# 1986 Z-24 inconsistent idle



## PittBull (Jun 5, 2013)

New member, first post. Came here to find help.
Bought this 5 months ago. Had a loud rumbling at 40-50 mph. Was hoping it was needing gear lube, turned out to be worn out pinion.
Replaced most front end ball joints, upper A arm bushings, front drive axles.
Good little truck, been getting 20-23 mpg.

Motor is a transplant. 250,000 on truck, not sure on motor.
Whoever did transplant was a dipstick. Vaccum lines incomplete, wiring a mess.
Straightened out the wiring, most of it. Still unsure about some vac lines.

My problem is inconsistent idle.

I read a few pages of the forum, found similar topics. Looks like could be a couple different sticky valves.
I bought a Chiltons manual. Seems like the Haynes usually were better from past experience.

Any suggestions?
Thanks ahead of time.:givebeer:


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## PittBull (Jun 5, 2013)

Sorry, incomplete thoughts I geuss.
I replaced the rear axle, found one with gears that didn't show any wear, looked new.
$250, about 4 hours in the swap.
Truck always starts and runs good. It'll drop to low idle and just about stall. Never has stalled though. Could be cold or warm engine. Makes no sense to me.
Is this a "throttle body"?
With injectors, 2 valves spraying in the carb body?
Sorry, all this is new to me.

Also, rear main seal leaks pretty bad. How tough is that to change?
Had one man tell me he could do it in about 2 hours........


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## wilburk (Dec 29, 2012)

Seems like figuring out the vacuum lines is a priority here--if they're mixed up or leaking at all, this could be the cause of your problem. I'd also consider getting a can of carb cleaner and MAF sensor cleaner. Just a few thoughts...


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## smj999smj (Jan 1, 2006)

Is this a '86.5 Hardbody (2 headlights) or an '86 PL720 (4-headlights) Nissan truck? 

I agree with making sure the vacuum hoses are correctly routed/installed. The rear main seal requires removing the transmission to access; two hours is pretty conservative, IMO. I would expect triple that time. 

NAP-Z engines have mechanical valves that can be adjusted. I've never heard of any issues with them "sticking." VG and KA engines had hydraulic lifters that would bleed down and tap, but that wouldn't affect your truck.


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## wilburk (Dec 29, 2012)

A co-sign from smj...yes! 

Another thought I had--have you tried reading the codes to see if you're throwing anything?


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## PittBull (Jun 5, 2013)

Thanks for the replies men.
Never checked codes, don't know how.
No clue where to find the maf. Always had Chev or Ford pickups. Last truck was an '05 dodge dually.

Major learning experience here.

Chiltons was no help on the vaccum lines.


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## Ding1 (Dec 7, 2012)

The air flow meter on the 86'-87 is mounted on the right side of the throttle body,looking from the front of engine.It's a rectangle type square black box.it looks like this
1986 1987 1988 1989 Nissan Pickup Mass Airflow Sensor 4 Cylinder Air Flow Meter ,

Vacuum lines

http://nissannut.com/projects/z24i_fuel_injection/z24_vacumn_piping.PNG

Reading codes

| Repair Guides | Electronic Engine Controls | Self-diagnostic System | AutoZone.com


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## PittBull (Jun 5, 2013)

To answer smj the truck is 2 headlamps. D-21 keeps coming up when trying to get parts.
Much appreciate the help guys. Woulda never found the AutoZone help guide.
Saved those links. Thanks for those D1.
Beat myself to heck in the yard and garden today. I'm bushed.
That vac line diagram even I could follow.
Loads of help.
What is special about MAF cleaner?
Something that won't disolve the plastic?

I'm assuming the code lights are seen through the top? Can you see them with a mirror? Is there enough room? Or do they stick out enough to view? Seems like a couple days ago I was reading another thread and man said he pulled his seat to see codes.....now that's fugged up.
Who thought of that the Japs?


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## smj999smj (Jan 1, 2006)

Two headlamps would be the '86-1/2 D21 Hardbody, which would have throttle body fuel injection. MAF sensor cleaner is very similar to electronic parts cleaner. It is much less corrosive than carb cleaner and much safer on plastic parts. As far as viewing the diagnostic LED's on the ECM, it is easiest to see them if you remove the seat. While that sounds like a pain, if you worked in a Nissan dealer, you would likely have access to a Kent-Moore "checker box." There's a big, black plastic harness connector usually at the left side of the dash or tucked behind the driver's kick panel. The "checker box" would connect to this and would have a toggle switch and green and red LED's. This allowed one to view the flashing LED's and switch through the diagnostic modes remotely, without have to pull the seat (or the kickpanel on other models). It's a crude system by today's standards, but it was "state of the art" when it came out.


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## PittBull (Jun 5, 2013)

Local mechanic that I had price the rear seal job said it would be $320. In the past I'd do it myself but I geuss I'm getting to be an old lazy fart.
He priced it at $320. Said time would be about same as an engine swap.

How could I boost my mileage? The older gentleman that said he got 33 with a 1989 D-21 has got me wondering.
That mechanic told me that all truck makers had problems with the throttle body injection. Said alot of guys swap out for old stle carburetor. What system is that 89 truck using?
Have any good recommendations for a carb swap?

Pull the seat. Fun, fun.


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## smj999smj (Jan 1, 2006)

20-23mpg sounds pretty good. My 97 KC 2WD KA24E AT got about 21mpg on the highway. I've never heard of anyone getting 33mpg from a Hardbody truck. Advertised mpg on the 87 Hardbodies with Z24i/2wd was around 18 city/24 highway. Not really much you can do to get better other than keep it tuned up, tires inflated and keep the foot out of the gas. You might try switching to synthetic lubricants.

$320 sounds pretty good. There's a good price estimator at this link:
Auto Repair Estimates - Get Honest Car Repair Costs

I think the mechanic that told you that all makers had problem with throttle body injection is talking out of his a**. Throttle body injection is simple and much more efficient than a carburetor. You might get a bad fuel injector or leaking gasket, but anything can break regardless of the fuel delivery type. With carbs, you still could experience leaking gaskets, but you also had a lot of moving parts (linkages, throttle shaft, float and needle, etc.) that wear over time. Only moving part you have on TBI is the throttle shaft. Also, carbs can't compensate for changes in altitude or temperature, but computer controlled fuel injection can make those adjustments. If you want to replace your carb, you can get a Hitachi 2 bbl. off of a Z24s or a Weber carb. I would recommend you stick with the TBI. Usually the mechanics that complain about fuel injection are the ones that don't understand how it works or do not know how to fix it when it stops working properly.


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## PittBull (Jun 5, 2013)

Thanks again smj.
I need to go to the library to make copies of the codes pages and the vac lines diagram.
Suppose I could draw one out for the vac lines. Don't go anywhere very often so not a major rush. I'll get to it before long.
Thanks much for all the advice and everyones time.
Need to pick up some maf cleaner too. I think I will have the oil leak fixed soon.


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## PittBull (Jun 5, 2013)

What would you recommend for cleaning the injectors?
Would sea foam be good?


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## Ding1 (Dec 7, 2012)

You can use a in tank fuel injector cleaner with a tank full of gas.You may also use a throttle body cleaner(spray) to douse your TB innards,open the plate up and hose it out with it,man what a difference that makes.Looks brand new inside.And do the MAF cleaner like SMJ suggested.As for the inside cleaner for the tank,I use lucas,a bit pricey @ around 5 bucks but it's good.I run 1 bottle to/for every 3-4 tanks of gas.I haven't used sea foam,yet.I'm thinking I might do it,just to clean the sludge from my engine.


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## wilburk (Dec 29, 2012)

I'd stay away from cheap/off-brand in-tank injector cleaners. Have heard some not great stories...


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## PittBull (Jun 5, 2013)

Just went over the vac. lines. Couple routed wrong. Possible cracked hose on back of carb base.
In the diagram, the grey box in lower left, solenoid valve, I've got one but no hookup for it, no elec plug for it.
It's out of vac cirquit for now.
Truck idles even and consistent now. Replaced air and gas filters also. Sprayed throat out and cleaned MAF sensor. Haven't gotten to codes yet.
Why are there 2 screws that effect idle? One is on base of carb, one is on the moving throttle. I've been adjusting the moving one to set idle. i was able to back off 2 turns or more. Idle is now set with base screw, less than 1/2 turn.
What is the second screw for?
Do I really need the elec solenoid valve on the vac system? Again, I have no elec. plug for it.
Again, thanks for everyones' help. Truck runs a little stronger now too. Might be partially due to a clean air filter.


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## PittBull (Jun 5, 2013)

Just a bump to get an answer to the 2 idle screw question.........

What about that solenoid valve?


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## PittBull (Jun 5, 2013)

Update. Haven't checked the codes yet.
This morning the darn truck is idling down and back up. Almost to stall, then I turned up the idle a bit (both screws) to keep it above stalling level. Got home and it's cycling up and down.......
Any geusses? Yeah, I know, check the codes.


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## PittBull (Jun 5, 2013)

Seems mileage was real down today too. Filled before going to a flea market this morning, drove about 50 miles, used top 1/4 tank.
4 gallons or so for 50 miles, not good.


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## PittBull (Jun 5, 2013)

Pulled the seat. checked the codes. 23,24 and 13.
The wiring at the throttle sensor was almost broken off. Pulled the plug, couldn't get the spade connectors out......ground off part of the plug and wired new wires to the connectors. Soldered those wires to the old wires.
Second check I'm getting 23,24 and 12. I've already cleaned the maf, is it bad?
I never got a 44 code after working the clutch and gears.
Went looking for the clutch switch. It's wiring was cut and had a wire nut for "always short" condition. Just finished fixing that wiring, I did check the switch, it works.
Taking a break, will check codes again. Truck does not stay running on it's own at all now. Spit.
I'll spray the maf sensor again.

I notice there is a window on the front of the electronic box, I think I could see codes without pulling the seat.


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## PittBull (Jun 5, 2013)

Sprayed the maf through the throat, pulled it the first time. Only getting codes 23 and 24 now.
I'm thinking replace the throttle position sensor? Thats the one I repaired the wiring.
Idle is now cycling up and down just a little. Not stalling.
Dang these little trucks can be a pain. Maybe I shoulda sold it for $2800 when I had a coupla buyers?
I always had chev or ford pickups, older ones. I know most of their workings. Stick with what I know?

Replace the throttle position sensor? Would it cause unsteady idle?


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## dtkana (Jun 10, 2013)

I have recently learned how sensitive these trucks are. I went from running perfect to nothing after an exhaust manifold change. Turns out the guy loosened the EGR valve and that was the entire problem, only noticeable if you grabbed it and tried to move it and had barely any play. I went from no idle and barely firing along with backfires to perfect idle after tightening the two bolts on the EGR. These things obviously HATE a vacuum leak! During this I was getting codes 11,12, and 24. I have heard 24 is not much to worry about especially if it is a manual transmission. My research, while not extensive, does not indicate a TPS effecting idle.

Good luck and sorry I might not be of much help.


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## PittBull (Jun 5, 2013)

Thanks dt. Maybe I'll look harder for vac leaks. Spit.


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## PittBull (Jun 5, 2013)

More troubles. I was just going to the GF's parents house for her moms' birthday. Truck started fine, backed up, stalled. Doesn't want to start. If I get it started I have to keep high idle. If you run it fast idle it loops up and down....
Ideas?


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## PittBull (Jun 5, 2013)

Well, I've got it running. Pulled the maf again, cleaned again. "O" ring was a bit chewed. Not real bad but I replaced it.
Only code I'm getting now is 23. Went through the whole list of checks, not getting a 24 or a 31 or a 44.
Still idling up and down. After a short drive it was doing this, I revved it once, then it idled smoothly.
Any thoughts?

Are you guys now ignoring me or what?
I appreciate the help you've all given so far.
I hink she's getting listed on Craigslist today and I'm getting and older Chev or Ford or Dodge, something I know a little better.


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## PittBull (Jun 5, 2013)

I'm still getting the idle cycling trouble. Runs good, mileage back up, just won't idle steady.
Only code is 23.
checked vac lines again. No intake leaks, checked with carb cleaner.
Ideas?


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## dtkana (Jun 10, 2013)

I am not saying it is the same problem I had, but when I was searching for my vacuum leak that turned out to be a loose EGR it had no response to spraying carb cleaner around it. I too was convinced I did not have a vacuum problem until I found it loose, tightened it and solved all my problems.


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## PittBull (Jun 5, 2013)

The EGR is on the back side, I felt around back there couldn't find any indication it's loose.
Would I be able to tell just feeling around?
How is it attached? What fasteners and what size?
Wouldn't hurt to put a ratchet on and check for tight.
Won't be doing it today, it's stupid hot out.
Thanks.


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## Ding1 (Dec 7, 2012)

The EGR has 2 bolts going to it to mount to the manifold.It also has a large "tube" attached to it along with a vac hose and another "smaller tube" mounting.It could be a cracked vac line to it.It could also have a cracked/broken gasket to the EGR.Best thing to eliminated the EGR would be to take it off and clean it,put a new gasket on,about 3 bucks from autozone or your favorite flavor auto store and make sure it functions afterwards.To test it,start the engine,reach around to the EGR and with your finger,feel under the EGR and you'll find a "diaphram",push up on it slightly and if it cuts/stumbles the idle then it is working,you can do this before you take it off,if you take it off.If nothing happens or you cannot push it up then the EGR valve is non functioning.

Just a thought here.You can check for leaks in the vac lines by buying a dollar cigar and removing a few vac lines(one at a time during the test) and blowing smoke from the cigar down the vac lines and watching where it comes out.Sometimes there can be a crack at a bend or under a line that is connected to the nib or on the nib(the tube that comes from the part that the vac line connects to) that won't open up till it gets warm or under vacuum.I replaced all my lines with new stuff.You can also check the PCV valve line also,they can get brittle and crack.Or you could have a bad/worn lobe on the cam shaft,you could do a compression check,lotta things could be wrong or overlooked.Sorry for the long dialog here.


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## hejuluz (Jun 28, 2013)

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Lot of 35 Vehicle Keys Ford Nissan Toyota Dodge Chrysler Chevy and Kia | eBay


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## PittBull (Jun 5, 2013)

Thanks for that long reply Ding. Covers alot of possibilities.
Quite a bit cooler this morning, I might get out and check it over. 
I thank you sir.
Pretty sure I thoroughly checked all the vac lines. Although I thought I did the first time, I found one cracked at the "nib" at the back of the motor when it quit on me.
I'll look again.


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## PittBull (Jun 5, 2013)

Pushed up on diaphram, it does make engine stutter, drop.
Was able to turn up idle and it is/was steady. drove to bring up to operating temp and it dies down to idle at about 1700 rpm, doesn't die, just drops to no power and low idle.......
neighbor mechanic suggested disconnect of battery to reset computer, doing that now.
Sprayed the big rusted pipe fitting on the back of the egr to help loosen it. I geuss I'll pull it and look it over. Clean with some WD40?
How to check?


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## PittBull (Jun 5, 2013)

Found in the Chiltons' how to check EGR valve. It looks real good. Gasket looked good, no signs of a leak.
I wonder if pushing up on it caused a chunk of something to lodge in place to make it inoperable? Causing the high rpm die out?
I don't know, it quit that, adjusted for smooth idle, maybe 900 rpm, drove fine.
It still is cycling from 800 rpm up to maybe 1200 rpm and dropping back down every 5-6 seconds.
Checked all vac lines again.....

I'm stumped.


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## Ding1 (Dec 7, 2012)

OK,as for the EGR,IF you remove it all you need is some carb cleaner or brake cleaner.The best stuff I have found to un-F*&k a stuck/rusted part like manifold bolts etc is PB Blaster,stinks like hector but it is great stuff.Once you have the EGR in hand,look at where it connected to the manifold.A small hole will be there on the flange that has the gasket along with where the tube(s) were.Spray those places with cleaner,use an old tooth brush to help remove the carbon build up.Also check the tubes to.They can be clogged with carbon.Cleaning is pretty straight forward PB.Sounds as though it is working if it stumbles.

Sounds like your idle is discombobulated.I believe you have a "thermo wax" type idle cam,that may have went south on you or the coolant hoses that go to it got clogged up.I think/believe the best way to check that is to,while engine is cold,start it up and watch to see if it retracts while it warms up.There was a detailed write up somewhere by a gentleman named Tully that gave a great in depth description on how to replace and adjust it.I actually believe that may be your fast idle head ache from all the descriptions you just gave.


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## PittBull (Jun 5, 2013)

Thanks for the reply.
What do you mean by "retracts"? One of the coolant hoses colapses?
Which one or which location?


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## Ding1 (Dec 7, 2012)

Hope this helps PB.It's hard to explain and describe what is involved but this will get ya what ya need.All credit goes to TAllyHB for this in depth procedure.

Replacing the Wax-Type Fast Idle Solenoid (Z24i engine)


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## PittBull (Jun 5, 2013)

Thanks Ding. I'll check that out.
Would I be able to see that moving the throttle every 5-6 seconds (that's the time duration of the idle fluctuation)?
The link also answers one of my earlier questions, what the screw S2 was for.
I was originally using it for idle adjustment. I'll bet it's out of adjustment.
Wonder if that's the problem?
Going today to look at a 1983 3/4 ton 4X4 4 speed Chevy PU.
GFs' brother said he wouldn't own a 6.2 diesel......They listed it for 2000, already came down to $1500.
Needs glow plugs for sure he said. $10-15 each.
I've had a few old Chevys, Pretty good looking truck, a little rust but body is real good otherwise. 4 speed. Might even pull my old 10,000 lb 5th wheel trailer. Also hearing they should get about 20 mpg.
We'll see.


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## PittBull (Jun 5, 2013)

Bought the 77 GMC. Good motor but rusty body. Already replaced the fenders and bed.
Need a smaller carb tnan the 750 Holley. Less than 10 mpg I think.

I adjusted the wax idle 1/2 turn at a time, screwing it in. I was previously using it like an idle screw, didn't know better.
I got back to a smooth idle. Truck is running good right now.
It did idle up and down the other day I think after this adjustment. 
Maybe time to replace wax idle control.


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## PittBull (Jun 5, 2013)

I just posted another thread, same subject. General consensus seems to be a vacuum leak.
The vac hoses on this thing are all buggered up.
Thanks for all the replies gentlemen.
I would have replied much sooner but have not been able to log on for a year.
Truck still buggered up. New timing and oil pump gear and crank gear for that. $175!!!
Way too much money spent for truck that i still cannot sell or drive..........


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