Dewie
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Post by Dewie on Feb 15, 2010 9:52:54 GMT -4
Guys where can I find a good Chev truck forum? I've tried a few but none seem that great... (I will continue my quest for the forum after asking here, but you guys kick ass so much I figured I'd drop a line here in the mean time)
I'm having an issue with my Chev 1/2 ton. It is a '98 with a 4.3L V6.
When the truck is cold it idles fine but, under normal driving, when it hits above 1500 RPM it starts missing - back-firing, bucking, shuddering, etc. If I ask for power (really put my foot into it, or am hauling a heavy load) it comes out of it, until I start I try driving a normal RPM and throttle load.
Initially it only did when it was damp, or until it warmed up. Now it seems to be happening more and more.
I have replaced the plugs (gapped properly) and wires, I cleaned the distributor contacts (they were messy, however it didn't help one little bit), I've run numerous tanks of injector cleaner through it
The damn thing doesn't throw any codes while acting up but will occasionally throw some "Efficiency Bank Lean" code.
I don't know the exact code right off hand but it is fresh in my memory as last-night I hauled a horse/trailer over to PEI and the thing worked great. On the way home it was shuddering/acting up.
In doing a bit of reading I guess I should try cleaning the MAF... will have to research what is safe to clean it with.
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Dewie
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Junk Lord
Yeah thats right - I drive a Lada :P
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Post by Dewie on Feb 15, 2010 10:03:44 GMT -4
I should add the Truck has O2 Sensors which are only a couple years old...
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dan
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Post by dan on Feb 15, 2010 11:09:17 GMT -4
change out your distributor cap. I know you may have cleaned it, but they are bad for letting moisture in and causing trouble like that. buy a GM cap, not a Napa one too, the cost difference is well worth it. I used to have a company Astro van, and it would go through Napa caps every 15-20k, OEM caps lasted over 100k.
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bill richards
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Post by bill richards on Feb 15, 2010 11:20:06 GMT -4
Very true... coworker of mine ran into this dist cap issue as well. Was on a blazer in this instance though. OEM cap, and problems went away.
Bill
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chevystroker
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NEVER CONFUSE HAVING A CAREER WITH HAVING A LIFE ! ! ! ! ! !
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Post by chevystroker on Feb 15, 2010 11:20:34 GMT -4
Check your EGR valve. I think they were known for carboning up on the 4.3's, and it may make the valve stick open. It will act like an ignition problem, as the EGR is diluting the fuel mixture when it shouldn't be open. The pasage can also be completely blocked, not letting EGR gases through when the engine is expecting them.
You can also check the EGR itself. Disconnect vacuum hose, push up on diaphragm, put finger over nipple. Diaphragm should stay up. If not, diaphragm is bad, letting extra air into engine. With engine running, pushing up on diaphragm should make the engine stumble and quit, meaning it is working properly and not blocked completely.
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Dewie
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Post by Dewie on Feb 15, 2010 11:33:27 GMT -4
I plan to check the EGR valve this evening - I think I may try the SeaFoam treatment as well...
If that doesn't work I will definitely try a cap, I may do so anyways - but if it were the cap I'd have expected it to be more constant, or fail more under load when the power demand is higher
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Creepy
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Post by Creepy on Feb 15, 2010 11:35:13 GMT -4
my 98 4.3 Chev is the exact same unless you run premium fuel.
good plugs.wires, etc, etc. runs like a top. regular gas almost leaves you in the side of the road. my dad got rid of the truck because of it. I run premium, its fixed. really weird.
i read about bad cam gears that screw up the timing....buttttt i just put the good gas in it and don't think about it much.
link a forum if you find one, I can't get thru the crappy ones to find the 'pirate' of chevs.
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chevystroker
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Post by chevystroker on Feb 15, 2010 11:50:29 GMT -4
my 98 4.3 Chev is the exact same unless you run premium fuel. good plugs.wires, etc, etc. runs like a top. regular gas almost leaves you in the side of the road. my dad got rid of the truck because of it. I run premium, its fixed. really weird. i read about bad cam gears that screw up the timing....buttttt i just put the good gas in it and don't think about it much. A build up of carbon on the piston and the combustion chamber can raise your compression ratio, possibly enough to need premium. But, your knock sensor should take care of the problem, though it would mean less power as the timing will be slightly retarded. Premium has less tendency to spark knock. You can check the knock sensor by putting a timing light on the engine, and tapping the block with a hammer. The timing should retard when you tap. Getting the engine warm, opening the throttle a bit, and very slowly pouring water into the throttle body is supposed to clean carbon out of the engine. It is an old trick.
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Dewie
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Yeah thats right - I drive a Lada :P
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Post by Dewie on Feb 15, 2010 12:48:12 GMT -4
I've tried running premium fuel - should have added that. Not a lick of difference, and I'm talking run it empty and put in premium (well I ran out, put some from a jug in, then went to the gas station to try just premium)
Really leaning towards the SeaFoam thing - I've heard about people misting water in, not pouring... the non compressible water vapors loosen up the carbon buildups.
Am also curious about what the MAF and intake look like...
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Hawkes
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Post by Hawkes on Feb 15, 2010 18:28:07 GMT -4
You can also check the EGR itself. Disconnect vacuum hose, push up on diaphragm, put finger over nipple. Diaphragm should stay up. If not, diaphragm is bad, letting extra air into engine. With engine running, pushing up on diaphragm should make the engine stumble and quit, meaning it is working properly and not blocked completely. I think they're all electric now, at least my '94 is, my '91 was vacuum.
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Dewie
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Yeah thats right - I drive a Lada :P
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Post by Dewie on Feb 16, 2010 8:00:14 GMT -4
Well I ran the sea-foam through last night... I was skeptical, but figured for the $11 what the hell... The truck just rolled over 300,000 so it's no spring chicken. It is from BC and the previous owners had maintenance records for everything they ever did to it - it's been well taken care of, but it does have fair bit of km's on it. I took the truck for a drive to warm it up (worked like crap) as instructed then got home and poured 1/3 a can into the valve-cover vacuum line turned upside down and watched it fast/idle like crap. I then removed the intake plenum and ended up using the remainder of the can to get the engine to actually stall-out on the stuff... and let it sit for about 15 minutes while I played with the Genesys to clear the codes (Misfire detected was the only code present) I think it worked I started it up afterward (had to crank it for a bit to get it to fire) and watched the smoke show... I had to go get hay but I wanted to burn the crap out before hand so I went for a drive up the road.... no more hesitation, no more back-firing and studering... Once I got the hay trailer on I found it hard to tell if it was still acting up or not (pintle hook + bumpy roads aren't the smoothest combination) however it seemed better. I will take it for a burn tonight when I get home/the trailer off and see what it is like with the engine cold and report back.
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Creepy
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Post by Creepy on Feb 16, 2010 14:11:47 GMT -4
frig, let me know.
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Dewie
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Junk Lord
Yeah thats right - I drive a Lada :P
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Post by Dewie on Feb 17, 2010 15:10:34 GMT -4
Well it was just an odd coincidence about the SeaFoam - still working like crap.
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Creepy
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Post by Creepy on Feb 17, 2010 15:47:34 GMT -4
meh.
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Hawkes
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Post by Hawkes on Feb 17, 2010 17:14:45 GMT -4
Well it was just an odd coincidence about the SeaFoam - still working like crap. The truck has a mind of it's own, it's needs diversion, like the cool smoke screen the seafoam caused. A lot of Chev owners hang chrome stuff, and real neat stickers, like Nascar stuff. Maybe try that. It appears stickers placed appropriately make them go faster.
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