LT1 Idle Issue
12-13-2009, 01:51 AM
#1
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LT1 Idle Issue Hey guys,
I have a '97 with a bolt-on LT1 and 6-spd. It has shorty headers, single-cat conversion, slp cai, and a new ignition (opti, plugs, wires). It has also been mail order tuned by madz28 tune for the mods. The car runs fine when the weather is nice, but here's the problem: when its really cold (like less than 20*) it runs poor on start up, like its only on 7 cylinders. When it warms up it idles like a champ at 1k rpm. Any ideas on this problem? The car has also been averaging about 11 mpg combined, which seems exteremly low even for an lt1 with 4.10 gears.
Also, it has an issue finding idle when the car comes to a stop. This happens warm or cold, doesn't matter. What happens is when you come to a complete stop the idle will drop low, like 600 rpm and the car will almost wanna stall (this is with the clutch disengaged obviously), then it will quickly return to 1k rpm and idle fine. Does this seem like some kind of pcm issue?
If someone can give me some insight, or if anyone has had a similar issue I would appreciate input. Any help would be greatly appreciated. Thanks.
I have a '97 with a bolt-on LT1 and 6-spd. It has shorty headers, single-cat conversion, slp cai, and a new ignition (opti, plugs, wires). It has also been mail order tuned by madz28 tune for the mods. The car runs fine when the weather is nice, but here's the problem: when its really cold (like less than 20*) it runs poor on start up, like its only on 7 cylinders. When it warms up it idles like a champ at 1k rpm. Any ideas on this problem? The car has also been averaging about 11 mpg combined, which seems exteremly low even for an lt1 with 4.10 gears.
Also, it has an issue finding idle when the car comes to a stop. This happens warm or cold, doesn't matter. What happens is when you come to a complete stop the idle will drop low, like 600 rpm and the car will almost wanna stall (this is with the clutch disengaged obviously), then it will quickly return to 1k rpm and idle fine. Does this seem like some kind of pcm issue?
If someone can give me some insight, or if anyone has had a similar issue I would appreciate input. Any help would be greatly appreciated. Thanks.
Last edited by mrnorm_hemicide; 12-13-2009 at 10:05 PM.
12-13-2009, 03:43 AM
#2
Hey guys,
I have a '97 with a bolt-on LT1 and 6-spd. It has shorty headers, single-cat conversion, slp cai, and a new ignition (opti, plugs, wires). It has also been mail order tuned by madz28 tune for the mods. The car runs fine when the weather is nice, but here's the problem: when its really cold (like less than 20*) it runs poor on start up, like its only on 7 cylinders. When it warms up it idles like a champ at 1k rpm. Any ideas on this problem? The car has also been averaging about 11 mpg combined, which seems exteremly low even for an lt1 with 4.10 gears.
Also, it has an issue finding idle when the car comes to a stop. This happens warm or cold, doesn't matter. What happens is when you come to a complete stop the idle will drop low, like 600 rpm and the car will almost wanna stall (this is with the clutch disengaged obviously), then it will quickly return to 1k rpm and idle fine. Does this seem like some kind of pcm issue?
If someone can give me some insight, or if anyone has had a similar issue I would appreciate input. The car doesn't appear to have an IAT on it, I'm assuming the previous owner had it tuned into the pcm and removed it, could this be a possible cause? Any help would be greatly appreciated. Thanks.
I have a '97 with a bolt-on LT1 and 6-spd. It has shorty headers, single-cat conversion, slp cai, and a new ignition (opti, plugs, wires). It has also been mail order tuned by madz28 tune for the mods. The car runs fine when the weather is nice, but here's the problem: when its really cold (like less than 20*) it runs poor on start up, like its only on 7 cylinders. When it warms up it idles like a champ at 1k rpm. Any ideas on this problem? The car has also been averaging about 11 mpg combined, which seems exteremly low even for an lt1 with 4.10 gears.
Also, it has an issue finding idle when the car comes to a stop. This happens warm or cold, doesn't matter. What happens is when you come to a complete stop the idle will drop low, like 600 rpm and the car will almost wanna stall (this is with the clutch disengaged obviously), then it will quickly return to 1k rpm and idle fine. Does this seem like some kind of pcm issue?
If someone can give me some insight, or if anyone has had a similar issue I would appreciate input. The car doesn't appear to have an IAT on it, I'm assuming the previous owner had it tuned into the pcm and removed it, could this be a possible cause? Any help would be greatly appreciated. Thanks.
12-13-2009, 10:03 PM
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No codes, lt fuel trims are roughly -5.8 bank 1 and -0.6 bank 2. Also the ave voltage for the o2s are like .45v bank 1 and .35v bank 2. Im assuming that this means there are some random injector flow issues, because the st fuel trims bounce around at will. The maf reads a consitent 1 lb/min at idle, and the map reads 9.2 inHg at idle. So idk what the deal is, the car seems to run fine, the motor sounds healthy, so the only thing I can really think of is that the injectors need cleaning, and maybe the pcm/tune is funky. Anyone have any more input? Thanks.
12-13-2009, 10:14 PM
#5
Are those o2 readings while the car is at operating temp or cold start up?
What is your IAC readings on cold start and operating temp?
Does your ses light work, turn on and off?
Do you have a vacuum leak at all that you can think of?
Are your clamps tight that hold on your couplers for the c.a.i, maf, t.b that can cause a surge especially at stopping?
What is your IAC readings on cold start and operating temp?
Does your ses light work, turn on and off?
Do you have a vacuum leak at all that you can think of?
Are your clamps tight that hold on your couplers for the c.a.i, maf, t.b that can cause a surge especially at stopping?
12-17-2009, 12:22 AM
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On another note, I started it up this morning when it was like 7* F outside, and it was hard starting and when it fired up it was running rich as hell.
12-17-2009, 12:25 AM
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Are those o2 readings while the car is at operating temp or cold start up?
What is your IAC readings on cold start and operating temp?
Does your ses light work, turn on and off?
Do you have a vacuum leak at all that you can think of?
Are your clamps tight that hold on your couplers for the c.a.i, maf, t.b that can cause a surge especially at stopping?
What is your IAC readings on cold start and operating temp?
Does your ses light work, turn on and off?
Do you have a vacuum leak at all that you can think of?
Are your clamps tight that hold on your couplers for the c.a.i, maf, t.b that can cause a surge especially at stopping?
