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Old 08-10-2012, 12:35 AM
mister bean mister bean is offline
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Join Date: Apr 2012
Location: Boulder
Posts: 11
Default 100 Series P0307

My LC has had some trouble starting, is idling rough, and is obviously missing, particularly at slower engine speeds.

For the first couple weeks I was getting the above symptoms, but no codes. Dirty throttle body seems to cause similar symptoms so as a first step, I cleaned it out. It was dirty, but there was no improvement afterward.

Finally got a CEL - P0307 (misfire on cylinder 7). This is usually a coil pack so I swapped them between cylinders 5 and 7 and cleared the code. As expected, same symptoms again, but when the code finally came back it was P0307. So the problem didn't move to cylinder 5 as expected.

Next I pulled the spark plug from cylinder 7. It's an irridium plug with lots of miles, but it looked okay for the most part. The only unusual thing was what appeared to be some deposits at the base of the plug. Almost as if some gases were making it past the threads. I don't know if it matters, but it's worth noting.

So I changed the plug on cylinder 7. Cylinder 7 is a pain in the ass to get to, so I didn't have time to do the plugs on the other cylinders. But that's the only cylinder with a misfire so I figured it shouldn't be too big a deal for now. I'll do the others when I have a chance, maybe tomorrow.

I started the engine and it was running terribly. Definitely worse than before. I pulled the plug, checked the gap again (still okay), put it all back together and it started up without problems. It was obviously still missing, but better much better than after the last test, and maybe better than originally. Still, the next day I got another P0307.

Just to make sure, I swapped the coils again. No change. So at this point there have been three different coils on that cylinder and it always has problems. Other cylinders never do. So at this point I feel like I can probably rule out the coil.

Since coil and spark plug seemed to be good I got a multi-meter to test the injector. I tested the injectors on cylinders 5 and 7 so that I would have a control. The manual said that they should be in the 13.4 to 14.2 ohm range. Both injectors measured at 14.1 ohms.

Thinking I may have skipped a step, I went back and tested for spark. To do this I pulled the coil from cylinder 1 (which was the one that was originally on cylinder 7 when all of this started), put in a brand new spark plug, connected it to the harness for cylinder 7 and started the engine. Lots of visible sparks. So that seems good.

When driving today I pulled the codes again just to see if anything had changed. This time in addition to p0307 there was a p1300 - Igniter circuit malfunction. Now the last thing I had done with it was test for spark so I don't know if that is a contributing factor in the code or if it came from something else. I cleared codes again and the only one that has come back since then is good ol' p0307.

Any thoughts on where to go next with this? A real injector test would probably be a good idea, but I don't have Toyota's tech tool to run the diagnostic described in the manual. And I would also have to pull the injector which is a fairly involved process.

Any thoughts on what to try next?
- '99 TLC
- OME T Bars and 866 Springs
- Borla exhaust
- Funky front bumper
- Scratches and dents
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Old 08-14-2012, 12:35 AM
Tuckytres's Avatar
Tuckytres Tuckytres is offline
Event Coordinator
Join Date: Jan 2007
Location: Denver
Posts: 359
Default next possible steps

How many miles are on your truck?
I don't know if the injectors are visible but if you can get a listening device on it you can hear the injector clicking. The clicking often indicates the injector is at least opening and closing.(the spray pattern maybe poor still)
A compression check should also be done to make sure the numbers are in line with at least one other cylinder.

Good luck with the diag...
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