Fpr ?

[Todd]

I'm having engine problems and from what I have read from searches leads me to think it may be the FPR. The car is hard to start, especially when hot. Most of the time I have to floor it to clear the injectors. After it starts it misses for 5 or 10 seconds before i smoothes out. Then when I'm driving down the road at 1500 to 2000 rpms it tries to die by stuttering. If I wasn't rolling it would. The idle goes up to 3000 and will stay there sometimes for a short amount of time. Sometimes longer. If I'm at a red-light it will rev to 3000ish and then die. At this point is when it is the hardest to start. Sometimes taking a couple of green light cycles to get it going again. Very frustrating in heavy traffic. When it does start, you can smell the gas.
I have an 84 with the 255 upgrade with stock FPR. I also still have the inline pump hooked up..
How can I find the problem???

[Gator]

The idle problems tell me that its your IAC is gunked up and that your TPS is out of adjustment. Not running/starting when its hot throws me for a curve....but if the TPS is way out of whack....it can actually cause a car not to start ( But it happens regardless of temp.)

I would check those first, and run some codes on it before buying things.

Usually 9 times out of 10....when a FPR goes, you can unplug the vac line at the top and gas will squirt out.

[JonProphet]

Did I read somewhere if you go to a high pressure 255 lph pump, you need an FPR? Something about the stock FPR can't handle that much pressure? Could be wrong.

-JD-

[DAVEZ84SVO]

Todd, my 84 has the 255 lph pump with a motorcraft factory FPR.. I've had no fuel issues with this combo.. I was told that unless you have some serious mod's that the factory FPR is just fine.. I would also tell you to toss the HP factory pump.. If it is bad, like it is putting out low fuel pressure, I don't think that the big pump in the tank is going to over ride the HP one.. Understand?? So as Mike said, the lack of fuel when hot will cause the hard start..

How does it run when cold?? Start on first twist of key when cold?? Or does it take a little bit?? Check the wiring.. 84's are known for having cr*p wiring.. I found a lot of wiring issues on my car.. & it has been sitting since '91..

Good luck.. Dave

[DAVEZ84SVO]

Did I read somewhere if you go to a high pressure 255 lph pump, you need an FPR? Something about the stock FPR can't handle that much pressure? Could be wrong.

-JD-

I don't think that it runs at a higher pressure, just puts out more volume.. Although I have been wrong from time to time, that is how it was explained to me..

Dave

[Todd]

The idle problems tell me that its your IAC is gunked up and that your TPS is out of adjustment.

That was my first thought so I'vee cleaned the IAC and the tps with KOEO is spot on at .94 no throttle and 3.72 WOT.
Fuel pressure is 38 with KOEO. I haven't let it set for 20 min yet but it held for a few min. I'll check that and drive it with the pressure gage on and see what happens
Starts easier when cold, runs better when hot, like after 30 or 45 min.
Could it be the inline pump?
All ran fine until recently and then this started. Then it cleared up for a few weeks and now it's back with a vengeance.
Mike, could low fuel pressure cause it to idle at 3000? It will actually push you down the road. I either have to ride the brake or find a gear that will run the speed limit at 3 grand. And then the idle will drop and I go through the whole cycle again.

[NY eric]

All ran fine until recently and then this started. Then it cleared up for a few weeks and now it's back with a vengeance.

How much fuel do you have in the tank? We had a few members that would have sputtering problems @1/4 tank but full tank no issues. Just curious?

[SVOeric]

BTW :: The stock FPR can handle the volume of the 255.

I can't think of a good reason to keep the in-line pump connected, but I wouldn't think it wouldn't cause major issues...

[leadphinger]

My v8 used to do the same thing...

Check and replace your fuel filter if you haven't already

[XXXXXXXX]

I had the hot start problem with my 84. I followed what mike said. I found my fuel pressure dropped after I shut the car off. I replaced the filter and inline pump with a new bosch. 119 bucks. Starts right off the bat, every time now. X

[Todd]

Ok. Here is the latest update of things I have done.
1 Cleaned IAC= no change
2 Replaced IAC with another I had= no change
3 Cleaned that Iac= nochange
4 Visually inspected IAC and TPS wiring back to where it's combined w/ other wires in the harness, found a bad spot on TPS wiring and fixed= no change
5 Changed FPR= no change
6 new fuel filter= no change
7 Unpluged inline pump= no change
8 TPS base @ 0.88 WOT 4.72 (engine off). Checked with engine running and it stayed @ 0.88 even when idle went up to 3 grand
9 Different dizzy= no change
10 Changed plugs and wires (#1,3 and 4 were uniform #2 was wet and nasty)= no change
11 Checked injector harness from plug to injectors and it show good conductivity
12 Checked fuel pressure, KEEO 38lbs held same for over 30 min. with engine running there was no fluctuation in pressure when idle went to 3 grand
13 Changed out the computer= no change
Is there an easy way to check for a bad wire without taking apart the wiring harness? This thing is going to put me in a home for the mentaly insane

[svobrown]

Check the o2 sensor, EGR, change vam, or just drive the LX of James and kick his butt on the track.

[under pressure]

Have you tried another coil? Do you have a Cat?

[Ernie Orwig]

Is it possible that you might have an air leak after the VAM. If your TPS is not moving at idle then it could idle up. It would do the same thing as a IAC. How do you know that the IAC is not all the way open. I would suggest that you remove the IAC and plug the holes with something that won't suck in and see if your idle settles down. I have a holley EMS standalone and can check the IAC pretty easy. I don't know if there is a diagnostic that checks it or not with the factory EEC. Just a thought

[GAboySVO]

Checked with engine running and it stayed @ 0.88 even when idle went up to 3 grand

I think you found your problem. Get an analog meter and see what the needle does through the entire range from 0.88 to WOT. The voltage should rise immediately with the opening of the throttle plate. At 3 grand, the throttle plate cannot be at the CT position.

Also in your list of things that have been done, you didn't list cleaning the VAM. Do that.