If the motor mounts are wearing out, you'll get a slight shake like this.
GM 4.3L V6 owners - question re: engine shake
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Mine does, but that's because it has no balance shaft...
Mine is a 17 year old Astro Cargo Van, all metal, 127k on it. What does "smooth" mean?
Seriously, most V-6's shake unless they have a split-journal even-fire crank (78+ GM 3.8) or balance shafts. A V-8 with a 90* block will fire evenly but a V-6 needs a 60* block. Most V-6's are 3/4 of a V-8, including the GM 4.3.
Seriously, most V-6's shake unless they have a split-journal even-fire crank (78+ GM 3.8) or balance shafts. A V-8 with a 90* block will fire evenly but a V-6 needs a 60* block. Most V-6's are 3/4 of a V-8, including the GM 4.3.
JHZR2
Staff member
AF 3500 mi ago
cap & rotor 10k ago
Plugs less than 3000 mi ago (wires too with MSB 8mm ones)
Fuel Filter 12k ago.
I don't think its a miss. It is far too slight to be evident as a miss to me, based upon my experiences with misfiring engines. But, out of curiosity, what would you define as a 'slight' miss? does this mean it only ahppens occasionally, or what? Plus, Ive never had a CEL since the vehicle was new, all plugs came out looking nice and clean (my thought was that maybe the Pt plugs werent good for 100k, but I was mistaken, they looked as good as the brand new delco ones).
I think that it is the nature of a 90 degree v6. And, the fact that since Ive never driven another v6 vehicle, I couldnt compare.
Out of curiosity though,m if an EGR valve wasnt closing corectly, could that cause a constant rpm but rough idle?
JMH
JHZR2
Staff member
do late model (1998) 4.3L V6s that came in the S/T10 series truck have balance shafts?
I thought that balancers were mainly in I4/I5 engines?
JMH
I thought that balancers were mainly in I4/I5 engines?
JMH
Yes, they do.
Even though I have a non-balance shaft 4.3, I had a slight vibration/shake at idle that I could tell was not normal.
Went away after running Regane...
JHZR2
Staff member
Hi,
I'm curious, does the 4.3L v6 inherently have a very slight shake at idle?
My 98 s10 zr2 runs perfectly, and is really smooth and powerful when driving. However, at idle, particularly hot idle, it is apparent that there is some engine shake that is felt through the cabin.
I bought the truck new, but cant remember noticing it when it was brand new. Worse, this was the first v-engine I or my parents ever have owned, so I cant really compare.
Its not bad, doesnt feel like a miss, no associated noise, emissions pass just fine, etc. I just notice it, and can see that the engine shakes a bit when running.
Are the engine mounts glycol filled or something smilar, that they may be an issue?
Or is it just the nature of the beast? As I understand it, a 90 degree v6 is far from optimal.
Thanks,
JMH
I'm curious, does the 4.3L v6 inherently have a very slight shake at idle?
My 98 s10 zr2 runs perfectly, and is really smooth and powerful when driving. However, at idle, particularly hot idle, it is apparent that there is some engine shake that is felt through the cabin.
I bought the truck new, but cant remember noticing it when it was brand new. Worse, this was the first v-engine I or my parents ever have owned, so I cant really compare.
Its not bad, doesnt feel like a miss, no associated noise, emissions pass just fine, etc. I just notice it, and can see that the engine shakes a bit when running.
Are the engine mounts glycol filled or something smilar, that they may be an issue?
Or is it just the nature of the beast? As I understand it, a 90 degree v6 is far from optimal.
Thanks,
JMH
Redline S-1 helped the idle on my 99
it might be the mounts.
i know that on my accord, one of the mounts has a vacuum line running from it.
i believe it is a hydraulic mount where the ecu controls how much to open the valve when idling or driving.
when it goes bad (doesn't hold vacuum), the engine shake will be more pronounced in the cabin.
like others have noted, my car didn't shake when new, but it does it a lot more now when sitting at traffic lights.
i know that on my accord, one of the mounts has a vacuum line running from it.
i believe it is a hydraulic mount where the ecu controls how much to open the valve when idling or driving.
when it goes bad (doesn't hold vacuum), the engine shake will be more pronounced in the cabin.
like others have noted, my car didn't shake when new, but it does it a lot more now when sitting at traffic lights.
His mounts aren't as fancy as yours, seotaji, but your point is still very valid, which is why I suggested it too. The upper mounts should be inspected for any gaps in the rubber that aren't supposed to be there. Replacing them is not a difficult job on most vehicles
I had the 4.3 in a 1994 fullsize Chevy van and it had the shaky idle like you are describing. I wouldn't really worry it. If you have a broken motor mount you'll know it. You will usually break the fan shroud with the fan and the motor will jump around all over the place. BTW the 3.9 V-6 in my 2001 Dodge 1500 pickup truck shakes slightly at idle also and has since new. When you are driving it isn't noticeable, though.
V6s, regardless of split journal cranks, balance shafts, or bank degree spacings, inevitably have untamable harmonics at certain engine speeds. It's just inherent, though different designs are more or less susceptible and at different speeds. The larger the displacement, the worse, too. Engine mounts - especially hydraulic, and really especially electrically valved hydraulic - can all but mask it to passengers, but those untamed harmonics are always present. If you want a smooth six, buy a fully counterbalanced, seven main, inline six. (Can you say, "BMW"?)
Ray H: right on for a smooth engine. Like a Porsche H6 or H12 or my old Jeep 4L 7 mains in-line 6. Even my H4 is smother than a 90 degree V6 and it doesn't need balance shafts or split conrod bearings, to correct a mistake. ed
An interesting post, as it reveals the essential truth about the 4.3L V-6. It is an extremely durable engine, but it is about as unsmooth as it is durable.quote:
Originally posted by JohnnyO:
Mine is a 17 year old Astro Cargo Van, all metal, 127k on it. What does "smooth" mean?
Seriously, most V-6's shake unless they have a split-journal even-fire crank (78+ GM 3.8) or balance shafts. A V-8 with a 90* block will fire evenly but a V-6 needs a 60* block. Most V-6's are 3/4 of a V-8, including the GM 4.3.
V-bank angle is an interesting question. GM goes about 50-50 on this. The venerable 3.8 and the 4.3 are 90 deg designs. The 3.8 with the split crank pin arrangement is very smooth. But GM's other main series of V-6s, the 2.8/3.1/3.4, etc. family are all 60 deg designs, but oddly enough, they aren't very smooth. They seem to suffer from vibration and harshness resulting from their pushrod valvetrains. The Japanese V-6s seem to be more smooth than the US designs because, IMO, they combine 60 degree V-angles with SOHC or DOHC valve gear. Then there are the oddballs, like VW's VR-6 which arguably isn't a V-6 at all. It's more like a snaggletoothed I-6, with offset cyls in one block. I forget the angle, but it's something absurd like 12 or 18 degrees. And someone, I cant recall, is making a 48 degree V-6. Anyway, I digress. Your 4.3 is a good, robust engine, but it's in its nature to shake some. Hey, it's a "truck engine."
I used to have a 93 S-10 4x4 that I bought new that had the 4.3L and it shook at idle. My 98 Silverado 4x4 with the 5.7L does the same thing and has done so since new. I think its just a characteristic of a lot of GM's V type engines.
My 4.3 was a very noisy engine though, not like my 5.7 which is pretty quiet at idle.
Wayne
My 4.3 was a very noisy engine though, not like my 5.7 which is pretty quiet at idle.
Wayne
I have a 93 chevy truck that had 93K miles on it when i bought it and it idled rough. I figured that a tune up would fix it but it didnt. I obsessed over this idle for a while. I believe i have changed every sensor on it, motor mounts (did help a little), complete tune ups, and vacuum lines. Nothing ever fixed it. It idled just rough enough where the side mirrors would vibrate at a red light. Truck now has 235K miles on it and still runs great and idles poor. i really hate the way it idles. My 01 4.3 vortec always idled much better but not completely smooth and i bought it brand new.
We run a bunch of them in my business and they all vibrate at idle like a 617 with bad engine mounts, I don't think GM ever really balanced this motor. They just keep adding insulation but it still vibrates.
Hopefully the new 4.3 idles better, but I have not driven a 14 yet.
Hopefully the new 4.3 idles better, but I have not driven a 14 yet.
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i have a 91 4.3L 224,000 miles and it shakes but... 1992 was the year they added more counter balances.
Originally Posted By: Ray H
V6s, regardless of split journal cranks, balance shafts, or bank degree spacings, inevitably have untamable harmonics at certain engine speeds. It's just inherent, though different designs are more or less susceptible and at different speeds. The larger the displacement, the worse, too. Engine mounts - especially hydraulic, and really especially electrically valved hydraulic - can all but mask it to passengers, but those untamed harmonics are always present. If you want a smooth six, buy a fully counterbalanced, seven main, inline six. (Can you say, "BMW"?)
And yet...one of the smoothest engines ever built is a 90-degree V6: the justly-legendary Buick 3800. You can balance a quarter on an idling Series II engine! I had a 4.3 in a Caprice...it was a 1986, which was the first with a balance shaft. It DID idle smoothly.
OP: how many miles? 1998 is the MPI Vortec...I wonder if you may simply have a dirty fuel injector.
V6s, regardless of split journal cranks, balance shafts, or bank degree spacings, inevitably have untamable harmonics at certain engine speeds. It's just inherent, though different designs are more or less susceptible and at different speeds. The larger the displacement, the worse, too. Engine mounts - especially hydraulic, and really especially electrically valved hydraulic - can all but mask it to passengers, but those untamed harmonics are always present. If you want a smooth six, buy a fully counterbalanced, seven main, inline six. (Can you say, "BMW"?)
And yet...one of the smoothest engines ever built is a 90-degree V6: the justly-legendary Buick 3800. You can balance a quarter on an idling Series II engine! I had a 4.3 in a Caprice...it was a 1986, which was the first with a balance shaft. It DID idle smoothly.
OP: how many miles? 1998 is the MPI Vortec...I wonder if you may simply have a dirty fuel injector.
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