Just do yourself a favor-check fuel delivery first. The fuel filter is a PIA
on a coupe too-just remember to take the gas cap off first-or you're gonna have an eyeful.I think when you hook your fuel pressure guage up you're more than likely going to see it bleed down rapidly-just hook it up to the schrader-turn the key to the on position-read it-turn the key off and watch it-bet it drops severely in a short period of time. Then turn the key back on and start it-keep it reved-watch your fuel pressure guage-bet it holds better.

 

Is your MAF functioning properly? This is critical for proper mixture. One more thing to consider.

If you have datamaster plots, what is your MAF AFGS gm/sec at idle? (when it will idle). As a point of reference, on my 88 I see 9.5 gm/sec at 900 rpm. This should be roughly proportional to rpm.

For a second data point, at 1800 rpm, I see 15.2 gm/sec.

Do you seen any anomalies in the MAF data?

 

Thanks Rick I'll check that first. I see where your going with this. You figure while the pump is pumping at a good rate the pressure will stay up relatively well, but when the pump slows down the pressure pushes the gas past the pump back into the tank. Interesting.

Tequila, I will check my Datamster log. I actually tried two MAF sensors. Both were working so I doubt they both went south at the same time. Especially with one sitting on a shelf.
I want to do another scan tonight so I have the most recent one.
I just moved into my house a month ago. The neighbors are going to love me. I'm the guy who sits in his car in the driveway or garage and revs the engine over and over every night.
Shoot, I would hate me.

 

That's pretty close-bad check valve in the pump is kinda where I'm comming from. just my thoughts-could be wrong-but it costs nothing but time to check.

 

Can the check valve be replaced or would I need to replace the whole pump? If that;s the problem.

 

Don't know whether it can be repaired-check it first, then call the parts store. I figure if I have a FP problem, why just repair a portion if possible-just to have something else go wrong with it. Used to replace diaphrams in the old ones lol. In the US, the pump is under $100, as a mattter of fact, FP, sock and filter was less than a $100. at NAPPA. And don't forget to pinch off that return line when you check it.

 

A bad check valve in the fuel pump will allow the system pressure to drop off (bleed down) when the pump isn't pumping. It has nothing to do with the fuel pressure when the pump is running. It is a CHECK valve. It prevents a back flow of fuel, when it might flow backward. With the pump running, there is no back-flow. The fuel pump must be changed to change the check valve. The check valve will NOT affect the idle. In fact, all a bad check valve will do is require a longer cranking period, while the pump refills the fuel system.

RACE ON!!!

 

Thanks Rick and CFI.
I just got home and checked my fuel pressure right away.
I'm holding pressure.
Turn the key and the pressure goes to 44 lbs. very shortly after that it drops to 40 lbs where it stops and slowly goes down. After 5 minutes it was at 30 lbs. I tried it a couple of times.
My fuel pressure seems fine.
I have a bunch more things I want to try tonight so I'm on the way back outside.
I'm going to look at the injectors to see if they are pulsing. I'm going to check my coils, Check the timing again, try to set the IAC again,and the idle speed, try to set the TPS, get a datamaster scan of the car and maybe take it for a drive hoping it will let me.
I'll let you know how I make out.

 

What you're saying now-compared to post 52-is it is holding pressure.
Do your other tests now and let us know! Don't know if CFI-EFI read that-but your fuel definetly went somewhere-either a stuck injector, bad check valve or FP regulator.

 

Maybe I wasn't clear on post 52. I said when i pulled it out in the spring. That was weeks ago. The fuel pressure corrected itself at the time and it seems to still be corrected.
I hadn't checked the fuel pressure since this recent problem started so it's good to be able to cross it off the list. Add one more thing to the list of things we know is not the problem.

It seems to be running better.
I was able to reset the timing. The car actually ran with the ESC wire disconnected. I also checked all the injectors and the light on my tester would flicker. Same for all 8 injectors. I figure they are all working normally.
Then I went back to the IAC and idle. Got the iac set, brought the idle down but not all the way down. It seemed to need to be turned too many times so I left it around 700 rpms.
I wasn't sure how to do the TPS and haven't found it i the FSM yet.
I hooked the car up to my laptop and recorded another session with Datamaster.
Before I started recording I loostened the torx screws on the TPS and moved it a little. The reading on Datamaster had the TPS voltage low. I brought it up so its a little too high but so is my idle. It's sitting at .6X.
I went for a drive and it stumbled a little but didn't stall. The idle does not seem to hunt or surge as much but it is still doing it.
I think I need to go through the process again of setting the IAC, idle speed and TPS.
I want to do this all correctly and together because I see how they effect each other.
I will try to get back out later tonight.
I forgot to mention. It ran without someone touching the gas.
I was able to do the timing and IAC with the car running on it's own.
Last time I tried this it wouldn't idle.

I also checked my spark again with my timing light. I put it on each wire to see if the light would flash. It flashed the same on every wire.

Thanks again.

 

I think I had some crud in my fuel rail from having it off and polishing it over the winter.
Once I played with it a bunch the crud seemed to pass. I think it came out through my fuel pressure guage because it stopped working for a while too.
Again, this was weeks ago and it has been fine since.

 

And it could be-since it seems to be running better-that the additives to remove water in the fuel are working. To check-set your TPS, get 3 jumper wires, disconnect the TPS harness from the switch, notice on the harness ABC,put the 3 wires in the harness and switch, take your digital voltmeter to terminals A and B, with the key on, but engine not running, at closed throttle rotate theTPS switch to get a reading of .525 plus or minus .075 volts.You know-you might just need to take that puppy and run it.

 

I'll get it all set right tonight.
True about the fuel additives.

 

It's hard for me to say that it is working but I think it is.
I went back out and reset the IAC again, set the idle and set the TPS.
It seems to be working as good as it has in the last while.
I don't think it likes the low idle very much but it keeps running.
With 1.6:1 roller tip rockers should the idle be set normally or increased a bit?
I got the TPS exactly to .540V. At full throttle it hits 4.6V. is this right?
I'll go look it up.

I'm not counting my chickens until I see how it runs tomorrow.
I have to turn the key twice to start it. The first time it stalls, second time it runs. This is new.

Thanks again.

 

Sounds like you're on the right track. When you first turn the key to on-do you hear the fuel pump prime for a few seconds?

 

Correct, and it sounds like you might have to play w/ the min. idle a little more. 450 in drive w/IAC disconnected is what the helms states. If already at 450 in drive try bumping it up to 500 rpm. Use another tach if possible not the one in the dash.

 

My minimum idle gives me a little trouble now.
When I try to turn it down the idle stops going down before I stop turning the screw. The screw comes off the piece of the throttle body that it moves. I end up setting it so that it is just touching but hasn't started to move anything yet.
This had the idle around 500 in drive.
This is according to the tach on the dash. It's the only one I have unless the datamaster is more accurate. I could use it.
I was thinking that my tach could be off a bit but didn't know how to check it.
I have a new datamaster file from last night, if anyone wants to look at it, I can email it to them.
Thanks

 

When I am refering to playing w/it, this is w/ the IAC out of the picture (after grounding at the aldl for 30 sec. unplugging etc.) Adjusting the min air screw w/IAC still plugged in will not give you the idle you want, as the IAC will still try to compensate. The car needs to be in closed loop (O.T.), if it is still in open loop, it will be ideling on pre-set values not using the input of the sensors, etc.
What you are trying to do here is allowing the IAC, when plugged in, to be within the control (range) of what the computer can adjust in closed loop. Your datamaster should show you counts on a stock set-up I belive it is around 20 (I believe this info is in your FSM, as mention to checking w/tech 1 scan tool). It really needs to be close enough to be within the ECM's range to controll it. Actual target rpm with the IAC plugged in, is programmed in the chip (prom, which should also be available info on a scan).
This is why I mentioned when idle is going down, or to low, it is out of range of where the comp. can adjust. Your scanner should be a more accuratte source of RPM as the comp. "sees" it. The dash tach does not define 450, 475, 500. etc. let alone the accuracy of them is suspect to begin with.

 

Thanks Mseven.
I haven't adjusted the idle screw with the IAC connected, just disconnected but I would bet that I didn't always wait for the car to go into closed loop.
How long does it take a car to go into closed loop if the engine is warm but has just been started again?
If it takes a few minutes I may have figured the car was up to operating temp because I was just running it but I didn't wait until closed loop.

I'll have a look tonight and check my scan. I'm at work now so I don't have the scan with me.

I understand the 20 counts and how the computer needs to be able to raise this or lower it to adjust the idle. What I am missing (likely in the FSM) is how to adjust the counts. How do you get them to go up or down to get to the 20 that is desired?
Thanks again.

 

I'm not sure. I have tried listening for this before and don't know if I can hear it or not.
I may need to get a hearing aid or a second oppinion.