Well this problem just seemed to start out of the blue last night.

A quick backdrop: I just had finished a T2 driveline swap a little over one month ago. The starter harness stalk seemed to be "shorting" on something last week, keeping it from starting after the severe rains we had here. But I guess after I tweaked it a bit, the problem went away although I did notice one of the connectors for the 5th gear sensor from the transmission had been severed.

Yesterday: Im at a friends. The car floods when I go to start it which I expected. Upon doing the fuse pull trick it started right up but my friend noticed a spark by the starter, possibly from the harness short? Everything else seems normal. So I began driving off and upon getting on to the main streets, I accelerate past 3500rpm. When I hit 3800rpm under anything more then 45% throttle, the car seems to hit something similar to a "rev limiter". It's not fuel cut because I have a defencer which has worked prior to this and I can be at less then 7psi but its just the magic 3800RPM transition when this occurs.

The injectors have resistors on them as my ECU is high impedence and the injectors are GSL-SE units. I dont think that can be the cause either because wouldnt the difference in impedence have caused other damage to the ECU?

So im really not quite sure what it can be other then electrical problems at this point but im not sure where to begin from. Any ideas or insight in the matter would be appreciated. Thanks in advance.

 

This is the magical 3800RPM hesitation. Do a search.

 

Thanks for the common sense heads up. I was aware of this problem but didnt think it was appliciable to my situation.

Seems like it may be though. One point I came across was that theres a main ground from the battery to the starter and im thinking this may have had a play in it.

But this is more then just hesitation, the car cannot rev over 3800rpm(in the previously described manner). Is this still something a bad ground would bring up?

 

repost

 

reground all the ecu grounds and possibly the pressure sensor after doing the ECU first

 

Look for a bad or sticking secondary injector, or a wire leading to it from the ecu. When you hit a "wall" at 3800rpms, it means at least one of the 2 secondary injectors is not coming on, starving one rotor for fuel. SO you have to look for problems with the secondaries.

BTW, there is no such thing as a "high impedance ecu". The injectors and harness, as a set, determine impedance. All 2gen ecu's want to see about 13 ohms, just like most car stereo amps want to see about 4 ohms. You can run any injector/resistor combo as long as the end result at the ecu is near 13 ohms. Either an 87 or 88 ecu will run an 87 or 88 car, with properly set up injector/harness.

Just this week, I had a customers car with a t2 swap I installed that had run for about a week and had 50 miles on it. All at once, it goes to running on one rotor. Compression was strong and so was spark. SO I check fuel, and find the rear primary injector not opening. I replace the computer to no avail. Turns out it wasn't recieving the injector pulse/ground trigger from the ecu. A shorted wire between the ecu and injector. I run my own wire directly from the ecu to the injector but the problem persists. Come to find out, the short burned out injector drivers in the ecu on both the original and the second ecu I tried before I found the bad wire. So a wire AND a new ecu fixed this problem.

I have also seen a car with a bad injector resistor pack (86-87 models or 88's with a harness swap) cause this...the single resistor out of 4 in the pack that completed the circuit with one of the secondaries went bad, thus causing an open circuit, and no injector power th that one. A new pack fixed it.

So, look for a bad injector, bad plug or wires to it, bad resistor or resistor pack (if applicable), or bad injector driver in the ecu.

 

Thanks for clearing up the impedence information. I'll have to look into it further in the next couple weeks/months.

Im also considering just biting the bullet and going with a new custom harness suiting for a Power FC or using a Haltech unit. Not too sure yet...

 

It seems that my primary ground which I mentioned earlier was not connected so what could this have damaged?

I guess this eliminates the possiblity of a short coming up in the line between the ECU & injector.

Also, if it damaged my resistors to the secondaries, wouldnt that have caused more damage to the ECU then just not firing the secondaries?

It seems, at this point, that chances are that the injectors or ECU were damaged from this. How can I go about testing the both of them? Can anyone else verify these conclusions? Thanks.

 

Not having a ground connected makes an open circuit, and **** doesnt work. Once you reconnect the ground, stuff should work again. Other than that, there should be no lasting damage. Now shorting a wire from the ecu (in the harness) can cause damage, which is what I describe above. Just leaving something loose or unhooked should not.

 

I guess the only ground in that area would be the ECU ground then? Theres the primary ground from the negative battery terminal, another on the bell housing to firewall, where to where does the ECU ground go to? I'll double check the grounds and if that doesnt do it, the wiring to and from the injector. Thanks again.

 

up^

 

^ for diagnostic procedure.....

 

^