke and no miss fires and I don't have to open the throttle all the way to clear it. listen to what I am saying, just because most cars have bad injectors doesn't mean that's my issue so instead of force feeding this fuel issue down my throat how about throwing some actual electrical advice my way so I can rule that out if you think its not my issue. then if you prove its my issue is not electrical which I doubt you will then you can start sending me in other directions.
But until then prove me wrong
But until then prove me wrong
Clearly you don't want help, you want others to confirm the assumptions you have made.
03-15-2018, 10:28 AM
#31
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Try disconnecting the Cold Start Injector and then it's temperature switch and see what happens. I know that you don't believe that it has anything to do with it but just give it a try.
I replaced my cold start injector and when going thru the pile of them I had one just stay wide open which would cause havoc with your idle.
Have you verified that the Temperature readings coming from the sensors? A bad temperature sensor can give you a bunch of problems all by itself. A lot of cold start issues we deal with here have something to do with the temperature sensors. When they go bad the engine is not seeing the correct temperature and will either assume that the engine is very cold or possibly very hot. On my 1988 C4 I have two temperature sensors, one for the ECM and the other for the dashboard gauge. If the engine sensor fails there is no indicator or warning that the engine is seeing the incorrect temperatures. These sensors fail regularly. Another reason for sensor failure is that they don't have a good connector or even a faulty source of voltage or a bad ground. My dashboard gauge temperature sensor's connector dried out and became very brittle and crumbled when handled.
As mentioned earlier you should really check your vacuum hoses to be sure that they are all connected properly. Check for any vacuum leaks near the brake pedal inside of car, then check near Cruise Control and finally the EGR and the solenoid where the EGR gets it's vacuum source.
A faulty EGR can cause strange idle characteristics. You might be sure it is operating properly. These EGR's require vacuum to work on the L98 engine.
Many years ago I bought a set from Mid-America that has several tools that make setting up your fuel injection and diagnosing problems MUCH easier. They are short plugs that go in between the harness and the device you are testing.
In my understanding the O2 sensor has to get fully warmed up to allow the car to run in the "Closed Loop". Have you verified that your O2 sensor is plugged in and working properly? When you first start the car what are the readings that the O2 sensor is sending you? Unless this car has been retrofitted with a heated O2 sensor it is unlikely to go into the Closed Loop mode within a couple minutes.
I wish you the very best in solving this issues with this Corvette that you are working on!
I replaced my cold start injector and when going thru the pile of them I had one just stay wide open which would cause havoc with your idle.
Have you verified that the Temperature readings coming from the sensors? A bad temperature sensor can give you a bunch of problems all by itself. A lot of cold start issues we deal with here have something to do with the temperature sensors. When they go bad the engine is not seeing the correct temperature and will either assume that the engine is very cold or possibly very hot. On my 1988 C4 I have two temperature sensors, one for the ECM and the other for the dashboard gauge. If the engine sensor fails there is no indicator or warning that the engine is seeing the incorrect temperatures. These sensors fail regularly. Another reason for sensor failure is that they don't have a good connector or even a faulty source of voltage or a bad ground. My dashboard gauge temperature sensor's connector dried out and became very brittle and crumbled when handled.
As mentioned earlier you should really check your vacuum hoses to be sure that they are all connected properly. Check for any vacuum leaks near the brake pedal inside of car, then check near Cruise Control and finally the EGR and the solenoid where the EGR gets it's vacuum source.
A faulty EGR can cause strange idle characteristics. You might be sure it is operating properly. These EGR's require vacuum to work on the L98 engine.
Many years ago I bought a set from Mid-America that has several tools that make setting up your fuel injection and diagnosing problems MUCH easier. They are short plugs that go in between the harness and the device you are testing.
In my understanding the O2 sensor has to get fully warmed up to allow the car to run in the "Closed Loop". Have you verified that your O2 sensor is plugged in and working properly? When you first start the car what are the readings that the O2 sensor is sending you? Unless this car has been retrofitted with a heated O2 sensor it is unlikely to go into the Closed Loop mode within a couple minutes.
I wish you the very best in solving this issues with this Corvette that you are working on!
the reason I believe the iac is the issue is like I said in previous posts if I let the car sit outside overnight till its ice cold and I remove the iac from the throttle body and plug it in to the electrical plug and turn the key on shouldn't the pintle retract being as the ecm should be seeing a cold temp? or am I wrong on that?
03-15-2018, 10:30 AM
#32
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don't let the door hit you on the way out of my thread. diagnosing is ruling out all possibles not forcing someone to think they are wrong with out any proof they are or aren't.
03-15-2018, 10:32 AM
#33
Race Director
Lol ... that's pretty funny coming from someone who has utterly failed to diagnose a very simple problem.
03-15-2018, 10:51 AM
#34
Yup, start simple, that's exactly where I would have started. Too much air getting in behind TB plate, IAC won't open. That may not be it but it needs to be ruled out first.
03-15-2018, 11:03 AM
#35
Did anyone mention the cold start sensor on the front of the intake?
When I start my engine it idles around 800 till she warms up and the computer takes over
and sets it at 600 rpm. It is unlikely the computer is controlling the engine at full cold start. Just a matter of the 9th injector supplying extra fuel.
Better check the sensor so the computer knows it is cold when starting.
Good luck it sounds fixable
When I start my engine it idles around 800 till she warms up and the computer takes over
and sets it at 600 rpm. It is unlikely the computer is controlling the engine at full cold start. Just a matter of the 9th injector supplying extra fuel.
Better check the sensor so the computer knows it is cold when starting.
Good luck it sounds fixable
03-15-2018, 03:29 PM
#36
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ok so just to let everyone know I put a fuel gauge on the car and have a nice 36 lbs when you crack the key on. it takes about 5 min to bleed down to about 15 lbs. now if I squeeze off the feed and return it takes about half hour to bleed down to about 15. now I probably have an injector or that are a little drippy but this isn't underlying issue. when the car runs It holds a steady 32 lbs. and all of the injectors ohm to 16 ohms when cold so should they be replaced to run optimally yes but this isn't the issue to why it wont idle up when cold. I need more air not more fuel.
03-15-2018, 03:56 PM
#38
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, 03:56 PM
#39
Assuming cold start injector is functioning, measure vacuum during the cold start, you should see at least 18 if not 20in of steady vacuum on the gauge. Then clamp off each line, 1 by 1, coming off the manifold while checking the gauge. Also check the front and back intake silicone seal.
03-15-2018, 06:01 PM
#40
Le Mans Master