I have a 91 skyline gts-t. When i first got the car is seem to run awesome but after driving it for awhile it dosen’t seem to have and power. It’s hard to even get the wheels to spin.
I have changed the fuel filter(300zx N/A), spark plugs(iridium). I’ve cleaned my MAF, throttle body, and AAC valve. It used to idle about 1200rpm but after cleaning these parts and adjusting my idle screw a bit it idles perfect at 900rp.
It still has lack of power. Now i’m thinking about the ignition timing could be off. I looked at the CAS and i have the RB20 and the CAS says RB25DE, could this be my problem? How do i go about checking my timing with this type of ignition system? Also after all of the poking and playing around with this engine everytime i have reset the ecu to it’s new or cleaned parts. Any suggestions will help cause i’m running out of ideas, thanks.
your problem is its an rb20…you are most likely used to the power…or lack there of! time to start modding!! 
Something like this happened to my 25 and then it eventually didn’t start at all (Luckily this happening in the middle of that -40C cold snap :roll: ). Turns out that a lot of people have problems with running iridium plugs in their rb engine, which turned out to be my problem. I’m sure some people will swear by their iridiums here, but I purchased some copper ngk’s and I found that starts and the general engine response is better.
I’ll get you the plug number if you’d like, they’re about $3 a plug, and could be a easy (and cheap) swap to see if that’s the problem. If this is the problem, that would kinda suck, because I know how expensive those iridiums are (read: for a plug).
I know it’s only an rb20 but it should be smooth through the rpm range. It’s like it goes up then hit’s a wall for a bit then i push harder then it goes up again. It’s just not smooth.
Even when i come to a stop and have the clutch in the rpm is at like 1500 then slowly goes down to my idle(900rpm). Is this normal? I’ve searched 100 sites on hesitation, stumble, and idle issues and pretty much have done everything that was mentioned to check, clean or replace and it runs alot smoother but still has the hesitation.
Are far as spark plugs go, i got the plugs with the car. So if anyone has part numbers or a specific plug they use and have had good results let me know. Also if someone could tell me how to check my ignition timing with a light let me know. That’s where i’m at right now.
BCPR7ES
Like mentioned above copper NGK. They are pre gapped to .8mm, which is what you want.
Good i’ll pick some up tomorrow and see if that helps. Thanks.
So i replaced the spark plugs and it didn’t change much. I have this problem though with my idle air valve. I cleaned it twice now and it still does this funny thing. It will work fine when first started then i drive for about 20 minutes and stop at the store, turn off my car. I start it back up and it stays at 2000rpm while i’m idling. I drive for a bit, go to a stop light it’s still at 2000 and then it will start to come back down to normal idle(900).
Does this mean my idle air is messed up? It’s done this for the last three days.
I think they’re gapped to .7mm, which is how those ones come anyway (double check each one of course). I’m not sure on how big of a difference .1mm is for spark plugs.
Have you checked your ecu for codes?
That’s the first thing i did when i got the car. No code at all, everything normal. Everytime i a play with anything to do with the hesitation problem i always reset the ecu and idle the engine unitl it up to normal operating temp.
I don’t know what else to do. If anyone has a AAC valve let me know cause i’m pretty sure mine is no good.
do you backfire during the lull in power? does it happen right around 4000 rpm? and last question, how much boost are you running?