Idle surging, bucking, Lord Help me......

Originaly posted on 5/18/11. I have had this TurboCoupe for three years now. Was surging, bucking, and eratic idle when I bought it. Brought it home and pulled the tank, cleaned it out, replaced the pump, fuel filter and fuel regulator. This problem of eratic idle, surging, bucking usually happens when she warms up after about 20 min. If I shut her down while acting up, she will still act up as soon as I start her even after cooling down. It happens no matter if I let it run in the driveway or if I drive her to that 20 min. mark. So..... over the years I have changed the oil, oil filter, coil, spark plugs, wires, cap, rotor, TFI, PIP, air filter, EGR valve, VAM, TPS, IAC. I had good checks on the old TPS, VAM, and cleaned the heck out of the IAC, but then just replaced the over 20 year old parts to be safe. Today I swaped out the EEC(computer) with an extra I had from the last TurboCoupe I owned(no change). Nothing seems to be going right for me on this. Paulie, Pete, and Natmac3 had gave me advise on my original post. So I finally got a Fuel Pressure gauge, checked it and it presurizes to 40psi then goes to zero within 2sec. Started it up and it stays about 32psi. Shut the car off and back to zero in 2sec. Jumpered the test connector to ground to check the fuel pump and it stays at 40psi until I take the jumper off ground and pump stops(to 0 in 2sec). Took the vacum off the fuel regulator while it was running, plugged the vac line with my thumb and it stayed at 40psi, put the vac line back on and it stayed at 32psi. Pressure remains at 32psi when it is running good and/or acting up. Thought about the check valve in the fuel pump per the test procedures for the fuel system, but I replaced the pump and all first thing with no change. Injectors don't seem to be leaking and no gas visible during the pressure checks. So I'm getting pretty frustrated now. Everything I have done has not helped the problem which I am sure is not that bad I am just not on the right track. When I changed the oil today I had a 1/2" round piece of gasket looking material come out with the oil(it was just small enough to come out the hole) and was intact(not pieces).Timing stays good and steady even when acting up. SO....I have read so much I may need my head examined, but I am thinking PCV valve, EGR solenoid, ACT, MAP, ECT. I also noticed today the temp gauge does not move much but the fans come on as normal as I would expect and there is no signs of over heating. And the fuse box metal bracket was not properly bolted down under the dash(ground problem?)Fuel lines seem ok, Sentry system does not work at all(under the radio and AC)I read up on the PCV and it would seem to me like it could be backfiring through the crankcase(bucking, surging, eratic idle). The car has 140k miles on it. When it is not acting up she runs like brand new(good boost, smooth excelleration, good idle) then when she acts up I pull over until it clears up or turn her off and wait 10-20min. then try to go again. It has to be something I am just overlooking. Seems Like PCV but I don't know if it was bad would it cause it to not keep itself pressurized. I figured it would slowly relieve itself but not in 2 seconds. Does the check valve on the fuel pump run off voltage or pressure? I hope I have enough info here for some one to wake me up. I have to travel 275 miles with this car Sept.25th for my new job in Louisiana. Been unemployed for a year and three months...... NEEDING SOME HELP FELLAS>>>>>>>> THANKS AND I STILL LOVE THESE BABIES, JUST NEEDING HELP... DAVE.

I had a problem like this and it was a pressure valve that was leaking. There is an additional valve relief thats in the plastic fuel line directly after the plastic cover thingy that houses the wiring against the firewall. It will be on the drivers side of the firewall coming out of that plastic wire loom cover. You wont see it leaking if you are in the car, but if you rev the car from under the hood, you might see it leaking or smell fuel.

The item in question...
http://i158.photobucket.com/albums/t97/b...C02767.jpg

Hope thats your problem

Dave, the 2 second bleed down for fuel pressure is a problem. I don't know if that is the whole problem but it is an issue

The PCV valve should be easy enough to check. You should be able to easily blow through the big end. Then, holding it straight up and down, you should not be able to blow anything at all through the small end. Replace it with ONLY the Motorcraft part, EV-127-A

Have you ever pulled the codes?

Thanks RDOG. I'll look into that. I have pulled the codes Pete and then had a local shop to pull them to mke sure I was getting things right. Code 34 and the Knock sensor code. That was it and I understand from past articles not to concern myself with these codes.

The other night I got home and while it was still running I checked the fuel pressure and it was 32psi. I was suprised though when I shut the car off and whatched the FP gauge it actually held and slowly went down( what I would think as about right.) BUT only that one time out of about 20 periodic FP checks. I checked my Bronco and Mustangs for a refrence and it loses pressure way to fast to me.

Pressure loss is either a leaking FPR or a leaking check valve in the fuel pump.

Just checked the PCV. It seemed good but blowing through it felt kind of sticky. I had an xtra on my old motor. So I swapped it out. No change. The EGR selenoid has 73 ohms on it. It has 12vdc-13.8vdc whith key on or running. Tried the fuel pressure check again. It did not want to pressurize, checked the fittings and tightened them a little more by hand. Still did not want to pressurize. Turned it over and while it turned over the pressure went to 40psi. Did not crank, pressure down to zero in 2 sec. It is actually 3 sec. when the needle on the FP gauge bottoms out. Then it started on second go. Pressure stayed at 32psi. and within 30 sec. it started acting up. When it stutters/bucks the fuel pressure goes up a little to close to 40psi but not quite(just spiking). I ran her until she cleared up then shut her down. Pressure loss the same. Turned the key on and it pressurized to 40psi then dropped to zero in 3 sec. I don't see where you are refering to RDOG. Can you tell me more.

Seem to be getting closer..... My wife helped me ground the test pin for the fuel pump. Sometimes it will stay pressurized( saw it stay at 38psi once and 20psi twice.) and held the pressure for more than two min. Wile it was pressurized I crawled underneath, wiggle all lines, connectors, wires, aand beat on the bottom og the tank. Never lost pressure. turned the key off then back on and would not hold pressure. Then it did. Traced fuel lines all the way to the fuel rail. Shaking them the whole way(while pressure held) and no external leaks. Seems like sticking check valve somewhere. I don't mind pulling the tank(it's almost empty), but not if I don't need to. Can anyone explain the whole fuel delivery system better.

Thanks Jeff. FP regulator is new. Fuel pump was replaced 3 years ago when I first got it with this problem. It made a 6 hr trip back home and acted up pretty much the whole way. Is the fuel pump check valve on the pump and are there any other relief or check valves in there not connected to the pump? I'll sure replce it if it seems to be the culprit to you guys. Thanks.....

Well yesterday I swappped out the FPR. I had an old one on my extra motor. Idle pressure went from 32 to 38psi.,but still have intermittent pressure loss. Also replaced the ECT sensor. No change in engine performance. Still (mostly after warming up) will run rough stutter, surge, buck. I ordered a Barometric Pressure sensor. I also am ordering a Holley 255lph fuel pump today to hopefully resolve the pressure issue. I believe I have two different problems and I am trying to get both problems fixed by this weekend. If not, it will be driven anyways. Pretty upset now. A lot of money, time, and stress put into this bird and I almost ready to call this one a lemon. I have to drive it on the 250 mile trip though this Sunday. I hope the BP sensor resolves the problem....