Having stumbling, hesitation issue 94 LT1. Insight greatly appreciated.
01-29-2019, 10:37 AM
#1
Advanced
Thread Starter
Having stumbling, hesitation issue 94 LT1. Insight greatly appreciated.
First off hello, first post on this site.
Ive had my 94 LT1 6-speed for a few months.
2 owner, 69,000 babied miles. Car looks and performs like new other than one issue.
When she warms up to temp and I lug it down in a higher gear for speed and want to accelerate it kind of hesitates and bucks. Not like a backfire or anything just doesnt like what Im doing I guess. Also does it sometimes under hard acceleration in lower gears as well.
Ive replaced the original ICM and ignition coil. I can tell a definite change in the throttle response and drivability since just changing the above parts. Have not gotten around to replacing the plugs and wires yet.
Any insight to a fix is greatly appreciated. Thanks.
Ive had my 94 LT1 6-speed for a few months.
2 owner, 69,000 babied miles. Car looks and performs like new other than one issue.
When she warms up to temp and I lug it down in a higher gear for speed and want to accelerate it kind of hesitates and bucks. Not like a backfire or anything just doesnt like what Im doing I guess. Also does it sometimes under hard acceleration in lower gears as well.
Ive replaced the original ICM and ignition coil. I can tell a definite change in the throttle response and drivability since just changing the above parts. Have not gotten around to replacing the plugs and wires yet.
Any insight to a fix is greatly appreciated. Thanks.
01-29-2019, 12:10 PM
#2
Le Mans Master
I'm going to jump right to the end with my opinion as I have had the exact same symptom as others had. I replaced same parts as you and tested everything I could. You can check for codes but will probably find none Your opti is bad. Thats what causes this effect.
Back when you could get original GM parts. Now not so much and people have had problems with the optical sensor in the new units because the optical sensor are crap. But now there are new companies making the opti where 10 years ago there were no choices.
I always replaced the whole opti. But today if I have the same symptom again I would consider just replacing the cap and I believe those problems are caused by the cap.
I'm sure many will chime in who have had experience with the newer opti and you can make a decision what direction to go.
Back when you could get original GM parts. Now not so much and people have had problems with the optical sensor in the new units because the optical sensor are crap. But now there are new companies making the opti where 10 years ago there were no choices.
I always replaced the whole opti. But today if I have the same symptom again I would consider just replacing the cap and I believe those problems are caused by the cap.
I'm sure many will chime in who have had experience with the newer opti and you can make a decision what direction to go.
01-29-2019, 12:32 PM
#3
Advanced
Thread Starter
Thanks for your opinion. I wasnt wanting to say it was the Opti. It possibly could be. I dont think it has ever been changed via my records from previous owners.
01-29-2019, 01:01 PM
#4
Welcome to the optispark blues club, LOL.
Seriously though, if you haven't already, check fuel pressure, key on ign off, then use a gauge you can tape to your windshield, check at cruise and WOT. If fuel pressure checks out then it's probably ignition.
When the opti went bad on my '96 with 153K, it would miss under light load but be fine at WOT. Also, my intake would get extremely hot to the touch, normally maybe warm, not burn your finger hot. I'm a little old school so I just put an inductive timing light on each of the plug wires at idle and could tell right away that it was ignition (opti). 3 out of 8 cylinders were showing super fast pulses like it was at 3000+RPM when it was idling. Like you I did, plugs, wires, ICM, and coil before I figured out it was the opti (by coming here and searching).
Seriously though, if you haven't already, check fuel pressure, key on ign off, then use a gauge you can tape to your windshield, check at cruise and WOT. If fuel pressure checks out then it's probably ignition.
When the opti went bad on my '96 with 153K, it would miss under light load but be fine at WOT. Also, my intake would get extremely hot to the touch, normally maybe warm, not burn your finger hot. I'm a little old school so I just put an inductive timing light on each of the plug wires at idle and could tell right away that it was ignition (opti). 3 out of 8 cylinders were showing super fast pulses like it was at 3000+RPM when it was idling. Like you I did, plugs, wires, ICM, and coil before I figured out it was the opti (by coming here and searching).
01-30-2019, 07:51 AM
#5
Le Mans Master
I was having the same issues with my old 94 and I replaced the opti, plugs, wires, ICM, and coil and the issues went away....for a time. Once the issue presented itself again, I replaced the opti and the issues went away.....for a time... I battled the stumbling at light throttle the entire time I owned the car. Often if I let the engine warm up for a few mins before driving it, I had no issues. Other times, not so much. Replaced the opti and it would be fine for a few months and come back. Very frustrating experience.
01-30-2019, 10:41 AM
#6
What is your coolant temp when this is happening? This is the same problem I just solved, but I don't want to chime in unless this is happening when engine is under or over 200 degrees.
01-30-2019, 11:41 AM
#8
Racer
stumbling
If you can find some one local to run a live scan, while driving the car and make sure all perimeters are correct would be best bet before replacing opti, not every shop has the proper software.
01-30-2019, 11:43 AM
#9
Racer
stumbling
If you can find some one local to run a live scan, while driving the car and make sure all perimeters are correct would be best bet before replacing opti, not every shop has the proper software . Also a good tuner with a dyno. and make sure they are lt1 savy,
