A different idle problem,,, I think
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
A different idle problem,,, I think
My '85 starts up instantly but does not want to stay running on it's own until I keep it running for a minute or so. I can't put it in gear without it dying. Once it gets a little heat in the engine it will idle perfectly. Once it's just slightly warmed it has absolutely no issues with idle whatsoever. Coolant temp sensor is good as is the signal from the ECM. Min. air idle is set perfectly. What can possibly be causing this small glitch? I have a BBK throttle body and am beginning to suspect it, when I did a search I found another owner was having very similar problems and it was his BBK at fault. I might mention that there are no vacuum leaks anywhere. Please, don't respond just to bash BBK, it may not be that at all.
Safety Car
Joined: Oct 2007
Posts: 3,816
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From: :45 minutes from everywhere / E-I-E-I-O
My '85 starts up instantly but does not want to stay running on it's own until I keep it running for a minute or so. I can't put it in gear without it dying. Once it gets a little heat in the engine it will idle perfectly. Once it's just slightly warmed it has absolutely no issues with idle whatsoever. Coolant temp sensor is good as is the signal from the ECM. Min. air idle is set perfectly. What can possibly be causing this small glitch? I have a BBK throttle body and am beginning to suspect it, when I did a search I found another owner was having very similar problems and it was his BBK at fault. I might mention that there are no vacuum leaks anywhere. Please, don't respond just to bash BBK, it may not be that at all.
I'm thinkin' not enough fuel or cold start injector problem (if '85 has csi).
Maybe it's goin' into open loop right at cold start up, givin' little fuel for cold runnin'.
Some one will chime in with a test to see if it's goin' into warmed-up mode right away on a cold start.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
How 'bout a hot re-start? Any problem?
I'm thinkin' not enough fuel or cold start injector problem (if '85 has csi).
Maybe it's goin' into open loop right at cold start up, givin' little fuel for cold runnin'.
Some one will chime in with a test to see if it's goin' into warmed-up mode right away on a cold start.
I'm thinkin' not enough fuel or cold start injector problem (if '85 has csi).
Maybe it's goin' into open loop right at cold start up, givin' little fuel for cold runnin'.
Some one will chime in with a test to see if it's goin' into warmed-up mode right away on a cold start.
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
Hot re-start is flawless, perfect idle and instant ignition. I haven't checked to see if it's going into open loop right away or not. I plan on doing that tomorrow. Cold start switch and injector are not very old but that means nothing. I'm assuming everything with the cold start injector is fine since it does fire up immediately when cold. I'm running a heated O2 sensor with long tubes so maybe the sensor has died.
Melting Slicks
Joined: Aug 2003
Posts: 3,400
Likes: 396
From: Lakeville MI
It sounds like you need more air.
When the engine first fires and the revs flare up, the air in the plenum is quickly consumed. You want to have enough intial airflow (IAC and throttle opening) to support around 1200 rpm (cold idle rpm).
Additional air to keep it running must flow through the throttle and IAC valve to keep up with the demand.
Either try some additonal throttle opening (increase the min air) or get into the tune and increase the IAC start position. You may also have too much/too little start-up enrichment which influences about the first minute of running time.
If it clears up after a minute or so, the open loop vs coolant temp enrichment is in the ballpark, so I would focus on the initial airflow and start-up enrichment.
When the engine first fires and the revs flare up, the air in the plenum is quickly consumed. You want to have enough intial airflow (IAC and throttle opening) to support around 1200 rpm (cold idle rpm).
Additional air to keep it running must flow through the throttle and IAC valve to keep up with the demand.
Either try some additonal throttle opening (increase the min air) or get into the tune and increase the IAC start position. You may also have too much/too little start-up enrichment which influences about the first minute of running time.
If it clears up after a minute or so, the open loop vs coolant temp enrichment is in the ballpark, so I would focus on the initial airflow and start-up enrichment.
Supporting Vendor
Joined: Mar 2008
Posts: 1,762
Likes: 14
From: Cumming Ga
jack
the cold start flows about 12lbs of fuel per hr. your car need this rich addition of fuel to run cold. After it warms up of course it shuts off. usually a minute or two. So I would start there. you can check it like a reg injector.
the cold start flows about 12lbs of fuel per hr. your car need this rich addition of fuel to run cold. After it warms up of course it shuts off. usually a minute or two. So I would start there. you can check it like a reg injector.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Today I disconnected the cold start injector and the car wouldn't start by itself like it should and normally does. Hooked the csi back up and it fired right up. Not sure how long it is flowing though so I will check that with my noid light. The O2 is okay, it's going to closed loop just fine. I did find a code 23 which is MAT showing excessive low temp. This is because I relocated the sensor to the air inlet in front of the MAF. At least I think that's why, I couldn't get it to re-set the code again once I cleared it.
I will check the csi with the noid and see what I find and report back.
I will also increase the throttle opening to see what that does.
I will check the csi with the noid and see what I find and report back.
I will also increase the throttle opening to see what that does.
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Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Tequilaboy, I increased throttle opening just a bit and reset TPS to
.54, problem was still there and it then also had a bad hunting idle so I put everything back where it was. I am noticing a rich exhaust smell so your idea of not enough air sounds right but??? I don't have the capabilities to alter the tune but I've had this chip now for some time with no issues before. This has just showed up over the winter, and I filled the tank with fresh gas before storage and added Sta-bil. I also started it about once a month and let the temps get up to normal before shutting it down.
FIC, I checked cold start injector, it was getting power during crank mode which according to FSM is correct.
Once this thing reaches about 130 degrees water temp you would never believe a problem existed.
.54, problem was still there and it then also had a bad hunting idle so I put everything back where it was. I am noticing a rich exhaust smell so your idea of not enough air sounds right but??? I don't have the capabilities to alter the tune but I've had this chip now for some time with no issues before. This has just showed up over the winter, and I filled the tank with fresh gas before storage and added Sta-bil. I also started it about once a month and let the temps get up to normal before shutting it down.
FIC, I checked cold start injector, it was getting power during crank mode which according to FSM is correct.
Once this thing reaches about 130 degrees water temp you would never believe a problem existed.
Safety Car
Joined: Oct 2007
Posts: 3,816
Likes: 0
From: :45 minutes from everywhere / E-I-E-I-O
If your gas mileage is good, I'm layin' odds too much csi fuel at start-up...
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Problem solved! And anyone who wants to give me a swift kick in the ***, go ahead, I deserve it. I had quit working on it today to watch the Coca-Cola 600. I couldn't quit thinking about what I had done, going back over everything. All of a sudden it hit me, I had done the min. air adjustment just the way you're supposed to,,,,, with one small exception, I forgot to ground the A-B terminals in ALDL before disconnecting the IAC. I have no idea how I got such a good warm idle but I did. I immediately went out and re-set everything then let the engine cool down to about 120. Fired it up and it did exactly as it is supposed to do and never even offered to die. Tomorrow morning will tell for sure but I just know that it's okay.
Thanks to all you guys who gave me great advice.
Thanks to all you guys who gave me great advice.