OK guys, heres my situation, I need advice.

I put in a cam about a week ago and its been running pretty good since with the exception of an oil leak. I had noticed a little part throttle stumble but no WOT stumble.

We took off the intake and oil pan today to replace both gaskets, and buttoned it all back up... fired right up, took her for a test drive. All systems seemed good but the part throttle stumble was pronounced in the cooler night air.

Got back after a few WOT blasts to check for leaks... didn't find any leaks. We claim victory and clean up the garage.

So then I go to leave... I make it 10 feet out of the driveway... I feel the stumble again, the car surges, then stumbles, then surges, then outright dies. I coast to a stop and push it back into the garage. We screw around with stuff checking for unplugged crap. All fuses are good, no vacuum lines unplugged, everything seems normal... just no start.

Mechanically it sounds perfect when cranking, no discernable sound that is out of the ordinary. Oil pressure was perfect when it died. What puzzles me though is that I seem to be getting some spark when I get a plug wire to arc to the head or something. Just no start. At all.

I'm kind of confused... it doesn't seem mechanical. I can smell fuel I think. It doesn't even sound like it tries to catch. I'm going to take the valve covers off tomorrow to make doubly sure I didn't loose like... a rocker arm off the stud... or something like that. But honestly it seemed PERFECT, then stumble, die.

Opti is around 30,000 miles old and was installed w/ the crate motor.

Can an Opti cause behavior like this??? 300 trouble free miles w/ the cam and then just... won't start.

 

Car started this morning but ran like crap generally.

Replaced the opti today with a brand new AC Delco unit...

Started the car up... seemed to run perfect in the garage and at idle. Bled the coolant system and got her warmed up. Started backing out of the garage, got out onto the street, and it sputtered and tried to die, just like before. I limped it back to the garage.

We changed the ICM with my old AC Delco unit that I had replaced as a matter of troubleshooting in the past, no luck.

Unplugged the MAF, no luck. Unplugged the MAP, no luck. Swapped back to my original OBD2 PCM, no luck. Checked all vacuum hoses, everything. Nothing seems out of place. Don't have a coil to try but could a coil do this? It only seems to want to die under load. I just don't understand because of how rapidly it died.

Could it possibly be the coil? Everything with the car sounds fine mechanically. I don't know what else I could possibly replace ignition wise aside from the engine harness maybe being screwed up.

Someone please help me, my car is stranded!

 

TTT someone please help my car is stranded and I have to move it/tow it soon!

 

I'll just throw some stuff at ya to try since it's hard to diagnose a car over the net. Is fuel pressure good and steady, is your fuel filter good, are your ground wires good, what color was the spark when you tested it,wiggle the wires around on the ign module etc, see if they are compromised.

Does it surge then die or just begin to run crappy then die?

 

I will check all those things....

The ground wires are good as far as I know, they appear to be fine.

It surges and stumbles. If I really try I can keep her running enough to limp back to the garage. Then if I just let it idle it will stop stumbling and run seemingly fine. Just under any kind of load it screws up.

What really confuses me is that it ran PERFECT even at WOT about 15 minutes before this all started.

 

Does the water temp have any bearing on it? does it behave different warm as oposed to cold?

 

Id check fuel pressure if its getting spark.

 

Well it seems like its related to temp but then again we never get it out on the road right at startup. I do think it does run crappier up to temp though, but not perfect still when cold.

As I said it does idle. It starts and idles and it sounds perfect. You just can't drive it.

I will check fuel pressure as soon as I get a guage.

Could my plugs be fouled?

 

It would take some really fouled plugs to not start, You didnt happen to change injector size did you?

Are your sparkplug wires all in the right spot? Is your MAF in backwards or damaged?

are all vacuume lines in place? Just a rundown of everything basicly...lol

 

Well the car does start now. The problem with all those theories is that the car ran PERFECT, it screamed at WOT, then I parked it. Didn't touch ANYTHING under the hood. Cleaned up the garage, and then it started and then died within minutes. It isn't that something is plugged in the wrong spot because it wouldn't have run right the first time.

Anyway, my friends car refused to start because of fouled plugs once... but I'm just lost on how they could fail that fast. Something has to have physically broken or something.

 

Have you checked your O2's? On a cold start it would run OK, but once it goes open loop (ie, warms up) they can cause the car to die.

 

I will check the O2s as soon as I get back to the car today.

 

AHHHHHH ITS FIXED!!!!!!11one

Broken engine temp sensor on the water pump getting intermittent contact.

Running without it for now, fans run constantly but it RUNS.

 

Good to hear that you found it. The sensor is only about 15$ so I would replace it soon. What youre car is doing now is running in limp home mode.