Somebody help me or I am going to kill myself

[shikzachaser]

The car is freaking me out. It had been running rough after constant highway cruising for maybe 100 miles. The fuel pump finally went out, I replaced it and everything seemd great. I drove it yesterday for about 100 miles to a friends house, it was great. Coming home after 80 miles it started the cutting out again, bad, especially w/ low RPM and a load ie: 5th gear @ 300RPM. Also when this occurs it will not idle, it dies, very much like a large vacuum leak. I can keep it running with the throttle but as soon as it's under load, it cuts out. I went out this morning, it starts right up and everything is great. I have new injectors, wires, rotor, cap, seals, vacuum lines, Linsey fuel rail, etc all w/ less than 4K miles on them. I love the car but I've got to get this sorted out.

ANY IDEAS????

steve

[Razorback1980]

That sure sounds like a large vacuum leak to me Steve. Double check the vacuum tube on the bottom side of the j boot right in the corner. Also check the other larger vacuum line to make sure it isn't cracked anywhere. The next thing I would check is the intake manifold...spray some WD40 or carburetor cleaner around each of the places where it joins the head and where it connects to the throttle vavle. With it causing that much of a problem, I would guess it's in a place where it can cause a big leak. Also check the vacuum booster for the brakes, that's another bigger vacuum line.

These are real tough problems because you can't get it to do them constantly where you can diagnose it. When you change something, did it fix the problem or fix itself again for a short time. It's much easier when they permanently break so you know when you find it. Let me know if you don't find anything.

[Techno Duck]

Check the vacuum lines running to the fuel pressure regulator and the dampener. If these are disconnected or have a leak they will cause the car to stumble and misfire. Make sure everything is connected at the throttle body.

Buy a $10 vacuum gauge from PepBoys and verify its a vacuum leak also.

Another good trick is to use some rubber hose (say 3/4 to 1 inch diameter) and put one end up against your ear and move the other end around the engine with it running. Run this next to all of the vacuum line connections and you will probably hear a hissing sound coming from the tube when you get close to the leak.

The last and best solution to this problem is find someone with a smoke machine. Seriously. My friend's got a SnapOn smoke machine at his shop to test intake and exhaust leaks. Basically you remove the AFM or MAF from the car and stick a plug into the J-boot which pumps a very thick white smoke into the intake. The smoke will come out of any leaks in the intake, vacuum or exhaust system.

How old is your fuel filter?

[shikzachaser]

Boots new, fuel pump and filter are new, all vacuum lines are new, regulator etc is on the Linsey rail and are new. It also sounds like vacuum to me but when the old pump finally died and I replaced it I was sure that was the problem. I about had a heart attack last night when it started cutting out again. It may still be pissed at me for putting it on EBAY. I explained to it that it was all a misunderstanding, I still love it, it's no longer for sale, etc but it may still have a grudge. The smoke machine thing is interesting, I may call around and see if anybody has one, that is one I have not heard of.

Steve

[shikzachaser]

One more thing that may or may not be related. Every since I can remember the car has had a weird hesitation when you shift to second gear. It's like it hesitates for a second or two then recovers. This goes back to way before I did anything to the car.

Steve

[Razorback1980]

Originally posted by Techno Duck

The last and best solution to this problem is find someone with a smoke machine.

Cheech and Chong's garage?

The vacuum guage is a good idea as well. But because this is only occasional, it would be great if you could put it inside the car so you can read it when the car does it.

Other ways to test are to put the engine at TDC and pressurize the intake system with say 10psi and listen for leaks...using Techno's rubber hose idea or a stethescope would help. I'm just trying to think of something that could be used to plug the J boot so you can pressurize it. Maybe a pvc pipe with a piece of plastic glued on the end. drill a hole and put a tire valve in the plastic to hook the compressor to. By having the engine at TDC, no valves should be open and the pressure should remain the same...within a reasonable amount of time. Of course if you can figure out a way to put in smokey air (like dry ice), that would be a plus.

[924Sman]

I like thinking outside the box........Fuel filter on in the correct direction for flow? How is the damper? It controls fuel pulsation to the injectors. Vacuum hoses on the TB and reg/damper in the correct position? There are 2 on the TB and EZ to swap one for the other, reverse those and see what happens.

Dal

[SoCal Driver]

Ignition switch, coil to dist HV cable, fuel pressure, DME relay, speed and reference sensors.

[shikzachaser]

It really does feel like fuel pressure. It coughs and picks back up. When it starts doing it I can press in the clutch, the engine revs normal, when I let it out it cuts out under load.
Also it will not idle when this is happening. Most of the time it just dies, some times it fluctuates between 300-1000 RPM. I can keep it running with the throttle.

When the old pump actually died I was really excited as I felt I had it nailed down. It ran great and then the same cutting out. It did this prior to going with the new injectors and the Lindsey regulator so it kind of rules those out. Pump is new, filter is new, DME relay is new. I even switched the old one back in and it did the same. It had this same problem prior to putting in a new coil and new Magnacor wires so it kind of rules these out also. Can the speed and / or reference sensors cause this type of thing? Have you seen them as a heat related issue? It really seems somehow either heat or time related as it only will do it after running at highway speeds for extended periods. It really is frustrating as I want to reliably get in it and go. This is one of the most frustrating things I have had in any car. I appreciate any input as I am not the sharpest pencil in the box.

Steve

[tnporsche]

Attach a Fuel Pressure gage temporally to the end of the rail. That way if and when it does it again you will know what the pressure is doing, and can rule fuel out. Be sure "no leaks" in temp hose. Don't what a fire.

[Eldorado]

my vac line under the intake manifold was loose... might be another place to look..

[shikzachaser]

I already have a pressure regulator gauge built into the regulator. It shows 41PSI except when the pump died ..... duhh

Steve

[Mike B]

Two other things to consider...an electrical problem or residue in your fuel tank. A pile of crap can collect in a tank in 22 years and can cause symptoms like you're experiencing. Best of all, draining a tank is FREE!

[onZedge]

OK, my $0.02. Clogging cat? Sticking AFS door? (Hey - that ACTUALLY HAPPENED to me!)

[shikzachaser]

Actually the tank was one of the first things I thought of as it was so intermittant. Tank was drained and flushed when I did the new pump. Tank screen was cleaned, it really wasn't too bad to start. Thanks for the input though Mike. This may be one of those go to the dealer and hold my ankles as I back gently into the bill. Currently the rate in St Louis is $115 / hr / flat rate with no idea on time on something like this...and well....this is obviously not a stock car ......we can't assume any liability for anything.....I am just waiting for the rubber gloves to snap....please at least talk nice to me...maybe buy me dinner....I need a hug...

Steve

[shikzachaser]

Definately not the cat. I replacd the stock one w/ a quasi legal mini one.



The old rail and regulator pictured have been replaced



I still somehow feel it's fuel related. It's just weird how the pump definately went bad and I replaced it and have similar intermittant problems w/ a new OE one.

Thanks:

Steve

[Schumi]

I don't know if this is OK for our cars, but i have used the method to find vac leaks on my toyota with great success-

Get a car of starter fluid (Ether) and spray a small amount around each vacuum fitting, one at a time, pausing to listen. When the car revs up after spraying one of the fittings, you know that it is that fitting which is leaking.

[shikzachaser]

I'm ordering all new metal vacuum fittings tomorrow from Dave Lindsey along w/ clamps and hose. I have heard good and bad w/ regard to the silicone. Anybody had any results of the silicone hose collapsing under vacuum? I am also going through it w/ a can of brake cleaner as Mike suggests, it's less flamable than ether and will yield pretty much the same result.

Steve

[Schumi]

After going on a run for chinese food yesterday, I finally admitted I need to do a run over my Toyota's vacuum system also. It's now having trouble idling at normal idle, instead opting most of the time for the 2500 mark.. it's carbed and has a even more daunting vac system than the 944's, if that can be imagined.. I'm thinking it might also be the cause of some dieseling on shutdown.

Strangely enough, the more trouble it has running good at idle/low rpm's... the better and better it seems to run up around 7K or so...

[74goldtarga]

Probably not helpful advice here - but I had really intermittent and troubling problems and when it was all said and done I had worn out plug wires - yours look new anyway, just a thought.