Replaced plugs while diagnosing misfire now it won't run. Doh!

Maintenance/Repairs
1

1989 Nissan pathfinder. 6cylinder - VG30i - Manual trans

Engine was misfiring (running okay but putt, putt, putting) so I pulled be plugs to check for signs. Other than wear and wide gap the plugs looked okay, but I installed new plugs as they’re cheap and I was already pulling them. I replaced them one at a time so didn’t mix up the wiring. I went to restart the engine and now it turns over and starts but then immediately dies. If I really slam on the pedal I can get it to rev up a couple times, but it really wants to completely die right away.

It’ll start but won’t run

–Side notes and thoughts–

  • I took the battery lead (neg) off for a few days - maybe that reset something?
  • I had a very empty gas tank - so low that I thought it might be out of fuel. I put two gallons in just to make sure. Because I can slam on the gas and get it to revving I’m not sure being out of gas is the issue.
  • I removed the distributer cap to check for wear but reinstalled (picture attached).
  • I sprayed some Mass airflow sensor cleaner into the throttle body to clean up, the throttle body valve blade was pretty clean.
  • I’m doing this test without the air filter in. The old one was so dirty I removed it and didn’t bother putting it back on. Going to buy a new one today.
  • It cannot pass smog due to this misfire (obviously not detonating fuel so it’s polluting)
  • The engine was start up readily before I started tinkering. It would seem strange that adding new plugs
  • I didn’t gap the plugs.

–Next steps–

Look for any wires knocked loose or hoses disconnected.
Pull the error codes (check engine light is on cuz, it’s uhh not running)
Check Vacuum and diagram and hoses.
Check ignition system wires.
Check fuel pressure.
Check Cylinder Compression.

Ultimately I’m trying to tune it up (and fix misfire) anyway, not just change the plugs, so doing more diagnosis is okay. It’s also not my primary car. I haven’t worked on cars in a while so I’m a little rusty and also needing to get necessary tools to complete the tasks. But it’s fun I hope I can get this car running well again soon.

If you have any insight I would really appreciate it.

2

Have you checked the wires for no insulation breaks and continuity? It’s entirely possible that you ganked the wires when you were taking them on and off.

3

Wouldn’t it still run, just really rough? My multimeter is dead so I can test resistance. Next step was to test each wire with tester plug or just to ground. The coil wire looks pretty thrashed but pulling the wire completely makes the car doesn’t turn over at all. I was going to try and replace just that or maybe buy new multimeter to test the resistance.

Maybe the coil is to blame but it ran before. So I’m just trying to get it back to that state and rule out the plugs (since I replaced them).

4

You said you are running it without an air filter but did you reconnect the air cleaner to throttle body tube?

5

The rotor looks a little bad…but it should run.

The coil wire looks pretty thrashed but pulling the wire completely makes the car doesn't turn over at all.

I don’t understand how pulling the coil wire prevents vehicle from turning over. That makes no sense what-so-ever.

Make sure the wires aren’t touching any metal. If they are old…they could be arching. Start the engine at night and see if you can see any arching.

6

I agree with shadowfax. You should rule out the wires, especially if they are old.

I had a similar problem after changing plugs and wires. Turned out that I knocked the MAF sensor loose. I had codes to help me track it down. Do you have codes?

7

@MikeInNH

Sorry I mis-spoke, it turns over it just doesn’t start.

Thanks for the note about the rotor. I’ll probably just replace it.

8

Is the breather to throttle body hose connected? See @Nevada above…

What brand spark plugs did you install? If they were any of the off brand “super plugs” get rid of them. The underhood emission label should specify the correct plug and it is worthwhile to use that plug.

9

The business edge of the rotor is clearly fried and the business surface of the distributor contact at about the 8-o’clock position (the only one I can see) is also fried. Whatever else it needs, it definitely needs a new rotor and cap. I’d start there. And add new wires for certain.

Comment: this isn’t your problem, but reusing the same plugs, even if the electrodes look good, isn’t advisable. You have square-shouldered plugs with metal crush washers that get crushed by the shoulder of the plug body and seal the interface. They’re designed to deform on the first application, but once they do they should not be reused. They’ll not seal properly again once deformed by the first application.

The rest is “back to basics”. You need to check for spark, check for arcing of the wires, if you have no spark at all check to see if you have spikes coming out of the coil, if not check to see if you have 12VDC to the coil primary.

And then check for fuel supply and proper metering. You, my friend, are headed down the right path. Keep in touch.

10

Tell you the truth it sounds like a fuel issue or MAF. I don’t know if two gallons in an empty tank is going to be enough to prime it again and get a good fuel flow going. The fact that it starts and revs a little then dies to me sounds like fuel.

So I don’t know, I guess I’d add five gallons of good gas and check for fuel pressure (or is this a carb?). Also check for spark. But I’d go back over every step you took to recheck your work. I told the story before but way back I was changing points in my 59 VW and afterwards it wouldn’t start. Finally had to call mechanic friend of my dads who came over and right away spotted that I had installed the insulating washer on the distributor in the wrong sequence so it was grounding out. First rule is to recheck work.

11

The distributor rotor is not likely to cause a problem like this.

Per Nevada above, what about the intake tract being properly secured…

I’d also recommend going back over any vacuum hoses to verify that one of them is not dangling loose or split.

12

Just a shot here. If the car won’t run at all, then it isn’t plug wires, because not all of them would go bad all at once. The coil wire however, now if that goes bad then you get no spark to any of the plugs. Put a known good coil wire on there and see what happens.

A bad cap and rotor would still allow the car to run, crappy but still run. The rotor would have to be coming apart and I just see normal wear at the tip. This is pretty basic but make sure the rotor is down fully on the shaft and correctly in the notch.

13

Just to clarify, the OP stated that it would start and even rev but only momentarily before it shut down again. Seems like there must be at least some spark for that to happen. Almost like fuel pump is not running after the initial charge.

14

You’re right Bing. I missed that detail.

To the OP: you may want to try putting the key to ON a few times for perhaps 4 seconds each before putting it to START. That’ll see if the pump is repressurizing an empty fuel line… and it’ll also give you a chance to listen by the tank to see if the pump is running or not.

Post back with the results.

15

That can be the result of a leak in the intake bypassing the MAF as @Nevada_545 suggested @Bing

16

How about a shot of ether . . . ?

If it runs on the ether for a few seconds, you may have a fuel problem

Have you even verified the fuel pump is getting power and ground?

Have you measured fuel pressure . . . since this is a Japanese truck, there’s an extremely good chance this engine doesn’t even have a fuel pressure test port, so in that case measuring fuel pressure would mean teeing in

I wonder if this engine has some kind of inertia fuel shut off, like on the Fords . . .

Have you used a spark tester? You should have a very bright blue spark, not a weak and pathetic orange spark

17

Thank you everyone for the responses, it’s much appreciated. I’m not able to work on the car today but I’ll follow up when I have more details.

I have a hunch that because I left the battery unplugged for a couple days and there wasn’t much gas in the tank (okay, no gas) I lost the prime in the fuel lines didn’t get it back due to the shortage.

If you’re interested here’s little back story… I bought this car on a whim for $1200 from an old stoner who was hard up for cash, I"m in CA where a 80’s Nissan truck with 200+K miles will still sell in the $2-$3k range. This engine has a reputation for be exceptionally durable and I like the small 2-door pathfinder format. No blue smoke from the tailpipe, manual /4x trans feels solid. I heard the misfire but I figured I’d take the gamble and would like to have small durable truck I can tinker on. I’m prepared to throw at least few hundred bucks to get it solid and have some fun brushing up on my auto skills. What I’m trying to avoid it just throwing parts at it, not because I’m cheap but because it can be a unnecessarily / unsound approach, one that I’m often tempted to take. So I’m going to fix this problem and ultimately test the systems all around. Just not sure which will come first =).

Fill the tanks with a few more gallons.
Check the vacuum system at large.
Confirm / test intake control systems
Test the spark coming from each cable. I’ll likely replace the some ignition parts but I’d like to rule out a blown head gasket (maybe between cylinders).

  • Got my self a new Bosch multimeter for testing electrical paths / components (my old one died)
  • Getting a vacuum gauge
  • Borrowing a compression gauge

I’ll keep you posted.

18

The “i” means it is fuel injected, right?

From what I can tell it was running ok, but not perfectly, missing a little. So you did the following

  • Disconnected the battery
  • Removed the air filter
  • Changed the spark plugs (yes, the gap looks wide in the old ones, did you measure?)
  • Cleaned the MAF sensor

You left it like this for a few days, then connected everything back up but left the air filter off, reconnected the battery, and it cranks ok, but struggles to start and even if it starts it won’t run hardly at all. Is that more or less correct?

hmmm … well, you could be right about the battery. It wasn’t so common in 1989, but newer cars at least, the computer learns how to keep the car running smoothly due to things that happen naturally with gasoline engines, like carbon build up in the throttle body area, etc. But when you disconnect the battery it can cause the computer to forget all it learned. So when you first start it up it might struggle, or not start at all. We’ve heard reports here of owners having to tow the car back to a dealer so the can reprogram it so it would at least idle, after disconnecting the battery.

I’d discount that though b/c like I say this learning behavior in car computers wasn’t common in 1989. I doubt that is the problem. But if it is, if you can get it idling and keep it doing so, the gradually driving it around, eventually it will relearn. Worth a try anyway.

My guess is this has something to do with cleaning the MAF or running the engine without an air filter. It’s not a good idea to run without an air filter. There can be hidden debris in the thing that holds the air cleaner that will get swept into the intake manifold when you start the engine for example. That could hang up on an intake valve or on a sensor in the intake path. It’s hard to un-ring a bell, so can’t say for certain, but that’s a possibility.

It could be the case also that this engine simply won’t run well without an air filter installed. The MAF is very sensitive to the air flow patterns in the intake path, and the air filter evens out the flow patterns probably. So try installing a new air filter.

Cleaning the MAF can sometimes damage it, especially if you use an incompatible product, so that’s another possibility. Good idea to check the codes, like you plan to. You may have affected the electrical connection to the MAF too, so double check that. You may have to replace the MAF with another known good one to rule this out.

Other ideas, the rotor problem as mentioned above, the coil might have been damaged by running spark plugs with too wide of gap, the new spark plugs might have some kind of problem so you disprove that by putting the old ones back in, spark plug wires could have been damaged disconnecting/reconnecting.

19

As mentioned above, I think I’d add that rotor and distributor cap to one of the first things to do. Its likely not the current problem but it needs to be done anyway. Now the other thing is if it was really out of gas, it might have picked up a bunch of debris from the bottom of the tank and plugged the fuel filter.

20

@Funkyfresh

In regards to that broken multimeter . . . if by some miracle, the old meter was a Fluke brand, the company stands behind their products for life, and will repair and/or recalibrate, as needed, provided it isn’t due to obvious abuse/operator error

As for that MAF sensor . . . here’s how you can narrow it down. Unplug the MAF sensor’s electrical connector and try to start the engine. If it immediately starts and stays running, the sensor is most likely defective

I also live in California, and can only agree with you about older Japanese trucks holding their value.