Intermittant misfire (1 Viewer)

[OffRoadScott]

Recently my 94 Land Cruiser has developed a miss fire. The miss is not a constant misfire it will go away and then the miss. What I mean by go away it will smoothen out a couple of cycles of the motor and then it will reappear. It will miss a couple of times then the idle will smooth out. It takes place under load, at idle, in gear, park and neutral. While driving down the highway/freeway it got really bad and could feel it pretty bad. So it was taking place at high RPM (2100-2200). Also, this started yesterday after washing the LC while the motor was running spraying the undercarriage.

The head gasket was recently replaced along with the plugs, cap, rotor, and wires. I am still assuming it could be something with the ignition but really hoping it is not the head gasket again. It has been only 1000 miles since the head gasket was replaced. The idle can be erratic at times too which I believe can be a vacuum issue. Could a vacuum leak cause a miss? Also, it sounds like there is a leak too, but the weird thing is that it appears to be coming from the top of the intake manifold. I put my hand on the top and the sound disappears, could of overtime the manifold thinned out and now cause a vacuum leak?

One thing I did notice though, was the wiring harness that ran/runs next to the EGR is in pretty bad shape but do not see any frayed wires.

I tried to chase down the issue today with no luck of totally eliminating the issue. I pulled the intake hose and checked it for cracks, there were no cracks. I pulled the wire covers and made sure the wires weren't crossed causing shorts, pulled the wires to the coil and added dielectric grease, I also pulled the coil wire. There was some moisture, liquid on the steal/metal nipple that connects the coil to the distributor. At first, I was thinking it was dielectric grease so I went ahead and checked the rest of the wires, none of the other wires had any liquid or grease on them.

 

[Tools R Us]

...
One thing I did notice though, was the wiring harness that ran/runs next to the EGR is in pretty bad shape but do not see any frayed wires.
...

Is the harness tied in place, to the mount peg?

 

[OffRoadScott]

Is the harness tied in place, to the mount peg?

Zip tied, it was done shortly after I spoke to you after getting my LC, talk about being a PITA. I verified the zip ties were/are still holding strong.

 

[ppc]

More than likely water has gotten into the O2 sensor connectors from the spraying you did on the undercarriage.

 

[Tools R Us]

Zip tied, it was done shortly after I spoke to you after getting my LC, talk about being a PITA. I verified the zip ties were/are still holding strong.

They should be new, have to be removed to get the head off.

 

[ajax1]

If it started after you washed the engine I would assume you got water in the distributer and in some sensors

 

[Tools R Us]

How long has this been happening, is it related to the washing, or happening prior?

 

[OffRoadScott]

More than likely water has gotten into the O2 sensor connectors from the spraying you did on the undercarriage.

I know where one of those connectors is and I disconnected it and cleaned aired it out. The one I am referring to is forward of the cats and runs up the inner fender lining and connects to the wiring harness next to the diagnostic terminal. Where is the next one?

 

[OffRoadScott]

If it started after you washed the engine I would assume you got water in the distributer and in some sensors

Most of the washing was from under the rig, I might have splashed some up into the top half of the engine bay but the top was not washed directly, more indirectly.

 

[ajax1]

Sounds like water in plug , especially since you say it started after washing the engine

 

[OffRoadScott]

Sounds like water in plug , especially since you say it started after washing the engine

I will have to crawl underneath again Thursday and check all the plugs/connectors

 

[ppc]

On my 94 model each O2 sensor has approximately 12 inch pigtails and the connectors I'm referring to.

 

[ajax1]

There is also ttv vacuum lines under manifold on drivers side maybe you blew one then off

 

[OffRoadScott]

On my 94 model each O2 sensor has approximately 12 inch pigtails and the connectors I'm referring to.

I will google and see if I can locate the O2 sensors and check them for condensation.

 

[OffRoadScott]

There is also ttv vacuum lines under manifold on drivers side maybe you blew one then off

Most of my spraying was at the frame level, nothing was done in an upward angle. But I will check those too.

 

[ppc]

You need to add a signature in your profile with model year and other pertinent info. You will get better answers to your questions.

There will be a O2 sensor close to the front of each catalytic converter.

 

[OffRoadScott]

You need to add a signature in your profile with model year and other pertinent info. You will get better answers to your questions.

There will be a O2 sensor close to the front of each catalytic converter.

I will update that signature and thank you for the lead on the other O2 sensor.

 

[OffRoadScott]

So got up early this morning (0430) here in AZ I went out and disconnected the other O2 sensor to allow it dry/air out. There is some greenish crap on one end of the plugs. I have a nylon brush that I will use to clean out both ends of the plugs and then reconnect them and hope for the best.

In the past, I put dielectric grease on the other O2 sensor. Could that affect the signal the O2 are sending to the ECU? I did it to protect them from water, but I will probably get large heat shrink tubing to protect if not only from water crossing or raining days/large puddles during monsoon season.

 

[bajaphile]

In my experience, if an O2 sensor fails, it does not result in a misfire. It will throw a CEL and the ECU will run in the closed loop mode. But I suppose it is possible. When using dielectric grease, you really want to use a minimal amount on the connectors themselves, and more "around" them to keep water out. The grease is actually an insulator (current will not flow) so you don't want to jam pack the metal connector area.

Doesn't sound like you pulled the distributor cap off yet. You should check that there is no water in there.

You may want to google search site:forum.ih8mud.com misfire water wash or something like that and see what pops up. It sounds like it is definitely related to your undercarriage spraying.

 

[bajaphile]

@OffRoadScott please post back with your findings/fix. Curious to what it is.