canadianjerkey

Hey all, I posted this in the noobie thread, but I figure it might be better to bring it here, maybe have a few more eyes on it.

I have recently bought a 2000 Tacoma PreRunner, 2.7liter 3rz-fe, got a good deal on it because the engine light was on. The previous owner couldn't figure it out, and had a good deal of work done to the truck to get to that point! The truck runs, drives fine (aside from the auto transmission not being a manual) and the only real indicator that something is wrong, is a bit of a rough idle once it's slowed down to around 700rpm. That, and of course the CEL.

So here is how it sits:

Codes
- po300 (random miss fire)
- po302 (cyl no. 2 miss fire)
- po1305 ( bad connect to igniter cyl no. 2)

Work done to truck (because it had been throwing same 302 300 codes)
- Plugs all replaced with new Denso
- Cyl no. 2 has had coil replaced
- Head pulled, machined, replaced one ex. valve Cyl no. 2
- Head re-installed

What I've done so far trying to track down cause
- Swap coil 2 and 1. (CEL did not follow coil)
- Clean MAF
- Clean Throttle body
- Compression test (190+-3psi all around)
- replace negative battery terminal (because it looked grubby, and I'm running out of ideas)
- New Air filter
- New Fuel filter

** Added **
- Checked EGR, which opened and closed easily, no build up.

So I'm left at a bit of a loss now, my two options that I can think of now, are that there is a random short in the harness somewhere, or that the ECM has a grudge against the truck.

Is there any way to test for that? Would someone have a spare ECM to help me test this theory out? It's somewhat telling to me that the codes continued after all that engine work. And I'm somewhat worried that I'll burn up a valve if I keep driving with this miss fire. Any help would be greatly appreciated.

Cheers

canadianjerkey

Ok, I went ahead and swapped injector no. 2 for no. 1. When I pulled the rail, 1,3,4 came off with the rail, 2 stuck in the head and had a good amount of fuel behind it. Shook out old fuel, got curious to see if I could blow air through it, heard a little bit, then decided I didn't want gasoline in my mouth. The no. 2 injector looks as if though it has been replaced before (theory, this was before the properly diagnosed bad exhaust valve in cyl. no. 2, and driving on the bad valve gummed the injector?)

The p0302 code has gone away and since been replaced by p1130 (AirFuel sensor is now triggered).

My thoughts: maybe shaking ˟˟˟˟ around and blowing into the injector helped unclog something? However unlikely that seems, the engine is running much better now, much smoother idle. I'm looking into replacing that injector, or maybe the whole set. In the mean time I'm running some B12 fuel injector treatment to see if I can clear them up and out.

Any thoughts or warnings before I go inhale more fumes would be appreciated!

canadianjerkey

Ok! It came back! Of course it did, why wouldn't it after all? So it got P0300 (multiple mistfire), and P0302 (misfire cyl no. 2). The code so far has not followed the coil, or the injector. To be safe I'm swapping plugs, although they were all new, it can't hurt and better safe than sorry and what not.

I also cleaned the IACV since last time, and while it was indeed dirty, it hasn't really helped. Ran a tank of Berrymans B12 through as well, in hopes that if it was an injector thing, they would be cleared through whatever leftovers with it.

Still the code persists.

I've also gone and started hitting things with a multimeter. The only two things out of spec when it comes to Ohms/resistance are the A/F mix sensor, and the Cam Sensor Position sensors. The Cam Position Sensor is what worries me the most, giving a reading of 1350 which is a lower resistance while cooling off (still slightly warm) than if it were cold proper (which had a lower range reading of 1650ish iirc). Does anybody have any experience with the CPS possibly triggering misfires without throwing it's own code?? Could that explain the P0300? Maybe even the P0302??

Anyway, the other part where I will post up and hope that someone actually replies is this: I measured with a multimeter the incoming voltage to the injectors. That reading was a somewhat steady .40 +- .5 But once I revved the engine a bit, that reading went up as far as 1.4! I'm going to do some searching to figure out what that voltage is supposed to be, but maybe there is a chance the ECM isn't giving the proper voltage to the injectors at idle? Shooting in the dark a little, if anybody has any insight, or even a random comment please don't hesitate to post.

Thanks

canadianjerkey

Right, more information that I'll send off to "the internet".

I've begun re-checking work to see if I've just fibbed something up. Compression checked again, 180 all through nearly perfect. Plugs all gapped, such and such and such.

New though, I've gone and checked the ECM voltage to injectors! I got a reading of 4.5 volts, spec should be 9-14v. So it's looking pretty solid like a bad ECM.

Does anybody have a good source for a new ECM? 2000 Tacoma Prerunner 4x2 automatic 3rzfe 2.7 liter.

Cheers

roland750

Check with the Toy Connection in Santa Clara. Jeff should be able to help with either an ECM or troubleshooting your problem.

canadianjerkey

Thanks for the reply man, I actually got an ECM off eBay which just came in today. The misfire seems to have gone away (crossing fingers that it stays away), but I'm still getting P1130, which I suppose makes sense given the age of the truck. A new Denso comes in tomorrow and we will see if I've got a properly sorted truck!

Or worst case nothing changes and I'm left digging again! Will post up with results.

canadianjerkey

Ok, well ECM replaced, as well as A/F sensor to take care of the P1130 code. Half a tank of city driving and no codes pending or otherwise! The idle isn't the best though, sometimes it's good, sometimes it's not. I'll be checking for more potential vacuum leaks next, and somewhat suspect an out of spec Camshaft position sensor (checking ohms). Is there any chance that would be causing rough running without tripping a code?

canadianjerkey

To wrap this whole issue up, it was indeed the ECM. Having replaced the ECM with a used off eBay the problems have gone away. Several thousand miles at least one oil change and still going strong.

Anybody know what to do with the broken ECM? The pack rat in me doesn't want to throw it away.