Test editing

 

Test results to come...

 

The forum will not let me post my results.

 

First part:
(PREVIOUS STRING WAS "MISFIRE CODE")

Well, I ran the compression test the other night and the offending cylinder is definitely #8. To prepare for the test, I removed the TB because I wanted to inspect and clean it anyway, and I removed and numbered all plugs with magic marker. Plug #8 was wet with fuel and all others were dry. (May explain why the previous #8 plug was stuck in the hole.)

 

Second part:
The compression gauge I used is a high quality screw-in type, made in the USA that I have owned for about 25 years so I trust the readout.

 

Third part:
Here are the results:
1 = 175
2 = 185
3 = 170
4 = 175
5 = 175
6 = 180
7 = 185
8 = 145 1st test
8 = 200 after 4 to 5 shots of engine oil
8 = 180 after removing the tester and letting excess oil blow out the hole. Produced 2 to 3 consistent 180 readings after that.

 

Fourth part:
How I interpret the results: Yes, there is an obvious problem, but is it a head crack, burnt valve, rings, or were the cylinder walls just washed clean by the unburnt fuel? It seems to me that it would be the rings before it was a head crack.

 

Fifth part:
Could a plenum leak cause #8 to consistently misfire? BTW, I also checked the coil and it checks out OK. I'm stumped, but I don't want to tear down the engine until I've exhausted all other possibilities.

 

Sorry for the multiple posts, but DF will only let me post a little at a time.

 

Just spoke with a master engine mechanic and he said next step was to perform a leakdown test. Pressurize the cylon BDC power stroke and then listen to exh pipe, TB intake, and crankcase Hope it's not the bottom end!