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Discussion Starter #1
Ok i have around stock terminator CR with 8.5.1. I have a 99 cobra and the motor is brand new. I have a battery light on. I plug in the battery charger and leave it on. I start it up and everything is good. I will run for 2 days straight if i want. Then if i shut it off and try to start again its really hard and sometimes it wont start even with the battery on the charger.

Heres the kicker. I know if you hold the gas all the way down it kills the injectors. Lower CR needs more spark. It will start like this but hesitate upon starting.

So will a tune fix this?

My spark plug gap is .025 i believe and thats what i need. if i remember right.

Only thing other than that i could think of is maybe the alternator is bad? idk. I pops alot on idle but i believe its because its tuned a little rich and the pistons havent seated yet.
 

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That's an awfully tight gap, that will produce a tiny little spark--the factory spec is 0.052" to 0.056"...
 

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could be just a dead cell in the battery..... or starter bad? also gap the plugs between .30 and .35
 

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Discussion Starter #4
I took the battery out of the mustang and put it in my jeep no issues whatsoever. I tried taking the mustang for a ride. Heres the weird thing. It will idle for hours with no problems. But when i tried driving down the street it would die every 100 ft. Then i would jump it and it would die again.

Its cranking fine so i dont think its the starter. While i was on the side of the road. I could turn the radio on and a/c and lights on and they all worked good and were not dim.

O and the car jerks and sputters erratically.

Battery and check engine light are on.
 

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Your spark plug gap is to small man. Need to open those bitches up. Gap them at 0.035. You'll actually make more power with a bigger gap. But their supposed to be capped between 0.030 to 0.035. I think that's your problem.
 

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Discussion Starter #6
Well they are the same plugs as before. I didnt touch them. I THOUGHT they were .025 but maybe not. Theyve been in the motor for 2 years and before i built the shortblock i didnt have these issues so i dont think its the plugs.
 

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Is your iac stuck? But it idles okay from what you said. It's when you start driving. Tps sensor working okay?
 

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yeah was just gonna say check your iac and tps....start the car and unplug the iac and if it keeps running then bad...
 

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Discussion Starter #9
Well i started the car and then un hooked the battery and it shut off. So that means bad alternator i believe.

So i spend an hour or so taking my vortech etc off to get the alternator off. I take it to town and it passes twice and o reileys auto parts but fails twice at autozone WTF!!!

idk what to do.

Car idles fine. It just pops and backfires and **** on idle.
 

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Backfiring on idle isnt good, is your MAF dirty or anything? Id pull the plugs to get an idea on how the car is running. While your at it, replace the plugs. Might as well if there 2.5 years old, these types of spark plugs dont last as long.
 

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Discussion Starter #11
Backfiring on idle isnt good, is your MAF dirty or anything? Id pull the plugs to get an idea on how the car is running. While your at it, replace the plugs. Might as well if there 2.5 years old, these types of spark plugs dont last as long.
idk yeah its probably dirty i guess not sure. The plugs were checked while the motor was apart and they looked great ( 30 year for engineer told me i never seen the plugs).

Im not so much worried about how its running right now. My main concern is keeping it running so i can drive it for more than 30 ****ing feet before it dies. :mad::mad::mad:


A buddy of mine that builds motors told me that the alternator is probably bad and its having voltage spikes making the car run like **** but idk.

It doesnt so much really backfire just loud pops. I mean this is a brand new motor with 0 miles. The pistons are not seated yet so maybe its normal.
 

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If the car is popping at idle, It must be either a missfire, or a fuel issue. An overly rich condition will cause that, an overly lean issue would cause that. If you dont have a wideband, I would do some datalogging. I would look at your short term fuel trims. Check MAF counts, fuel pressure at the rails. Etc...
 

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Discussion Starter #13
lol dude i dont have a scanner, a tunner, a wideband, or anything. Only thing i have is my two eyes and a boost gauge.

It does have brand new injectors but they are the same flow matched 42lb injectors.

My maf might of got destoryed i guess. When the motor was out. I took a sheet of cardboard and put it over the intake tube in the fender. Then i put a few rags over it and power washed the engine bay. Maybe it got wet idk. I cleaned the IAC like 2 months ago.
 

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yeah its underneathe by the transmission.

You can datalog with your handheld. Dont need a laptop, itll just show on the screen.

I would check for any ripped wires by the MAF/TPS.
 

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Discussion Starter #16
yeah its underneathe by the transmission.

You can datalog with your handheld. Dont need a laptop, itll just show on the screen.

I would check for any ripped wires by the MAF/TPS.
i dont have a handheld or anything at all man.

Yeah tomorrow im going to trouble shoot. My guess is the MAF/TPS has nothing to do with dieing randomly though.
 

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Oh **** no handheld? Damn. Anyone that you know that have one?

If the car isnt staying running, the TPS and IAC definatley could have something to do with it. Idk though, its hard to say. Good luck man, hope you get it figured out.
 

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Discussion Starter #18
It will run for days at idle. But i drove about 4 miles and then it shut down. Then it would shut down every 60 feet. The longer i left the jumper cables on it the longer it would go without dying. I dont think it has anything to do with the TPS or IAC. Like i said if your just idling and not moving it will run for 2 days straight without dying.
 

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I'd start double checking all your electical connections (especially the grounds).

sounds like an electrical issue.
 
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