Hey guys so have a s5 turbo2 swap done into my 86gxl With a s4 turbo harness and computer. Aem pump and upgraded injectors(I'm not sure on the size although I was told they weren't far from stock sizes). Fuel pressure is set to 36-38psi I believe. tps is set as well . Ever since I did the swap my car has been running rough. Even after adjusting all those things also checked for vacuum leaks and there was none. So whenever I start the car it idles like it wants to die it's constantly hunting from 200- about 1000. Then when I drive it and I come to a stop it idles fine for about 2 seconds and then it starts hunting once more then the rpm gradually drops lower and lower and if I don't give it some gas it shuts off. This gets worse when I have the lights on. Is there an electrical draw somewhere ?is this mechanical? Any help would be much appreciated.

 

Question number one is what else is done to the car? If you have fuel mods done to a stock car with a stock ECU, that's where I'm pointing the finger first. No need, so either go back to stock, or upgrade the ECU and evaluate from there.

 

what he said about the stock ecu and bigger injectors. or your TPS is completely broken or you have a vacuum leak imo

 

All I have aftermarket wise is a 2.5inch racing beat downpipe into a 3 inch exhaust a bov, an aem green pump, and the injectors which my mechanic said was close to stock. I'm not sure on the size. Koyo rad. I've changed the tps and the Air flow meter they both tested to be good. Also when I'm driving at a certain rpm 1500-2500 if keep it there the cars bucks and jerks like crazy, I have to clutch in or let go. I was told that there's a flat spot or lean spot. Maybe injector wiring wrong ?

 

Just unplug the TPS and see what that does. And initially make sure you have the coil wires running to the correct spark plugs.

 

i will try that today thanks. and I've double checked the plug wires they're correct

 

Okay so I had the car running and then I unplugged the tps then the car died. If I revved it with the tps unplugged it revved it just wouldn't keep idle on its own. Also I squeezed one of the fuel lines coming off the fpr and the idle smoothened out.

 

Are you certain you squeezed one of the fuel lines or the vacuum hose of the FPR?

 

It was the feed line I believe definitely not a vacuum line Came off the fpr and went to the rail. I'll try to post a video up

 

That tells me your injectors are too big, or your fpr is el junko

 

The injectors I have are Marren injection I believe they are 550cc or 525cc I will have a definite answer tomorrow.



The pressure while idling (excuse the gauge) it's close to 40psi





When I squeezed the line it dropped closer to 30 and the idle smoothened out.

 

Do you have the fuel resistor relay incorporated into your fuel system?

 

To be honest I don't know. I'll have to check

 

So i do have a fuel resistor relay incorporated into my car's system. after thoroughly checking for vacuum leaks and finding nothing i'm about to pull the upper intake manifold off and check the harness. would the injector plug being plugged incorrectly or perhaps a wire being broken give me an issue like this? also the injectors that i have are marrenn injectors in the 500's again not sure on what exact size but they aren't that much bigger than stock.would that still be an issue even if they are slightly bigger than stock? again thanks for all the help

 

So when taking off the upper intake manifold I found that the lower intake intake manifold had a crack in it.

 

How in hell does that happen?

 

I have no clue. I'll take pics tomorrow when I can. The front runner on the lower intake had a crack,when I took the upper manifold off, the end of lower just broke off completely. Upon further inspection I found that the rear runner has a crack on the inside. I was told this could happen from over tightening.

 

Quit using that 1" impact gun.

 

no impact gun was used to tighten those. Just a 3/8 drive ratchet.