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Rb20Det R32 Gtst Rough Idle

BaileyH

By BaileyH,
in Forced Induction Performance

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BaileyH Apprentice

BaileyH

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Hey guys.
im new to the "SAU", im just wondering if i could get a little bit of help, sorry if the thread is in the wrong spot, feel free to move it.

But, i have a r32 gtst with an rb20det.
It has a rough idle, but when you rev it and its on boost it revs cleanly.

Has anyone had this problem before?
Any ideas on what it is?
I have a feeling its an injector or something :\

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R_34 Community Regular

R_34

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I'm having it right now, the brake booster have a little leak from time to time. When it happens the AFR at idle goes up to ~16 AFR (instead of 15), the idle becomes rough and the vacuum lowers to -0.55b.

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BaileyH Apprentice

BaileyH

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Mind you, this car has been sitting in a padoc for 6 months plus.
It has old dirty fuel in it.
Its not at my house though yet, i only recently just bought it. But the guy is trying to fix it for me before it comes to mine.
Would old fuel, and old fuel filter make a difference?

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R_34 Community Regular

R_34

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No an old fuel will not act like this.

I had my S13 lying for a year before the swap, I managed to start it with difficulty (very very low compression on 2 cylinders), after some minutes of warm-up it ran great. No miss or rough idle, the engine was running on all cylinders and performed "normally".

The old fuel filter if clogged or soon to be will restrain fuel flow so the engine will have difficulty to run when it weel need fuel flow. A friend of mine never changed is fuel filter, when the filter finally clogged, the engine was running like a charm at idle but couldn't move the car, as soon as it was giving some gas the engine would die.

Check for the vacuum leak (especially around the injectors), plugs and coil, rusty earth etc...

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R_34 Community Regular

R_34

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It looks like a vac leak, am I sure without having the car under my eyes ? No.

Thing is there is a lot of R&R to search, find and fix a vacuum leak, especially on a RB because the injectors seal are difficult to reach.

You can use some brake cleaner to find a leak with ease. Spray it around all the gasket/vacuum hose you can reach and listen to engine rpm change.

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R_34 Community Regular

R_34

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I don't know the RB enough to answer this question.

I didn't wired the OBD light on my S13 and I don't have a consult to check the codes when the leaks on the brake booster appears.

If the OBD light isn't ON on the dash i doubt there is a code to read but double check this with a more experienced RB owner.

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R_34 Community Regular

R_34

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No but an erratic airflow signal might throw a code, or the ECU could hit the limit when it's trying to trim the AFR with the O2 sensor. ;)

I don't know if the ECU is advanced enough to find a abnormal behavior from its sensor and throw a code.

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Ben C34 Grand Master

Ben C34

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The ecu is definitely not smart enough to spot a vac leak .

op have you paid for this car?

It amazes me how people are happy to buy cars woth problems and set a step learning curve for themselves to fix it.

Good luck with it.

Edited by superben
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BaileyH Apprentice

BaileyH

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Hey superben, not sure if you're trying to say we are idiots or if you are actually saying its good..
But nah, i know jack shit about RB's.
I told him i dont know much about them, my mate does who is helping me and ive learnt a little bit.
But nah he's gonna fix it and then give it too me. Im just trying to help him fix it, by asking around seeing if anyone else has had many problems.

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Ben C34 Grand Master

Ben C34

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Im not saying you are an idiot, its just that buying a car with problens is a whole lot of pain, especially if you dont know about what you are buying.

Did you buy it of your mate? In that case I'm sure he will help you sort it, I thought you bought it off someone else who would just say they will sort it but not actually fix it.

Lots of small issues can cause misses.

You haven't mentioned what revs the car is idling at when missing.

I would be checking the timing and pressure testing the pipework to find any leaks, and replacing spark plugs and inspecting coils/ coil loom.

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BaileyH Apprentice

BaileyH

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Okay, well my mate who is mechanic said...
"It sounds like a bad plug, or a weeping injector.. More so injector because if its revving clean when on boost it sounds like 1 cylinder is getting a tiny flooded from the weeping injector and is sorting itself out when high revs".

Does that sound right?

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