Absolute RB20DET Headache (Stalling, Rough Idle, etc)

[NathaNZ]

Hey guys, hopefully someone can shed some light or point me in the right direction because I'm feeling pretty fed up with this car at the moment. ?

I've got a series of issues which probably all relate to one problem.

- Car will stall 90% of the time when coming to a set of lights as soon as you clutch in (same with trying to park)

- Car is running incredibly rich, strong smell of fuel, plugs are fouled

- If you floor it, it slowly creeps through 1000-3000rpm and then 3000 onwards takes off alright (feels like some mental lag for a stock rb20det turbo)

- Can sometimes get it to idle around 600 if I'm lucky but as soon as you give it the slightest rev, the revs fall down and it wants stall out

- Generally idle hunts between 300-600 rpm.

Another thing I have found odd is the idle screw on the IACV doesn't affect the idle what so ever.

Things I've done:

- Cleaned MAF

- Cleaned IACV (Also manually put 12v on the IACV and it does click)

- Removed vent to atmosphere BOV as I've heard RB's can play up with these

- Checked for vacuum leaks with carb cleaner around all vacuum lines

- Checked all couplings and intercooler piping for any visible cracks

- Set TPS to 0.48v

From one desperate dude to another, please help. ?

 

Edited May 10, 2020 by NathaNZ

[Duncan]

well, the all of those things point to horribly running rich, and assuming standard setup (or previously working aftermarket setup), the easiest way to get that is to have a reasonable sized air leak after the air flow meter and before the engine.  I know you said you checked your intake piping but I'd pull each bit off and have a closer look to see if you can find a loose clamp, split intake pipe or some sort of crack somewhere.

BTW, assuming you have changed or cleaned the plugs, you might need to do that often while trouble shooting

[NathaNZ]

3 minutes ago, Duncan said:

well, the all of those things point to horribly running rich, and assuming standard setup (or previously working aftermarket setup), the easiest way to get that is to have a reasonable sized air leak after the air flow meter and before the engine.  I know you said you checked your intake piping but I'd pull each bit off and have a closer look to see if you can find a loose clamp, split intake pipe or some sort of crack somewhere.

BTW, assuming you have changed or cleaned the plugs, you might need to do that often while trouble shooting

Hey Duncan, thanks for your reply man.

Completely stock RB20DET, stock ECU as well.

I'll have an even closer look at each individual coupling tomorrow. Plugs are black and fouled, but I didn't want to chuck new plugs in as I figured they would get fouled with the car running rich as well which would ruin the plugs. Could I be wrong?

Cheers

[Duncan]

glad i mentioned, unfortunately there's no point looking at anything unless the plugs are good.  ultimately if they can't fire because too fouled, fuel won't burn and you get mega rich smell and symptoms. you need to put good plugs in and try again, just use cheap coppers as they fire best and are cheapest to replace again if you have to

[GTSBoy]

2 hours ago, NathaNZ said:

Set TPS to 0.48v

Not relevant on an RB20.

Won't be a vacuum leak, as your idle is low, not high.

What is the timing set to?

[NathaNZ]

14 hours ago, GTSBoy said:

Not relevant on an RB20.

Won't be a vacuum leak, as your idle is low, not high.

What is the timing set to?

I've had a chat to one of the mechanics at work and he reckons these symptoms sound like the timing belt being off by a tooth, could that be a viable conclusion?

[GTSBoy]

Possible. Both the effects on the cam timing and the ignition timing will affect how it runs.

[jessr33]

Nathan you mentioned -  the idle screw on the IACV doesn't affect the idle what so ever.

On my RB25DET, I've had to adjust the TPS & the idle screw on the IACV on several occassions to find the happy medium to stop my 33 from stalling. She would barely hold her idle at any point in time, especially on approach to lights (ultimately any time I put the clutch in I'd have to feather the throttle whilst braking to prevent her from stalling, even turning her over she would just stall unless i gave her revs). It took a lot of playing around if I'm honest given the sensitivity of the TPS & idle screw and the final result was putting thread tape around the idle screw on the IACV and then adjusting until she retained her idle.

I only thought this may be relevant since you mentioned your idle screw on the IACV doesn't affect the idle.... hope it may be of some assistance as I essentially had the exact same issues for quite some time.

[GTSBoy]

The idle screw is probably full of crap. Unless you pull these things apart completely, you can never be sure that they've go an air passage through them.

[jessr33]

1 hour ago, GTSBoy said:

The idle screw is probably full of crap. Unless you pull these things apart completely, you can never be sure that they've go an air passage through them.

can you elaborate further as to why the idle screw is full of crap as it completely resolved my issue and i was having the exact same problem?! if he has cleaned the IACV thoroughly and the idle screw I don't see why it wouldn't have an air passage through it? My idle screw had too much air passing through and hence the thread tape is actually what alleviated the problem in the end. Apologies if I'm incorrect in my suggestion; but that is what worked for me

Edited May 11, 2020 by jessr33

[BK]

I think you need to re-read the post you quoted...

[NathaNZ]

15 hours ago, jessr33 said:

Nathan you mentioned -  the idle screw on the IACV doesn't affect the idle what so ever.

On my RB25DET, I've had to adjust the TPS & the idle screw on the IACV on several occassions to find the happy medium to stop my 33 from stalling. She would barely hold her idle at any point in time, especially on approach to lights (ultimately any time I put the clutch in I'd have to feather the throttle whilst braking to prevent her from stalling, even turning her over she would just stall unless i gave her revs). It took a lot of playing around if I'm honest given the sensitivity of the TPS & idle screw and the final result was putting thread tape around the idle screw on the IACV and then adjusting until she retained her idle.

I only thought this may be relevant since you mentioned your idle screw on the IACV doesn't affect the idle.... hope it may be of some assistance as I essentially had the exact same issues for quite some time.

Hi Jessr,

Thanks for that, I'll definitely have a look to see if I have the same problem.

[NathaNZ]

Right guys, we are getting closer, all my "lag" issues and running rich issues are sorted, the car drives really well after I noticed that the knock sensors have been fully cut and there has been no resistor put into pin 23 and 24 of the ECU which places the ECU into a knock map to avoid damage. So today I went and got two 470k resistors and soldered them into 23 and 24 and the car runs nicely while driving.

Sadly however the idle hunting, stalling when coming to a stop and low idle (400ish rpm) are still there. 

Edited May 17, 2020 by NathaNZ