Rough & Rich at Idle 87 D21 Truck 2.4L TBI Auto 2WD

[pastorerik]

Hello,

New to this forum but from what I can see there are a lot of knowledgable folks here.

I recently purchased a 1987 Nissan D21 pickup with a 2.4 Z24 engine and Throttle Body Injection. The Truck has an Automatic Transmission and 118k miles.

Has new plugs, cap & rotor, air filter. Runs ok except at idle which is a little rough and you can smell that it is running rich.

I Followed the procedures and found no fault codes..(the only code that came up was, I think 44, which meant everything was working ok.

I pulled the MAF and everthing was clean and intact. I cleaned the connectors to the MAF just in case, they were clean.

The idle screw was cross threaded so the idle was very low, I removed it and tapped out the hole and replaced it...after that I was able to bring the idle up but it is still running rich.

Any advise on what to check or try would be appreciated. I really need a good fuel mileage vehicle for work.... By the way when I first got it I could smell that it was running rich so I figured at 118k an O2 sensor couldnt hurt, so I replaced that too....Interesting that with the first tank of gas before I replaced the O2 I got 22 mpg and the second tank, after the 02, cap and rotor I only got 17-18 mpg. It may have been less highway miles though I am not sure. I am still monitoring the mileage with each tank.

Thanks in advance for your help!

[MaximA32]

I would check the timing to make sure that it is timed correctly. If the timing is too advanced or too retarded, it could cause the rough idle and poor fuel mileage. I would also pull the spark plugs and see if they are beginning to get fouled out by too much fuel.

[pastorerik]

The timing was nearly fully advanced. And I had noticed a little valve rattle before it shifted at high rpms. I backed it off and it helped a little but I need to borrow or buy a timing light to dial it in right. The spark plugs, at least on the exhaust side look good, a little on the white side though. I did not have time today to pull the intake side plugs...The previous owner said that he had just replaced the plugs....the exhaust side has Autolite No. 64 Plug.

Thank you, I really appreciate your valueable help and time.

[MaximA32]

Get rid of those Autolite plugs. They are one of the worst plugs to have in an import. The Autolite was designed around a domestic.

[pastorerik]

What do you like? NGK?

Thanks

[MaximA32]

NGK or Denso.