Engine Problem, Maybe Fuel

[yoshiii335]

Hello,

I have a r32 gtst with the rb 20det.

My car has a rough idle/shake. When the car is started it has a rough idle/ shake but goes away after driving. The car drives smoothly and accelerates fine. If the car is driven a little hard, when it comes to a stop, it has the rough idle/shake.

About three weeks ago the weather started to become colder (17 degrees celcius). The car developed the rough shake/idle at start up. It was bad. Also as I found out later, a cylinder was missing. The power of the car was down. At the same time I believe I got a bad batch of gas.

The car had a weird coil pack set up that the previous owner had installed. The coil packs were mounted next to the windshield wiper motor. There were orange spark plug wires connected from the coil park to the spark plugs. All of the tuners that I went to said that the coil packs would have to be returned to the stock set up before they would tune the car.

I had some extra coil packs and had them tested at Nissan. They said that the coil packs were good to go. I did a compression test and the readings from the cylinders from the front of the engine to the back was: #1 140 psi. #2 135 psi, #3 135 psi, #4 135 psi, #5 140 psi, and #6 135.5 psi .

I changed out the coil packs and the coil pack harness. All cylinders worked after that. But the rough idle/shake was still there as well but the power had not returned fully to the car.

I changed out the spark plugs to HKS Iridium's M35's (had the same in there before). When taking out the old spark plugs, a friend mentioned that one of the spark plugs looked as if the cylinder it was in was running lean.

After changing the spark plugs the rough idle/shake went away some. I used a fuel cleaner, Seafoam, to clean out the fuel system incase some of the problems are fuel related. I think it may be fuel related.

The car's power came back and the car began to drive much more smoothly and quickly. The rough idle was pretty much gone(going away) When starting the car, it was smooth. But the weather is colder now and when I start the car it has the rough idle/shake and when the car is driven a little hard, it comes back when the car is stopped.

The weather is now in the 10-14 degree time. Winter is coming.

So could this be fuel related? Are my cylinder psi readings good? The car has about 138,000 km on it. I am using a GTR fuel pump and I changed the fuel filter to a new one earlier this year.

Could the fuel pump be going out?

Edited December 10, 2015 by yoshiii335

[Ben C34]

Put a neo in.

[KiwiRS4T]

Compressions are ok.

Have you tried this: http://www.sau.com.au/forums/topic/110431-diy-aac-valve-cleaning-idle-reset/

(not sure if it applies to RB20DET)

Maybe time to pull the injectors out to clean and test.

[yoshiii335]

Compressions are ok.

Cool.

Think it could be the pump?

I am about two to three months out from either tuning this engine or changing to a rb25 or rb 26. I want to make sure this engine is working. until then.

Edited December 10, 2015 by yoshiii335

[wildeagle44]

Fuel pump would likely give issues under load not so much idle.

Stock injectors? Maybe get them cleaned.

Clean afm.

[Dose Pipe Sutututu]

Put a neo in.

and use RB20 as a boat anchor

[GTSBoy]

Obvious suspect with changes in ambient temperature would be AFM.

[zebra]

Put an LS in.

fyp brah

[Dose Pipe Sutututu]

fyp brah

wot you say?

[yoshiii335]

Obvious suspect with changes in ambient temperature would be AFM.

Thanks everone.

Forgot to mention the idle/shake is not as bad as before I did the changes.

Will try cleaning the afm.

Maybe aac valve.