Generation IV Internal Engine - ls2 402 won't start, Help!

Hey guys I am having more problems with my 402. I had my car tuned last month by Rapid Motorsports and I have been having trouble getting it to idle. Last weekend it got worse and now it won't even start. Here is what I have tried so far with no improvement. I have changed 02's, IAC sensor, TPS sensor, spark plugs and drilled the hole bigger in the NW throttle body. After I swapped out the plugs the car fired up and seemed to be running fine until I tried to restart it while it was hot. I let the car cool down and still it wouldn't fire. Out of desperation I unplugged the MAF and it fired right up but it would not idle. I shut the car off and swapped out the MAF and it fired right up. Once it got up to operating temperature I shut it off and tried to start it but got nothing. I am completely stumped. Anybody got any ideas?

stupid question, but did you swap the wires on the cam sensor?

stupid question, but did you swap the wires on the cam sensor?
Yeah, I ran into that when I first installed the motor. The car ran fine for the last month except for the wondering idle.

crank position sensor.mine just did the same thing.but that was my car and sensors are expensive.

crank position sensor.mine just did the same thing.but that was my car and sensors are expensive.
Did your car throw any codes or did you find that through the process of elimination?

What do your plugs look like? Are they clean or carboned up?

-Geoff

What do your plugs look like? Are they clean or carboned up?

-Geoff
My plugs look clean as long as it starts.

Chris, let's try an SD tune. Maybe something with your MAF.

Mikey

You say it only dose it after it is hot?
Correct me if I am wrong, I believe the Coolant temp sensor adjust timing for starts as well?
This might be something to look at.

Chris, let's try an SD tune. Maybe something with your MAF.

Mikey
I wouldn't be apposed to a SD tune but could that still be the problem considering I swapped in another stock maf with no change? I am going to go over the intake one more time tonight and see if I can find a vacuum leak. I am debating swapping my ls6 intake on to the motor to see if that helps.

You say it only dose it after it is hot?
Correct me if I am wrong, I believe the Coolant temp sensor adjust timing for starts as well?
This might be something to look at.
It doesn't only do it when it is hot. It just gets worse when the motor is hot. I may try the temp sensor if I don't find anything wrong with the intake. Thanks

Before you spend money on parts you need a engine scaner. You need to check for trouble codes first. Then you need to see what type of data you have on the scaner. With out knowing this you might get lucky and buy the right part or spend money you don't have to. Drop me a line if you need help or just send some of that money you would spend on parts you don't need

Before you spend money on parts you need a engine scaner. You need to check for trouble codes first. Then you need to see what type of data you have on the scaner. With out knowing this you might get lucky and buy the right part or spend money you don't have to. Drop me a line if you need help or just send some of that money you would spend on parts you don't need
Ha Ha. I do have autotap and my car is not throwing any codes. As far as data, most things look ok to me but I'm not completely sure what all of the readings are supposed to be exactly. I don't know exactly what the maf and map readings should be. Anybody know what range they should be in?

Just to clarify:
* The car starts on *initial* cold starts, but does not start on following warm/hot startups.*
* The car started and idled fine at one time, but the problem has gotten progressively worse.

A couple of things to check:

* Verify fuel pressure is 55-60 psi at cold start and warm start. Should be the same.
* Using Autotap, verify rpms are showing when cranking the engine.
* Check the 3 Afterstart Enrichment Tables (based on ECT) in the tune. These control fuel right after start up. I doubt this is it, but at least worth checking.
* With the engine cold, Check the ECT temp and compare it to the IAT temp. There should be no more than a 5 degree variance between the 2. A faulty ECT sensor can force the COT (if enabled) to cause hard starting.
* Does the engine crank fast? Verify battery voltage.

Intermittent problems are hard to diagnosis and pinpoint. The only consistent part is the problem gets worse as the engine gets hotter. So obviously heat is the culprit.

Just to clarify:
* The car starts on *initial* cold starts, but does not start on following warm/hot startups.*
My car will not start at all now. Occasionally it will start but it is very random.
* The car started and idled fine at one time, but the problem has gotten progressively worse.
The car started great at first but the idle has never been perfect. This problem started about about 400 miles into the break in period.
A couple of things to check:

* Verify fuel pressure is 55-60 psi at cold start and warm start. Should be the same.
Checked out fine
* Using Autotap, verify rpms are showing when cranking the engine.
Checked out fine.
* Check the 3 Afterstart Enrichment Tables (based on ECT) in the tune. These control fuel right after start up. I doubt this is it, but at least worth checking.
I do not have tuning software to check this.
* With the engine cold, Check the ECT temp and compare it to the IAT temp. There should be no more than a 5 degree variance between the 2. A faulty ECT sensor can force the COT (if enabled) to cause hard starting.
This seemed to be working fine.
* Does the engine crank fast? Verify battery voltage.
I have a brand new battery so the motor turns over fast but does not even try to start hot or cold.
Intermittent problems are hard to diagnosis and pinpoint. The only consistent part is the problem gets worse as the engine gets hotter. So obviously heat is the culprit.

Recently I have checked the intake for leaks again and checked everything on this list. I replaced the crank sensor but that did not help. I checked for spark at the wires and used a noid light to make sure that the injectors were firing and everything checked out. I changed my plugs again which were soaked with fuel again from the hard starting but that didn't help either. Any other ideas? I am getting to the point that I feel like selling my car.