86.5 Z24i Engine cutout SOLVED!! - Page 2

saudade · Jul 21st, 2012, 05:34 PM

If it cuts off, how did they verify spark across the "entire" rev range? Another cause of the same symptoms is a bad Intake ignition coil. Both intake and exhaust fire until about 2500rpm, then the exh cuts off and only the intake fires. If your int coil is bad, then it shuts off completely until the RPMs drop.

I had this happen too once before. Both coils are the same so you can swap them to see if that's it.

burvis · Jul 21st, 2012, 08:09 PM

Thanks Saudade, looks like we have the same truck...

Not sure how they verified the spark, not too impressed with the shop overall, won't go back. Here's the update. I sliced open the bundle coming off the throttle body, there were no splices. I found one splice nearer the firewall, but it was intact. I opened the plastic block junction that connects the wires that run to the injectors. I tugged on all the wires going into both sides of the block and they all seemed firm. I noticed there was a lot of engine oil inside the block. Weird, but it's close to a vent hose for the rocker cover on the passenger side, and that hose is cracked. That's the only way I can figure that oil might have gotten inside the connector block (?!?). Anyway, I wiped out as much of it as I could, put it all back together, and guess what? It's running great. I think it's probably a coincidence, and I bet this problem comes up again until I find the real solution. Maybe it was the oil, who knows? Running good now....

jumpin1 · Jul 23rd, 2012, 11:22 AM

Nice job finding your problem, I have the same problem with my HB. I would like to read the other thread where can i find it.

saudade · Jul 23rd, 2012, 11:49 AM

This was started by someone else but I joined in.

http://www.nissanforums.com/hb-truck...-high-rpm.html

jumpin1 · Jul 23rd, 2012, 12:17 PM

checked the harness, no splices. Anyone think it could be the ascd switch at the top of the clutch pedal?

saudade · Jul 24th, 2012, 01:59 PM

I don't see how it would.

You going to have to go back to basics. You first need to establish if you're loosing spark or fuel.

jumpin1 · Jul 25th, 2012, 11:17 AM

I bought the truck 6 months ago and had the bucking problem. I thought that the problem was fixed. recently I replaced the trans, clutch, slave and master clylinder. went to put the thing back on the road and all the bucking problems re apeared. the only thing i can tie together with the tranny is the ascd switch at the top of the pedal. I read up on it and it turns out to be a rev limiter type thing ????????

burvis · Aug 19th, 2012, 06:28 PM

OK, I have now pulled apart and resoldered a few places. But still have the intermittent bucking/surging/rev cutout problem. I have learned that if the coutout problem shows up, I can simply shift into neutral, cut the ingition and restart and the problem vanishes. I'm forming the superstitious opinion that some kind of IC chip somewhere is failing. Does anyone know of a circuit that changes the voltage to the injectors over a certain rev limit. Is it possible that over a certain rev range, some IC chip sends a signal that cranks up the voltage to the injectors, sort of the way an old four barrel carb's two second chambers would open up at higher revs?

saudade · Aug 25th, 2012, 09:41 AM

Well, it doesn't work quite like that. The ECU determines the length of the fuel pulse to adjust the F/A ratio for any given condition. So it sprays for longer or shorter times, not more or less pressure/flow rate. The injectors themselves are either on (open), or off (closed).

Having said that, intermittent still certainly implies an electrical issue. So we need to determine if the electrical problem is affecting the fuel delivery or ignition. You mentioned earlier someone checked and said it's fuel. So let's verify.

Assuming when this happens, it also happens in neutral so you can rev the engine up by hand and get the surging. If so, get a can a started fluid. Remove the top of the aircleaner. Rev the engine until it surges. Spray some starter fluid (short bursts at first) down the throttle body. If it now revs up, you know it's a fuel issue. (Mine did this). If not, then it's likely an ignition issue.

Let the engine idle for a minute, and try again to see if it repeats. Don't go too crazy with the spray.

ozarkian · Nov 15th, 2012, 07:52 PM

I am going to highjack or perhaps just join in on this thread.
I have a 94 v-6 4x4 doing the exact same thing.

It did this last year at this same time of year (weird). Last year I thought it was dirty injectors and ran a few cans of fuel treatment through it at it cleared up. I was under the hood poking and proding all day as well. I could have jiggled the harness and "fixed" the problem temporarily.

Regardless it is back with a vengence and no amount of fuel treatment is making it better.

Do you boys think it is a problem with splices like your 86 ? Or maybe something else you have discussed?

What I have done up to this point is: Fuel filter
Throttle position sensor
checked codes. 14, and 34, and 51
Don't freak!! They were old codes and I cleared them and drove thetruck and redid the codes and only got the knock sensor.

Please help me fix my baby

thanks in advance

crystal

burvis · Nov 16th, 2012, 09:13 AM

HI Crystal,
Reading through everything I could find on this problem, it seems there are a couple of things that can cause the same symptoms - bucking while under load or cutting out over a certain rev range, making it sound like you are rapidly gunning the engine in neutral.

First, figure if it is spark or fuel. Saudade gave me an easy test, take off the air cleaner cover and get a can of starter fluid. Start the engine and rev up to where the cutout starts happening, and spray starter fluid in the intake. If it smooths out and revs normally, you have a fuel problem. That's what I have.

Some folks have said a bad coil will cause the same symptoms. But that would kill your spark, and I haven't investigated it because my spark is OK.

In my case it was happening because something was cutting off power to the injectors. I wish I could say I have found a definitive answer as to why it is happening, but I can't. I have split open the harness, looking for bad splices, and resoldered a couple connections just to try something, but the problem kept returning.

It sounds dumb, but the last couple times it happened, I killed the ignition just as it started bucking, and restarted the engine. Since doing that a couple times, the problem went away and hasn't come back. Who knows why. It has been running great for months. I have a feeling I'm not done with this adventure though. Good luck!

ozarkian · Nov 19th, 2012, 09:11 AM

Thanks for the input Burvis.

Let me try to clear up what is going on.

When driving, and only when driving. Each time you change gears and the RPM's drop to below 2500, as you try to come back up the truck will "bog down or lug" Not so much as to stop you, just enough to make the engine vibrate and shake.

I picked this thread because after an exhaustive search of this site this is the thread that most closely resembled my particular problem.

I understand that this was a TBI engine and mine us multi-port and a few years newer.

The fact that the problem sound so similar gives me hope.

It is almost impossible to tell any difference in the engine while it is in the shop and just sitting in nuetral even though I rev it up to the 2500 mark. It only seems to happen if the truck is under a load. I live in a very mountainous area so the loads are worse going uphill, which we seem to do alot LOL.

MY fuel economy has fallen off and of course the performance stinks. This problem is driving me nuts!!

PLEASE HELP!!

I know you guys have the answer I need.

crystal

saudade · Nov 19th, 2012, 09:55 AM

Well a few words/questions then.

Is is consistent or intermittent? Have you moved the injector harness around to see if it clears?

Go up a long hill with a spark plug wrench and let it bog/lug. Then stop, let it cool a bit and pull the plugs and check their color.

Check your fuel pressure.

Check your compression.

Also, I think you'd be better off in a separate thread. My title is aimed specifically at owners with the same engine as mine. Given it's age, I'd bet it gets overlooked by others with same engine as you.

Lastly, I had a similar problem with my Cherokee. Occasionally, it would run rough and even backfire a bit under load. Then it would miraculously clear up before I could check it out. Turns out it was a break in an injector circuit inside the main harness along the valve cover. I can only guess that the torque under load caused the engine harness to flex ever so slightly but enough to make or break the circuit.

ozarkian · Nov 30th, 2012, 06:44 AM

thanks anyway. i will try a new thread.

yellowrosefarm · Jan 12th, 2013, 07:29 PM

I picked the wire harness apart on my 86.5 and found the splices just as described. They were not corroded but I soldered them anyway since I was right there. Then I moved over to the 88 and picked that harness apart. No splices all the way to the firewall. So Nissan, in the spirit of continuous process improvement must have deleted the troublesome splices some time before 88.