Rough Idle, And Stalling Issues...

[En!gmA]

Hello SAUWA!

I have recently been experiencing a very strange problem with my R33 (RB25DET) that has me at wit's end! After searching the forums and finding write-ups regarding similar issues, I thought I would post here for clarification.

I am not a man of a mechanical background, and have little experience with these types of issues...

During periods of low revs (such as circumventing speed humps, pulling up to park, pulling up to a traffic light etc) my car will often run very roughly, and will generally stall. This does not happen during all drives however, and quite often the car will run perfectly.

During these 'rough' periods, the vehicle will idle highly irregularly... almost stalling, then revving on it's own accord (if it doesn't just flat out stall).

I have uploaded a video via Youtube which depicts one such occasion of 'rough' idling.

My engine is mostly stock, but I am however running a brand new set of split-fires.

Any Ideas as to what problem is occurring here?

Before I take the car into a professional mechanic I would just like to run it past the SAU community.

Flooding? Dirty AAC? Vacuum leak? Battery?

Any help/advice is deeply appreciated! Cheers!

[colt75]

give your IACV a clean, there was a thread a few days ago about the same thing.

Vac leak can also make the car idle quite rough. - so check your vac lines.

flooding, unlikely. if the above fails, start ur car up at home, and let it splutter and stall. then take out ur spark plugs and check if theyre wet/smell like fuel.

[syfon]

Hey mate,

I have been having the EXACT same problem with my R33 in the last week.

I found out a few days ago that it was the gasket that sits between the upper & lower parts of the intake manifold had been "sucked" into the manifold itself. Therefore, what was actually happening was that extra air was CONSTANTLY being sucked in where the gasket should have been sitting.

As this extra air was "leaking" in, my car has also been running very lean (the AFM & computer can't detect this "extra" air).

This evening i removed my intake manifold (holy flerking schnit), and took the old gasket out - i think it had just dis-lodged but seeing as it is now out and i have a new one, the new one will go in!

I also notice that the 'bananas' (pipes the the air flow through to the cylinders) were progressivley darker in colour as i looked at cylinder 1-6 (1 being at the front of the engine). Cylinder 1 was almost clean - the manifold looked brand new there, however cylinder 6 was completely black. Now i am assuming that this is because of the air leaking where the gasket had dis-lodges - i'm not sure.

Anyway, sorry for the long write-up, but that was why my car was not idling properly and stalling/revving on it's own accord. I have not checked the AAC Valve (Auxilary Air Control Valve, located at the back of the intake manifold next to the firewall - this controls the idle speed of the car).

I hope this info helps you identify the problem you have at hand!

Cheers.

P.S. I havn't put the new gasket on yet or put the manifold back on, so i'm not sure if that was the only problem causing the idle to be rough etc etc.

[En!gmA]

Hey mate,

I have been having the EXACT same problem with my R33 in the last week.

I found out a few days ago that it was the gasket that sits between the upper & lower parts of the intake manifold had been "sucked" into the manifold itself. Therefore, what was actually happening was that extra air was CONSTANTLY being sucked in where the gasket should have been sitting.

As this extra air was "leaking" in, my car has also been running very lean (the AFM & computer can't detect this "extra" air).

This evening i removed my intake manifold (holy flerking schnit), and took the old gasket out - i think it had just dis-lodged but seeing as it is now out and i have a new one, the new one will go in!

I also notice that the 'bananas' (pipes the the air flow through to the cylinders) were progressivley darker in colour as i looked at cylinder 1-6 (1 being at the front of the engine). Cylinder 1 was almost clean - the manifold looked brand new there, however cylinder 6 was completely black. Now i am assuming that this is because of the air leaking where the gasket had dis-lodges - i'm not sure.

Anyway, sorry for the long write-up, but that was why my car was not idling properly and stalling/revving on it's own accord. I have not checked the AAC Valve (Auxilary Air Control Valve, located at the back of the intake manifold next to the firewall - this controls the idle speed of the car).

I hope this info helps you identify the problem you have at hand!

Cheers.

P.S. I havn't put the new gasket on yet or put the manifold back on, so i'm not sure if that was the only problem causing the idle to be rough etc etc.

I'll have to get this looked into...

Thank you both for your prompt replies!

[mosquitocoils]

+1 AAC/IACV clean. Pretty easy to do with a basic toolkit, even if you're not mechanically minded. Link is in my sig. Saved me a lot of headaches!