We're working on a 2004 Nissan Frontier here at work, and it's got all of us puzzled. Sometime when it's cold, when you try to start it it has no compression. After you crank it over for ten to fifteen seconds, compression builds up and it starts fine. When it's warm it has even compression across all cyls and runs great. It isn't throwing any codes. My head hurts.
Lifter problem? Is there any time of vairable-timing on there that could be out of whack??
I was kinda thinking the same thing. There's no variable valve timing, so that's not the problem. The things that have me questioning the lifter theory is:
A. If the lifters were causing the valves to not close all the way, wouldn't they hit the pistons? This is an interference engine. I guess it might be possible to open up just enough to loose compression and not hit.
B. Isn't that usually backwards from the way lifters work? They compress more before the oil pressure builds up, that's why some engines tick for the first few seconds upon start up.
C. What are the chances of this happening to at least one lifter per cyl. when it happens, and to none when it doesn't?
Check for stuck/worn rings. Pour a bit of oil in each cylinder when the engine is cold and see if it pops off right away.
not super familiar with that engine, but what about a t-belt tensioner on it's way out?
sounds like a worn out engine. I was always told that an engine that slowly builds compression needed an overhaul
93gsxturbo wrote: Check for stuck/worn rings. Pour a bit of oil in each cylinder when the engine is cold and see if it pops off right away.
+1, if ALL the cylinders have low compression. If that's the case, try the oil in the cylinder test. If this jacks the compression way up, a possible fix is to use GM's Top Engine Cleaner. Basically, you dump it in the plug holes then let it sit several hours then start the engine and kill mosquitoes for miles around.
OTOH, if only 1 or 2 are low I'd look for sticking valves. That can come from fuel residue, there's some kinda sticky yellow crap that will build up on the intake valve stems. This stuff will harden overnight, meaning that any cylinder with the valves open will have those same valves stick when the engine starts. Generally, if the ambient temp is above 50 degrees or so, the condition lasts only a few seconds. If it's below that temperature, the valves will hang open until the engine warms sufficiently that the stuff melts.
It got even weirder. We have the vehicle sold, and it's already been paid for. They want it yesterday, and my boss doesn't wand to spend a bunch of time diagnosing it, so we're putting an engine in it right now. I really doubt it's worn out, since it only has 21k miles. So the mechanic that is working on it started unbolting the torque converter, and when he started cranking the engine over by hand to get to the converter bolts, it had compression. Took out one bolt and started cranking it again by hand to get to the next bolt and it suddenly lost compression in all cylinders, spinning freely. He drove it into his bay and it ran fine. It's like it looses and gains compression on all four cylinders at the flip of a switch. Weird.
compression verified by compression test, or simply by resistance to cranking?
Both kinda. The mechanic working on it did a compression test on it about 30 minutes before the boss decided to just put another engine in it. 185 all the way across the board. When he was turning it over and it suddenly lost compression, that was verified by resistance, like, it didn't have ANY anymore. Spun freely like it didn't have any spark plugs in it.
now that is just bizarre.. I hope you tear the engine down later to see what is wrong with it
Yeah, no kidding. I hope I get to tear it down.
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