pushrod36

I just got my 2000 LS1 running in my 68 GTO, but there are some difficulties. When I start the car it idles very high (no tach hooked up, but I would guess about 1700rpm). I am assuming that this is some warm up logic in the ECU. The strange part is that when I push the gas pedal it causes engine speed to drop, not increase. My best guess is that I have some kind of a vacuum leak, but that doesn't explain the stalling in my mind. I think that the engine would continue to rev with throttle application if that was the case.

Has anyone experienced this before, or do you have any suggestions? FYI, I also installed a big-ish cam.

Thanks!

IWGF

iTrader: (6)

How big is big-ish? It could be as simple as a vacuum leak, PCM relearn, or it could be tune specific.

pushrod36

The cam is .588/.588 duration is 228 deg @0.05 for intake and exhaust (it's the texas speed 228R cam). The only difference on the tune is I made it 3% rich for safety's sake while I shake it down.

How bad do engines run if the PCM has no learned after a cam swap? I do not have a lot of experience with GM stuff, but I know that Hondas are very particular.

Big Chuk

iTrader: (11)

maybe Throttle Position Sensor?

Damian

iTrader: (89)

You need to get someone to log what it's doing with some kind of tuning or diagnostic software. Too many variables to guess.

BTW, a 228r isn't a big cam.

pushrod36

I did some more testing. If I roll on the throttle very slowly the engine will rev up as it should. This tells me that one of the following sensors is bad: MAF, MAP, or one of the two on the throttle.

I did have to extend the wires going to the MAF because of my intake layout. Is there sensitivity to that? I am going to check those connections, and also try unplugging the sensors one at a time to see if I can force it into a failsafe mode.

Damian

iTrader: (89)

If the MAF fails or is failing it will fall back into VE/speed density mode. This is basically a back up table that the MAF references to for part throttle fueling, but can also control the engine if the MAF is failed completely. The simple way to check if it's the MAF is unplug it and go drive around.

You need to log some data and watch your MAP reading, see what the TPS is doing, etc..Right now you're simply guessing.