I have been fighting my car for the past week. I'm desperate now.

Heres the deal:

My TII is an 88, so it runs high impedance injectors. It has always run perfectly smooth. I got two 720's to put in my secondaries from a friend. They are low impedance, so as per someones advice, I soldered some 10 ohm resistors in each power wire.

Also I added a hybrid turbo at the same time. While I had the intake off, I removed my primary fuel rail and tapped it for a fitting so I could do away with the pulsation dampener.

I get the car put together, go to start it up. Everything is fine. Running perfect like it did before. All of a sudden, it starts hunting for an idle sort of like a bad BAC valve would do. (Only thing is, I don't have a BAC valve. Or an ACV valve. Or a solenoid rack. Or pretty much anything else. All I have is the bare minimum the ECU needs to function).

There are no vacuum leaks or anything. I pull the upper intake back off and get to troubleshooting. I can't find anything amiss, so I figure maybe I didn't get all the metal shavings out of the fuel rail. I've even swapped the primary injectors and now it idles like it is one one rotor.

Driving around town at about 1/3 throttle causes it to buck and surge. Around 3800 when the secondaries come on, it will cut off for a second unless you are in boost. Even then, you have to gradually roll in the throttle for it to run smooth, and it doesn't always work. I'm assuming there is a problem with the primaries somewhere, but I can't figure it out. I've been through all the wires in the harness, replaced the injectors, checked for vacuum leaks, etc. I don't know what I am missing. I've even tried resetting the ECU, even though my little LED's show it throwing no codes.

This is really pissing me off because I can't fix it. Anyone got any ideas? You can check the link in my sig for most of the mods if it helps any.

Looking on the bright side, I can have my upper intake off in under 5 minutes

 

Looking on your mod site, I don't see a fuel computer. Do you have one?

Since you're going from high to low impedance secondaries, even with the 10 Ohm resistors, would this be more than the ECU can figure out? The ECU is looking for high impedance secondaries, so I'm wondering if the low-impedance + the resistors is affecting how the ECU "reads" when to bring the secondaries online.

Are the primaries and secondaries on the same circuit? If so, then could the resistors have an effect on the signals sent from the ECU?

And I know you've set your TPS... haven't you?

Just some thoughts. I might very well be completely off base, so don't flame me too bad. I claim no knowledge of fuel management in FC's at all.

At the worst, you could put everything back the way it was before you started, check it out to see if it's running right, then do it over to make sure you've got everything right. You might think of something that you didn't before.

Hope this gives an idea or two.


- JB

 

Wanna hear me do my best impression of a broken record? Here goes:

Your-yo-your-your TPS is bad.



Check it. I'll bet you $5 that's it. Classic example.

Brandon

 

" I've even swapped the primary injectors and now it idles like it is one one rotor"
----------------------------------------------------------------
Im a N/A 1990-1992 expert, but here goes...

Maybe you have one or both of the primary injectors mis aligned?

Did they turn freely in thier sets when you installed them?

I've seen this before on 1 turbo II your year...

That was the problem.
It acted like it wasnt getting fuel.

OR.....

you have a dead injector due to:
Bad connection
Intermittent or dead injector
Clogged injector (which would be emulated also by mis-alignment)

Thats my guess...

By the way....
Whats the prize?

Sniper_X
Always Tinkering

 

You would have lost $5 I've already checked it. I've racked my brain trying to fix this damn car.

Sniper_X, all the injectors are installed properly. Changing the primaries out did not change the symptoms much at all. The secondaries have very little mileage on them.

I am about to desolder the resistors and stick the old 550s in the secondaries to see if that changes them. I am not sure how the injectors are wired (series or parallel). Grr. I wish I had the money for a Haltech.

 

Did you replace/check the grommets or *injector cushion* that goes around the nipple of the injectors? Sometimes those get old and hard. Usually the Secondaries will not affect Idle so much but as soon as boost comes on it will run like crap.

On a second not I screwed my car up by installing 720's in the secondaries by doing the wiring wrong. The car ran real bad, sounded like a big sideport at idle and if you pressed the gas real fast it would just stop running altogether. Swapping the ECU did not help and everything on the car looked ok Until I hooked it up as a NA by conneting the AFM directly to the throttle body. In this configuration pushing the AFM open and close had zero affect on the running of the car.

I guess somehow by messing up the injector wiring the signal from the AFM was lost. Instead of fixing the problem I bought a Power FC and did away with the AFM.

 

Yeah, the first set of primaries caused my car to idle like a bridgeport. The set that is in it now makes it sound like the engine is blown.

I was told to solder the resistor inline with the power wire. I snipped the power wire to each secondary, and soldered the resistors in. I guess I will have to put it back stock with the 550s and run 5 psi until I can figure this out

 

damn u got me stumped!
one thing though, go buy a vac gauge, like $40 bucks. Eliminate the vac possibilty, then your only other possiblity is the fuel, im thinking u wired something wrong. I would definately put your originals back in. Good luck man.

 

I have a vacuum/boost gauge. The vacuum is reading lower from the shitty idle. I've checked for leaks with carb cleaner and found none.

Anyone know where to get high impedance 720s then?

 

My 90gxl didn't surge when I had the secondaries swapped for lower impedance injectors wired to radio shack 3% tolerance 10ohm resistors. I checked the final resistance value and it was 14ohm, w/in factory specs. Man it's handful to figure out when so many mods are done at the same time.
The thing I notice from reading these threads of removing the throttle bodies and disconnecting afm is that over 50% of us gets those surging affects / erratic idle after reinstalling their intake systems. I had that problem as well where after reassembling it ,the car started fine for 5 secs then kaput it dies and had to be unflooded-but it ran fine after that. Strange!

 

I've had the upper intake off a couple times and it never gave me any problems. I had to have done something wrong, but I don't know what it is

 

You sure you put the fuel injectors in the right positions?
Are you running some kinda fuel computer to compensate for the larger secondaries?&nbsp If not, the car is going to run like ****...



-Ted

 

Yes the injectors are in the right place. Even with larger secondaries, it should still idle fine and drive fine below 3800 RPM, which it isn't doing. My turbo has an H3 compressor wheel, at 13 psi I'm not really worried about it stumbling too badly when the 720s come on

(Plus I want a Haltech, I don't really feel like getting a S-AFC only to sell it for a loss later).

 

I want to know where to get some high impedence 720s as well. Why don't you just take everything back off and save for a Haltech then do it all?

 

Pop quiz...which ones are primary and which ones are secondary?



-Ted

 

Because I'd have to run like 8 psi max on my new turbo, which would not be much fun

Plus, I have to stomp my friend's *** that owns a 5.0 Mustang.

 

Primaries bolt to the center housing, secondaries bolt to the top of the lower intake.

 

ok felix, are you sure that they are high impedance injectors??

you can tell by this, check the last 6 digits in your VIN number
chassis number 550168 and below have low impedance
chassis number 550169 and up are high impedance

check the last 6 digits in your vin number, and see if they really are high impedance

 

Pop quiz #2...how do the plugs off the engine harness plug into the fuel injectors?



-Ted

 

when i took my n/a apat a few weeks ago and had the same idle problem it was because there was some stuff built up in the lower injector air bleeds, their easy to remove.

 

Please elaborate. I don't understand what you mean. The wires are so old and crusted they can't be mixed up.

 

You have four fuel injector positions (front primary, rear primary, front secondary, rear secondary) - how can you tell which plug is which on the engine harness if that piece of the engine harness was totally removed from the top of the engine?



-Ted

 

Okay, I've basically skipped over most of this stuff, but I'm going to suggest its the ECU thats bad. Maybe something shorted with the injectors? I don't know. All I do know is that is the EXACT symptoms, on the dot, of what my car was doing when the ECU went bad. And I do mean on the dot. See if you can get your hands on another ECU just to try it out.

Michael

 

Felix,
Just for ***** and giggles, take a TPS off one of your known to be functioning FC's. Clean the pin with an emory board or sandpaper, and install it in your troubled 88 (dont' cheat and skip cleaning the contacts). I know you have checked the TPS, but sometimes there is a bad connection. Anyway, it is a 5 minute drill, what do you have to lose. Let me know if that is the problem.

 

Forget to plug in the AFM?