li_runner

Around 2 months ago I had the 120,000 Tuneup done and everything that it entails, timing belt, water pump, plugs, etc etc. I have put nearly 5 thousand miles on the truck since then, it was running perfect up until a check engine light came on last week (and running perfect up since the day I bought it). I had a local shop down the block from work check what was wrong the day the light showed and there first assumption was that the timing belt was incorrectly installed and that was the cause of the problem. I did not agree since I’ve been driving the truck for so long and no issues occurred up until then. (If your timing belt, and cam settings are off I’m sure I would have felt it the truck would run horrible). They cleared out the codes, and I left the shop I wanted to wait to check first with my usual mechanic before any $$$ work was done. In-between last week and today the light came back on.

Today I went to an my mechanic who I trust implicitly (who actually preformed the 120k Tune-up), and found out these were the exact codes

P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
P0305 Cylinder 5 Misfire Detected
P0306 Cylinder 6 Misfire Detected

The codes read out to be P0301 - P0306 meaning all 6 cylinders were misfiring, plus 1 other code I can’t remember that was showing. His first thought was since I have an Amsoil air filter that possibly the MAF was contaminated with oil or malfunctioning sending the wrong voltages causing all the cylinder's to misfire. We cleaned it, put it back in cleared the codes. Took the truck for a drive, this time with a nice little Snap-On diagnostic scanner in hand hooked up to the ODB II port. At random intervals my engine timing runs at +30degrees, +15degrees, and –15degrees. Also at 4100 rpm it seems as if the rev limited engages and the truck as best I can describe starts sputtering, it will not allow any increase in RPM’s and just hiccups going from 4100RPM to 3700RPM back up to 4100RPM then back down untill I let off the accelerator. At the moment my truck will not allow any RPM's over 4100.

At random intervals also this sputtering has occurred. On the highway yesterday after 5 minutes of normal running the engine began running horrible. This sputtering was happening all over the RPM range for about 2-3 minutes then, back to normal again.

Our best guess at the moment is that the engine computer is bad. Anyone have any other guess to what is going on, or think as well it may be the computer?

edit: And let me tell you if I have to replace the computer, new they run $1200+

Thanks in advance.

rimpainter.com

Was anything changed on the rig during those 5K miles after the maintenance - anything at all?

QIKRUNR

Was the other code maybe p0300 random multiple cylinder misfire or p0171 system lean malfunction. I doubt you are having an air flow meter problem if you didn't see the p0171. Also you usually don't get the cylinder misfires that bad with a bad airflow meter. Check the injector grounds on the side of the intake right next to the obd1 connector. I have seen this problem when someone does a tune up and doesn't get the ground tight. if that is not it, sound like you may be in for a new ecm.

li_runner

No nothing has been changed. That is why this started as such a mystery.

I still don't remmember the code, but I don't think it was a lean condition. I don't know if the 120k maintence entails any injector work, but I listed the items I wanted done to the mechanic, and that was not one of them (assuming that an injector cleaning is on the 120k list). It could have been PO300.

Argh, has anyone ever heard of a 3.4L ecm going out like this?

DMG

Check your tps? CHeck running fuel pressure? DMG

Unhappy99

Check these first:
Camshaft position sensor
Crankshaft position sensor
Ignitor

hth.

p.s. Your ECM may still be warranteed (8 years) under Federal Emission Controls Laws, as it is a major emissions component.

denverbikeguy

bad crank position sensor? That controls timing. No pulse (or dirty signal) and it could do what you're describing. Cam pos sensor too though that is used more I believe for timing of the injector pulse (i.e. valve lift duration).

check ALL of the connections to these components as well. Could just be something is corroded or loose. Physically unhook and reconnect the connectors to be sure. I've had stuff that looked secure until I touched it, at which point it came apart.

TStango

start with the simple things first and check your spark plugs and wires. They very well could have put in a bad plug that finally is causing problems My truck started to misfire with something like 130k on it. The check engine light immediately came on and I had to drive home with the engine skipping. The following day, I replaced the plugs with factory spec NGK's and replaced the wires with oem Toyota wires and crossed my fingers as I started it up for the first time. Sure enough the 3.4 was running smooth as glass again and the check engine light went off shortly thereafter. I'm not saying this is your problem but you never know.

li_runner

Thanks all.

These were our ideas as well, it seemed as if the engine was getting the proper fuel delivery, so he didn't think it was the camshaft position sensor. Plus we were not getting any codes relating to the crankshaft positioning sensor malfunctioning. It was almost as if the engine was running perfect and then it went to crap as soon as we hit 4100RPM. The check engine light does not persistantly come on and the sputtering does not consistantly happen at lower RPM, since it was cleared this morning it has not appeared yet, I've driven the rig probably 100miles today since then. Just adding to this

I don't have the time to rip apart the engine and get into checking every possiblity there are too many (my daily driver). If I bring it to Toyota then can probably rule out the ecm real quick by plugging one in and testing it out. That would get the other options down, and more manageable.

I'll let you know how it goes, hopefully this will not cut into the mod budget too much....

li_runner

Well here's my update:

The truck finally gave in yesterday 2 days before my appointment to get the problem checked out; I had it towed to my Toyota dealership. It turns out that, my mechanic even as much as I trust him, did not tighten all the bolts when installing the timing belt to there proper torques. The timing belt had been slipping and the camshafts were 180 degree's off, stopping spark from the cylinders. The crankshaft pulley needed to be replaced, timing belt re-done the tech who seemed pretty honest did his best to salvage the horror he saw when the belt was running loose.

Truck is back and is running great, just really isn’t fun to pay twice for the same work to be done.

SLC Punk

I was just thinking that the belt slipped when I was reading through the posts. Good thing Toyota's are non-interference engines, or you would be screwed!

Glad you got it running now, paying for the timing belt twice is better then buying a new ECU!!

rimpainter.com

Why isn't the tech that did the timing belt originally liable for this?

li_runner

It wasn't Toyota who orginally did the work. Technically the person who did is liable I guess but since he's been such a stand up guy with my family for so many years (so many cars/trucks) I'm not going to push anything on him. I'm sure when I mention what happened he will make it up to me in the long run with no problem. I've had lots of small problems here and there where he would fix things, and refuse to take any payment at all some even taking a couple hours, past cars of course (can you say no more ford's ever for me).