Okay, I just picked this truck up from a friend, it is carbureated, z24s I think.. When it is cold, it will idle just fine, but as soon as it thinks it's starting to warm up it starts running like crud and blowing all kinds of smoke out the exaust. The longer it runs, the worse it gets. If you shut it off and let it cool down, it will idle again, but only for a short time. When it starts to run badly, if you rev it high it will keep running, but the smoke just gets worse and worse, until you pretty much have to keep it floored to keep it going. It's a manual transmission, 4x4 rig. Can't really think of anything else to tell you, I checked the gap on the plugs and noticed that there is some black carbon on them.. I also removed the exaust system from the cat to the tail pipe, to remove that as a possible problem, ran the same(well, louder) without the exaust as it did with it, plus I could still see through the cat anyhow. Any ideas as to what the problem might be would be greatly appreciated! Maybe EGR? Dunno, I'm at a loss.. Thanks!
i had almost the same trouble with my 89 when i would pull away from the lights when it got hot. Although it is fuel injected sounds like the same problem. My problem was the egr valve. The funny thing was it tested fine, it closed and sealed tight, opened with vacum what seemed normally, but after some trial and error we figured out that it was opening at way to early of an rpm, causing a massive vacum leak in the engine. To make a long story short its probably easier and cheaper in time to just change it (and check all your vacum hoses too) than to chase it i don't remember it being very expensive
As it is carburated it should be exempt from all those funny problems that arise from a bad sensor just check the base plate of the carb for cracks/leaks and maybe the butterflies the sometimes are worn enough to leak lots but that stuff would have to be pretty extreme i'd lean towards an egr. oh yeah and check the intake manifold gaskets you never know
While the vehicle was warming up in the morning, (apparently the choke won't automatically decrease the idle) the idle started climbing really high until it was screaming fast, when the previous owner went to kick the gas to make it idle normally it backfired and shot some flames out the exaust. Since then it's been having this problem.
That change the possible diagnosis any or still probably the egr valve?
Okay, I've been googling around about the egr system and I should be able to see if this is my problem by simply unplugging the vacuum tube and plugging the line with something right?
Well, the problem goes a little deeper, when I turn the key to the on position the carburetor almost instantly begins to overflow gas out the top. Grr... Time to go junkyard shopping I guess..
Well, it turns out that there was just a little(bout the size of a grain of sand) piece of rusty metal stuck in the valve needle seat. It was preventing the needle from closing all the way, which was causing the carb to flood continuously. Amazing how small a problem can be and yet still cripple the whole truck.
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