My 4runner runs fine under normal driving. But you put a load on it and the engine shutters. Like drive up at steep hill or using lots of gas pedal. I already tryed to clean the maf sensor.

 

I would say your best place to start it by checking codes, even if the cel is not on. That will hopefully give you an idea of where to dig in.

 

Try checking the pressure regulator. Might be the issue

 

I have only gotten a cylinder 3 misfire code. It's only appeared once.

 

I also did new spark plugs hoping it would help. It did make it run a little better.

 

Did you ever diagnose the cylinder 3 misfire and see what might have thrown that code?

 

what plugs did you use? Have you replaced the fuel filter? hows the engine compresion? The early model fuel injectors for the 3.4 had problems and were known to fail.

 

I used ngk plugs. Haven't done fuel filter yet. I havent figured out what the misfire was yet.

 

I would begin trying to see if you still have the misfire. I'm assuming its a v6 so it may only be running on 5 cylinders but under a load is the only time its really noticeable. I would start by pulling plug wires. If it is in fact misfiring, that could lead you to diagnosis (ie. faulty fuel injector, fouled spark, burnt valve, etc.)

 

I did the driver side 3 and the rpm lowered with each one. I could only check the rear one on the passenger side because the air cleaner tube is in the way of pulling the wires off.

 

If I'm not mistaken I believe the cylinders are numbered like this:

5 6
3 4
1 2
Front

So, if I were you I would at least find a way to pull #3 plug wire just to rule it out since its an easy test. Search this forum for an easy way to get to those plug wires. If I happen to run across a good thread I'll post it on here.

 

Im going to try and check the other 2 cylinders tonight.

 

Here's what I have found so far.
-primary coil resistance cold .67-1.05 ohms
3-1.3 ohm
2-1.5 ohm
1-1.5 ohm

-secondary coil resistance cold 9.3-16.0 ohms
3-13.84 ohms
2-19.48 ohms
1-12.58 ohms

- compression 145-218
5-155. 6-not done
3-145. 4-not done
1-155. 2-156

I don't do cylinder 4 and 6 because my compression tool was giving me problems.

 

Can I replace one coil pack or should I replace all 3 of them?

 

I see you replaced the spark plugs, but you should also replace the wires...this is a classic symptom of bad wires. Also make sure the wires are in their proper clips and not touching any metal surfaces.

 

I didn't replace the wires yet. I plan to buy wires and a fuel filter on this coming Friday. I have one new coil coming because the number 3 cylinder is out of spec.

 

I doubt its a coil, since they are paired. The misfire would be in 2 cylinders intermittently if this was the case.

You should have swapped coils to see if the misfire would follow, checking resistances won't tell you the full story. Plus this is way easier, but I see you ordered a coil. Throwing parts at something just costs you money.

Fuel filter is not the issue, a clogged filter will never cause solely one cylinder to misfire.

You could have a fouled plug, so swap a new one in #3 and see if the misfire continues. Just make sure they are double grounded plugs. Vitaly had a good suggestion about it being an injector. I use this Injector Inspector which works really well. Other causes would be a cracked head, pay attention to if it misses more cold or hot. Your compression looks good though from the ones you measured, but do the rest. I don't know if you have access to a descent scan tool to check misfire count at idle, but this would be helpful. Wires would be a good call as well. That's pretty much all your options to cause this issue.

 

The problem happens warm or cold. You can feel it at low Rpms but you really notice it at more then half throttle. It sputters and and won't gain any rpm.

 

I switch the coil with the number one coil. It runs better but it still spudders under load. Couldn't get the check engine light to come on. I'm going to try and switch the number 3 spark plug when I get home and see what that does.

 

I put the new coil in the 4runner this morning andirons runs like it should. Thanks for the help everyone.