92 GMC Vandura 4.3 Liter V6 Engine Rpm not consente

My dad has a 1992 GMC Vandura 1/2 ton with a 4.3 liter work van. Recently he just replaced the engine. Before he replaced the engine, when the engine was
cold or when it was sitting for awhile, when you start it, the rpms would pulsate, from like 500 -1000 rpms, up and down for like 5 mins unless you stomped on it or drove it. Since replacing the engine, it still does this. We took the throttle body apart, cleaned it, put a new TPS on it, Idle Air Control Valve on it, and it still has the same problem. The van also has a new oxygen sensor on it, but it has no catalytic converter. I have some thoughts of what the problem might be, but would like any input on what you guys think it might be. Thanks
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<<My dad has a 1992 GMC Vandura 1/2 ton with a 4.3 liter work van. Recently he just replaced the engine. Before he replaced the engine, when the engine was cold or when it was sitting for awhile, when you start it, the rpms would pulsate, from like 500 -1000 rpms, up and down for like 5 mins unless you stomped on it or drove it. Since replacing the engine, it still does this. We took the throttle body apart, cleaned it, put a new TPS on it, Idle Air Control Valve on it, and it still has the same problem. The van also has a new oxygen sensor on it, but it has no catalytic converter. I have some thoughts of what the problem might be, but would like any input on what you guys think it might be. Thanks>>
Your problem appears to be heat related. You say that your van has no catalytic converter. Did it come from the factory like this? Does the engine have a smog pump? If the engine was produced with a catalytic converter and it now doesn't have one, this could be the problem.
Typically, the next phase would be to start replacing everything, such as the distributor, cap, rotor, wires, plugs, MAP sensor, fuel pump, oxygen sensor, fuel filter, throttle position sensor and EGR. However, if the computer thinks that there is a catalytic converter present when there is none, this may cause your open loop performance to be erratic.
I made the mistake of posting my bad experiences of the 4.3L Vortec V-6 on this newsgroup and found that this engine is a sacred cow. In spite of the large number of problems that I had with 3 of these motors, many others on this group testified that this engine is the greatest motor that GM has ever produced. I believe that the 4.3L V-6 made its debut in 1988, but it wasn't until 1993 that the 4.3L V6 engine received an internal balance shaft to reduce vibration, as well as some other improvements.
In any event, my post appearing under a "4.3 Liter" subject heading will draw a large crowd and assure that you receive the help that you need.
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all the sensors have been replaced except for the map sensor.

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Hardly possible... I've removed dozens of cats from OBD-1 vehicles without issue.

This is the way a moron works on a vehicle... don't just throw parts at it trying to fix it. FIGURE OUT what it wrong and then fix THAT.

Like we've said before, the main reason your insanely long post got shot down is because you whine and cry and make everything into a national issue with your repetitive 400 page long posts. I don't think the 4.3L is anywhere near the best engine GM created, but I don't think it's a bad engine either. (Then again, I like drum brakes so what do I know right Scott??)
BTW- it was 1996 that the 4.3 recieved balance shafts, not '93
-Tony
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> > I believe that the 4.3L V-6 made its debut in 1988, but it wasn't

My experience with the 4.3L V-6 was limited to the 1990-1993 models. GM knew that it had vibration problems (as well as other problems) with this motor and made changes. None of these changes benefited me and I feel cheated because GM used me as a guinea pig for its early, unreliable, poorly designed 4.3L V-6.
Are you sure about the 4.3 Liter V-6 balance shaft being introduced in 1996 and NOT in 1993, as I have suggested? I have been unable to find anything to contradict my original statement, other than your rebuttal:
1993: the 4.3l v6 engine received an internal balance shaft to reduce vibration.
http://www.mys10.com/downloads/s10_history.asp
1993: The four-speed 4L60-E electronic transmission was introduced, and a balance shaft was added to the 4.3L V-6.
http://www.sporttruck.com/techarticles/1420/index4.html
Series 4.3L - V6 GM
4.3L, V6, 1993-1995 NEW Long Block with balance shaft, & 12 bolt intake: $3295.00 + S&H, Warranty 3 Years.
http://www.abcjb.com/new_engine.htm
Chevy S10 Blazer 1993 Engine Size 4.3 L, 262 CID Engine Type V6 Notes CPI, balance shaft, roller cam, two temp/detonation senders in left head.
http://www.hiperformer.com/chevy-s10_blazer-1993-engines---HPGMC-262LRLB-3.html
1993 GMC Sonoma: The super-performance Syclone and its sporty GT cousin were gone. Both 4.3-liter engines got an internal balance shaft, designed to reduce engine vibrations.
http://www2.shopping.com/xPO-Gmc_1993_GMC_Sonoma
1993 Blazer: The 4.3L V6 engine received an internal balance shaft to reduce vibration
http://www.s10blazers.com/sserieshistory.htm
Shit, oh dear. Here I go again with another "repetitive" and "insanely long post."
Since you are so informed on every imaginable automotive subject, you should have been able to solve this erratic RPM problem.
By the way, the original poster asked the same question again and has received no solution to his problem. In spite of what you said in regard to the catalytic converter not being the problem, I am going to make another catalytic converter post under this new subject heading:
Subject: 4.3 Liter V6
You can post your rebuttal there and then proceed to tell me what a horse's ass I am for not being aware of the facts pertaining to this matter.
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Just a question. I used to have a 1994 S-10 with a 4.3 Liter Vortec which was Throttle Body Fuel Injected, and if anyone wants to argue this, the valve covers on it said Vortec. It came this way from the factory, but anyway, it had a internal balance shaft. I beleive it was when GM went to the "Vortec" line. I was told the Vortec's had them. The Vortec didnt come out till 94 for the S-10's, I am not to sure about the fullsize. Just thought I would throw that in there, by the way, you guys are to brutal with each other. Let people think what they want, if I think I know it all, then thats my problem? Isnt it? I think the same should hold true for others.

> > I believe that the 4.3L V-6 made its debut in 1988, but it wasn't

My experience with the 4.3L V-6 was limited to the 1990-1993 models. GM knew that it had vibration problems (as well as other problems) with this motor and made changes. None of these changes benefited me and I feel cheated because GM used me as a guinea pig for its early, unreliable, poorly designed 4.3L V-6.
Are you sure about the 4.3 Liter V-6 balance shaft being introduced in 1996 and NOT in 1993, as I have suggested? I have been unable to find anything to contradict my original statement, other than your rebuttal:
1993: the 4.3l v6 engine received an internal balance shaft to reduce vibration.
http://www.mys10.com/downloads/s10_history.asp
1993: The four-speed 4L60-E electronic transmission was introduced, and a balance shaft was added to the 4.3L V-6.
http://www.sporttruck.com/techarticles/1420/index4.html
Series 4.3L - V6 GM
4.3L, V6, 1993-1995 NEW Long Block with balance shaft, & 12 bolt intake: $3295.00 + S&H, Warranty 3 Years.
http://www.abcjb.com/new_engine.htm
Chevy S10 Blazer 1993 Engine Size 4.3 L, 262 CID Engine Type V6 Notes CPI, balance shaft, roller cam, two temp/detonation senders in left head.
http://www.hiperformer.com/chevy-s10_blazer-1993-engines---HPGMC-262LRLB-3.html
1993 GMC Sonoma: The super-performance Syclone and its sporty GT cousin were gone. Both 4.3-liter engines got an internal balance shaft, designed to reduce engine vibrations.
http://www2.shopping.com/xPO-Gmc_1993_GMC_Sonoma
1993 Blazer: The 4.3L V6 engine received an internal balance shaft to reduce vibration
http://www.s10blazers.com/sserieshistory.htm
Shit, oh dear. Here I go again with another "repetitive" and "insanely long post."
Since you are so informed on every imaginable automotive subject, you should have been able to solve this erratic RPM problem.
By the way, the original poster asked the same question again and has received no solution to his problem. In spite of what you said in regard to the catalytic converter not being the problem, I am going to make another catalytic converter post under this new subject heading:
Subject: 4.3 Liter V6
You can post your rebuttal there and then proceed to tell me what a horse's ass I am for not being aware of the facts pertaining to this matter.
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I should have stated it different... The VORTEC engines had balance shafts. They didn't start using Vortec engines in fullsizes untill '96. The S-10's got them in '94.
Pretty sure the 1993's didn't have them, since I've had two '93 4.3L engines and neither had the balance shafts.
Like I stated before... your problems with the 4.3 are very obscure. I've had 3 of these fullsize W/T's, each with over 200,000 miles on them. My current '93 W/T has 272,000 on the clock (original engine replaced at 240,000). 3 other people that I know have had about the same luck with their 4.3's
-Tony

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According to this source:
1992 blazer -- the high performance vortec 4.3l v6 engine debuts.
1994 pickup -- the high performance vortec 4.3l v6 engine becomes available on the pickup.
http://www.mys10.com/downloads/s10_history.asp
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I think that sorce is wrong. From what i understand, the vortec wasnt introduced till 94. I was told that my TBI 4.3L: V6 had a balance shaft. this is on my old 94 S-10. I now have a 97 in place of that one since I rolled it. I'll have to get some pics for you guys if I can ever figure out how to post pics with out putting them on this server. :-( But yes Tony, I agree my problems are obcure. I love my 4.3l, it keeps up with my S-10. But she also really isnt a 4.3 liter anymore either, she's a stroker, from 262 cu in (4.3L), to 292 cu in (4.8L). Block froze last winter. Dealership paid for it, since they are the one's who flushed the coolant.

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The original Vortec came out in the Blazer only in 1992, 190 hp/260 flbs using a very troublesome CPFI fuel injection system.
the engine didn't dbut in the P/U until 1993, which is also the year the 4.3 received the internal balance shaft.
CPFI injection was dropped at the end of the 94 model year and replaced with the CMFI system.
The CPFI system had fuel lines under the intake manifold that loved to crack, filling the crank with gasoline, These things failed at about 50,000 miles and dealer cost on repair was about $700.00
Sometime in the late 90's Vortec lost its meaning and became just another marketing ploy.
Whitelightning
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