2000 3.4l 4runner misfiring under load (1 Viewer)

[Devilmans Hand]

Sister has this occasional issue with her truck. We replaced the plugs and wires with ngk and this temporarily fixed this problem for 3 weeks, but it is happeniNg again or still. The PO had used bosch single ground plugs, so I ripped those out promptly.
We seafoam ed the pcv line on the intake and dumped in a bottle of bg44k.

The bucking shudder is a little weird. Happens around 1.5k rpm at 50-55mph uphill only.

Have not yet tested coils or injectors. Truck has about 200k on the odo.

If the misfire is bad enough the orange light will blink 5 times and previously the code from the scanner was a #1 misfire.

Any ideas? She's likely to drop the truck off at a garage soon.

 

[Stumpalama]

New wires? Injector? Test injector wiring. Also does it have coil packs? Swap one around and see if the problem moves to another cylinder.

 

[Stumpalama]

Also, what does the new plug look like after running now?

 

[OTRAMM]

the coil feeding #1 is most likely although that is DIS and should kill two cylinders at a time. Also check the valves. Tight valves that aren't sealing could cause compression loss and a miss.

 

[Devilmans Hand]

Plugs look newish normal after 2 weeks.

Tested coils hot and they're in spec and consistant. Doesn't necessarily mean they're good though, speaking from past experiences with coils.
I don't have an obd2 scanner just yet, so I can't clear the codes and swap the coil to another pair of cylinders. Might head to advanced auto in the morn and have them clear the codes, swap they coils, then drive around a bit.
A bit too dark to pull the injectors, plus I don't have spare o-rings for when they break when removed.

 

[Stumpalama]

I have a code reader you can borrow.

 

[Devilmans Hand]

Sis left early this morning and the truck will be droped off at the mechanic. Oh well.
Thanks for the advice.
The seafoam and bg44k seemed to smooth the engine out a bit, but the studder remains under certain conditions.
Now to acquire a good spare coil pack for my own emergency spare parts.

 

[Skrewball]

Just went through a similar situation with a family members 01. #3 misfire started real bad with old wires/plugs, new ones helped a lot. Still had occasional miss under specific conditions. Replaced #3 coil and all better now. Very common on the 3.4 motors.

This is what he replaced his with. Denso Coil

Oddly enough it didn't have any misfire symptoms on cyl #4. Since the same coil runs both of those cylinders i thought it would have issues on cyl #4 as well..

 

[Devilmans Hand]

Pretty much the same thing happened.
Thanks Vince
I was looking for a denso coil and they cheapest I had found earlier was $130.
I'll have to order one or two of those.