charlie31603

iTrader: (10)

OK. I am having a problem with the car and am running out of ideas. It's a 87 Z28 with the 5.7 tpi motor. So let me start off. I bought the car and it need the head gaskets done. So I did it and it ran and idle fine with no codes. Then I noticed a vacuum leak. Plugged it up and it started hunting for a idle. I checked the codes and found code 44 for it running lean. So I checked the book on how to test fuel pressure. It went up to like 40 with the key on then within about 20 seconds it went back down to 0. And the key was still on. When it was running it would be at 38. So I replace the fuel filter and fuel pump relay for the heck of it. And I checked the pressure again. This time it went up to 45 with the fuel pump priming the droped to 40 after the pump turned off for a few seconds. Then it would go back to zero after about 30 seconds. With the car running it would be at 38 and would go up to about 41 when it would hunt for a idle. But now when I check for codes I get nothing. But it still hunts for an idle. I'm new to this tpi stuff. And am wondering if the fuel pressure is OK. Or do I have other problems. Thanks in advance. Adam :-)

b_the_j

Your fuel pump only runs a few seconds when you turn the key on
if it is dropping like that it is either the anti-drainback valve at the pump or the fpr, check for gas in the vacuum line going to the fpr.
then pinch off the return line and prime the system, if fuel pressure stays constant then it is the fpr, if it drops it is the check valve.

I highly doubt that this has anything to do with your hunting Idle
do a search through this and the general engine forums for hunting idle---vacuum leaks---fuel injector flow problems etc...

The fuel pressure is fine, the fluctuations in pressure are from loss of vacuum, ..i.e. stumbling surging

charlie31603

iTrader: (10)

Thanks. I'll try the fpr test tomarrow(well today I guess). And where is the anti-drain back thingy. Please don't tell me it's in the tank with the pump. I tryed to read some post about the hunting thing. But I just get lost. One guy I talked to localy said to take the tb off and take off the tps and iac then trough the tb in a can of carb cleaner. Then spay the iac down. Thanks again. Adam :-)

Shagwell

cleanig the IAC would deffintely be a good place to start. nd yes, the anti-drain back is in the tank, but as long as you have good pressure running(which it seems you do) it's not your problem...

b_the_j

go to a ford dealership and get some of thier cleaner its great. Remove the t/b in order to clean it properly.

Shouldn't need to remove the tps, just the iac, lubricate the iac pintle with lithium grease before you put it back in. also check the condition of your throttle shaft bearings if these have any wobble the it is causing a vacuum leak/ and your blades will never close consistantly all the way.

charlie31603

iTrader: (10)

OK. I clamped the return line and turned on the key. The fuel pressure went to 60 then then 40 and stayed there for a few seconds and slowly made it way to 20. Then for the heck of it. I would turn the key on and the pressure would go to 40. Then I would clamp the fuel line that sends fuel to it after the pump shuts off and the pressure would drop rather fast to 0. I also didn't see any fuel in the vacuum line that gose to the fpr. But I did smell a very slight hint of it in the line. But what is the fuel pressure supose to be?

Now as for the surging. I let the car run all the way through the heat range it idled fine intill the fans kick in. Then it would start hunting again. Then for the heck of it I unpluged the tps. still idled like crap but the ses light came on. So I pluged it back in. Then I unpluged the iac and it idled smooth. And no ses light came on. And it still idled fine when the fans kick on. So I am guessing it would be the iac right.

I also used a propane torch around the intake and did not find any leaks.

One more question while i'm at it. Since it just had the heads done after the gaskest craped out. I am getting alot of white smoke out of the exhust. It's there alittle at idle but really comes out when I step on it. How long would it take for the smoke to goaway.

Anyways thanks for helping me out guys. Let me know if I am heading in the right direction.

b_the_j

No!!! the logic that the Iac would be bad b/c the idle settles down when you unplug it is easily understandable, however this is not the case, the iac is working fine, the ecm is meerly using it to try and compensate for a problem, so it is a symptom not the cause.

there are two ways the fuel can go when the fpr goes bad into the vacuum line(this causes a rich condition which you indicated that your plugs read lean correct?) or back to the tank. Possibly that your fpr is bad and still maintains pressure, but but volume is crapping out.

As for exact pressure number search the data section!!

As for the smoke,
black=rich
blue=burning oil
white=steam

If you are continually adding water to the resevior (spelling?) then your head gasket replacment may have been unsucessful.
Other wise your exhaust is full of coolant from the previous blown gasket and will go away eventually. Perhaps drill a small hole in the lowest points of your exhuast then seal it back with jb weld, or disassemble your exhaust.

If possible pull your plugs, and lay them next to each other on a piece of white paper labeled 1-8 and post a good close-up

charlie31603

iTrader: (10)

Well the motor runs like a raped ape but yet purrs like a kitten. lol. I had 2 of the local guys come over friday night to just look at the car. And when they showed up. It wouldn't start at all. We went trough EVERYTHING. And then by luck and a little thinking we found a wire loose that comes off the battery positve side. Who ever put the cables in tought that by twisting the wires to gether and putting a little elictracl tape would work. So it would brake contact when it wonted to and that explains alot of problems. Then today we put a o2 on it and it add back so milage. And one thing I want to get for this car is a scan tool. One of the guys had one and I swear I would of replace a crap load of parts till I found the proplem. Thanks again for the help guys! Adam :-)

P.S, I still think my feul pressure bleeds off way to fast. Down to zero with in 30 seconds. I am going to get a afpr anyways. So I am going to see if that helps.

burnout88

If fuel pressure is bleeding down that quick your injectors are probably leaking. Very common on higher mileage cars.