Rb20de"t" running lean

[WierdblueR32]

Yes I know there's a few forums but none have been able to lead me to a fix for my 89 r32 gts-"t"

The reason I use quotes around the t is because this car is a factory 1989 skyline gts rb20de 5 speed. I've just bought the car and the previous owner had told me fuel pump has just been done. Car is turbocharged with rb20det parts using det intake, turbo, manifold, and probably various other things to swap to det (also has large front mount intercooler). I do know that the timing belt has just been changed right before I got it, and has new coil packs on it. I've put about 120 miles on the car and pulled the plugs and the car is running very lean. It's noticeable with a rough idle and breaking up at high rpm under boost. Changed fuel filter thinking that was it but did nothing though it was dirty. Changed MAF as well because it was filthy, cleaned it, still ran bad, so I bought a new one to no avail. Ive sprayed starting fluid all around the intake and hoses and I am unable to trace a leak anywhere. So I am stuck at the moment and starting to lean towards a dodgy fuel pump or stuffy

injectors, but it runs great with MAF unplugged, although I'm only able to rev it to what is it like 3 thousand in limp mode. Also with it unplugged it idles at like 1200 rpm. Idk just want some more feedback from people who know these cars better than I do. 

[KiwiRS4T]

 When you say you got a new MAF is it a brand new genuine item and the right one for the application? Have a look at the plug wiring - sometimes resoldering the connections will help. The unknowns are - do you have a suitable ECU and are the injectors right for the application? Did you get receipts for the fuel pump? Is it brand new or used? Can you get the use of a fuel pressure tester?.

[Ben C34]

Get a wideband. 

[WierdblueR32]

6 hours ago, KiwiRS4T said:

 When you say you got a new MAF is it a brand new genuine item and the right one for the application? Have a look at the plug wiring - sometimes resoldering the connections will help. The unknowns are - do you have a suitable ECU and are the injectors right for the application? Did you get receipts for the fuel pump? Is it brand new or used? Can you get the use of a fuel pressure tester?.

MAF is genuine nissan. Connections look good but will do further inspection of them. Will ask previous owner about this.ill try to get ahold of him, but if the fuel pressure was low then why would it run fine in limp mode?

Edited June 30, 2020 by WierdblueR32

[WierdblueR32]

5 hours ago, Ben C34 said:

Get a wideband.

Will do

[KiwiRS4T]

4 hours ago, WierdblueR32 said:

MAF is genuine nissan. Connections look good but will do further inspection of them. Will ask previous owner about this.ill try to get ahold of him, but if the fuel pressure was low then why would it run fine in limp mode?

You don't know that it runs fine in limp mode - only that it delivers enough fuel for 3000 rev/min

[robbo_rb180]

Confirm its running lean with a Wideband first
If lean check the following:
-Vac hose is on fuel reg
-It has around 43.5-45psi of fuel pressure at idle (Plumb in a guage between the filter & fuel rail)
-check fuel pump filter
-Depending on what fuel pump it has it may need the relay mod & correct wire size
-Plug into consult port and check AFM voltages (google search for pc software)
-Take it to a mechanic that knows what they are doing (Does not need to be "Import guy"... its basic stuff to fault find)

All simple stuff

[ossy]

Timing is possibly out? 

I've got a R33 that was doing the exact same thing and I couldn't figure it out for a looong time. Some times power was great and other times it drove like crap. Took it too some Skyline specialists and turns timing was out badly and the fuel pump was leaking  back into the fuel tank so wasn't getting enough fuel either.

Mine had a new timing belt done by the previous owner as well but didn't do it properly

[WierdblueR32]

2 hours ago, KiwiRS4T said:

You don't know that it runs fine in limp mode - only that it delivers enough fuel for 3000 rev/min

Whenever running it with it, getting really bad studder down low, unplug throttle response seems to improve and engine runs quite a bit steadier.

[WierdblueR32]

42 minutes ago, ossy said:

Timing is possibly out? 

I've got a R33 that was doing the exact same thing and I couldn't figure it out for a looong time. Some times power was great and other times it drove like crap. Took it too some Skyline specialists and turns timing was out badly and the fuel pump was leaking  back into the fuel tank so wasn't getting enough fuel either.

Mine had a new timing belt done by the previous owner as well but didn't do it properly

That what I am thinking too!!! Will double check this because I don't think someone does a timing belt on a car that runs lean.

[WierdblueR32]

6 hours ago, WierdblueR32 said:

That what I am thinking too!!! Will double check this because I don't think someone does a timing belt on a car that runs lean.

Ok so car ran good a few weeks before I bought it. (After belt was changed) it developed a misfire and he replaced coil packs to no avail, and that's when I bought it (knowing it had a misfire) So I was troubleshooting the fuel system today and unplugged vacuum from fpr to fuel rail and see if it would increase pressure and make it run rich while also checking vacuum. It has good vacuum at idle, but the car still runs lean. Now I'm targeting fuel pump issues whether its voltage or pump weak.

[Ben C34]

If you buy a car with issues I would expect you know what you are doing, not just randomly unplugging things.

 

Fuel pressure gauge, don't guess.

wideband, don't guess

Timing light, don't guess.

 

 

 

 

 

 

[WierdblueR32]

1 hour ago, Ben C34 said:

If you buy a car with issues I would expect you know what you are doing, not just randomly unplugging things.

 

Fuel pressure gauge, don't guess.

wideband, don't guess

Timing light, don't guess.

 

 

 

 

 

 

Ok I'll stop being dumb, I'll try doing it the right way before I break something. 

[WierdblueR32]

Hey, figured id pop back in on this. I did wind up getting the car running right again with no breakups at high rpm, poured in some fuel injector cleaner/octane booster with 5 gallons of fresh high octane gas, problem gone after it ran for about 30 minutes revving here and there. Drove it around an out about 20 miles on it in the days after with pulls up to like 6800 rpm I wanna say, didn't go too harsh on it but did get to full boost a few times, and plugs were no longer super white like they were, and now look perfectly fine. I did also double check gap on all plugs, checked vacuum lines, checked fuel pump pressure, voltage, timing, everything was good. Hard to believe just stuffy injectors can throw you through a loop, but when you start doing dumb things as I did, it wastes your time. Thanks for help and slapping me on the right track, appreciate it!

Edited August 13, 2020 by WierdblueR32