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Running Rich and Random Misfire


CO_pathfinder
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I've got a 1992, so I think my recent findings may help out.

 

Get that injector Cap fixed ASAP. It could be allowing unmetered air into the cylinder, a diflection of injector pattern into the runner, puddling of fuel, ect. Im not positive, but I may have an extra sitting around the garage if you can't find one locally/ebay/junk yard.

 

My 92 was having some issues that kind of mimic what you're describing. I would check all of these in this order.

 

1.Clean your MAF. Pull the sensor out of the housing, and clean it. 2 screws and 2 minutes of time.

 

2.Check the resistance of your coolant temp sensor. Measure across the two terminals of the sensor.

Here's a chart:

68 degrees......................... 2.10 - 2.90 k ohms
122 degrees....................... 0.68 - 1.00 k ohms
176 degrees....................... 0.30 - 0.33 k ohms

 

3. You can check your Oxygen Sensor, for voltage but I have found that even tho it show's the correct voltages, it still does not work correctly. Mine would test good, then throw random 33 codes. Took a while to throw them too. I am not at home at the moment, so I can not look at my FSM but I will in a few hours. I replaced mine becusae of the symptoms I was having, plus the random 33 code that would show.

 

Both of these sensors deal with fuel and the delivlery. I having a bad stumble, hesitation, and overall loss of power and when I replaced these two, it cleared itself up.

 

I got my Temperature Sensor from Ebay, as well as my Oxygen Sensor.

 

Temp: http://www.ebay.com/itm/251124807703?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

Oxygen: http://www.ebay.com/itm/300970435107?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

I hope this helps, as when I did swap my two sensors, and clean my MAF the results were tremendious.

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I'll try messing with the injector cap here in a bit, need to do some packing first. I'll also try swapping the CTS in the truck for a clean looking one that I found at a JY.. doesn't hurt to try. MAF was cleaned a week ago, and not even a smudge came off of it

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Need to pull the upper plenum (or at least lift it up) in order to get to the injector.. not enough clearance to loosen and remove the rear screw.. probably going to just whack it back into the sleeve with a mallet and see if that changes anything..

Also, I'm cutting and replacing the exhaust, cat back, with a 2.25 straight pipe.. tired of the whistling noise the muffler makes

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One thing I found recently when removing the upper intake. The rear hoses do not need to be removed from the small pipes. You can just lift the intake up, and prop it so that you can reach the injector cap. This may save you time and frustration. HTH

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Got sidetracked by moving back in to college.. and now that classes have started, things are going to go even slower than before. I looked at the FSM, but I really couldn't tell what all needs to be removed/where the bolts are that hold the intake in place.. any hints?

 

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  • 6 months later...

*% these vacuum hose clips in the back.. im socked in because of a blizzard, so i cant just cut them and replace them, because my truck is the only vehicle here at the moment (aside from the tractor) that could make it to the store. Mashed my thumb with a mallet too, so that doesnt help.

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UPDATE: decided to just cut them anyways. I plan to drive the tractor to the store tomorrow (hahahaha) to get a new plenum gasket and a 12" length of vacuum hose. Thanks Nissan for your excellent engineering - wish I could have cut your engineers instead of cutting my vacuum hoses

 

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UPDATE #2: My injector is finally (after 2 years) fully seated. Somehow, by an act of God, at some point the injector cap sheared in half (which makes me wonder what the heck could have caused that to happen), and the injector was unseated all the way past the first seal. I replaced that seal, hammered the injector in space, and screwed the junkyard new cap in place. Fingers crossed that this fixes my god awful stumble.

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It was hung up on the two coolant lines in the back that splice off of the main steel heater line, right up against the firewall - its the two that get in your way when you try to fiddle with plug #6... speaking of.... I refuse to leave it in there, so it looks like its time to McGyver some 3/8s extensions!

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More updates, because why not, it is my thread after all! Fixed the stupid vac leak that sprung up - check all the connections that you've done yourself! Clip that holds one of the older vac lines in place wasn't in the right spot, and so the hose slipped a bit and was leaking around the edges.

 

Replaced the CTS, didn't start the truck after doing so though, because my new O2 is coming in tomorrow, and I'm just going to replace that as well before starting the truck up. If neither of those fix the misfire, I'm going to start looking at the vacuum based valve systems, namely EGR, IACV, and PCV. Here's to! :beer:

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The EGR, IACV, and PCV will not cause misfires. They would cause poor idling, bad gas mileage, failed emissions test, and burning oil (pcv).

Edited by adamzan
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FWIW I just swapped a new to me engine into my 95SE and I had half the vacuum lines unhooked, egr not hooked up right, and IACV unpluged, and it still ran halfway decent lol.

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Adam, thats because you have a magic 95 that likes to play nice ;)

 

Upon using a laser thermometer, it seems like the misfires are only occurring on the left bank (cyl 2,4,6). This was found because the manifold temps for cyl 2 and 6 were 25*F lower than the other 4 cylinders. So, that narrows it down to timing, fuel, and ignition issues on cylinders 2 and 6. Brand new plugs, somewhat new wires... would rotating the distributor fix this issue easily, or is it going to be a money gremlin that requires me to replace wires and the ignition coil? Is a trip to the mechanic for a compression test in order potentially?

 

Also, found out through a real CARFAX that my truck does indeed only have 91k original miles!!! Not too shabby for a truck built in 9/1990. Probably explains why it doesn't have power loss, even with 2 cylinders acting up. Anyways, any thoughts or inputs are always appreciated.

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If you are driving it like that, and it is an ignition miss, you will be dumping a lot of raw fuel into the cylinders, which will dilute the oil and wash the oil coating on the cylinder walls away. This will kill your motor in short order.

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Good thinking testing with the thermometer. If it's running properly on four pots and bad on two, it's not your timing. It could be the cap (+1 on checking that). A compression check wouldn't be a bad idea. I'm also wondering if you might have a fuel delivery issue on those two, maybe a couple leaky injectors? Did you notice any fouling when you changed the plugs?

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What were the results of the new O2? If your having issues on 2,4,6 I would tend to think you have a bad bank 2 sensor 1 O2. If you can check it with a ranging multimeter you should see a sine wave of it quickly fluctuating between 200mv sweeping up to 850mv and back, anything 50+ mv outside that range at all would indicate a bad or failing sensor.

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Its a WD21, there's only 1 O2 sensor...

Starting with Slartibarfast, leaky injectors are certainly a possibility. Is there any way to test them without pulling the upper intake to get them out? Something noteworthy: the truck does not start in 1-2 crank revolutions like it used to. It now requires me to actually let my injectors prime fully before starting. Could my fuel pump be going out (it makes a high-pitched whining noise when the truck is running)

 

I'll pull my cap off to take a picture of it for you guys, but as far as I could tell last week when I was doing the plug change, the cap looked to be in fine condition, apart from what looked like normal carbon buildup on all 6 posts..

 

A far as fouling, I dont remember it looking like there was any on the plugs when I pulled them, but then again I'm pretty new to working on cars myself, so I'll have my dad take an up-close picture of the plugs when he gets home so that I can share them with you guys (I'm back in my college town)

 

If I end up taking it in for a compression test, I'll probably be going all the way and having them work on it until the problem goes away, but that's big $$$ so obviously last resort.

 

I'll try to keep my driving to a minimum Adam, thanks for letting me know that.

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Just be sure to pull the coil wire off of the dizzy before you test. Compression readings should be within 15 percent.

 

If you have a low cylinder, put a bit of oil in it. If the reading jumps up significantly, your rings are the issue.

 

If not, you may have a leaky valve.

Edited by PathyAndTheJets
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