2004 Tacoma misfire on cylinder #1, replaced cracked exhaust valves ,misfire continues ...

So the compression test the mechanic ran came back much lower than I expected (had hoped ) #1 @105 (was 57) and #3 @150 (was 121) (He said that the cylinders looked fine when he took the head off but that maybe there might have been a leak between cylinders 1 and 3 as the gasket looked a bit thin there ? )
He says the engine is now running rough at idle and vibrating better on the road. It is now producing random error codes on cylinders 1, 3 and 5 as well as O2 sensor codes. Mechanic rechecked the timing markers and all connections. He thought maybe weak lifters ? I'm wondering if it has something to do with fuel rod and injectors or IAC ? I suggested a engine scope to graph out the injectors... at this point kinda just shooting in the dark....

 

He checked the timing belt marks but is the exhaust cam in time?
Exhaust cam is driven off the intake cam by a gear and they have to be timed correctly when the cams are installed. IIRC one of the cam gears is spring loaded and must be held in place with a bolt during assembly, I'll look it up when I get home.

 

That whole bank is off.
Something isn’t right. I agree.

 

Thanks, that would be much appreciated, I agree with both you and TnShooter, that head definitely seems suddenly out of sync, would this account for the engine vibration?
I forwarded this on to the mechanic, hopefully I will hear something back before Monday !

 

Yea I mean if you have 3 cylinders that aren't breathing properly and the other 3 are it will throw everything off.
Everything having to do with the cylinder heads and timing belt in the files below.

 

Hey Guys, sorry for not following up on this sooner, the details were a bit vague ..... turns out the mechanic hadn't connected one of the wires correctly, I never did get the whole story, I think he said it was to a coil or fuel injector...? he was a bit vague about it. Next it turns out his compression tester was sticking and giving incorrect and low readings. turns out all 6 cylinders came in at 180 and above. Bottom line he got it running and and there was a significant improvement in power. Truck has been running nicely ..... until this week. Looks like I'll need to start a new thread...;(

 

Now what?

 

I started a new thread but here are the details so maybe this is a good place to continue as it has also all the recent background...

I had a P0301 about 6 months ago due to a cracked exhaust valve. I had the exhaust valves replaced and machined. This restored compression and eliminated the misfire.

Last Tuesday I started the truck and I immediately could tell it was not firing on all cylinders. Prior to this it seemed to be running well. I threw P0301, P0302, and P0300. Lots of vibration and above 80km/h its was pretty rough but smoothed out a bit with acceleration. I was out of town for the weekend and was trying to get home to work so drove it the 100km.
In the past year I have:
-replaced the plugs (Toyota)
-replaced High tension leads ( Toyota)
-Air filters, oil, both engine and differentials
-timing belt, water pump, kit, belts, etc.

in my attempt to diagnose:
- I swapped the #1 and #3 cylinder coils which had no effect on the location of the misfire.
-I checked with a light circuit meter the plug to the cylinder #1 fuel injector and it flashed so appeared to be functioning properly. (An ohms meter test showed the old fuel injectors all at 14.5, the new one I tested measured 15.5.)
At this point I assumed it to be fuel injectors ( relatively new OME plugs and high tension wires, and ruled out the coil) so purchased a set from Motor West performance. I had them shipped to Ogdensburg NY borrowed a friends car and drove over the border to get them so I could install them this weekend.
Finished Installing them today and the misfires continued with no change.
-preformed a reset of the ECU, engine still feels like its running on 4 cylinders. At present only the P0302 is coming up on my reader but the others may just be around the corner as it feels the same.
In addition before this all came to a head, I did get codes P0446 Evap system vent control circuit, P0442 EVAP system small leak detected, and H02S12 circuit malfunction. I assumed these only affected my passing an emission control test and not performance so had basically ignored them....
Just wondering if anyone has any ideas of in what direction I should head next...?

 

Bringing this thread back to life as I was going through a similar situation. I was lucky to avoid the removal of my heads to view the valves though by using this guys borescope trick:

https://youtu.be/KLyy8ZCNYv4?si=kLBDgXSzdDzqk8XG

I just pulled the spark plugs from my problem cylinders (#5 and #4) put in the borescope and got these pictures. A lot quicker and easier than pulling heads! Now I have to figure out what to do with my cracked exhaust valves…