Will a LT1 with a Check Engine Light Always Throw A Code?

[NitrousJunkie]

Had a check engine light on for about a week, car finally died and won't restart, cranks and cranks and if you put your foot to the floor it starts to choke but won't fire, brand new Walbro 255 + Filter + Plugs.

Had a friend at NAPA bring one of those cheap plug in scanners when the car was running last week, fans came on but the check engine light never flashed.

With the light on will it always throw a code or at least flash? I heard it's suppose to flash 12 times at first to let you know the computer is good, it didn't flash once.

If the PCM is bad I'd actually be halfway happy, heading over right now (It's in a parking lot) to check all the plug wires.

Thanks.

[Speed Density]

The light on means its throwing a code, what year is it?

[NitrousJunkie]

It's a 94.

Went over, checked the plug wires going to the plugs, they all seemed snug.

Went to start it up and it fired right up, few seconds later the check engine light came on.

WTF! LoL

Anyways I'm going to try and scan it again tomorrow and see where I can stand I guess, If I get a code I'll be sure to post it.

[gregrob]

Like on ls1tech I believe its the opti, but if you would take the time to diagnose it, you would know.

Sounds like the opti got some moisture and quit, then dried out enough to let it fire again. 94 is non vented so I bet you could see signs of this on the cap and rotor. They might even be visibly burned from arcing due to losing contact because of the moisture.

Good luck,...

[NitrousJunkie]

Yeah I'm going to check all the voltages tomorrow as mentioned in the sticky on Cz28.com, that should narrow it down but I'm thinking its the cap, we shall see.

[NitrousJunkie]

Scanned It.

Got two codes at first, one was a code 48 which is the MAF, I re-tightened everything up and cleared the code and scanned again and it was gone but I also got a code 29 which said EAS Electrical Fault, when I looked it up it said this.

Secondary air injection pump circuit voltage was wrong for 26 seconds.

Isn't this the air pump used for emissions?

All the Emissions are going to be taken off when I replace the water and PS pump this weekend.

But how would this stop it from starting? Unless that was the MAF Problem, but it still doesnt explain why it doesnt start after it rains or when the humidity is high....I'm still thinking cap, I need a voltage meter to test the wires, have to buy one though.

[NitrousJunkie]

Got rid of the MAF code like I said, just had the code 29, took it around the block and got about halfway and floored it and it died on its face, obviously that can't be the emissions crap.

Going to try and find a volt meter tomorrow to test the opti and go from there.

[crows93z]

yup... welcome to my past 3 weeks of trial and error hell. i fixed what was throwing codes, and nevertheless, it still runs like ass. now there's something wrong that isn't throwing a code... so that's cool.

[Louvit]

does the air pump work on motor vacume? may be a major vacum leak

[dubonous9c1]

I've got a 95 lt1 9c1 and am having the same problem.... All signs said opti so i changed that out and the car started but still has the crank time... 3 to 4 secs and it will turn over.:taz: so checking the MAF out and going to check my codes tomorrow. Try tracing the vacuum lines from opti and see where they lead you.