EFI Cutting out at 3500rpms

[EricLar80]

It is not advancing properly. I have been reading back on some posts recently, and ran across this a number of times and its from when something is not hooked up right (and it always dies at 3500)... It has something to do with timing.

I would check the following:
-check PIP sensor; see this thread
-that you have your advance plug on the distributor attached (easy one)
-that the tfi is in working order

Eric

 

[HGM]

So, couple of things..

What year is the processor for? And, what do you have for a scan too? The "10" code is actually a seperator code, codes before it should be continuous(memory) and codes after should be on demand (there now). Snapping the throttle is important to check the TP as mentioned above.. The thing that catches my eye is 2-digit codes on a MAF PCM, I woul dexpect them to be 3-digit. I would begin by making sure your TP is about .9V at idle and its running near 650rpm. If the idle is high, the IAC cant lower it, then you get a code.

Does your scan tool show you Short and Long Fuel Trims? The should all be near 0%.

 

[TDavis]

Definitely going go give the PIP sensor a shot since it's an easy change and its definitely not going to hurt anything. The computer is out of an 89 and I'm scanning it with a newer snap on solus pro scanner. I honestly don't know if it will show me the fuel trims or not.

 

[TDavis]

Ok new reman distributor with new module are in. Same exact problem, nothing changed. I put an adjustable fuel pressure regulator on it and got the fuel pressure up to about 38 psi and through the throttle it doesn't ever drop pressure. I took the computer out and ran it in a friends car and it seems to run his car fine. I did notice something today checking the timing again. When you rev it the timing advances until about 3500-4000 then drops to almost tdc. Any suggestions now? I tried testing the voltage to the module like my Chiltons says but I definitely could have been doing it wrong. I'm starting to feel like I was ripped on my wiring harness!

 

[Viperwolf1]

Well that loss of timing advance will cause it to fall on it's face. Just like leaving the spout unplugged. Might want to trace out the spout wire.

 

[EricLar80]

Ok new reman distributor with new module are in. Same exact problem, nothing changed. I put an adjustable fuel pressure regulator on it and got the fuel pressure up to about 38 psi and through the throttle it doesn't ever drop pressure. I took the computer out and ran it in a friends car and it seems to run his car fine. I did notice something today checking the timing again. When you rev it the timing advances until about 3500-4000 then drops to almost tdc. Any suggestions now? I tried testing the voltage to the module like my Chiltons says but I definitely could have been doing it wrong. I'm starting to feel like I was ripped on my wiring harness!

I think that if you are not getting timing past 3500/4000, then your problem lies either in the distributor or the computer. Smart money goes on the distributor if the computer is giving you codes (a good indicator it is working).

If it were your wiring harness, it would give you issues no matter the RPM.

I assume the engine runs fine (full throttle and light throttle) all the way up to 3500?

Eric

 

[TDavis]

I think that if you are not getting timing past 3500/4000, then your problem lies either in the distributor or the computer. Smart money goes on the distributor if the computer is giving you codes (a good indicator it is working).

If it were your wiring harness, it would give you issues no matter the RPM.

I assume the engine runs fine (full throttle and light throttle) all the way up to 3500?

Eric

Engine runs great all the way up to about 3500.

 

[DirtDonk]

Could it have anything to do with the pin differences between automatic and manual transmissions? I know Ryan's harness has a pair of wires you swap if you have one or the other type, but don't know about yours. What harness did you get off of e-Bay?

What about the two types of TFI modules? Is yours black or gray? I forget if the wrong one will even work with the wrong computer, but if it will, then perhaps this could cause an issue.

Are you back to the A9L computer now? If I'm not mistaken, that should be the gray TFI module type.

What about the cam? Is it a new flat-tappet? Or is it a roller cam?
I don't think the cam would necessarily have anything to do with a timing drop at a specific rpm, but a flat-tappet cam that is going bad (from improper break-in or insufficient lubrication) would give some of the other symptoms.

Paul

 

[TDavis]

The harness was purchased from a guy who's name was hotcarls69cougar off of ebay. Since then I am totally unable to find any trace of him on there. I do have the A9L in there with a gray module. The motor is out of a bone stock 60k mile grand marquis that I drove home, revved the crap out of and it ran awesome in the car. I used the mustang upper intake and fuel rail and switched from tan to orange top injectors is the only thing I changed on the motor. ?:?

 

[70EB]

The motor is out of a bone stock 60k mile grand marquis that I drove home, revved the crap out of and it ran awesome in the car. I used the mustang upper intake and fuel rail and switched from tan to orange top injectors is the only thing I changed on the motor. ?:?

You switched the fuel rail and injectors (went up a size) but did you switch the MAF to match the injectors? or are you using the original Grand marquis MAF?

If you did not switch the MAF to match the injectors, this could be part of the problem.

 

[TDavis]

Mustang MAF that came off of the same car that the computer and injectors did.

 

[HGM]

Have you tried a Marquis PCM? The cam firing order should be different. The Marquis was not an "H.O.". It will run because of the injectors being bank fired, but not well.. Your symptoms dont quite match, but it sounds like you've covered about everything else..

 

[av bronco]

What o2 harness did you use, there is some good
Info on o2 stuff at corral.net

 

[DirtDonk]

And, just to cover all bases, did you add a hundred and ninety two new grounds to the system?
Just kidding, but seriously, do you at least have a very good ground strap from the engine to the body, in addition to the ground directly from the battery?
And is the body grounded directly from the battery as well?
And is the frame grounded to at least one of those? Both tying them all together is best, but at least one is better than nothing. A ground wire straight from the negative of the battery, or a simple strap from the engine block to the frame or body to the frame?

Does the factory engine harness have it's own ground strap loomed up inside to bolt to the manifold?

You probably have all that covered, but I thought I'd ask, as insufficient grounding can rear it's ugly head in the most unusual ways.

Paul

 

[IFLYHOOKS]

I just fixed the same problem on my Bronco. I read this post: http://www.pirate4x4.com/forum/archive/index.php/t-581482.html checked my wiring schematic and then checked the two middle wires on the wiring harness TFI plug. I had constant 12v on both wires, one should be constant the other should be start 12v. I cut the wire that was supposed to be start 12v as described in the post, the engine started like normal and now revs as far as I dare push the pedal.

Scott

 

[EricLar80]

I just fixed the same problem on my Bronco. I read this post: http://www.pirate4x4.com/forum/archive/index.php/t-581482.html checked my wiring schematic and then checked the two middle wires on the wiring harness TFI plug. I had constant 12v on both wires, one should be constant the other should be start 12v. I cut the wire that was supposed to be start 12v as described in the post, the engine started like normal and now revs as far as I dare push the pedal.

Scott

Good find - now that is a hard one to diagnose...

Eric

 

[blazinchuck]

I just fixed the same problem on my Bronco. I read this post: http://www.pirate4x4.com/forum/archive/index.php/t-581482.html checked my wiring schematic and then checked the two middle wires on the wiring harness TFI plug. I had constant 12v on both wires, one should be constant the other should be start 12v. I cut the wire that was supposed to be start 12v as described in the post, the engine started like normal and now revs as far as I dare push the pedal.

Scott

curious, i didnt see a wiring diagram in the link. if you only need one constant 12v and one start 12v...did you take the wire you cut(from constant12v) and reconnect to a start 12v? or left it completely disconnected?thanks


i take that back...i found that diagram

 

[IFLYHOOKS]

curious, i didnt see a wiring diagram in the link. if you only need one constant 12v and one start 12v...did you take the wire you cut(from constant12v) and reconnect to a start 12v? or left it completely disconnected?thanks


i take that back...i found that diagram

I left it disconnected.

 

[blazinchuck]

THANK YOU IFLY!!!!! i cut the 3rd wire from the top and SHAAAAAZAAAAAM!!!! I have a supa Badazz motor now!!!!! 6grand on tap cmon!!!!! i was hoping it might help the long start ups...but guess not. anyway, i can rev til the cows come home now....i ran roast the forty2's easy as pie, thanks again,Chuck

 

[IFLYHOOKS]

thank you ifly!!!!! I cut the 3rd wire from the top and shaaaaazaaaaam!!!! I have a supa badazz motor now!!!!! 6grand on tap cmon!!!!! I was hoping it might help the long start ups...but guess not. Anyway, i can rev til the cows come home now....i ran roast the forty2's easy as pie, thanks again,chuck

awesome!!!