Running rough then stalls

[grantf]

You're trouble seems different than mine but you do have the same car and you're symptoms seem similar. Perhaps you're vacuum leak is from a bad manifold gasket??

[garretthes]

I don't think I have a vacuum leak. Isn't there something else that could cause low vacuum?

[garretthes]

Finally got my fuel gauge hooked up today after a trip to Ace. I had 3 pounds of pressure in the rail. No wonder it wouldn't run. Pulled the fuel filter off (again) and poured the contents into a bowl. You can see what it looked like. I decided to drop the tank. After I got it out I pulled the sending unit out.

OMG

It was totally corroded. The tank is full of sludge. It never had a chance.

So I pulled the sending unit from the parts car. It looked great! The tank looked great! Pulled the tank off the parts car and was cleaning it up when my wife noticed a small hole.

Great.

So now I'm patching the hole.

Hopefully I will get it all back together tonight.

[garretthes]

Well I solved the low fuel pressure problem (gas tank sludge) and replaced the bad injector. It still runs rough though. I'm hoping it's the plugs. I'm picking up a set of NGK plugs tomorrow. I'm praying this fixes it because I'm out of ideas.

As of Tuesday I will have been working on this car 1 year. I REALLY want to let my daughter take it for a spin.

[garretthes]

Installed NGK plugs and it still runs like crap! Running rich, blowing black smoke. And what's VERY frustrating is injector #4 is not working! I just pulled the fuel rail and replaced #1. This is insane

[garretthes]

OK, false alarm, the injector is now working. But it is still running very rich. I took it for a drive around the street and it runs strong, just rough. That's promising.

[garretthes]

So here is what it's doing now: Cranks OK but idles VERY low. It basically lopes along at 500rpm. The exhaust smells like gas. It runs rough at idle and higher rpm.

I have ruled out the AFM, cold start injector and all the electrical connectors have been cleaned. After replacing the plugs then running it a few minutes I pulled one of the plugs and it was black and damp. What to check next?

[240260280z]

Maybe clogged return line is driving your fuel pressur up?

Used compressed air to blow out lines back to tank.

For some reason you have too much fuel. The only causes are high fuel pressure, wrong size injectors, or EFI system not working. I think you checked all of these?

[Zed Head]

I looked back through your thread but don't see an actual fuel pressure number with the fuel pump running, only the "3 pounds" number (not really sure what that means either). Have you measured it? The stock fuel pump can, according to the FSM, pump up to 64 psi before the internal relief valve lets go, and the typical aftermarket pump will pump up to 90 psi. That is a lot of extra fuel. The factory spec. is 36 psi. If you have a blockage you could have some high pressure.

One other possibility is a blown FPR. The diaphragm can tear and the engine will suck unregulated gas straight through the vacuum port. You will see gasoline in the hose from the FPR if that was the case.

Just thought of one more possibility - if you connect the fuel rail up backwards, the FPR will act as a blockage, causing your fuel rail pressure to increase to the maximum the pump can put out.

[garretthes]

Sorry guys. I must have forgot to post the fuel pressure. It's running at 30-32 depending on engine speed. When I disconnect the regulator vacuum line it pops up to 34 so it appears the regulator is working properly. There is no gas in the vacuum line.

Also the vacuum is running low. It's between 5 at rough idle and 13 at higher rpm.

I'm wondering if the injectors are dirty and staying open too long. We had the car running well BEFORE I drove it the first time. I'm guessing the drive shook up some of the crud in the tank (there was a LOT!) and caused the filter to clog. I'm also guessing some of the finer crud got through and has clogged the injectors.

So today I'm getting another bottle of seafoam to add to the 4 gallons of fresh fuel in the tank. I will run the car again for 15 minutes or so and see if it doesn't improve. If not, I guess I should get new injectors.

[garretthes]

Also, watched the fuel pressure gauge. Runs at exactly 30 then as soon as you shut it off it pops to 25 but doesn't move, even after a few minutes. I'm thinking there are no leaky injectors.

[Zed Head]

It's not very common but the ECU can go bad. I had a spare that I tried out just to make sure that it was good (it wasn't), it ran well for about one mile, then started cutting out and running very rich. Then it killed the engine and only started a couple more times, dying quickly each time after it started. I put the original "same part number" ECU back in and the engine was right back to where it was before I put the funky ECU in.

I've also read at least two accounts of a sudden "running very rich" problem being solved by banging on the ECU or wiggling the ECU plug.

As I said, uncommon, but a possibility to consider.