Cylinder 1&3 Misfire - Coil packs replaced still CEL

[bajaphile]

Hi All,
This is on my wifes 2005 4Runner, 2UZ-FE. 150k mi. Was hoping you could help me out on this.

CEL came on a month ago, cylinder 5 misfire. Pulled spark plug, looked fine. Assumed a failing coil pack. Got the Denso from Amazon and replaced it. Cleared code and now it came back with cylinder 3 and 5 misfire.

The truck doesn't drive any different, but has a slight miss. Coolant level is good and there is no coolant in oil. I just replaced the oil 2 weeks ago, and it looked great.

Next is a leakdown and/or compression test I guess. Bought the truck this year from a friend who was the original owner and babied the thing. I can't imagine a blown head gasket...? Anything else I should check that would cause misfire on two adjacent cylinders?

Thanks

UPDATE 9-27-17, STILL HAVING PROBLEMS. List of things checked
- Swapped coils and replaced spark plugs
- Checked ECU via FSM
- Verified timing belt did not skip teeth
- Cleaned MAF and TB

UPDATE 10-11-17
- Compression on 3&5 @ 90psi -- Possible head gasket failure.

Update 2-10-18
Confirmed blown head gasket between 3&5.

Update 2-23-18
Head gasket replaced, with valve job. 1 exhaust valve on 5 was burnt. small breach between 3&5 in gasket. Truck running like new again.

 

[Dwight S]

Try swapping the two coils to the other side, clear the codes and go for a test drive to see if the codes come back or if the codes follow the coils. That will give you a better idea of what's going on.

It's not unusual to have multiple coils fail together or one after another.

 

[bajaphile]

OK Just swapped coils over.... Something I was thinking about doing but thought it was weird that the new one would also be bad.

Just saw the PCV hose was disconnected... Not sure that would cause a misfire code, but we'll see.

 

[Muddy Bean]

Also several times when I replaced my coil pack, if it did not fix the problem, replacing the spark plug always did. If you got it out just replace the spark plug with a new and NGK iridium plug and that will probably solve your issue.

 

[bajaphile]

Still getting my misfire codes, but no actual misfire after replacing spark plugs and swapping coils. Still showing misfire on 3&5.

I think the crank shaft position sensor is what actually monitors misfires? I am wondering if whatever sensor monitors misfires, it is failing. My 2UZ-FE FSM seems to be missing diagnostic information, I may need to find another version. If anyone has any ideas or checks, please let me know. Thank you.

 

[2001LC]

Have you confirmed spark on 3 & 5?

Remember to disconnect fuel pump power first or the injector at cylinder/port of test.

Next Id check injectors. First test is use stethoscope to hear ticking of each injector with engine running. Should sound same as others, loud.
Then:

 

[Muddy Bean]

He must have spark if he's not actually misfiring. Something else is up.

 

[bajaphile]

I haven't actually tested for spark, but I have a hunch I am getting it. I've disconnected the coil wire on each cylinder and it definitely runs a lot worse. The miss is very light if anything. I do think that the idle is a little rough compared to my dad's 2UZ-FE on his Tundra.

Finally found the FSM which outlines a P0300 (Random misfire) along with cylinder specific codes.

• Open short in engine wire harness - Assume this would be a hard misfire
• Connector Connection
• Vacuum hose connections - Verified my PCV hose was off, so I re-attached assuming that was the problem. Cleared codes and within 2 trips, lights are back on. I used my un-lit propane torch around the entire engine and didn't find any vacuum leaks. I have a smoke machine I might use next to verify vac leaks.
• Fuel Injector - Might be an issue
• Fuel Pressure - Need to test
• MAF - Don't believe this is my problem
• ECT
• Valve Timing
• Valve Clearance
• Ventilation valve and hose
• ECM

FSM states the crank position sensor monitors fluctuations in crank speed, and the camshaft position sensor then identifies the actual cylinder at that moment that misfires.

Since I think the idle is a little rough, I am assuming it may be a small vacuum leak somewhere. The truck hauls butt off the line and on the freeway. Are there any problem vacuum hoses I should be looking for?

 

[Julian Stead]

Remove spark plugs and check the burn on them, see if any are different, then carry out a compression test if you have the gauges. If you can read the ECM then look at the fuel trims, this will help find out if any cylinders are running lean.

 

[bajaphile]

Remove spark plugs and check the burn on them, see if any are different, then carry out a compression test if you have the gauges. If you can read the ECM then look at the fuel trims, this will help find out if any cylinders are running lean.

Already replaced all the plugs with the Denso Iridiums PN which was in the FSM. They all looked great/normal. No sign of running rich, lean or signs of coolant.

PCV valve appears to be new. I'm checking vacuum lines, and there are two which go behind the engine and between the firewall that look to be hard to swap out. Is there a trick to reaching these?

 

[Spike555]

Vacuum leak will not cause misfires.
Dirty fuel injectors will.

My money is on dirty fuel injectors.
At idle the spray pattern is not fine enough to combust properly causing the rough idle, at higher RPM and higher fuel PSI the spray pattern is not an issue.
Thats why it idles not as smooth but runs liked a raped ape at hard throttle.

 

[Julian Stead]

Your fuel trims should point you in the direction of bad injectors, it will try and compensate for this. You will normally get a code associated with a lean mixture if your injectors are blocked. But maybe they haven't reached that threshold.

 

[Muddy Bean]

BTW, side note, if you're 100 is that fast when you're on the throttle, something is def wrong. I've never had an inkling to describe our hundys as fast...they are actually quite modestly slow.

 

[bajaphile]

BTW, side note, if you're 100 is that fast when you're on the throttle, something is def wrong. I've never had an inkling to describe our hundys as fast...they are actually quite modestly slow.

haha, yeah this is on my wife's 2005 4Runner. I just thought I'd post here since I trust MUD more than other's.

 

[Muddy Bean]

Oh didn't catch that in the first post. Forehead smack.

 

[bajaphile]

Well I haven't done much in the way of researching fuel trim. But here's after a drive and at idle.

 

[Julian Stead]

Running too rich – High negative fuel trim corrections can be caused by MAF sensor problems, high fuel pressure, leaking fuel pressure regulator diaphragm, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks/pinholes before the O2 sensor, coolant temp sensor problems, and base engine issues such as low compression and incorrect camshaft timing.

 

[Muddy Bean]

Have you used MAF cleaner and cleaned it? Please trucks respond well to cleaning the MAF

 

[bajaphile]

Ok, good suggestion. I haven't cleaned the MAF. I am also going to remove the throttle body and give it a cleaning as well.

A little update that I might as well mention... I disconnected the battery for about an hour yesterday morning. We drove around all day yesterday, and wife has gone to work, lunch and run a couple errands, and no codes/MIL. Usually the MIL would light up within a minute after the second "trip".

Uncertain if maybe now it has to go through all its readiness checks or what. Not convinced that solved the problem and it was just a faulty code. Next up may be a leakdown test on both #3 and #5. Timing belt was replaced about 8 months (10k mi) ago. Reading how hydraulic tensioner tends to go. Not sure if the mechanic fixed that or not (was done by PO).

 

[Muddy Bean]

Ok report back after MAF and throttle body cleaning. If your issue is solved it's just another one for the books