Ghost Codes?????????

**kensz28** · 11-08-2010, 06:33 AM

O.K. I know this should prob go in the LT1 section, but I think the codes apply to LS1's as well. My slightly modded Roadmaster [.030 over, alum head, headers & intake] has been giving me ABSOLUTE FITS!!!! The SES light comes on and off. Some mornings is starts good and idles normal, then it might idle high or idle so low it almost stalls .Today at at drive thru it did stall. I had it scanned twice and both times is comes up as #34 mass/map low signal. I cleaned the mass air with brake cleaner and it did have some crap on the wires but it really didn't do anything. I also put another MAP sensor on it and it did nothing. The car has 128,000 miles with 37,000 on the engine. Now I know that the IAC and the TPS work to control/adjust the idle. I have changed TPS earlier before I had it scanned. I also put a junkyard IAC on it and it made the problem way worse. So that's when I had it scanned. Now. I am still leaning towards the IAC. If it's out of range and the idle is affected wouldn't you have low manifold vacum? And, wouldn't you also have low signal at the mass air flow sensor due to the decreased or increased (at idle) amount of air going through it and it doesn't jive with what the ECU has preprogrammed in it? I really don't want to start throwing part at it since most parts stores do not accept returned electrical parts. So, is it the IAC that is my problem here? Causing ghost codes? Or could it be a faulty ECM? Thanks in advance

**kensz28** · 11-08-2010, 04:13 PM

Nobody wants to help me???

**JAKERED08Z06** · 11-09-2010, 08:25 AM

Sounds like ECU to me.
Did you have to jump your car lately? Sometimes a bad battery or low voltage can cause problems.

Just and idea.

**thearborbarber** · 11-09-2010, 01:25 PM

The optispark is the bane of all LT1's.

**kensz28** · 11-12-2010, 07:40 PM

Originally Posted by thearborbarber

The optispark is the bane of all LT1's.

I am leaning towards that too. I also wouldn't rule out the ecu either. Neither are cheap fixes. I can get an ecu alot cheaper than the opti. I can see the opti going bad since it original with 129,000 miles. I can change NP. Today it was idling very erraticaly. Like a bad miss. Guess I'll look into a new distributor.

**thearborbarber** · 11-12-2010, 09:18 PM

My 94 Z28 had opti issues. When it was the least bit damp it would do weird things with missing, wouldn't rev, wouldn't start ect. Not only does the opti fire the plugs but all the engines timing is located in their too.

The LT1 is an awesome engine and the opti is a neat idea but having the spark traces over top of the other wasn't such a great idea.

**Too Fast** · 11-13-2010, 03:30 AM

Also look for any vacuum leak. If you have unmetered air going in the engine, that would show up as an unsteady idle, even a stalling issue, but would not misfire once you get going over ~1500 RPM.

If you are misfiring, that should show up at all RPMs. And yeah, Opti-spark could be the cause, but I'd be looking real close at all vacuum lines, and maybe the intake for a vacuum leak as well.

**kensz28** · 11-13-2010, 05:37 PM

Originally Posted by Too Fast

Also look for any vacuum leak. If you have unmetered air going in the engine, that would show up as an unsteady idle, even a stalling issue, but would not misfire once you get going over ~1500 RPM.

If you are misfiring, that should show up at all RPMs. And yeah, Opti-spark could be the cause, but I'd be looking real close at all vacuum lines, and maybe the intake for a vacuum leak as well.

I'm not finding any vacum leaks. The manifold was resealed a few years ago too. I used to be able to spray the engine off while running but now driving through heavy rain will cause it to sputter. If I spray it when running it will die instantly. My basic question really was could a faulty IAC trip the engine into believing something was wrong with the MAP or MASS AIR. Due to a faulty/poor idle.

**Too Fast** · 11-15-2010, 04:01 PM

^^^No.

There is your answer.

95% probablility your issue is a secondary igniton problem since it only happens with H2O. And from my experience with LT1s, the most likely cause of your car dieing with a water spray is a corroded secondary connection at your ignition coil, the fix would be to replace the coil and the ignition wires.

The engine should not have any issues if the secondary wires/connections are in good shape, when sprayed (not soaked with a huge open source of water, like a garden hose!) with water. I talking about a hand spray water bottle.

Secondary wires are spark plug wire/coil wires, that carry high voltage (not the ~12v) for those who don't know.

**kensz28** · 11-24-2010, 06:16 PM

Originally Posted by Too Fast

^^^No.

There is your answer.

95% probablility your issue is a secondary igniton problem since it only happens with H2O. And from my experience with LT1s, the most likely cause of your car dieing with a water spray is a corroded secondary connection at your ignition coil, the fix would be to replace the coil and the ignition wires.

The engine should not have any issues if the secondary wires/connections are in good shape, when sprayed (not soaked with a huge open source of water, like a garden hose!) with water. I talking about a hand spray water bottle.

Secondary wires are spark plug wire/coil wires, that carry high voltage (not the ~12v) for those who don't know.

Totally understand. I replaced plug wires with some (msd-like) ebay ones, 9mm low ohm performance wires. I replaced module and coil too. I have a spare of both, might change them. I have a new opti/cap/rotor set coming in a few days. It's all getting replaced. As a side note, I used to be able to spray motor at the car wash!!!!!!! Never a problem.