Hey guys still got my '92 4Runner with almost 300k on the clock. But I got a missfire that doesn't seem to want to go away... Did a full tune up on it and checked everything except for the fuel injectors as they are not accessible. It started a long time ago and was only on start up for a min or so then it would go away. Then one day on my way home from work it started while driving and it just does't want to go away. I feel as if I got bad gas, but this thing has never cared what I put in it so im leaning away from that theory. Any suggestions?

Much appreciated!

 

Are you using any coolant? Are the grounds at the battery and engine bay in good condition?

 

Battery and cables are good, just replaced the battery not long ago and checked those. I replaced the water pump about a month ago. The coolant was the first thing I checked after the tune up. Also checked for sludge/coolant in the engine block as it over heated when the water pump failed. I was thinking after I had posted this, that it may have jumped a tooth on the timing belt...? Possible reason....

 

OK guys, im baffled!!!! I checked everything there is except fuel injectors and I am coming up with nothing. No reason why its doing whats doing. Winter is right around the corner and I am running out of time and options on how to get this thing running right...

ANY suggestions would be greatly appreciated!
Thanks!

 

No CEL?

 

you overheated it? may have burned a valve. You absolutely sure its not losing any coolant?

Clean the maf/vam? (whaterver they have) check tps?

 

Verified engine health...?

Compression test...?

Vacuum test...?

 

run fuel injector cleaner in it?

 

No Check engine light, I have ran a bottle of seafoam through it, compression and Vacuum seem ok, And no, no coolant loss. When it over heated, it was the end of winter last year. Everything was fine after I replaced the water pump. Like I said, it was running fine, then one day when I was returning home from work, it just started acting up, like a misfire. At a cruise it seems almost normal, under any acceleration its rough! After I put the bottle of seafoam in the tank, I took it out and gave it a "poor mans tune up" and it seemed to make it run better but still not any where close to normal..... I just don't know

 

I had a similar Problem in my 89' about a year or so ago, and it ultimately ended up being a bad fuel injector. Lucky for me it was the first one in front of the driver side of the engine, so i could pinpoint it, but i would suggest checking those ones with a stethescope/large screwdriver pressed to your ear and go from there. It just might be one of those ones,

 

A misfire could be a plethora of issues (yes, plethora).

Most common issues have to do with spark or bad sensor/wiring. Are your spark plugs good? If you have a spark plug wire tester ($5 if you don't), make sure each wire is firing like it should.

If that's not it, work towards the more difficult solutions. TPS would only affect it at low RPM's unless it's really off, like it was smacked to the other side or something. Could also be your Engine Coolant Temp sensor.

Have a compression test done, it's fairly cheap. This will indicate is there's an issue with your valves or possibly piston rings (not as likely). From there, check injectors to ensure they are all firing.

That will cover just about everything. If none of those are the issues, let us know.

 

Yes spark plugs are new, wires, cap, and rotor are also new. I have two spark testers and I have spark at all six plugs. I am leaning on a fuel injector, because After I ran fuel system cleaner through it, it seemed to run better. However I think an injector replacement is inevitable. I would pinpoint test them (if I could get to them) I do have multimeters and noid lights. Worked in an auto shop for almost ten years, so I have a great number of tools lol I think my next course of action is to pull the intake and test injectors (extreme?) maybe but with almost 300k on the clock that is what I think it is going to come down too. I will for sure post my results for future Yotatech members!