Guys and gal:
I have successfully installed a 240D and manual transmission in my Jeep CJ7. After some grief caused by a bad injector in the #4 hole the idle stabilized to the point that you could "balance a nickel on its edge". The aforementioned grief was due in part to replacing the injector with another that was also malfunctioning. A third injector from the old 5 banger suddenly stabilized the idle and I have since pressure tested and spray-pattern tested all of my spare injectors. (At least all of them that I could find.) I had 6 bad injectors out of some 20 spares. I now have a complete set of known good replacements for both my jeep and my daily driver, a 300td. But I digress.
Although the idle is now stable cold, when the engine warms up it has a pronounced miss. Cracking the lines reveals it is the #4 cylinder again. I adjusted the valves with the engine cold (not sure if that was the right temperature) and ran a compression test. All 4 holes are within 8% of each other cold - hence the decent idle when cold.
My question is - what might be the reason for it to start missing when it warms up. And since it is a diesel the obvious cause is a drop in compression to the point that it cannot get the intake air hot enough to ignite the fuel. Basic physics. There is no evidence of a head gasket leak that I can detect and that leaves rings and valves, and/or possibly an injector that malfunctions when it gets hot. And a change of injectors with one from another cylinder would prove/disprove the injector possibility.
Oh yeah - I measured my chain stretch and when the cam marks line up, the crankshaft indicator is about 5 degrees after tdc. I know this will affect the timing to some degree or another and since the IP is closer to the crank it should be somewhat less than 5 degrees. Your thoughts here are appreciated. I have not compensated for this at the IP, yet. Could this be part of the failure?
I am willing to accept that the rings fail when they warm up. I have never seen that and I certainly don't like the thought of doing a ring job even though I will if it is necessary. I am more inclined to believe it is valves expanding when hot beyond the clearance limits. But when the engine cools down it again idles fine.
Any and all comments and flames and . . . are welcome.
Color me perplexed.
Bogy.
"Hardware eventually fails. Software eventually works" - Michael Hartung
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Posted by: Bogy Wan Kenobi <polespearbogy@yahoo.com>
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