Background on the car.
'86 GXL that I just finished converting to a turbo. Used TII intakes and an s5 turbo and manifold. All TII electronics, N332 ecu. Corksport DP running to the stock cat to Apexi GT spec catback. No emissions save the cat and TB mod done (but still have BAC). Used s5 injectors, so soldered in new clips and removed the resistor pack and soldered all the wires to it together. TII fuel pump. Prosport boost gauge. Have about 15k on a rebuild.

After completing the turbo swap, car started up first try. Held a good idle and no oil or coolant leaks. After I double checked everything and made sure it was running well I took it for a spin. Once warmed up, I did a pull from a stop. Hit the dreaded 3800 hesitation (i think). Was like hitting a wall, threw me forward a bit After It stumbled it was very sluggish through the rest of the rpm range, which I will attribute to the stock cat which is probably clogged by now.

So over the past couple days I've been running through everything I can think of to fix this. I have done the following:
.checked all grounds to make sure they are all still clean (re did them a few years ago).
.added a ground from the pressure sensor to the body AND the engine.
.checked the output of the pressure sensor at atmosphere (~2.25v).
.back probed the ecu to see that the pressure sensor voltage was getting to the ecu.
.checked all the wiring to the injectors for continuity.
.rewired the fuel pump.
.injectors cleaned by WitchHunter during the swap.
.checked the grounds again by checking the resistance from the battery to various places in the engine bay (very little resistance).
.set the TPS using little lights at the clip.
.checked for codes thrown by ecu (none).

I can free rev without hesitation.
An interesting point: when checking the resistance from the battery to various places in the engine bay, it was always <1 ohm, until I turned the key to "on," then it jumped to ~40 ohms
I do have a bit of a boost/vac leak and can only boost to 4.5psi but I don't think that is the cause.
Car pulls pretty well up until 3800 rpm, when the stumble is very very noticeable.
Previous to the turbo swap, the car ran great. Pulled hard all the way through to redline.

I'm at a bit of a loss where to go next. Did i mess something up doing the swap? ecu bad?

 

Drove the car today to see if I could get a better idea of what's going on.

Accelerated somewhat slowly in second gear, right around 0 on the boost gauge. got to 3800 rpm and got "stuck" as in stopped accelerating and kinda bounced there. Had to floor it to get it going again. This to me points to the secondaries, but I can't figure out what's going on. Any ideas what to check?

 

I would check your connections at the injectors since you soldered them. You can run the car on the N/A ECU as long as you don't drive it hard to eliminate the ECU.

I'm not familiar with S4 electronics but I would double check the mods required to run S5 injectors with your setup. Good luck, glad to see another 6 port turbo running.

 

Thanks for the reply! I'm certain the injector connections are good since I checked their resistance from the ECU plugs.

How hard would be too hard for running the NA ecu? Like no boosting? Or a little boosting? And would i want to switch back the NA MAP and AFM? I don't really want to risk my engine too much :P

 

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/so-i-ran-my-tii-na-ecu-yesterday-794638/

Itswill ran his TII car on 10psi with the NA ECU with no problems, considering the difference in compression and say you run the 4.5psi you do now (half what he was running), and the fact that you will only do some quick pulls and I think you will be OK.

Not sure on the MAP/AFM but I would install them if you still have them to be safe.

 

My car idled fine with the n318 sensors and n326 ecu. I did not get into boost seeing that I only have 31 miles on a rebuild. With the n333 (rtek 2.1) ecu it would stumble like I had a vacuum leak, but it was fine with the n326 ecu. It came down to being my water thermo sensor not being full connected, and that was cause problems idling when is wasn't up to 176 degrees. For some reason the N/A ecu ignored this all together.

As for my car

S4 N/A block
s4 Turbo II manifolds and turbo with top mount
550 primaries, 720 secondaries, and fd fuel pump
Bonez downpipe, to midpipe with no exhaust (its on the car but a four inch gap in between)

 

dropped in the N326 ecu with the N318 electronics. Idled like crap but beside the point.

Did not hesitate in boost going over the 3800 rpm threshold so I must assume that the N332 ecu is bum. Damn. I guess it makes sense since it's clearly a secondaries problem, my grounds are awesome and nothing was wrong before the swap.

The search begins for a working replacement. Or do you think maybe this one is reparable?

 

It wouldnt be worth repairing when a good used unit only costs 100 bucks, if that.

 

OK, so got a new known working ecu in. Aaaaaaand the problem persists.
So back to the drawing board I guess. *sigh*

My friend mentioned something about the secondary wiring being reversed when doing a turbo swap. I looked at the FSM and I think I have it right but I dunno for sure. Light green/white wire is going to the front secondary injector on my car. He said this caused him a lot of problems when doing the swap. Anyone know anything about this?

Unless 2 ecu's from completely different sources can fail in the exact same way?

 

Could a large boost/vac leak cause something like this?

 

I don't think the ECU is bad if you tried another one. I don't think its a vacuum leak either but you can check engine vacuum to be sure, how much vacuum are you pulling at idle (at what speed)?

All I can suggest is maybe run the car open downpipe if the cat might be clogged, or spray test all the injectors but turning the CAS gear with the KOEO and the injectors ziptied to the rails.

I think the wiring being reversed is more likely since you just had the injectors cleaned and the problem occurs exactly at 3800rpm. I know its discouraging to doubt your own work but I would honestly check everything I did with the injectors first.

 

Well I'm pretty certain I have a leak of some size. I can hear hissing and I'm only hitting 4.5psi boost. Pulling around 15 mmHg at 1000rpm.

I'm pretty sure the cat is indeed clogged to a degree, haven't had air injection working on it for some time. But I can't imagine it causing the 3800 bog.

When wiring in the injectors, the clips I got did not specify polarity and was told it did not matter. Is this true? Does polarity matter on the injectors?

And sorry, what do you mean "KOEO"?

 

Yeah those two are unlikely culprits, KEOEO = Key on Engine Off.

 

OK, so the issue has been fixed.

Pretty much, I win idiot of the year award. When doing the swap, I ended up using the TII secondary fuel rail in conjunction with the stock NA primary rail. I ran new fuel lines and never gave it a second thought. Now after taking off the UIM and looking at it for a minute I see that the FPR came BEFORE the secondaries in the system I created. Essentially my secondary rail was not pressurized. FAIL. I swapped some lines around so the FPR comes AFTER all the injectors and now it runs and pulls like a champ.

Just thought I'd update everyone who was watching and for future searchers.

 

lol yeah I had that dilemma too when I was doing mine, its been so long that it didn't occur to me. IIRC with the two different rails the primary to secondary fuel line has two sharp bends and the lines look reversed. I've been running my car like that for a while with no leaks or issues.