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Old 10-29-2017, 10:17 PM   #1
BoganSpec
 
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Default 1989 Nissan D21 w/Z24 - breaking under load, under 2k rpm, post head gasket job

Hello, I'm new the forum and I'm hoping someone can have some insight to what is going on with my '89 D21, Z24i Engine, King Cab, 5MT, 2WD.

A little background, Ive messed with old Nissans for quite a while. Mostly a Mix of KA Hardbodies, Old Z's, and MANY S13s/S14s over the years. However this is my first Nissan with a Z24 in it.

I just finished doing a head gasket replacement. At 203k miles the head gasket blew between cylinders 3 and 4. Never mixed coolant into oil, I just lost cylinders 3 and 4. I bought the truck with 178k on it a few years ago. Well once I tore into it I found signs of a botched head gasket job well before I bought it. Head was clean and the head gasket i pulled out was a fel pro one. Biggest issue was that I found the ignition timing had been set @ 20 BTDC due to a botched oil pump install. So it ran that advanced for at least 25k miles, probably longer.

After sending the head to a machine shop I've used forever, they cleaned it, milled it .005", pressure checked it, and put new valve seals in it.

I put everything back together. Replaced the head gasket, head bolts, chain, guides, tensioner, and all related gaskets with mostly OEM Nissan parts. Only Non-OEM parts being the head bolts, and a couple misc gaskets that were not available. I also replaced plugs, wires, rotor, and cap.

Truck seems to run fine with one exception. When under load under 2k RPM, The truck breaks up BAD. Jerks really badly. After 2k, seems to run fine.

The truck did not do this before I did the head gasket so I feel that I messed something up.
Only modification I really did during the job was eliminate the EGR (Tube was cracked), I eliminated the vacuum line to the charcoal canister, and I eliminated the exhaust air pump. So I have essentially no vacuum lines at all anymore.

I have checked for vacuum leaks by spraying carb cleaner around the manifold and cannot find anything. The truck idles at a solid 800-900 rpm after warming up.

In the imgur album below I took pics of the mechanical timing about 15 minutes ago. You can see the crank pulley at TDC and the cam pulley alignment mark is straight up @ 12 o'clock. When I reassembled it I matched the timing marks on the chain (lighter colored chain links), however after rotating by hand and then running the engine, the mark never lines up with the cam gear mark again.


https://imgur.com/gallery/urDp4


Any input is appreciated. Thank you!
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Old 10-30-2017, 11:38 AM   #2
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Have you checked the codes? If you eliminated the EGR and vacuum lines to the charcoal canister and air pump, I'm not sure if the codes work anymore. That would be my way to look for issues, though.
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Old 10-30-2017, 06:48 PM   #3
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I would check connections and wires at the TPS, MAF and distributor. In that order.
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Old 10-31-2017, 12:55 AM   #4
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I did check for codes. Mode 3 returns 55, no malfunction. Modes 4 and 5 will not return codes. After switching the switch back to "normal" to indicate the mode, the red and green LEDs do not flash at all. Not sure why. I tried plugging the solenoids for the EGR control and Air Pump control back in (I kept them) and tried again. Did nothing.

I have checked connections for the MAF (also cleaned it with designated MAF cleaner), TPS, and Distributor. Ive applied dialectric grease to all connections as well. No corrosion is or was present.

However, there is one large change in the behavior of the engine. Instead of breaking up only under 2k and under load. Now its ALWAYS doing it. Even free revving it in the garage it breaks up now. So Something is getting worse.

I pulled the exhaust plugs and they are very black (rich) and it smells of fuel while running. I did a compression test and its a solid 150psi across the board.

Did you guys look at the pictures of my mechanical timing marks? I was slightly worried as the timing mark on the camshaft is supposed to be straight at 12 o'clock. Which it is. however the motor is slightly slanted to the driver's side. So I wasnt sure if I was supposed to take that into consideration when determining "12 o'clock"

regardless when I installed the timing chain I lined up the timing marks on the chain to the timing marks on the crank gear and cam gears. That put the crank right at TDC and the cam gear alignment mark pointing straight up, both cylinder one valves closed as they should be. Like in my pictures. It hasnt seemed to move.

Im pulling my hair out at the moment so any input is appreciated.
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Old 10-31-2017, 02:38 AM   #5
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I saw 3 pictures in the album, but I've got a V6. I don't know if your 4 cylinder is correct or not.

Sorry.
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Old 10-31-2017, 03:34 AM   #6
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Update: PROBLEM IS FIXED. Well at least for now.

I went over everything again. Mechanical timing. Ignition timing. EVERY single electrical connection on the engine making sure they were clean, had dialectric grease applies, and fully making contact. I also pulled all the plugs and checked plug gap. everything was kosher. I then checked spark against the head while the engine was cranking with fuel relay pulled. Spark looked weak.

I swapped out both ignition coils with some spares I had laying around. Now it fires up and runs properly. I test drove it and it no longer breaks up under load. Spark must have been getting blown out or washed out by fuel. I swapped both ignition coils at the same time, however I only tested the intake #1 plug. So Its possible only the intake coil was weak. One or both must have been on its way out and getting weaker, just coincidence that it got worse while it sat for 2 weeks, waiting for OEM parts and putting it back together.

Ill be driving it to work the rest of the week (short 3 mile commute) and around town. Need to get it on the highway at some point this week to see how it cruises @ ~60-70 mph. If theres a problem I will report back.
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Old 10-31-2017, 11:18 AM   #7
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A weak coil.

I don't know what a weak coil acts like, but I'm glad you found it and reported back.
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Old 10-31-2017, 01:15 PM   #8
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It's really weird.
When the early ignition systems (single coil) went bad, it was almost NEVER a bad coil. They were bullet proof.
Now? These single coil on plug units go bad regularly. Particularly Fords.

It's a sign of the times - I guess.
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Old 10-31-2017, 11:52 PM   #9
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Something I've always hated ever since getting into cars. Finding an old forum post from 2003 describing my exact problem and a solution was never reported back. I always make sure to post back whatever I find. Its getting even harder now with forums going down and Photobucket no longer supporting much of its image hosting.

From what I've seen, on older cars it is very rarely a bad coil. I honestly think this is only the second case of "bad coil" I've ever had on a Pre-OBD2 Nissan with the exception of an old S Chassis I had with a KA24DE in it that just sputtered and turned off one day. No spark at all. Nothing from the coil. Pretty easy to find. On this silly 8 plug 4cyl motor it was more of a bitch compounding the fact that it was just weak and not dead.
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Old 11-01-2017, 12:56 AM   #10
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Quote:
Originally Posted by Boozehero View Post
It's really weird.
When the early ignition systems (single coil) went bad, it was almost NEVER a bad coil. They were bullet proof.
Now? These single coil on plug units go bad regularly. Particularly Fords.

It's a sign of the times - I guess.
Don't even get me started. Fords love to spit out spark plugs unless it gets seized and breaks off during removal. Coil packs love to fail on GMs and mopars too, and of course if there's a v8 in there it'll be the 2 in the way back. But I digress.

Quote:
Originally Posted by BoganSpec View Post
Something I've always hated ever since getting into cars. Finding an old forum post from 2003 describing my exact problem and a solution was never reported back. I always make sure to post back whatever I find. Its getting even harder now with forums going down and Photobucket no longer supporting much of its image hosting.

From what I've seen, on older cars it is very rarely a bad coil. I honestly think this is only the second case of "bad coil" I've ever had on a Pre-OBD2 Nissan with the exception of an old S Chassis I had with a KA24DE in it that just sputtered and turned off one day. No spark at all. Nothing from the coil. Pretty easy to find. On this silly 8 plug 4cyl motor it was more of a bitch compounding the fact that it was just weak and not dead.
Yeah Photobucket's shenanigans ruined a lot of great threads. I haven't seen too many ignition coils go bad on old cars either. A little protip for those motors with 2 coils and 2 sets of spark plugs: the plugs on the exhaust side are more of an emissions thing than anything else. They fire on the exhaust stroke to burn off any excess fuel. Functionally it's like a more modern wasted spark system, but with more parts to replace. If you think one of the coils is bad you can try swapping the wires from the two coils to see if it makes a difference. The plugs on the intake side are the important ones. The old 2.3 in ford rangers is like that too, albeit with solid-state ignition modules and no distributor. Also, check the grounds first. It's almost never the first thing people check but it's a hell of a lot cheaper than buying a new part.
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