98 4runner cylinder 4 misfire

[soundmanlpte]

Hello,

I have a 98 4runner, 3.4 V6 2wd. 190k miles. I've owned since 136k.

Yesterday, it started shaking roughly while in gear and accelerating. It's like a really low rumble. It happens as soon as I shift into gear and accelerate, but stops once I get up to speed. Resumes when I get to stop light. Check engine light blinked intermittently when I was at full speed. It stops when I shift back into park. Here are a few thoughts as to what the problem may be:

- Misfire. Plugs and wires were replaced maybe 30,000 miles ago. I did not replace coil packs. Though if it were a misfire, the check engine light should remain on, correct?
- Transmission. It has been a long time since service so I think I will drain and replace fluid today.
- Drain and replace diff fluid?
- Clean IAC valve and throttle pack?

Any suggestions would be much appreciated.

Thanks!


UPDATE: I went to Advance and they told me it was reading cylinder 4 misfire.

I have changed the spark plug on cylinder 4. Ran fuel injector cleaner through the tank. Check the spark plug wires. Swapped coil packs around on the other side to see if that could be the problem, I'll know when I go back to Advance and get them to run diagnostic again. I also cleaned out the throttle body, MAF sensor, changed PCV valve, and changed the air filter.

I am down to changing the fuel injector. Any thoughts?

UPDATE 2: The misfire remained on cylinder 4 even after swapping coil packs. I've ordered a fuel injector from Advance and will be swapping this afternoon.

 

[T4RTahoe]

That's what happened to my 98 3.4 when the fuel injector went. Could very well be the issue.

 

[MAZE]

Experiencing the same issue on my 99 with 330K (km).
Plugs, coils, wires, and timing belt are all new and verified operating correctly.

About to order some injectors and plenum gaskets to do the job.


EDIT FROM THE FUTURE: Injector was the issue.

 

[Norwester]

Experiencing the same issue on my 99 with 330K (km).
Plugs, coils, wires, and timing belt are all new and verified operating correctly.

About to order some injectors and plenum gaskets to do the job.

Take a look at your valve cover gaskets and consider swapping out your coolant temp sensor while you have the plenum(s) off. Had a Homer Simpson "DOHHH!" moment a few weeks after changing my injectors when I realized I needed new gaskets. :frusty: The CTS is only $13-$14 and a little easier to reach with the plenum off.

 

[drallan]

Had the exact same thing (even cyl 4) happen to my '99 3.4 a few weeks ago. Tried all the usual "easy" fixes like you have (plugs, wires, etc). Ended up being the injector. Cyl 4 is on the driver's side so it is a bit more of a pain to get too, but it really wasn't that bad. Maybe an hour to take everything apart (take your time), and an hour to put it all back together. No special tools required. Pretty much used a 14mm open end, deep, shallow socket w/ extentions, a 10mm w/ extension, 17mm box for fuel rail, and a screw driver.

It's a pretty straight forward job. Just make sure nothing falls into the intake/injector holes. I actually took a shop vac and sucked everything up around the holes to make sure nothing got in there.

I don't have the link on me, but there is a decent write-up floating around. I went ahead and replaced all 3 on the drivers side (2,4,6) just so I don't have to do it again. I would have liked to do all 6 and get it out of the way for another 175k, but it wasn't in the budget this month, maybe in the spring.

After I got her all put back together she runs as good as new. I went ahead and changed out some of my cracked vacuum lines and cleaned the TB real well while I was in there. It will take a few sec for the fuel system to prime the first start. If it runs rough, make sure ALL vacuum hoses are connected properly. I had a mild heart attack at first because I forgot to attach the PCV hose and it ran like $hit at first. Once I found the culprit all was good.