deep trouble with 94 lt1
So it ran ok that one day and now it's back to doing the same thing?
When I first read your post these things came to mind in this order;
O2's because it doesn't do it till it warms up and goes into open loop
ICM getting
fuel pump, pump gets hot and psi/volume drops
trans O/D solenoid sticking/coming on at the wrong time
So when you put the seafoam in the tank and drove it, is that the first time it hasn't acted up or does it occasionally run better on it's own?
If that's the first time it's ran better I would probably lean towards the injectors.
Another thing it could be is a leaking intake gasket. With aluminum heads and intake things move quite a bit. You could have a gasket that seals when its cold but when things start expanding and moving around it will leak.
I know it's frustrating but don't give up. I fought a engine I built for my 89 T/A once. Would run fine when it's cold but after it was hot it ran like crap. Ended the machine shop decked the block wrong and the intake wasn't sealing.
Back to topic!
When I first read your post these things came to mind in this order;
O2's because it doesn't do it till it warms up and goes into open loop
ICM getting
fuel pump, pump gets hot and psi/volume drops
trans O/D solenoid sticking/coming on at the wrong time
So when you put the seafoam in the tank and drove it, is that the first time it hasn't acted up or does it occasionally run better on it's own?
If that's the first time it's ran better I would probably lean towards the injectors.
Another thing it could be is a leaking intake gasket. With aluminum heads and intake things move quite a bit. You could have a gasket that seals when its cold but when things start expanding and moving around it will leak.
I know it's frustrating but don't give up. I fought a engine I built for my 89 T/A once. Would run fine when it's cold but after it was hot it ran like crap. Ended the machine shop decked the block wrong and the intake wasn't sealing.
Back to topic!
Thread Starter
Teching In
Joined: Aug 2010
Posts: 22
Likes: 0
it confusing 9/10 i drive it it will like miss or stumble only after it heats up also changed wires again installed new iat sensor . once in a while (usally at night ) it will go longer with out acting up they day i posted that i didnt take that into account
i finally sat out with the car long enough for it to reach 180/190 in park and it stumbled all over the place at the end it was running some how at 100 rpm before i could shut it off (sounded so bad i was scared to restart the engine) i started it back up fine 2 seconds later miss.stumble.fail let it cool for a good 4 hours went back out runs like a dream gets hot miss.stumble.fail
starting to go insane i love the car but if i cant get it fixed soon wifes bit@hin it has to go . this is both of are only means of transportation
starting to run oout of time and thinking about throwing another optispark at it
i finally sat out with the car long enough for it to reach 180/190 in park and it stumbled all over the place at the end it was running some how at 100 rpm before i could shut it off (sounded so bad i was scared to restart the engine) i started it back up fine 2 seconds later miss.stumble.fail let it cool for a good 4 hours went back out runs like a dream gets hot miss.stumble.fail
starting to go insane i love the car but if i cant get it fixed soon wifes bit@hin it has to go . this is both of are only means of transportation
starting to run oout of time and thinking about throwing another optispark at it
On The Tree
Joined: May 2004
Posts: 183
Likes: 0
From: Orlando, FL
This sounds kind of like the problem I had after I replaced my cam and accidentally broke the PCM water temp sensor in the waterpump. It was only sort of broken so it was intermittent. It would run fine cold and then start to die out as soon as it warmed up. (For the record, everyone said OPTI OPTI OPTI, and so I replaced it and wasted a bunch of money)
Have you run a scan tool on it while it is acting up? What is the PCM doing then? Is it pulling a bunch of timing? What is the temperature saying in the PCM?
Also, what are your knock counts? (Did you check the knock sensor/knock module?)
Have you run a scan tool on it while it is acting up? What is the PCM doing then? Is it pulling a bunch of timing? What is the temperature saying in the PCM?
Also, what are your knock counts? (Did you check the knock sensor/knock module?)
Thread Starter
Teching In
Joined: Aug 2010
Posts: 22
Likes: 0
ive tried unpluging maf still did it unpluged both o2's still did it
i have a aldl cable and use datamaster everything is showing in spec goes frpm open to closed fine stays at close
only thing that seems out of place is fuel trim count at like 6-9 at idle and egr shows 0 then instantly 50 then 100 then closed
if it was the pcm would it only act up when warm ive tried bumping it with my palm with no effect
knock shows are 2700-3000 at start up (which i believe is normal) then stays there all the way though not even when it acts up does knock show
timing is advanced 12% at idle at around 2k (a4) advances about 16%
i have a aldl cable and use datamaster everything is showing in spec goes frpm open to closed fine stays at close
only thing that seems out of place is fuel trim count at like 6-9 at idle and egr shows 0 then instantly 50 then 100 then closed
if it was the pcm would it only act up when warm ive tried bumping it with my palm with no effect
knock shows are 2700-3000 at start up (which i believe is normal) then stays there all the way though not even when it acts up does knock show
timing is advanced 12% at idle at around 2k (a4) advances about 16%
Do you still have EGR? If so try unplugging it. My blazer acted similar to what you are describing and i tried everything and it ended up being the solenoid that controlled the EGR. That would make sense since it doesn't do it till it warms up.
Thread Starter
Teching In
Joined: Aug 2010
Posts: 22
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checked all the gaps ran the same with old plugs as it did with new plugs old was autolites new are ngk
as for the egr i have removed the vacuum hose connected to the egr valve and it makes no difference still misses
as for the egr i have removed the vacuum hose connected to the egr valve and it makes no difference still misses
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Thread Starter
Teching In
Joined: Aug 2010
Posts: 22
Likes: 0
so im dead set on the opti spark now i drove it to work about 6 am and had no problem came home at about 4 no problem went to leave to go out to eat missing (temp was less then 160) so im convinced its no long heat related and was only acting up after being used for a while the miss stumble surge has been haunting me as a opti failure this whole time even tho its a delco (guess my car just hates me)
what are your opinion on the dyna spark model
from what i can tell it looks to me as a upgraded cap so tht i can use the vacuum vents but ive read about them having bad optical sensors not using the orginal one made by mitsibishi
id like feed back on some people that own them not people replying on theory that you all for all this help so far
what are your opinion on the dyna spark model
from what i can tell it looks to me as a upgraded cap so tht i can use the vacuum vents but ive read about them having bad optical sensors not using the orginal one made by mitsibishi
id like feed back on some people that own them not people replying on theory that you all for all this help so far
Thread Starter
Teching In
Joined: Aug 2010
Posts: 22
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so as a follow up i replaced the opti spark and the problem went away for a while then it started to act up i added a new egr valve and had to replace my master cylinder .
went it ended up being was my vat system the vat would enable spark but would fault and not enable fuel (red connector A25) purchased a bypass module (these are not simple resister bypasses like the key bypass , these bypasses generate a 50hz signal to the fuel enable wire when ever the car is in ***. position (some pre 94 lt1/tpi require a 30hz ) once everything was said and done its been running fine
went it ended up being was my vat system the vat would enable spark but would fault and not enable fuel (red connector A25) purchased a bypass module (these are not simple resister bypasses like the key bypass , these bypasses generate a 50hz signal to the fuel enable wire when ever the car is in ***. position (some pre 94 lt1/tpi require a 30hz ) once everything was said and done its been running fine
That's an incredible journey.
After you did the 2nd opti..and the egr.
It started missing again!???!
So just to be clear at this point what your suggesting is the fuel pump was not getting it's full voltage? and working weakly and intermittently?
You then bypassed the VATS and it's been 100% cleared of the problem?
How long now if you don't mind me asking?
Dude if this is all true...this is an incredible find. What made you go there? wiring diagram? friend?
Headlines read "Opti cleared of all charges...sneaky vats tricks all via fuel pump....1000's swindled in pyramid scheme".
Baptism by fire; your an Fbody veteran.
After you did the 2nd opti..and the egr.
It started missing again!???!
So just to be clear at this point what your suggesting is the fuel pump was not getting it's full voltage? and working weakly and intermittently?
You then bypassed the VATS and it's been 100% cleared of the problem?
How long now if you don't mind me asking?
Dude if this is all true...this is an incredible find. What made you go there? wiring diagram? friend?
Headlines read "Opti cleared of all charges...sneaky vats tricks all via fuel pump....1000's swindled in pyramid scheme".
Baptism by fire; your an Fbody veteran.
Last edited by License2Ill; Nov 3, 2011 at 07:39 AM.
