98 Cobra starts but dies immediately - Help needed

[5.0calypso93lx]

5v? Reread my posts then.

TPS was initially 1.01 on the middle signal wire. Adjusted it and now I'm right at .99. Full 5v on the brown power wire.

 

[ar_snl]

Ill note the issues i had that caused this.
My TPS was faulty. It was causing the car to spit more fuel and back fire.
My MAF was messed up. I unplugged it and it ran. Not great but i could keep it idling with some throttle.
Check your IAC. There are two different brands of IAC valves. They are different from each other. The holes are opposite from what i read on identifix.

 

[ar_snl]

Check that the idle screw on your throttle body is 2 1/2 turns open. And lastly drain your gas and add fresh gasoline.

 

[5.0calypso93lx]

It was a combination of a couple things. I had a big vacuum leak on the intake lid adapter. I also got a known working throttle body and a new Motorcraft TPS. Car runs great now and made 318whp on dyno

 

[ar_snl]

It was a combination of a couple things. I had a big vacuum leak on the intake lid adapter. I also got a known working throttle body and a new Motorcraft TPS. Car runs great now and made 318whp on dyno

I have a question abou the theottle body. Does the throttle bosy have a hole on the middle bump? Because i am using a mach 1 throttle body I think and it doesn't have that hole and it might be a problem.

 

[5.0calypso93lx]

I have a question abou the theottle body. Does the throttle bosy have a hole on the middle bump? Because i am using a mach 1 throttle body I think and it doesn't have that hole and it might be a problem.

I am running a TB from a 96-98 without the hole. I know which one you're referring to. You need the TB that matches whatever lid you're running so if 96-98 lid like me you need a 96-98 TB. Had a buddy running a 96-98 lid and had idle issues with a C head TB. He swapped to a 96-98 TB and issues went away.

 

[ar_snl]

Thanks for that reply. I had noticed when i open the idle screw, it will turn on but after a couple seconds it will idle up to 2k rpm. If i have it adjusted, it will not turn over. Ill make sure to get that throttle body.

 

[5.0calypso93lx]

Thanks for that reply. I had noticed when i open the idle screw, it will turn on but after a couple seconds it will idle up to 2k rpm. If i have it adjusted, it will not turn over. Ill make sure to get that throttle body.

One thing I found interesting on Accufabs TB instructions for these cars was that if the set screw had been messed with whatsoever to have it sent back to Accufab for recalibration. I knew I had messed with my stock TB set screw so I found a different TB that hadn't been touched. Not sure if that was the difference or not, but something interesting to note

 

[ar_snl]

The gasket i have for the throttle body does not have a cut out for the little air holes that tha throttle body has. Most likely my problem. im gonna cut it out or get a new gasket and see how it goes.

 

[shelbycobra]

not sure if you are having the trouble still but when i installed the same jlt cold air you did on my 96 cobra mine did that would rev up then die i took it off and put my old one back on and starting running good just sayin

 

[5.0calypso93lx]

not sure if you are having the trouble still but when i installed the same jlt cold air you did on my 96 cobra mine did that would rev up then die i took it off and put my old one back on and starting running good just sayin

It ended up being a combination of a throttle body with a set screw that had been messed with, vacuum leak and / or a TPS. Car runs great now with that CAI and made 318rwhp on the dyno

 

[freebird50]

I am officially stuck

I've got a 98 Cobra that I recently built an engine over the winter. The full details can be found in my build thread on here, but a quick recap:

98 Cobra
-4.6 4v Teksid block with forged bottom end
-DB Casting C heads with 98 Cobra Cams
-Mach 1 Intake manifold with adapter plate running stock upper lid and stock TB
-COP swap (went back to stock coils and plug wires to eliminate the COP's. Zero difference going back to plug wires)
-Fore fuel rails with Fore FPR
-JLT CAI with stock MAF (and SCT BA 5000 MAF, I've tried both)

That's all I can think of at the moment.

What the car is doing:
-I did break the clock spring and have an airbag light (new one is enroute). Because of this car would initially not start. Just cranked and cranked. Tuner sent me a revised tune file with the PATS turned off and the car will now do what I have typed below
-Will crank and lightly hit but won't start 9 out of 10 times
-Every great once in a while the car will hit, start, rev up to 3k (sounds amazing) but then immediately dies. This makes me think there's no mechanical issue with cam timing, etc (had all brand new OEM timing components installed by a very well-known, pro local engine builder that has done a ton of these)
-I, at one point, was able to get the car running with the MAF unplugged for about a minute, but it eventually died
-Plugs are covered in fuel. They were brand new.
-White smoke coming out of tailpipe after cranking car that overwhelmingly smells of fuel. Car will backfire loudly every now and then like there's a ton of unburnt fuel in the exhaust that ignites
-I have the battery ground cable going down to the driver motor mount stud and then from there to the brake line bracket on the driver side. Verified with a multimeter that I have .9-1.2 ohms when I touch the alternator housing and the battery ground pole

The car ran and drove before I did the built motor over the winter. It was down on power, but it ran and idled. Has a brand new 255lph stock style (funky 98) fuel pump and new fuel filter.

I have to be missing something. What should the vacuum lines look like? What should the grounds look like? Any other suggestions?

One of my o ring seals for my imrc deletes popped out and caused a very similar issue.