'93 LT1 slight misfire
Thread Starter
Burning Brakes
Joined: Mar 2005
Posts: 800
Likes: 2
'93 LT1 slight misfire
I have noticed that my '93 has a slight miss, between idle and about 1200 rpm. I feel that it is idling too low, it idles in D at a dash indicated 5-550 rpm. The only time the miss is really noticeable is in stop and go traffic or traveling at a slow speed with rpm's around 1k or so. temp doesn't affect the miss at all, it does it dead cold up to when the fan kicks on to cool her back down. it is less noticeable when the A/C is on, i guess the additional load on the engine somehow makes it smooth out.
So far the things done to car, none of which were intended to fix this issue.
At 100k a new opti was put in the car, left the OE plug wires in place. Not sure how long plugs have been in, but they look recent. Bosch +2 plugs (i didn't put them in the car)
At 102k another opti was put in, the other new one lost low res signal. again, reused the OE plug wires.
At 103k Opti replaced again, this time with a NOS GM opti. Upgraded with MSD vented cap kit. rotor screws are loctited in place. New coil, cleaned ICM and reinstalled with new heat sink grease, new Taylor plug wires. Probably should have replaced the waterpump for good measure, however I have a receipt showing where the water pump was replaced at a chevy dealer at 95k miles. New seals installed in timing cover, though it still leaks oil from the intake.
The only code in the ECM is a H32, which i know is EGR but the shouldn't affect idle i wouldn't think. It doesn't always throw that code, sometimes after holding a steady speed for 20 minutes or longer it might set that code, not a consistent thing.
Any ideas what could cause the slight miss?
btw- car now has 105.5k miles on it, and has had this miss with the 2 previous opti's also. It is NOT the opti.
So far the things done to car, none of which were intended to fix this issue.
At 100k a new opti was put in the car, left the OE plug wires in place. Not sure how long plugs have been in, but they look recent. Bosch +2 plugs (i didn't put them in the car)
At 102k another opti was put in, the other new one lost low res signal. again, reused the OE plug wires.
At 103k Opti replaced again, this time with a NOS GM opti. Upgraded with MSD vented cap kit. rotor screws are loctited in place. New coil, cleaned ICM and reinstalled with new heat sink grease, new Taylor plug wires. Probably should have replaced the waterpump for good measure, however I have a receipt showing where the water pump was replaced at a chevy dealer at 95k miles. New seals installed in timing cover, though it still leaks oil from the intake.
The only code in the ECM is a H32, which i know is EGR but the shouldn't affect idle i wouldn't think. It doesn't always throw that code, sometimes after holding a steady speed for 20 minutes or longer it might set that code, not a consistent thing.
Any ideas what could cause the slight miss?
btw- car now has 105.5k miles on it, and has had this miss with the 2 previous opti's also. It is NOT the opti.
Instructor
Joined: Aug 2012
Posts: 213
Likes: 0
From: Carrollton TX
If I'm not mistaken, the EGR valve's purpose is for recirculating exhaust gases at lower rpm's (to lower emmissions, particularly when idling). If you're throwing EGR codes intermittently, then I'd go ahead and replace it (it's not too terribly hard to replace, just requires a little wrangling to get around the obstructions).
Thread Starter
Burning Brakes
Joined: Mar 2005
Posts: 800
Likes: 2
If I'm not mistaken, the EGR valve's purpose is for recirculating exhaust gases at lower rpm's (to lower emmissions, particularly when idling). If you're throwing EGR codes intermittently, then I'd go ahead and replace it (it's not too terribly hard to replace, just requires a little wrangling to get around the obstructions).
