Ok I know there are other threads on this problem but nobody seems to come back with the final solution for their vehicle so I am asking for help with mine.

Mine is a 99 4Runner SR5 3.4 V6 with approx 140000. Got it 6 months ago and service records show the timing belt/water pump service was done at approx 109000. When I got it I did an oil change, seafoam in all 3 places, fuel filter, cleaned the MAF and throttle body, replaced the air filter and got new tires. Was running fine with the exception of a slight squealing when cold but that would go away as it warmed up.

Fast forward to last week. Only drove around 2000 miles since the above things were done. It was fine first thing when it was cold, idle was good no lights. After driving around then stopping for a short period of time then starting it back up and driving, it had a rough idle in park and when stopped. At normal speeds it wasn't rough but power slightly low. On the freeway at speeds over about 80 the check engine light would flash only. Slow down and the CEL stopped. Stop and the idle was rough. Took it home and thought maybe a clogged injector causing a misfire. Seafoam again through the plenum and in the gas tank. Then pulled the EFI fuse and the negative cable on the battery to reset. Drove it around and it ran like a champ. Started right up, no rough idle and no CEL at any speed on freeway. Stopped, turned it off let it set for a couple minutes then started it up. No issues at all. Idle was good. Drove it home on the freeway with no lights no issues so I thought problem solved. Went back out about 2 hrs later to run an errand and the same issues, rough idle, low power and CEL at speeds over 80.

In California you cant get codes read at auto parts stores so I decided to take it to an AAMCO I trusted and get the codes read and a diagnostic. I gave them the same details as above. They called later and said the tech drove around with a scanner on and got codes for a misfire in 2, 3 and 5. Tech recommended replacing two coils and the wires as they are original to the tune of $520. I asked (knowing the answer) if there was a way to troubleshoot without replacing the coils as I thought it was weird they would both go bad at the same time. He said not really they had to start somewhere and that was what the tech recommended. I was disappointed with this answer and said I would pick it up later as I didn't want to throw $520 at the problem hoping that fixes it.

I will get the codes when I pick it up but was hoping for guidance and/or advice from the forum on how I should proceed from here. I feel fairly confident with most do it yourself mechanical stuff on cars and I need to get this running at some point. I'm not made of money though so I can't waste it on hoping to find a solution.

Thanks in advance and I hope I provided enough details.

 

get out the volt meter and check the primary and secondary resistance on the coils in question. you can also move the coils around and see if the missfire moves. You would have have the codes pulled agian.

good luck

 

You have wires with 140,000 miles on them??? (Toyota puts a date on the wires, check it)
How about those plugs?
Easy enough and that's where I would start.

 

Ok so I went to the shop to pick up my 4Runner and here is what I was told.

Initially they checked and there were no codes stored. They are using a snap-on scanner that can give real time data so they drove it around for awhile and were able to get it to read that 2, 3 and 5 cylinders were missing but the car still did not store any codes. All they could get was real time data. They attempted to pull codes from it when I was there with no luck as well. They said it was only when the vehicle was warm and at high speeds that they were able to get the codes and flashing CEL. The CEL would not stay lit either. When I drove it home there was no rough idle, no loss of power and no CEL. I am sure it will happen again when warm. They said the best place to start would be the coils and wires as they were likely the problem. They said it shouldn't be a fuel issue (pump and or injectors) as a fuel flow problem would be there warm or cold.

I am guessing I will tear it apart this week, buy a meter and a code reader and try to troubleshoot it.

Now my questions are:

Does all of this sound right?

What type of meter do I need and what am I looking for on the coils and wires?

Can I just get the cheap scanner that just reads codes?

 

My sister had a similar intermittent problem, and it ended up being a coil.

I had almost identical symptoms and it was a faulty injector causing the problems.

I'd agree with your shop that it's not the fuel pump and most likely your coils, wires, plugs, or injectors. Start swapping around coils, check your plugs and wires. If you can afford some downtime for the truck, send your injectors off to WitchHunter or somewhere like that.

 

Thanks Habaneros. That sounds like a better idea then trying to troubleshoot and buying a meter and code reader. I found a set of three coil packs new and Bosch wires at an online auto parts warehouse for about $113. Can't hurt to replace all and is a lot cheaper than the $520 they were charging.

Thoughts from everyone?

 

Thanks 98SR54RUNNER. I'm gonna start with the wires and coil packs as the injectors doesn't make sense since it doesn't happen all the time. I don't see how an injector would only act up once its warm.

 

I feel like I'm chasing you around on the forums.
Stay away from Bosch for the 4Runner, too many people wishing they did to ignore. Stick to oe, NGK or Nippondenso. Assuming you're doing this yourself save the coils for the next step. If you have to go there I like 98 SR54Runner's idea of swapping them around to see if your misfire moves.

 

Hab is spot on with the advice to avoid Bosch and to stick with OE, NGK or Nippondenso (Denso) for the electrical components.

 

I'd third the opinion that with coils/plugs/wires, stick to OEM. The cost savings will cost you more time and money in the long-run. You're still saving yourself tons of money doing the work yourself. My sister paid around $1000 at the stealership to have her coils replaced.

It may not be an injector, but mine had the same symptoms. Granted, mine was throwing a misfire code every time it acted up, but the problems were intermittent, nonetheless. It was even intermittent after warming up and started getting worse one day when I was about 100 miles into a 120-mile drive, so it was unaffected by being warm/cold.

Anyway, let us know what you figure out.

 

Ok this really sucks. Problem still there. Here's what I did today:

Pulled coils and replaced all three. Pulled wires (from 1999) and replaced with recommended NGK's. Pulled plugs and checked them, they looked fine no issues. Cleaned MAF and throttle body (again). Checked all the hoses I can see, no issues. Pulled the negative battery cable and EFI fuse to clear codes and restarted. Started right up with no idle issues. Drove around with bluetooth OBDII scanner plugged in and Torque app running. No issues, no codes.

Then I parked it and left it sit for about an hour and a half. Returned to the car and started up and immediately had a rough idle and felt like it was missing at low idle. Drove it with Torque app running and the CEL came on and stayed on. Got on the freeway and it started blinking at around 70 mph. Took it straight home and pulled the codes. It showed P0302 (Cylinder 2 misfire) and P0171 (System too lean Bank 1) again.

Any suggestions? Does seem to have narrowed it down to Cylinder 2 but what do I check/do next?

 

Off hand, how's the exposed wiring and connector to that offending coil? How does it run if it gets wiggled?

 

My son-in-law had a similar problem with his 2.4 Tacoma. No CEL, and no stored codes, but consistently ran crappy, at all heat levels. I tried to figure it out but couldn't. He finally took it in, and the shop replace one injector. Problem solved.

I would check the resistance on that injector ( s/b 20 ohms or so? ). Also, you can use an automotive stethoscope to see if that injector sounds the same as the others. If it fails either test, I'd replace it.

 

Runs the same. No change. I really think its an injector.

tantacoma thats my plan. Pulling the injectors today and checking them all with a meter. If any check bad with the meter I'll replace and the ones that check good I'm going to send to Witchhunter Performance. Can't hurt. For $22 an injector they clean, test and replace any part of the injector that can be replaced. We'll see...

 

All of the injectors show about 16 on the meter so I'm guessing they are ok? Guessing they could still be the problem if they are clogged or not spraying right so I will send them all off to Witchhunter.

Any thoughts or suggestions from anyone?

 

You pulled the intakes for the left side injectors? Check the wiring on the knock sensors since you're in there anyway only because it sometimes gets brittle and it's (hopefully) not often you'll pull the intakes and be able to see the harness.

 

So check the wiring with the meter?

 

Just look for brittle/cracking wire, maybe continuity. The connector is up front. Nothing to do with your situation now, just something that you can only reach by pulling the intakes and it's somewhat common for that little bit of wiring harness to go bad over time. Guess all that heat in there does it in. Just because you can.

Crossing my fingers for you that you're correct on the injector(s).

 

Thanks for the heads up. I checked and it all seems fine. Is there anything else I should do while this is tore apart? I'm guessing the obvious stuff like cleaning and replacing those gaskets. I sure don't want to pull that apart again and I'm hoping I can put it back together right. I used this guys blog with pictures to take it apart so I should be ok. If anyone needs it here's the link:

http://mattshowto.blogspot.com/2009/...44127321246682

Was a huge help and made a daunting task much easier. From talking to others and info from Witchhunter's site it sounds like its the injectors. Especially with the error code P0171 System too lean. That is possibly caused by an injector not functioning properly so along with the misfire in #2 I'm hoping getting them done at Witchhunter will solve this problem. If it doesn't I might have to throw in the towel and let the dealership diagnose it. Guess we'll see in a week when I get them back and install them. According to Witchhunter when I get them back they should be restored to like new.

 

Nice blog find, will be watching to see how it goes. You're in territory I haven't had to deal with....yet. The only other stuff I can think of checking because of better accessibility to the back and behind the engine is heater hoses/vacuum lines/ground strap and that sort of thing.