Red Top Rb20 Running A Bit Rough

[GTR81]

Hi guys,

Ive got red top 20 in my 31 that is playing up a bit.

I bought the car just over 18 months ago, it ran fine for a year and then it just wouldn't start one day.

So after trying for a while i worked out if i give it heaps of throttle while cranking it would fire but run very rough( previously didn't need to touch the throttle to start it).

from there once it warmed up it runs pretty good, there is a bit of hesitation when pushing in the accelerator but apart from that it will rev to redline and idle ok but

it only runs for around 5 mins then stops. If i give it a big rev and leave my foot off the accelerator it also stops where as a big rev and leaving my foot on to bring

it back to idle a bit slower and it will keep running.

The other thing is it will build boost while stationary, it does have a haltech ecu but i dont think it has anti-lag function turned on?

So far i have replaced coil packs, ignitor, spark plugs and fuel filter none of which made any difference.

Any help would be appreciated as im a bit lost on what to check next.

And before everyone says to ditch the 20 and put a 25 in, that is the plan but i dont have the time and space to do it at the moment.

Thanks

[Sinista32]

Fuel pump, fuel reg ?

Edit: Also run a fuel cleaning system additive like Liqui-moly through it.

Edited January 3, 2015 by Sinista32

[GTSBoy]

Check fuel pressure at idle and under load. Swap out AFM with a known good one. And/or clean the element with a spray of CO cleaner. Check ignition timing (properly). Check cam timing perhaps. Then you're on to looking at injectors perhaps.

[GTR81]

Thanks for the quick replys

The fuel pump is a reasonably new walbro and the reg is the standard one so ill check the pressures as suggested. Do i just tee a gauge into the feed line to check the pressure with a standard reg? as there are no ports on the standard reg.

It doesn't run an afm with the haltech so all good there.

Checking the ignition timing properly is that with a timing light?

one other thing is if i put a big fan in front of the car it does run alot longer so possibly something to do with getting hot? and also it wont start again while its hot.

[GTSBoy]

Do i just tee a gauge into the feed line to check the pressure with a standard reg?

Checking the ignition timing properly is that with a timing light?

Yes and yes.

As to the heat thing.......tough one to answer. Shouldn't play a part when you're talking cold starts. The crash stopping could be heat related, for sure. How's your oil pressure? Is your water pump working properly (ie not corroded away)?

[GTR81]

Ok thanks, i will check them on the wkend.

As for the oil pressure i need to get a new sender unit, and water pump well that will have to wait

[GTR81]

Ok fuel pressure seemed fine it was at about 33psi at idle and went to 45ish under boost and its running about 13psi of boost so that seems fine.

I still dont understand why its building boost while stationary though, is there any other reason it will do this or does mean that there is deffinetly a launch control/ anti-lag feature on?

[Ben C34]

Cam and or ignition timing being wrong would cause that.

[GTR81]

Ah well that makes sense, if the timing is out could it have been like that for a while and i would never notice it?

Im going to pull the injectors out and get them checked or replace them as 1 or 2 sound alot louder than the others and when the car first started playing up about 6 montha ago i was changing the plugs

after trying to start it so the engine was flooded and noticed 1 plug was dry, which at the time made me a bit suss about the injectors but after that i had got the car running so i never give it another thought.

[GTR81]

Ok so changed injectors and its still the same.

I'm thinking CAS next as i took it off to have a look at it and at some stage it has gotten very hot! Does anyone know if i can use a CAS off a GTR and just rewire a suitable plug on to the loom or are they different on the inside? Or is there any other models that are compatable with red top ones?

[Dylan454]

My rb20 silver top was being a pig. It would randomly cut out and jerk about really bad sometimes. I changed the AFM and the CAS and it fixed my problems. I think the rb25 CAS fits silver top rb20's, not sure about red. Good luck

[hypergear]

Check your water temp, some times the clutch in the fan worns that leaves your engine to overheat. I found the old water temp gauge on the Nissan would not go pass the mid section regardless of how hot the water temp is. This happened to my r32 many years ago.

[GTR81]

Thanks for the input guys, its got an aftermarket water temp gauge and its working fine.

Anyone else know if any other model RB's have a CAS that is compatible with a red top 20?