tmann

I have a 1998 TRD 4wd V6 Tacoma that gets an error code of Random Multiple Misfires.

I have replaced wires, plugs (NKG's), fuel filter, cleaned MAF, and ran Sea cleaner through the tank a couple times. I have also checked for vacuum leaks. I think I am down to it being the egr, one of the position sensors, or the O2 sensor. I just don't know which one. I pulled the vacuum line of what I think is the EGR at the back of the motor and tried to apply vacuum with no change on the motor but not sure if I just am not apply enough. I don't see how the vacuum line that I see goes through the manifold area to the back of the motor gets any vacuum though. The line goes to that canister that is part of the Air intake which would be little to no vacuum ever I think. I must be test the wrong line to it.

Here is the interesting part. My truck will not misfire in park or reving up the engine. I drive 30 miles to work in the mornings with no misfires. I can drive in the later evening with no misfires (thought I had it fixed a few times due to this effect). The misfire happens when I am coming home in the afternoons (I guess when it is the hotest part of the day outside) cruising at about 82 mph on the interstate. Then it will do it constantly until I turn it off for about an hour then it is evening and it will be fine again. The next thing I am looking at trying it the crank sensor but I wonder a about the EGR, Cam sensors, and O2 sensor. The only codes are random multipel misfires and sometimes it will give a cylinder number but that of course changes each time we check the codes so it is random also I think.

Anybody had this specific issue and found out it was any of the items I got left or how do I know which one. I am also open to sugguestions. I probably should just take it to Toyota but as long as I can do it would hate too.

Thanks,
Todd

rworegon

Gas cap gasket in good shape and cap is tightened properly?
Crank pulley bolt tight?
Timing marks all line up ok?
Are you losing coolant?
What did the plugs look like that you took out?
All the grounding wires in place and tight?
Condition of air cleaner?

It's interesting that it's ok when the air is cooler i.e. denser and acts up when the air is light. Given this, I'd double check for a vacuum leak. A small crack in a vacuum tube or in the intake can do crazy things.

tmann

Hello,
I think the gas cap is ok it clicks when I tighten it and seems snug.
The crank pulley isn't wobbling so must be good but I will check when I try and look at the crank sensor. I hope that sensor just has a 10mm bolt and comes out. Plus I hope it is that easy to put back.
I don't have a timing gun but truck runs great when it is hitting on all 6. No pinging or anything.
I checked on ground wires and all that I saw looked good and tight.
Truck doesn't leak a drop of anything.

The only other info I can say is it has been doing this for the last month or so and when it started I found a plug wire that was arcing out the side of a boot by accident. I put a new wire set on to fix it.

rworegon

But how is the gasket on the cap? I've seen 'em develop small cracks and some say that contributes to the P0300 code.

tmann

Seal seems good and when I loosen the cap I can hear air being sucked in. Must be sealing pretty good so I don't thing that is it.

The old plugs looked good just part of the electrodes burnt off due to the few years in the engine. Not black but more of a tanish white clean look.

Thanks

tunnelmotor99

A bad gasket on a gas cap will not cause a misfire, all it will do is throw a "Evap System Large Leak" code. Did you check the Mass Air Flow Sensor?

tmann

Hello, yes I also cleaned the Mass Air Flow sensor and unplugged it and plugged it back in.

Today was the same as every other day too. The only time my Truck misfired was on my 5-5:30pm drive home down the interstate. Don't notice any other time and I drive in on the same interstate in the morning with no misfire.

tmann

Ok. I have a question on testing egr. Does my truck have one? I may have testing a fuel regulator and thought it was an egr. I looked at a manual online and didn't even see anything labeled egr. Is the egr next to the fire on the back of the engine? How do you take it off to clean if it is? I can bearly even see it back there. Thanks for the help.

dntsdad

doubtful your 4x4 has EGR but not 100% sure. On the TSB's that I have, they only list EGR on 2x4

EGR would be here:

tmann

Thanks DntsDad. I was wondering if it had one and what I was testing I think was a fuel regulator or something. The thing I was testing has the metal tube going through the middle of the manifold casting and you see it in your picture right below your red circle which comes out in the back of the engine then a vacuum hose attaches to it. This goes to a metal thing that I thought could be a egr but from the manuals it may be some type of fuel regulator device. The vacuum is to it wouldn't even be strong enough if it was an egr. Thanks.

tmann

I did a crank sensor with no change. I think it is the Ignition Control Module but it is pretty expensive. The things I have not tried are cam sensor, O2 sensors, main computer, and the ICM which I think is the problem. Anybody got any better idea's out there because I am out of good ones.

BTW it set another code today of Multiple Random Misfire, cylinder 3 misfire, cylinder 4 misfire, and Multiple Random Misfire again.

tmann

Ok. Just to post what I found and did. First this has gone on for probably about two months. Secondly it doesn't seem to be missing and the engine light hasn't come on in a few days. The battery was bad too but I don't know if that would cause the problem when it would start but last weekend it was noticable that somthing wasn't right with it. I took the truck to where I got the battery and it was bad and got it replaced. I never had to jump start it or anything. That evening I think I noticed the mis on the way home, I think since it isn't far to my home, and I picked up the ICM from the parts store to put on at the house. Plugged in the new ICM and it ran worse with an obvious miss on cylinder 3. Had a obvious mis so I disconnected the battery and waited till computer was clear and reattached then it ran fine. The trucked has missed and the light hasn't came on. The thing I keep wondering if it was actually the ICM I replaced or the battery. I had a case when the alternator went out and the truck lost power while I was driving it making the engine barely run and die. Was it the new battery or the ICM? The battery could have been heating up and shorting out or something is what keeps running through my head. I don't want to try the old ICM on the truck since it is actually running good I don't want to mess it up. What do you think?? Could a battery been an issue for a couple months or was it the ICM I replaced that fixed it??

tmann

Unbelievable.....its back. I change something and misfire goes away for a week then comes back. I just don't get it. I am going to need to take it to Toyota. That will be another 500 to 1000 in the engine misfire. Ok well what I have noticed now is I think it is fuel to cylinder 3. Injector probably but that is covered up by the air intake so I don't think I want to tackle taking the manifold apart but then I wonder if I should replace all three on that side if it is injector on 3. They are all covered up on that side while the passenger side is easy to get too. I don't know what hold the injector in but the driver side looks pretty time consuming to get too. At this point probably isn't that either. This is the strangest misfire I think I have ever seen. Acts somewhat like an oxygen sensor on our old Envoy. The parts store people tell me that it would though a specific code for oxygen sensors, cam sensor, and crank sensor. I have not tested and I don't think I can the injectors on the drivers side. I did test the passenger ones which were all ok. The reason I think it is the number 3 injector is due to I know it has to be getting spark due to the arching I can make from the boot. Changed the plug a few times and it doesn't change the engine when I pull the boot off the plug while running. Plus I have the plug out and even started it to see if I smelled any fuel and I didn't really. Truck is falling apart at 145000 miles since I have had to fix some pretty pricey issues in the last 12 months. Has about 14 years on it too though! Just venting. I haven't done: Oxygen sensors, ECM, cam sensor, or injectors. Only does it after it is hot and in the warmer afternoons. Just strange!

tmann

I also haven't replaced the the pcv.

tommytuttle

Any update? how are you making out with this?

tmann

Took it to Toyota and 800 dollars later it is suppose to be fixed. They determined it was an injector and the service guy says he has only seen two time that it was an injector. This was the second one.