S13 RB25 running rich at idle

[KyleT]

Hey, we finally got my buddies s13 rb25 going and its running very rich at idle. Once the car is running the wideband drops to around 10:1, which is very rich for idle. Now when you try and rev it up it only will rev to around 3k rpm and seems like its hitting a revlimiter/bogging out. When you try and rev the car up the wideband goes full lean and comes back down to around 10:1 when the car revs down back to idle.

We tried unplugging the maf and the car dies, so I think the maf is working. But the car has a z32 maf which came with his motor swap. So Im thinking it should be wired up correctly since it ran before. Any way I can check?

Car has an aftermarket fuel pump and adjustable fuel pressure regulator which is set at right about 43.

Just did a boost leak test and didnt find any major leaks up to 20psi. Created a vacuum leak and the car doesnt run as rich(around 13:1) but still leans out under throttle. Basically im looking for some help at what to check next.

Forgot to mention the car has a greddy plenum and a q45 throttle body and the iac/aac has been removed.

[Sileighty_85]

Get the Correct RB MAFS, a Z32 one is not a plug and play unless the ecu is tuned for it, which your story leads me to believe it not.


Forgot to mention the car has a greddy plenum and a q45 throttle body and the iac/aac has been removed.

Thats fucking Stupid put it back on.

[KyleT]

Get the Correct RB MAFS, a Z32 one is not a plug and play unless the ecu is tuned for it, which your story leads me to believe it not.



Thats fucking Stupid put it back on.


Oh, alright. For some reason I thought I read somewhere that the z32 maf will work but I guess that is probably the problem.

And as for the air control stuff, it idles fine without it and seems like a hassle to hookup with the q45 tb

I want the pink e60 maf, right? Its a rb25det s2

[KyleT]

Got the correct maf and wired it up correctly. Car runs alot better and revs up fully now. Wideband still drops down to about 10:1 after about 20 seconds, and the car takes a while to start. air/fuel ratio goes a little leaner when the car is revved up but comes back to 10:1 pretty quickly.

o2 sensor is brand new. Re gapped spark plugs to spec. Boost leak test check out ok.

Still stumped why it runs so rich at idle.

[mantas]

Got the correct maf and wired it up correctly. Car runs alot better and revs up fully now. Wideband still drops down to about 10:1 after about 20 seconds, and the car takes a while to start. air/fuel ratio goes a little leaner when the car is revved up but comes back to 10:1 pretty quickly.

o2 sensor is brand new. Re gapped spark plugs to spec. Boost leak test check out ok.

Still stumped why it runs so rich at idle.

Idle control valve man. Mine was acting weird when i messed with it. Its not that hard to hook up.

[KyleT]

Would it make that drastic of a change in the air/fuel ratio though? I dont believe the guy he bought the rb25 swap from had it hooked up either. Crap, I dont even remember there being electric connectors for it there.

[mantas]

Idk but mine is running quite rich right now because i had to turn the idle down cause my tps is not adjusted. But im only in the 12.9-13.6 range on a cold start. Idk but i think the iac is there for a good reason. Worth a shot.

[KyleT]

I thought with the q45 throttle body(car has greddy plenum and q45 tb) you control idle just with the throttle body. For some reason I dont really see the iac changing afr's that much. I could be wrong though.

[RandomVelox]

You control the idle with the IACV. Set the TPS to the correct amount of volts.

[mantas]

You control the idle with the IACV. Set the TPS to the correct amount of volts.

Havent gotten around to the tps yet, hopefully will be able to do that this weekend. Lol

[RandomVelox]

Havent gotten around to the tps yet, hopefully will be able to do that this weekend. Lol

Lol I'm pretty sure it'll help. I need to adjust mine too.

[KyleT]

Could the tps be throwing off the afr's that bad?

[RandomVelox]

Could the tps be throwing off the afr's that bad?

The IAC (Idle Air Control Valve) controls the amount of air getting into the throttle body/intake to coincide with the correct amount of fuel to get the perfect fuel/air mixture for proper combustion. Too much or too little air will affect the performance of the engine at idle.

[RandomVelox]

But yes, of the TPS is off it won't idle and run correctly.

[KyleT]

Yea but with the q45 throttle body doesnt it just open the throttle plate to control idle? Thats why you run coolant through it, theres a wax that heats up and it closes to idle lower when the car is a operating temp.

[mantas]

Yea but with the q45 throttle body doesnt it just open the throttle plate to control idle? Thats why you run coolant through it, theres a wax that heats up and it closes to idle lower when the car is a operating temp.

I know it has coolant connectors on the tb but i dont even want to bother with hooking that up hahah. On the other hand OP my iac has a hose going to the intercooler pipe right before the tb. Id say hook it up, its not hard and i see no reason not to have it.

[KyleT]

Yea we didnt hook up the coolant lines either. And I would hook up the iac, but I dont remember there being electrical connectors there for it on his harness and he never got any of that stuff with his motor. And I have a feeling that if we would trace down all that stuff it wouldnt even make a difference.

We pulled on of the caps off a nipple on his intake manifold to create a vacuum leak and the wideband reads at little higher at like 12:1. I tried to create a bigger vacuum leak and it idle surges and runs horrible. Still cant get the afr's in the 14's

[RandomVelox]

Yea we didnt hook up the coolant lines either. And I would hook up the iac, but I dont remember there being electrical connectors there for it on his harness and he never got any of that stuff with his motor. And I have a feeling that if we would trace down all that stuff it wouldnt even make a difference.

We pulled on of the caps off a nipple on his intake manifold to create a vacuum leak and the wideband reads at little higher at like 12:1. I tried to create a bigger vacuum leak and it idle surges and runs horrible. Still cant get the afr's in the 14's

There's no connectors for it? Then someone screwed him over with a messed up harness.

[KyleT]

There's no connectors for it? Then someone screwed him over with a messed up harness.

Yea, Ill look again today and see if I see any connectors.

[mantas]

There's no connectors for it? Then someone screwed him over with a messed up harness.

I dont think you know the meaning of screwed up harness unless you would have seen mine before i fixed it hahahhahah. It was unbelievable. Most of the wires were just twisted together i had plugs that didnt belong anywhere omg i could go on forever.

[KyleT]

Yea there are definitely no connectors there for the iac.

Drove the car around for a while today. It idles a little better, but still on the rich side. Air/fuel ratio seems to jump around alot at idle. It will stay around 14-15 then all of a sudden its back down to 12-13 then sometimes goes up to 16. Think this may have to so with the idle going up and down a little.

Driving the car, afrs seem alright, still a little on the rich side and sometimes leaning out under throttle. But when you punch the pedal it sort of bogs and seems like it doesnt want to go and sputters a little bit under boost. It just feels like it has no power. The car doesnt completely fall on its face, it just doesnt pick up and go.

[KyleT]

Would it help if I got a video to better explain what the car is doing?

[KyleT]

Anyone know what could cause the air fuel ratio to jump around so much at idle? It goes from 10:1 all the way up to 16:1 and never stays at a consistent ratio.