Won't Idle: 370cc, T-Rex Pump, Z32 MAF, JWT SC Program
 

It cuts out shortly after startup--if I don't give it gas, it dies immediately. It won't even idle poorly.

I haven't tried rotating the MAF 90 degrees yet (I'm still using the Stillen charge pipe), but I assumed that it would at least idle poorly positioned as it is.

What could cause it to cut out like this aside from a huge vacuum leak? I figured that it could be too much fuel at start up, but shouldn't the JWT ECU correct for the larger injectors?

Thanks in advance.

A note on my previous setup:

Previously, I was running a Vortech FMU, 3.6 in. pulley and OEM injectors & MAFs.

The JWT should if it's programmed for those injectors. What is your FP.

I don't have a fuel pressure gauge, so I'm not sure of the pressure, but I'm using a stock FPR.

Sounds like it might be time for an AFPR and a fuel pressure gauge.

Did you have JWT build the ECU for you? Sounds like you bought it used from another member. If so, what are the specs of this JWT ECU??

Try rotating the MAF first and see if that solves your problem (although this is difficult with your current setup). When I installed my Z32 MAF, I blindly followed IanSW advice and positioned it upright. I've always wondered in the back of my head if I would experience the same symptoms as IanSW if I had the Z32 MAF oriented like the stock 4th gen MAF.

After it dies, pull one of the plugs out. If it is doused with fuel ,then your fuel pressure is too high. Right now I'm running 25PSI with 370 injectors. I had the same prob when I first put on the Emanage.

My JWT ecu was fairly lean at idle. I added fuel pressure to accomodate. It works fine now.

I bought the ECU used. I was told that it was programmed for "up to 740cc injectors", z32 MAFs, and a customized timing map. I'll try rotating the MAFs later today.

I just pulled one of the plugs and it was a little shinny but when I smelled it, it didn't smell very strongly of gasoline. I could just be that I'm used to the smell at this point, so I'll have my brother smell it too.

When I rev the car to keep it from dying, I hear a distinct popping noise--which I assume is backfire--so, I guess I could be running lean.

One quick question, which is going to make me sound like a newbie. When redoing the fuel lines after removing the FMU, I ran it from the in tank pump, to the T-Rex, to the front of the fuel rail, and from the rear of the fuel rail to return. Is this the correct way to route it? Second, to be sure, is the fuel return line the one with or without the fuel filter inline?

What size injectors was it programmed for though? They can do whatever size you need, but it isn't an any and all program, it is specifically for one size.

I'm really not sure. I was told "up to 740cc" and was told that 370s would work; the previous owner was using 450cc injectors. I might try using my original ECU to see if I have any luck.

That sounds a little fishy. It's my understanding that JWT programs the ECU for a specific cc injector. ie 370cc, 440cc, 555cc etc., not a maximum cc.

Edit: 96sleeper beat me to it. I type too damn slow. :o

You can always call JWT, give them their serial #, and they'll tell you exactly what the ECU was programmed for. :)

I'm going to contact the seller to see if he can help me sort this out. If they are indeed programmed for 740s, that could explain my lean idle.

Could someone please clarify my question about fuel line routing in post #8? Thank y'all for your help so far.

edit: I just tried the car w/ my stock ECU and it was easier to keep alive w/ the gas pedal and didn't pop as much, but I had more or less the same issue.

you bought wunfastmax's ecu right? He was running larger injectors.

Backfire usually means you're running rich, not lean.

Your fuel lines are hooked up correctly. The return line is the one w/o the fuel filter inline.

Wasn't he running 450s?

Yes he was . Have you tried to pm him and see if he had similar problems?

Just got off the phone with Ben at JWT and he told me that if I try to run this ECU w/ my 370ccs, it will run lean at idle and pop a lot (and it's definitely popping), and will run rich throughout the power band. Looks like I'm going to have to get it reprogrammed.

Is the car driveable with the stock ECU, Z32 MAFs, and 370s?

I'm going to try flipping the MAFs and recheck my fuel lines today to see if I can get it running.

Yep. Hope to hear back from him soon.

Do you have a afc of some sort? I mean i think you can get away with it but i wouldnt drive it hard at all.

Nope, I don't have an AFC. I was hoping that the JWT would take care of everything. (A local member had great results with the JWT alone, and I was hoping for the same.)

IMO, in order to acheive the same great results as the previous owner, you're going to have to setup your car exactly like his. ie same injectors, MAF, AFPR etc all the way down the line...

I take it you do not have a WB02 setup.

Nope, don't have one installed.

I was actually referring to a local .orger and not the previous owner of this ECU. The local .orger is running the same fuel setup and MAF as me (although w/ a Walboro instead of a T-Rex) and the JWT works very nicely for him. Hopefully, I'll have the same results once I get mine reprogrammed for the 370s.


So, I replaced the JWT w/ my stock ECU, rotated the MAFs, and installed a new upper plenum gasket; it now idles nicely. I'm too afraid to drive it w/o a tune, so I'm going to hold off until JWT reprograms my ECU.

When I try running the JWT ECU now, it will start up and then die. The seller told me that it worked fine with no correction w/ his 450CCs, but I suppose my 370s are a bit smaller.

Thanks for the help, everyone.

I just saw this thread. I know that they specify that the what size injector the progam should be ran with, but I do infact have 450cc injectors. I also have an afpr w/gauge. As you asked me about the correction, I did have an emanage hooked up to it, and at first i tried to correct it by putting in 450 to 740, but it ran like total crap. I then put 450 to 450 and the car ran great after that, I used the emanage for nothing else other than to see where my mafs voltage was as at.

As for drivability, I drove the car as my daily. The car made 15psi of boost and was raced often. I had no problems other than the when I first got it and tried to correct it. The video I posted in the for sale thread was of the car w/jwt ecu installed.

Im sorry for the grief your having with this. I did write you back if nothing else works, I will do what I told you in the pm.

I got the ECU back from JWT this week. My bro popped it in and says the car runs like stock--can't wait until I get the car out here (in CA) and throw on some drag radials. Fifteen PSI at 7200+ RPMs should be a blast!

dont blow your motor. :)

You'll need timing retard for that psi won't you? Definitely get a wideband, that is almost a must for any boosted vehicle to see where your afrs are at.

JWT pulls lots of timing. I'll have my A/F checked out on the dyno soon and will consider getting a WB later.

It is a blast. Glad to see everything got worked out.