I have 1986 Nissan 300zx car idles rough and rpm fluctuates

Asked by Jun 27, 2012 at 03:01 PM about the Nissan 300ZX

Question type: Maintenance & Repair

Up and down until the car wants to die. It only does this in Idle not in drive( 5sp) , as long as you give it
gas it will run but when it fluctuates this way it makes it had to kick it into neutral at a stop  light and
feed it gas to keep it running. Please help have changed plugs, wires, distributor cap and rotor button.
New air filters in car as well.

8 Answers

17,345

Sounds like a classic case of bad or out of adjustment TPS (throttle position sensor). Some can be adjusted and others cannot, idk which type you have.

2 out of 2 people think this is helpful.

I dont know for sure which type I have but I have adjusted the Idle up and it runs but it still will return to the fluctuating idle and will about die ... Thanks I will try to replace the tps and see if that helps. By the way I dont know if it helps but I have the standard 6 cyl. in the car no turbo or anything.

17,345

yours should be adjustable, the screws are on a slider. I would try to adjust it first before spending the cash on a new tps. loosen the screws and with the car idleing rotate the tps. You should be able to tell a difference in the rpm's when you turn it. Here is a cool video about it: http://www.youtube.com/watch? v=LmgYPuJkUuY

5 out of 5 people think this is helpful.
40

I would check for Vacuum leaks and all Vacuum LINES,, for cracks etc ... ..THE TPS,, Is not YOUr Problem .. NOTHING to do with your symptoms also if its a Turbo... the FICD should be cheecked.. CHECK your Engione Codes ...

3 out of 3 people think this is helpful.

We have the same problem. The TPS has been replaced and there are no codes. Does anyone have any other suggestions?

105

I agree with jcesp vacuum leak also check the TBS plug for corrosion might not be getting good contact

10

I finally got my 1986 300ZX to pass smog here in California. New EGR valve fixed the NO problem, but it still had HC and CO way too high to pass. I found a great Smog Repair station on smogcheck.com and the mechanic found the problem to be corrosion in the plug that goes into the TPS. He cleaned it up and it passed just fine and it fixed the idle problem I had too. So, a little corrosion at the plug made all that trouble. It is usually something simple, especially in an old car like a 1986, corrosion will work it's way right up a wiring harness or battery cable where you can't see it.

1 out of 1 people think this is helpful.
10

Correction to my post. I found the Smog Repair Station on smogtips.com, NOT smogcheck.com. And I found all the reviews for them on yelp.com Don't want to steer anyone wrong. My mistake!

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