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Discussion Starter #1
I purchased a 90 mustang for cheap a couple weeks ago that came with an 88 (speed density) motor under the hood. I was given a cobra mass air conversion (cobra computer, factory MAF and 24# injectors) and istalled them a few days ago.

When I pulled the old computer I realized it had a chip in it. When I finished the conversion the car fired then died several times and then idled poorly for a few minutes before dying again. The next day the car would not start and I found the (new) plugs were fouled. After I cleaned then and put them back it this has not happened again over the last week or so.

Looking for help I read through the threads on corral and done the following:

1. Cleaned 10 pin connector, tightened connections
2. Set TPS to .95
3. Cleaned IAC
4. Reset EEC overnight

Since doing these things the car will drive without dying after running for about 5 minuted, but it still dies several times while trying to get to the five minute mark generally runs and sounds like sh*t.

Prior to conversion the car idled at 1500 rpms (the computer I took out was chipped), now it idles between 700 - 800 and sounds like it is struggling to stay on. Once the car is moving there doesnt seem to be any hesitantion or surging, but it seems like it pulled slightly stronger before the conversion

The car is fairly stock and the idea behind the cobra equipment (even with it's shortfalls) was a factory idle.

You guys have any ideas?
 

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Was this a 4 banger conversion to a 5.0?

Also, if it was a 88 motor what computer was in it?

If it was a 90 5.0 originally and they put a 88 motor and a 88 computer and didn't change some of the pin outs then there will be issues.

If it was a 90 2.3 and they swaped in a 5.0 from a 88 and a computer from a 88 and the motor is stock it should have run fine. If done right.

I don't think you answer is to try to mess with a cobra MAF conversion before you figure out the history of the car and the motor (unless you know already, please post)

What was the Cobra conversion you did, did you change PIN outs on the computer ect ect.
 

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Discussion Starter #3
you're right - it is a four banger to 5 liter conversion. I just bought the car and have no history other than what I have pieced together.

It is an 88 motor and it ran great outside of the idle being set? at 1500 rpm prior to the MAF conversion. When I did the conversion I changed pin locations for the thermactor pump and I spliced in the VSS signals.

Now it wants to die when I start it unless I give it gas to bring it above 2 grand- when I do this I get what sounds to be a backfire from the exhaust manifold. After running for 5 - 10mins, it no longer dies but struggles in idle (like its barely chuggling along), with minimal rpm hunt.

Is it possible I am running rich due to the increased injector size - I thought the cobra computer would expect this.

I'm at a loss, there are not a lot of performance shops around - the regular shops just want to know why I did what I did and I don't want to drive it to prevent damage.

Any help is appreciated....
 

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Did you run the codes?

Other than that, it looks like a wild goose chase. If the motor is stock, I think you should go back to Speed Density and try to fix the problem, than after you figure out why it idles so high, then do the MAF converstion.

However you may be past that allready.

I think you might want to look into the compatability of the wireing harnesses and find out what ones you have in the car.
I dont' know if the 4 banger dash harness is compatable with a 5.0 computer and 5.0 engine harness.
If its not than that may be your problem.

I'm sure someone else will know.
 
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