robyw1

I think this is the key to fixing your problems. At idle a bad pump can create plenty of pressure to make the mechanic think it is working properly. However I have diagnosed many HP EFI cars fuel pump problems by monitoring the pressure at full throttle. If it drops off when the car is under load it feels like an ignition problem. Trust me on this. Now this problem won't be so pronounced if your EFI system is the throttle body injection. However if it is port injected you can't tell the difference between a fuel or spark problem w/o test equip.

Roby

rchevelle71

iTrader: (1)

NOT EXACTLY 100% TRUE!!!

I had on one once where the catalyst had broken loose, and was just rolling around in the converter, but was in chunks too big to blow thru the pipes. It was fine when first starting, and for a mile or 2, then I guess it would finally find its way up to the exit pipe, blocking it, and losing bigtime Power. Replaced it, and problem gone.

robyw1

I had this problem in my found on road dead Mustang GT. It broke loose and would rattle around making the sound of an engine that was fixing to let go of a rod. I replaced it and it worked fine. After that the engine let go. Oh well Thank you Ford.

Roby

bford1

If you can make a friend at the muffler shop or if you have a welder you can do this yourself.

It is very easy to put a hole in front of the cat and then go run the car (yes it will be loud) and see if it still does the same thing. If it does then it's not the cat and you just weld up the hole and look elsewhere. If it is then the hole can be welded up when the cat is replaced.

It's a pretty easy way to check.

merlin540

sounds like the substraight in the cat has broken loose and gets clogged in the pipe downstream.

rchevelle71

iTrader: (1)

Well, Mine was on a Camaro, so I guess it works both ways!!!

On my Mustang GT, I gutted the cats before even bolting the duals on(it was an '82, only came with single), so I used an H-Pipe, and headers from an '89.

FlyFast

I am really getting kicked here but I have a new clue. I took the car to midas and asked for a new cat. They did a temp test on the cat and said it was ok. I bought a fuel injection tester and ran the pressure tests both key on engine off and engine running. 41 psi key on engine off and 38 to 45psi with the engine running. this seems to within limits.

The car needed a smog test and some are the numbers are really different from last year:
last year this year standard
HC 0.06 0.10 1.00
CO 1.83 7.28 12.00
NOX 1.06 2.10 2.50

The co and nox have really gone up. What does this all mean? The car is still having the same problems.

Thanks

FlyFast

smallpp I changed the erg valve. I will know in a couple of days if it helps.

Thanks