1998 vortech cobra will not idle and die suddenly

[freebird50]

Hey guys. I thought my alternator was bad but I guess I have another issue here. Went for a drive and all was fine. Then I pulled in my driveway and my car suddenly won't idle and it just dies unless you give it throttle. It runs great when you give it throttle. It was like a switch being turned on. Problem happened suddenly. Any way here are the things I have investigated or changed all to no avail. Vortech supercharged.

Replaced alternator

Replaced 02 sensors the ones to the computer

Replaced my plug to my MAF because it had some corrosion.

Tightened all intercooler pipes

Checked for vacuum leaks

Checked fuel pressure

Checked all fuses

No codes

No exhaust leaks

Any other suggestions I can investigate? Thank you.

 

[96dreamer]

Have you tried diagnosing anything instead of just throwing parts at it? That can get costly very quickly. A sudden change to idle that is remedied by giving throttle would point to the iac to me. Could be stuck open/closed.

 

[freebird50]

Have you tried diagnosing anything instead of just throwing parts at it? That can get costly very quickly. A sudden change to idle that is remedied by giving throttle would point to the iac to me. Could be stuck open/closed.

Replaced that. Took it back to store after it didn't fix my issue.

 

[2003RedfireVert]

You need to look at some data and do some proper diagnostics. I wonder what the fuel trims are doing, I wonder wha the MAF is reporting, I wonder what the IAC duty cycle is doing, I wonder what the O2 sensors are reporting, are the fronts switching properly, what’s fuel pressure, etc…none of us will or can help until you get some data. I good scan tool that can view live data is needed here.

 

[freebird50]

You need to look at some data and do some proper diagnostics. I wonder what the fuel trims are doing, I wonder wha the MAF is reporting, I wonder what the IAC duty cycle is doing, I wonder what the O2 sensors are reporting, are the fronts switching properly, what’s fuel pressure, etc…none of us will or can help until you get some data. I good scan tool that can view live data is needed here.

I don't have a good scanning tool

 

[freebird50]

I don't have a good scanning tool

I'll just go to my mechanic I guess. Just so far I live in the middle of nowhere

 

[2003RedfireVert]

This sounds like a classic vaccuum leak but hard to tell not being there.

 

[bird_dog0347]

Will it run better if you remove the supercharger (or just the belt)?

 

[freebird50]

Will it run better if you remove the supercharger (or just the belt)?

Have not removed the supercharger or belt. What could that mean if it runs better with no belt?

 

[bird_dog0347]

If you remove the belt it simply removes a variable and allows you to focus on trying to find the root cause.

 

[96dreamer]

Did you check all the grounds, bad/ intermittent connection can cause goofy issues.

 

[dan1982]

If you remove the belt it simply removes a variable and allows you to focus on trying to find the root cause.

I Would just remove the engine and replace with a 632.

 

[03cobra#694]

I Would just remove the engine and replace with a 632.

Why are you always a douche? Getting close to a long term vacation.

 

[freebird50]

Why are you always a douche? Getting close to a long term vacation.

My 4.6 will smoke your 632. Get out of here.

 

[dan1982]

Why are you always a douche? Getting close to a long term vacation.

its a joke. In this particular case, it was suggested in another thread that this particular car has electrical woes or an underlying issue. he burnt up 5 alternators. FIVE. They ran 26 pounds of boost through it and it made 670HP, or somewhere in the 600 range. He is gonna bring it back to his mechanic that set it up originally. It most likely has an issue that the original mechanic never found, power should have been higher. Nobody has suggested a good shop local to him. Its in DIRE need of good diagnostic work. Sometimes the solution is right there in front of them but the OP doesnt want to find a shop more suitable to intricate diagnostic work.

 

[freebird50]

its a joke. In this particular case, it was suggested in another thread that this particular car has electrical woes or an underlying issue. he burnt up 5 alternators. FIVE. They ran 26 pounds of boost through it and it made 670HP, or somewhere in the 600 range. He is gonna bring it back to his mechanic that set it up originally. It most likely has an issue that the original mechanic never found, power should have been higher. Nobody has suggested a good shop local to him. Its in DIRE need of good diagnostic work.

Jeeze this is getting annoying. When I was making around 17 pounds of boost I went to my tuner and the car made 507. Then I actually did take it to AED and changed nothing and I made 590. My car is not slow and it doesn't have any major problems Jesus christ. I bet if I were to go to AED id put down almost 800. And when I have the time and money I'll do that to verify and I'll post the results.

 

[dan1982]

Jeeze this is getting annoying. When I was making around 17 pounds of boost I went to my tuner and the car made 507. Then I actually did take it to AED and changed nothing and I made 590. My car is not slow and it doesn't have any major problems Jesus christ. I bet if I were to go to AED id put down almost 800. And when I have the time and money I'll do that to verify and I'll post the results.

i know u invested alot of money into this and respectfully, it needs to be put right. Probably something small, but sometimes the small stuff really matters. SOMETHING burnt up those alternators. Its probably had a small electrical issue since day 1. it happens. Hopefully someone chimnes in with a shop that has a real good eyeball. The 632 thing was JUST a joke. I didnt mean to be insulting. Hopefully some resident experts back me up here and point you in the right direction. For YOUR benefit. They have some real hardcore cobra guys here, but diagnosis by svt post is often impossible.

 

[freebird50]

i know u invested alot of money into this and respectfully, it needs to be put right. Probably something small, but sometimes the small stuff really matters. SOMETHING burnt up those alternators. Its probably had a small electrical issue since day 1. it happens. Hopefully someone chimnes in with a shop that has a real good eyeball. The 632 thing was JUST a joke. I didnt mean to be insulting.

I replaced my alternator and it wasn't the problem. It has lasted 2 years so far with a 3.2in pulley. I replaced it because I thought it could of been the problem but it wasn't. Dumb of me to shotgun parts. I appreciate you were joking though so thanks.

 

[freebird50]

I replaced my alternator and it wasn't the problem. It has lasted 2 years so far with a 3.2in pulley. I replaced it because I thought it could of been the problem but it wasn't. Dumb of me to shotgun parts. I appreciate you were joking though so thanks.

And this idling problem started just about a month ago. Made an appointment with my mechanic to diagnose it and see.

 

[98 Saleen Cobra]

Why are you always a douche? Getting close to a long term vacation.

So he's not really being a douche, the man has a point.. I'm not going to throw this kid under the bus to hard, but he has multiple thread, multiple issues that I've pointed out and has been ignored. He has thrown apparently 5 alternators. I have given this kid advice from literally 20+yrs of messing with these cars WITH a vortech on it. 26psi on 670 or whatever hp. Says his car is fast and is making more etc. I know Nexgen I know he's mainly a Chevy guy as well. I've seen approx 0 fast mustangs out of that shop personally. I recommend he take it to Shawn at AED, but at this point I'm about to call Shawn and warn him of this car.

Still like to go to Shawn one of these days hopefully soon. To verify output. Smoked another alternator too I've been through like 5 of these things lol. I tried js alternators but they don't make one for the 98s nor does nations or anyone I can find. But other than that the car seems ok. Trip to aed will happen when I have some time. And a few extra bucks.

Brother I'm going to tell you this one last time, and really I'm going to just stop giving advice after this lol. Stop driving the car. There is something wrong with it. Alternator issues, boost to HP doesn't make any sense, car is now dying. Tow the car to whatever shop you want to diagnose it.

Pull the plugs and check them if you want. Make sure you didn't torch a cylinder. Again stop driving the car.

I'm done with advice lol.