LT1 misfire and popping (Page 1/2)
str8maxn APR 25, 11:44 PM
I have an LT1 swap and I have a misfire. Any insight on a troubleshooting path would be appreciated.

Would a clogged injector cause a misfire?

I purchased a Stethoscope, I seem to hear a different sound coming from 2 injectors. but I am not sure what it should sound like.


I can post a video is it helps.
cyrus88 APR 26, 03:22 AM
what year engine?

Optispark distributer is the usual culprit. MY optispart had oil in it and I had to take it apart and clean it to clear misfires.
Will APR 26, 08:44 AM
Or get an LS coil conversion...
str8maxn APR 26, 11:17 AM


CYRUS88 >>> The LT1 is out of a 93 Vette.
How hard it to replace the optispark on a scale of 1 to 10. Ten being the hardest?

WILL>>> Wow, I didn't know LS Coil conversion was possible.

InTheLead APR 26, 11:19 AM

quote
Originally posted by cyrus88:

what year engine?

Optispark distributer is the usual culprit. MY optispart had oil in it and I had to take it apart and clean it to clear misfires.





I had the exact same issue as this, the crank hub seal was leaking, water pump drive seal and the Optispark seal was crumbling. Cleaned the Optispark carefully, replaced those three seals.. got less then 1200 miles and the Optispark failed.

Decided to either do a full LS engine swap or what Will suggested. Since my engine was already built for boost I opted to convert the ignition, used an expensive but high quality kit from Torqhead.com
Will APR 26, 12:06 PM

quote
Originally posted by str8maxn:

CYRUS88 >>> The LT1 is out of a 93 Vette.
How hard it to replace the optispark on a scale of 1 to 10. Ten being the hardest?

WILL>>> Wow, I didn't know LS Coil conversion was possible.



Waterpump has to come off for opti-spark maintenance, so it's an extreme PITA in a Fiero.


quote
Originally posted by InTheLead:

I had the exact same issue as this, the crank hub seal was leaking, water pump drive seal and the Optispark seal was crumbling. Cleaned the Optispark carefully, replaced those three seals.. got less then 1200 miles and the Optispark failed.

Decided to either do a full LS engine swap or what Will suggested. Since my engine was already built for boost I opted to convert the ignition, used an expensive but high quality kit from Torqhead.com




Good find for the vendor!

EFI Connection also has retrofit parts to use newer engine management on the LT1/LT4 Gen II engines.
https://www.eficonnection.c...-covers/lt1lt4-chevy
str8maxn APR 26, 12:22 PM
Let me start off by saying I am not a mechanic; so if I sound like a dumbass please forgive me... I recall the last owner replaced the OptiSpark with an MSD vented version. I do have a small pickup air line coming from the air intake filter. and have paper work for the MSD unit.

How prone are the MSD Opispark to failure?
Is there a way to test the MSD Optispark?

In another site, Someone had the same problem and it turned out to be the ICM. Could this be the problem? How can I test the ICM?

Going back to my original question, do you think a sticky or a clogged injector could be the cause. I remember the last owner saying that the car was running great until it was not. A few years later, while talking to his father in law; who's car left him stranded because hose line that was used inside his gas tank that had turned into playdoh didn't allow fuel to be picked up.

As it turned out, he did the same when he ran the stock fuel pump for the vette inside the fiero tank.
Will APR 26, 12:40 PM
Consistent or intermittent misfire? Idle or only loaded?

There are a number of troubleshooting techniques to find a misfire... Unplug the injectors or spark plugs one at a time, for example.
str8maxn APR 26, 02:32 PM

quote
Originally posted by Will:

Consistent or intermittent misfire? Idle or only loaded?

There are a number of troubleshooting techniques to find a misfire... Unplug the injectors or spark plugs one at a time, for example.




On cold starts it idles fine for the first 3-5 minutes. After which I start to hear the popping coming from the exhaust. The popping is also present during normal driving.

Thanks.. Looking forward to your input.

[This message has been edited by str8maxn (edited 04-26-2021).]

cyrus88 APR 26, 07:03 PM

quote
Originally posted by str8maxn:
CYRUS88 >>> The LT1 is out of a 93 Vette.
How hard it to replace the optispark. . .



It's fairly simple, just tedious. I can't put it on a scale because I don't know your skill/knowledge level. For me it was about a 1.

If you have an LT-1 water pump, then it's more involved because you have to drain coolant, remove and reinstall pump, etc. I have a remote electric water pump, so I didn't have to touch the cooling system. I did have to tilt the rear of the cradle down to get the balancer and optispark out, though.

Be careful about the MSD opti, the rotor can fall apart inside (do a google search).