# Fine if easy, rough after hard acceleration.



## erikgil (Nov 9, 2006)

Hey all, new here, been lurking. 

Got a nice 91. Well taken care of. It seems that no matter what I do: Let it warm up, drive it cold, etc. -- If I drive it without hard acceleration (like passing gear) it keeps a nice easy fine tuned feel to the motor. Runs on all 6 cylinders. It's an auto if that matters.

Anytime I gun it, passing on highway, straight off at a light, then the engine immediately feels and acts as if it's running rough and is missing some cylinders?

Coils, Techron, injectors? Have not tried any. I've searched a bit but not apparently seen this exact issue documented.

Thanks in advance for any advice, gleanings, requests to RTFM, etc. LOL


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## 123 (Oct 31, 2006)

could be many things. however, check your plugs/wires. to do this, hold the brakes down, put it in gear, and push on the gas a little, but dont let the car move. if it starts to sound like it's missing, or dieing at all, go ahead and replace the plugs/wires. the other thing it sounds like is fuel delivery. make sure injectors are clean, pump is working well, and lines are good.


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## erikgil (Nov 9, 2006)

123 said:


> could be many things. however, check your plugs/wires. to do this, hold the brakes down, put it in gear, and push on the gas a little, but dont let the car move. if it starts to sound like it's missing, or dieing at all, go ahead and replace the plugs/wires. the other thing it sounds like is fuel delivery. make sure injectors are clean, pump is working well, and lines are good.


OK, I'll try the brake/rev test. If that's some indicator, I'm leaning towards the fuel as the suspect. Some techron will go into the tank tomorrow night just in case.

If anybody has any fuel additive/cleaner ideas, please expouse.


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## 123 (Oct 31, 2006)

seafoam works well for...everything


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## i3ulldog (Oct 29, 2006)

If you haven't figured it out already..

It sounds like a fuel delivery problem. I'd check your fuel pressure, it may pass the pressure test. Be sure to do a volume test as well. Culprit would be the fuel pump getting old and wearing out... Not pumping enough volume to keep up with the supply needed to get the motor spinning at higher rpm.


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## blackonblack (Jul 7, 2006)

If is not an injector issue, or a comprehensive tune up, or a MAF issue... It could definitely be a fuel vacuum/pressure issue. Here are a few questions. Does you car reek of raw gas from either your exhaust, your trunk, or right under the car without any clear signs of a leak? When you go to fill up, do you hear a certain fizz (or the absence of it) when you pop open the gas cap? If you don't hear it - it is a definite sign that there is no pressure/vacuum effect in your gas like. Thus making your ride very rough. 

I noticed on mines, thanks to this forum 

http://www.nissanforums.com/j30-1989-1994-chassis/123163-rough-idle-gas-smell-rear-left-help.html 

that every now and then after a fill up, or gunning the car, the rough idle disappeared. furthermore, after gunning it and popping the cap of the tank for a fillup the fizz returned... after noticing its absence for a little more than 6 months. I took GreenMax's & MattSE advise, and took a look at the fuel hoses... the evaporative hoses to be precise, and sure enough they are worn and cracked. I tried to replace them myself but sure enough the space is just too tight for a do-it-yourselfer like me. I plan to take it to a shop soon to get the job done and get raped by the pros. But save yourself the anguish and check your fuel hoses, and you fuel line for that matter. It is cheaper than replacing "bad injectors"


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