Misfire only when HOT

[Spanky_swizzelteets]

Hi fellas! I am new here (obviously). This is my 1st post and I am really hoping you guys can help save me a bunch of money. BTW... I have searched existing threads on similar issues and completed relevant suggestions.

The problem: My 1998 pathfinder has a misfire (with blinking check engine) but ONLY if I restart it after running it until it's warm. It never transitions from running smooth to the misfire; it only has the misfire if I start it after the engine is already warm. In fact, I can usually turn it off and restart it a few times until it starts clean (without the misfire)

The code is P0301.

I have already checked the compression (145psi), replaced the plugs/wires, replaced the distributor cap, replaced the fuel filter, verified the fuel pump pressure, and am currently running a can of BG 44k through the tank.

The shop wants to replace the injector in cylinder one if the 44k doesn't do the trick. Does this sound like an injector issue to you? It only does it when I restart while hot and it never starts misfiring once running smoothly.

Thanks in advance for your time.

Edited July 21, 2014 by Spanky_swizzelteets

[Quaintbucket]

Did you check for vacuum leaks? That was the biggest contribution to my random misfire problem. After fixing the air intake duct boot to the intake manifold (and replacing it when the part came in), I have not had any misfires since then.

 

Usually an easy and cheap fix. The tough part is finding it.

 

Here's the FSM for your vehicle. It's on page 261 of the file under EC - 255. Got a nice step by step procedure. Did you pull any other codes?

[Spanky_swizzelteets]

I'll ask the dealer if they checked for vacuum leaks. I believe they did.

 

Yes, the other code was P1444 so we replaced the charcoal canister, purge valve, vent valve, and cleaned out the vent tube.

 

So far, this has been a very expensive fix. I'm about $1,500 into it (counting the emissions items noted above).

 

ideas I've read, elsewhere, include:

1) Get a leakdown test for leaky or burnt valves

2) Check for loose wire on O2 Sensor

3) check for bad head Gasket

4) Replace injector and Ignition Coil

5) Replace ECU

[Precise1]

Oh, no! I'm pretty sure I know this one as it happened to me.

 

P0301 is Cylinder #1 misfire, and mine only did it once warm, then shut off, and then restarted. The #1 injector was failing only when hot. Check the resistance of the two wiring contacts of the injector when it is cold, it should be 10-14 ohms IIRC, then warm it up, shut it off and check it again. I bought a set of used injectors and some new O-rings and just replaced the one, been running great ever since.

I can't say that is your issue 100%, but I'd bet on it and start there for sure!

http://www.nissanpathfinders.net/forum/topic/27522-p0301-cylinder-1-misfire/?hl=p0301

 

Injectors are color coded, what color is yours? (I have spares)

I'd request a detailed, written itemization as to what the mechanic has done to diagnose the P0301 code at this point...

 

B

[rick88ss]

Could be the distributor also. Do you have a know good one to swap it with?

[Leo98]

The '98 Pathfinders VG33E are known for bad distributors, maybe a little attention there. It's too bad you didn't bring that code P1444 charcoal canister and purge valve to the forum, i could of saved you $$$. Did a fix on mine that cost about $5.