# 87 D21 Z24 2.4 TBI Runs Rich & Rough at Idle No Codes



## pastorerik (Jul 15, 2008)

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.

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.

Thanks in advance for your help!


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## zanegrey (Dec 5, 2005)

just as a test unplug o2 sensor and see if you milage goes back up..

you should check you timing first.
kinda sounds like it might be advanced ..

also check that both coils are operating ..
what do you know about the spark plug wires??

what plugs did you put in..?


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## pastorerik (Jul 15, 2008)

Thank you for your reply..... I did notice a bit of "valve rattle" or detonation at higher rpms if it does not shift in time (automatic trans) and I was thinking it may be a bit advanced. I notice no difference in the way it runs at idle when I unplugged the O2 sensor.... What would better fuel mileage without the O2 sensor indicate?

As to the plugs, I bought the truck off a guy whose friend had it on his used car lot/repair shop...They told me that they replced the plugs so I am not sure what the number is....I pulled one today out of curiousity...I pulled the 1st and the 3rd on the exhaust side....they were light tan to white which normally I would think would indicates a lean condition??? But I am not famillar with the exhuast side plugs, do they usually look white or at least whiter?

I forgot to mention before that it does have a bit of a misfire at idle but does not stall. I upped the idle to a little on the high side, it seems to run better that way. Any help is greatly appreciated...I am new to Nissans


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## zanegrey (Dec 5, 2005)

put the timing at first positon and then check the oil pump timing.

did you check the coils to see if both sides were working?

the plugs will look the same on either side .

i was curious to see if there was an affect from the o2 sensor being unplugged.

since it does not and you do not have codes ..discount it for now.
what type of spark plug did they use??


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## pastorerik (Jul 15, 2008)

Not familiar with putting the timing at "first position or the oil pump timing.....If its not too much trouble and it is simple enough can you give me directions for these checks...I have a Haynes manual, but its not that great. I will check the plugs for type etc tomorrow and get back with you. Thank you very much for your help


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## zanegrey (Dec 5, 2005)

there is a short cut to see if the oil pump timing is off.

remove one the hold down bolts to the dizzy and loosen the other one so you can remove it by hand.

with out disturbing the dizzy position start and warm up engine.

then carefully remove the remaining screw and rotate the dizzy very carefully one way then the other to see if the perfomance improves and the misfire goes away..


you must do this carefully and slowly no big movements..

you should be able to turn it and the rev it a little to see if it is better or worse.

if it is better out side the range of the hold down screws then chances are the oil pump timing is off a tooth or so..


make sure you are understanding what i am saying before you attempt this..


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## pastorerik (Jul 15, 2008)

The only part I did not quite understand is the part about removing the dist. I get the part about adjusting it and that if it is out of the range of the normal adjustment then the oil pump timing is off a bit. I did notice that the dist. seems to be at the end of the range...fully counterclockwise I believe. 

Thank you very much for your help. I will look into this tomorrow.


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## pastorerik (Jul 15, 2008)

How to I check the coils?

Thanks


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## zanegrey (Dec 5, 2005)

at no point did i suggest to remove the dizzy..

check the coils by starting the engine and pulling the coil wire off one at a time check for
spark and then replace..


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## pastorerik (Jul 15, 2008)

Sorry a about that in re-reading it you meant so that I could remove the retaining bolt by hand so that I could adjust it outside the normal range..... Ok. I checked it today and in the exhaust side they installed Autolite 64 Spark Plugs. I did not have to time to check the intake side today. The Distributor still has a little more range to one side and it ran worse when going all of the way (advanced, I think) When going fully the other way it would almost stall....I had marked it before moving it just for reference. I ended up adjusting it about 1/8 or an inche at the retainer and it did a bit better as far as idle but I lost midrange and highspeed power. I am going to see if I can borrow a timing light and adjust it. What timing would you recommend? I use regular unleaded gas.

Thank you.


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## zanegrey (Dec 5, 2005)

you should use ngk spark plugs. and be careful to gap them correctly.

the timing is not a suggestable thing .
it is either in time or not.

if your engine is not ruuning right with the dizzy in the middle of its range then it is possible that you are a tooth off..

when trying the short cut ..both bolts are removed and the dizzy is turned past its range in both directions to see if it runs better ..

did the coils check out??


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