Missfire after valve adjustment

[northernz]

So I finally got time to work on the car. I had not been driving it as it was getting progressively harder and harder to start when cold. Cap ,rotor, wires , and plugs are all in good shape. I decided to adjust the valve clearance and wow am I glad I did! The valves were all tight, only one had any play with the cam lobe straight up. Adjusted intakes to.20 mm and exhaust to .25mm. Put her all back together and she fired up straight away! Unbelievable in my book especially as # 3 and 4 are not firing! I verified there is good spark at the wire, Is it possible I screwed up the adjustment so bad on those two that they won't even fire? I'm pretty sure I didn't, but I can't think of any other possibilities as they fired before the adjustment. Any thoughts?

[Gary in NJ]

In the title you say it's a misfire but in the body of the message you say it's a no-fire. Which is it? In any event, you can track this down a few different ways:

1) Compression test

2) Vacuum test

3) Spark test (place a spark plug in one of the wires of the dead cylinder and rest the electrode on the head)

Did you change the cap & rotor at the same time? Is it possible that one is defective or has grease/dirt on the conductive surface?

Edited September 22, 2012 by Gary in NJ

[silvey19k]

I had this i crossed 2and 3 spark plug wires check that

[LeonV]

Do the spark plug wires clip into the spark plugs tightly, or are they loose? I ask as I had a rough-running after valve adjustment issue and it was because somehow one spark plug wire became very loose. I close up the crimp and was was good to go.

[northernz]

Thanks for the replies, going to buy a compression tester today and start there. Sorry for the error in the title, it is a no fire condition, the engine starts much more easily now, but three and four are dead. I confirmed plug leads are wired correctly, and fit tightly. There is a good spark at the wire, cap and rotor are in good shape.Nothing was changed except for the valve lash so I am stumped as to why these cylinders suddenly stopped firing. Will post compression results hopefully tonite after work.

[olzed]

Check valve lash again.

[northernz]

Well the problem is resolved! Checked compression, it was 160-155-160-160-155-170 so no problem there. I reinstalled plugs in different cylinders to see if that was it, I did drop a couple during the process, thought maybe I broke something! Started car which ran rough for a few seconds then it settled down into a steady idle and ran fine on the test drive. I am stumped as to why those two cylinders didn't fire the first time around. Theories are welcome!

[olzed]

Well the problem is resolved! Checked compression, it was 160-155-160-160-155-170 so no problem there. I reinstalled plugs in different cylinders to see if that was it, I did drop a couple during the process, thought maybe I broke something! Started car which ran rough for a few seconds then it settled down into a steady idle and ran fine on the test drive. I am stumped as to why those two cylinders didn't fire the first time around. Theories are welcome!

If you dropped the plugs before the missing started, then I would say that was the cause.

Perhaps you had a couple of sticking valves.

[grantf]

Well the problem is resolved! Checked compression, it was 160-155-160-160-155-170 so no problem there. I reinstalled plugs in different cylinders to see if that was it, I did drop a couple during the process, thought maybe I broke something! Started car which ran rough for a few seconds then it settled down into a steady idle and ran fine on the test drive. I am stumped as to why those two cylinders didn't fire the first time around. Theories are welcome!

My theory is a cable not plugged in all the way. I know this sounds simple but on more then one occasion this has happened to me.

on a side note: did you have the throttle wide open when you performed the compression test? if not you're numbers may be even better.

[northernz]

My theory is a cable not plugged in all the way. I know this sounds simple but on more then one occasion this has happened to me.

on a side note: did you have the throttle wide open when you performed the compression test? if not you're numbers may be even better.

Spark plugs are the same and it runs fine now so that's out, could have been plug wires but that's the first thing I checked and the fit seemed fine and there was a strong spark.

I did not have the throttle open during compression test, what would that add?

Anyway problem solved! I'm off to watch my sons' Junior B Hockey game, more fun than the NHL any day!

[olzed]

I thought some of you guys might be interested in this, seeing as it belongs to a guy from US. Sorry to hijack your thread mate. Don't know anywhere else to put this.

http://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CCcQFjAB&url=http%3A%2F%2Fwww.ardmoreairport.co.nz%2FResources%2Flibrary%2FArdmore_Flyer_Winter_Edition_July_2012.pdf&ei=6xxgUIOOL4yziQf0-oDYBg&usg=AFQjCNH4fvHRoqnoUduwmiX4OVWuKpKK9w&cad=rja

Edited September 24, 2012 by olzed

[northernz]

I thought some of you guys might be interested in this, seeing as it belongs to a guy from US. Sorry to hijack your thread mate. Don't know anywhere else to put this.

http://www.google.co.nz/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CCcQFjAB&url=http%3A%2F%2Fwww.ardmoreairport.co.nz%2FResources%2Flibrary%2FArdmore_Flyer_Winter_Edition_July_2012.pdf&ei=6xxgUIOOL4yziQf0-oDYBg&usg=AFQjCNH4fvHRoqnoUduwmiX4OVWuKpKK9w&cad=rja

No worries mate! Thread was done anyways. That's pretty cool! I just saw an original Mosquito fuselage in Nanton Alberta a couple of weeks ago at their Bomber command Museum. They have a Lancaster and a Blenheim as well. My Dad's neighbor was a Navigator in the Pathfinders on Lancs, pretty interesting stories to tell!