Numerous Rb20det Issues (spiting And Backfiring)

[Drakey]

Hi all,

Had an issue with the RB20det for sometime and havent nutted it out.

RB20DET

RB25 turbo

Cooler

Cam Gears

3inch straight through

It used to run 14psi happily, but it then started to play up and i couldnt get full power once full boost kicked in, it just felt like i lost 40% of the power and made a wierd intake noise like it was struggling to get air.

I changed the boost to 9psi and it runs fine, but anything 10 and over it spits and back fires etc.

I changed the plugs thinking they could be blowing out, but same problem.... i have been over the engine bay and cannot find anything thats loose etc.

I am also noticing recently that when cold the idle is very iregular and wont sit still, and only sometimes when i first start it up it wont make any power unless i start to make boost. Almost like the struggling air situation i mentions above (weird intake noise)

Do you people have any ideas on what these issues could eb caused by?

Thanks for your time and help.

[ashr32]

well ill start you off,

first problem

1, your rubber intake hose that connects to the turbo could be collapsing in on itself.

(lots of threads about it on SAU)

It explains the sound and although it didn't do it before the rubber is getting up to 20 years old and was only designed for 10psi

second problem

1, your tune will be way out due to the r33 turbo causing over fueling and flat spots

i have the same problem and im guessing that as soon as your car is warm its gone?

2, clean valves (grab the guide) search "cold start valve" or "acc valve"

3, clean AFM (grab the guide) search "cleaning AFM"

4, check for air leaks (specifically check you vacuum at idle cold, and once warm

honestly it sounds like you have a classic rb20det cold start issue. ive tried so many times to fix it and so many hours. if its none of the above just DONT drive it cold. i dont and i love the car hahaha

good luck

ash

[dori34]

I am also noticing recently that when cold the idle is very iregular and wont sit still

had this issue on my old 32.

you got a faulty IAC (idle air control) valve.

common problem on rb20s,

spiting/backfiring - check your coilpacks & ignitor.

[Drakey]

Ok... lol

After taking everything apart... checking plugs, clean afm, learning how to use the computer diag...i still couldnt find the problem.

Until i found a boost leak which explains over 10psi why it made a weird noise lol

And now it runs awesome up till 14psi...

Tried 15psi and it wasnt bad but spat a little bit... but still not too bad.

im happy!