Cold start, won't hold steady idle, stalls at stops.
01-24-2011, 07:00 PM
#1
Cold start, won't hold steady idle, stalls at stops. Oh hey my LT1 brethren! Lets try this thread here, as the PCM section of the site hasn't been helpful yet.......
I'm hoping I can get some ideas here, this is driving me crazy.
I'm running the EFI Connections 24x setup, so I'm running a LS1 PCM. My problem occurs only during a cold start. The RPMs will vary from 500-1000 after the initial fuel from the pump priming cooks off. So say 5 seconds after starting or so. When coming to a stop the car stalls. When getting on the throttle from a stop the car feels like it is going to try to die for a quick second and then comes back.
So I will park the car for a few hours while at class, come out, car will hold a steady idle just fine and operate just as it should! So if it isn't a cold start the car does everything it should.
Tuner was seeing the problem where the TPS would not reset. He tried another PCM, issue still remains. So Sunday morning I start the car, same problem. I shut down it down (car ran maybe 15 seconds), ate breakfast, picked up a new TPS. Installed it and it looked promising, car held an idle, granted a high one around 1500rpms, but it was steady. So I adjusted the throttle stop screw twice, I was back down to being around 900 rpm idle.
Turn on the car this morning, idle was up and down again, stalling out at stops also.
The tuner says the IAC counts look good at cold start, he may have said they were maxed out or close to it. IAC counts when the car is warm are around 55 I think.
This is a new wire harness and the issue only occurs during a cold start.
My question is can the IAC read like it is doing its job but its not? Original IAC from 1994, has almost 200k on it now. I'm kinda hoping this isn't the issue, just looked the IAC up, price wise is painful! (well it was on advance auto's website, looking at rock auto the price wouldn't be too bad)
Well thanks for any help I can get, this is maddening.
Oh and it is a Summit 58mm throttle body. I had this on the car for two years now, with the LT1 PCM I never had this issue, it has only occurred since the 24x conversion. -Corey
I'm hoping I can get some ideas here, this is driving me crazy.
I'm running the EFI Connections 24x setup, so I'm running a LS1 PCM. My problem occurs only during a cold start. The RPMs will vary from 500-1000 after the initial fuel from the pump priming cooks off. So say 5 seconds after starting or so. When coming to a stop the car stalls. When getting on the throttle from a stop the car feels like it is going to try to die for a quick second and then comes back.
So I will park the car for a few hours while at class, come out, car will hold a steady idle just fine and operate just as it should! So if it isn't a cold start the car does everything it should.
Tuner was seeing the problem where the TPS would not reset. He tried another PCM, issue still remains. So Sunday morning I start the car, same problem. I shut down it down (car ran maybe 15 seconds), ate breakfast, picked up a new TPS. Installed it and it looked promising, car held an idle, granted a high one around 1500rpms, but it was steady. So I adjusted the throttle stop screw twice, I was back down to being around 900 rpm idle.
Turn on the car this morning, idle was up and down again, stalling out at stops also.
The tuner says the IAC counts look good at cold start, he may have said they were maxed out or close to it. IAC counts when the car is warm are around 55 I think.
This is a new wire harness and the issue only occurs during a cold start.
My question is can the IAC read like it is doing its job but its not? Original IAC from 1994, has almost 200k on it now. I'm kinda hoping this isn't the issue, just looked the IAC up, price wise is painful! (well it was on advance auto's website, looking at rock auto the price wouldn't be too bad)
Well thanks for any help I can get, this is maddening.
Oh and it is a Summit 58mm throttle body. I had this on the car for two years now, with the LT1 PCM I never had this issue, it has only occurred since the 24x conversion. -Corey
01-26-2011, 08:10 PM
#5
Yeah I'll know tomorrow, stabbed a new IAC in tonight. I'm at that point where I'm throwing parts at it, first TPS and now the IAC.
Debate on another website over MAF vs. speed density. Some claim because I have a non working MAF and the tuner tuned me speed density that is why it will run bad on a cold start and why they say I'm down to 337 rwhp instead of the 356 rwhp I was at before the 24x conversion? I have never heard of a speed density tune costing power and running bad when cold though?
Debate on another website over MAF vs. speed density. Some claim because I have a non working MAF and the tuner tuned me speed density that is why it will run bad on a cold start and why they say I'm down to 337 rwhp instead of the 356 rwhp I was at before the 24x conversion? I have never heard of a speed density tune costing power and running bad when cold though?
01-27-2011, 11:08 AM
#6
So with the new IAC it held a steady cold idle this morning, but when I stopped the car still stalled out. Gonna do a IAC reset I guess now when I go outside.
One question that bugs me, why was the 95+ IAC more expensive? I have a 94 so I snagged a 94 IAC, but was there some difference REQUIRED for OBD II?? Perhaps this can lead to my issue running the 24x setup???
One question that bugs me, why was the 95+ IAC more expensive? I have a 94 so I snagged a 94 IAC, but was there some difference REQUIRED for OBD II?? Perhaps this can lead to my issue running the 24x setup???
01-29-2011, 12:28 PM
#7
So I'm going to rule out that it would be a OBD I vs. OBD II IAC difference, if there is any at all. My friend has a 94 Z28 that also did the 24x conversion, he is still on the factory IAC from 94.
Someone explain to me better the IAC reset? I tried it the other day, should it be done on a cold start, or any time you start the car you can do it? It says throttle slightly depressed. When I did this the car well kept revving, so I'm assuming I had it depressed to far. How soon do you let up off the throttle, as soon as it fires off?
This is just madness. I'm getting ready to burn this car to the ground.
Someone explain to me better the IAC reset? I tried it the other day, should it be done on a cold start, or any time you start the car you can do it? It says throttle slightly depressed. When I did this the car well kept revving, so I'm assuming I had it depressed to far. How soon do you let up off the throttle, as soon as it fires off?
This is just madness. I'm getting ready to burn this car to the ground.
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11-10-2012, 04:02 AM
#9
Im running the 24x and have a similar issue with mine. I have to let it warm up for a couple mins for it not to happen. When cold leaving and switching to 2nd gear it would stumble for a split second then come right back running fine. Ive had it tuned twice and still cant quite get rid of it. A big issue i had was i couldnt get it idle to under a grand. My iac counts were high 120s so i drilled out the iac circuit and put a brass fitting in to correct the airflow and it helped tremendous. It now idles perfect at 800 without stalling. I would start by doing the drill mod in the iac port and adding a brass fitting to the iac circuit to prevent the stalling issue. As for the stumble im still looking for an answer.
11-23-2015, 08:24 PM
#10
ZOMBIE THREAD! I've got some other issue I am looking up on and saw this, figured I'd answer the question.
