Rough Idle

[BaliLover]

My SR is running, and I've checked and haven't found any vaccume leaks, but the idle is still a bit rough. Its idling aroung 800rpm+- but it misses and stutters a bit. I'm running an open downpipe at the moment (car isn't on the road yet) and I've had it suggested that the lack of exhause might be causing a slight idle problem.

Its a pretty noticible miss, but when I rev the engine (nail the gas) it revs fine, but when I let off it stumbles and pops a bit, but it is noticible.

Could this be just a case of dirty injectors or fuel system, or should I be checking things to make sure everything is the way it should be? Where should I start to look?

[9240sx]

i would check the spark plugs or the timing.

[christopher]

Mine is doing the same thing, I fouled some sparkplugs early on when I first got the engine in.

I replaced the plugs and it helped for a while, I stored mine for the winter (Minnesota) but when I get it back out I am going to replace the fuel filter and check my timing. I would do the same since it sounds like yours is doing the exact same thing mine is. That is exactly how I described mine on Zilvia.net when I got my car.

I tour with my band all the time so, I don't drive mine as much as I would like to. I have had my swap done for about 6 months and haven't been to find the time to drive it that much or shake it down properly.

[christopher]

I really think it is the timing, I would look there if sparkplugs dont solve the problem completely. It is a good move to replace the fuel filter anyways.

If it is your injectors, wich seems unlikely to me, they SHOULD clear out with some real use. Those injectors on a redtop are old and probably sat around for a while.

[BaliLover]

Okay, Timing is dead on 15 BTDC, spark plugs are brand new NGK Iridiums, the fuel filter is a new 300zxTT unit. 100% sure there are no vaccume leaks. Compression is a bit on the low side but I don't know if that would cause it to sound like its missing.

[9240sx]

did you check the gap on the spark plugs?

[BaliLover]

No, quite honestly I didn't. I assumed that they were where they needed to be right out of the box.

[FTRS14.5]

Nope, you gotta check the gap. I think you have to set it to like .028?? Also, have you tried the Idle Adjustment Screw?? It's a screw that sits between the #2 and #3 cylinders on the intake mani I think.

[BaliLover]

Okay, I found the problem; my gas cap. More specifically, the lack of one. Apparently I had the gas cap off and hooked to the back of the filler door at one time, and someone at the shop walk by it and knocked it closed and I forgot about it. Yesterday I went to put some fuel system cleaner in it, and found the cap wasn't screwed on. I put the cleaner in, tightened the cap and started it and it ran MUCH better, it still sputters once in a while, but no more than my honda does. It just seems to be running a bit rich.