4.3 V6 in a fullsize

Hey all, I'm looking at buying a '93 Chevy 1500 as a beat-around truck. It's got a 4.3L and automatic trans. Odometer has 267,000 on it, but the tranny and engine are not original, as claims the seller.

I test drove it and it runs and drives. But it has a hesitation, or roughness to it. I was just wondering if anyone had some tips as to what could be causing it. It runs fine at idle, and seems to run fine at full throttle. But just taking off and driving down the road normally, it runs rough. It has a noticeable shudder to it while running down the road. No check engine light at all. I didn't try to pull any codes off of it though.

Could this be a bad TPS? I looked into the TBI while it was idling and the injectors looked to be working normally. I don't know anything about fuel-injection or computerized vehicles, so any help would be great.

Thanks, Tony

Reply to
Tony Kimmell
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Honestly it sounds like it's the 267,000 miles. I'd beware of the seller. If I was selling a vehicle and it had a minor problem that caused it to shudder I'd fix it as I'd get more out of it. I know he says this isn't the original engine but it could be. Also if you plan to tow or use it for much hauling I'd avoid it and look for a V8 motor.

Brian

Reply to
el Diablo

I bought my '93 silverado a couple of months ago and it has 340,000 kilometers on it That's 204,000 miles for you guys south of the canadian border. :)

the truck runs and sounds with it's original 350 under the hood. The last and only owner which I know maintained it every 5000k / 3000m and it is as good as day one.

Reply to
Michael McNeil

Reply to
One-Shot Scot

Why would anyone want to buy a vehicle with that many miles? It must look really good.

Reply to
Sonny H

Tony,

I have recently had this problem with my car (see sig.). My car would idle fine... but at low RPM's if I went full throttle it'd studder like a

*bitch*. Then once it went past 3500-4000 RPM's it'd pull hard right up to 6k RPM with no problems. It's lower RPM's that pissed it off. I checked air filter, cleaned & air dried.. oiled, etc.. put back in. It was pretty bad, but it didn't help. I cleaned MAF sensor & IAT sensor. Helped a tiny bit, but didn't make the problem go away. I replaced TPS, the car felt like it had restored 10hp! But the studder was still there. Since I didn't even feel like checking fuel issues yet, I started checking the possibility of ignition problems. So I pull all the spark plugs one by one... I see *one* plug is gapped at 0.060 instead of 0.054 like the others. I re-gap the plug to 0.054... nearly all of the studder went away. I then start checking the resistance of the ignition wires... 2 of them were REALLY worn. I replaced all ignition wires with OEM wires (Ford Motorcraft--and I realize this is a chevy newsgroup, but take my advice or leave it). Studdering went completely away. A few months later... it came back. So I pull all of the spark plugs, put in some real nice NGK Iridium $7/plug spark plugs... car runs smoooooth and VERY nice. It's been a while since that.. and I've had 0 studder since then. Hope this helps (HTH).

-Mike

-- A happy kid behind the wheel of a 98 Mustang GT Cold air intake FRPP 3.73 gears Steeda Tri-Ax Shifter Full Boar turbo mufflers Hi-speed fan switch

255/60R-15 rear tires

Reply to
<memset

I guess it's worth a shot... I usually replace the plugs, wires, cap and rotor right off the bat when I buy a different vehicle. That is, unless I know they are still good.

I think I'll clean the EGR out and see if that helps. I'm at a loss as to what else it could be. I ran a can of Sea-Foam cleaner through it and it seemed to help, but it will still cut out and backfire every now and then. Other than that, it runs like a new motor should.

Tony

Reply to
Tony Kimmell

I'm beginning to think that maybe the injectors are at fault here. I took the EGR off and cleaned it good, but that didn't change anything. The reason I think the injectors may be bad is because the biggest improvement so far has been the can of Sea-Foam that I ran through it. It now runs alot smoother and rarely cuts out/backfires anymore, but still does it on ocasion.

Could bad injectors cause this condition? I was looking at the spray pattern while I goosed the throttle, and they seem to be kind of slobbery (more of a "sheet" of fuel than a spray).

Tony

Reply to
Tony Kimmell

bingo

Reply to
TranSurgeon

Ok... here's an update of the situation:

Replaced both fuel-injectors, throttle position sensor, coolant temp sensor, and rotor button. Cleaned EGR and throttle body. Also cleaned out the injector housing when I had it off.

Truck will still cut out and backfire every once in a while. It sounds like a very quiet, lean backfire. Only does it every now and then. It runs and drives excellent otherwise. Replacing the injectors made a world of difference. Runs much smoother now. And The new TPS got rid of an off-idle "stumble" when you first press the gas.

I'm going to put a set of plugs, wires, distributor cap and ignition coil on it next weekend, but might anyone else have an idea what else could cause this cutting out/backfiring?

Side note- I normally don't just "throw" parts at a vehicle like this in order to find a solution, but I want to replace all the original sensors and components anyway, since they are 11 years old and have

268,000 miles on them.

-Tony

Reply to
Tony Kimmell

Tony;

Have you verified proper fuel pressure ?

How's things up there in the 'ultra-flatland' ? Are they gonna close the Mitsu plant ?

Gary in Jacksonville

Reply to
TranSurgeon

Glad that you are making progress with your vehicle. As for plugs, give NGK Iridium spark plugs a shot. They *are* expensive compared to others, but man they make a world of difference for me!

-Mike

-- A happy kid behind the wheel of a 98 Mustang GT Cold air intake FRPP 3.73 gears Steeda Tri-Ax Shifter Full Boar turbo mufflers Hi-speed fan switch

255/60R-15 rear tires

Reply to
<memset

Three Great Truths about Spark Plugs:

1) AC-Delco for GM 2) Motorcraft for Fords 3) Champions for Mopars
Reply to
TranSurgeon

Motorcraft spark plugs screwed me twice. I am not using them again.

-Mike

-- A happy kid behind the wheel of a 98 Mustang GT Cold air intake FRPP 3.73 gears Steeda Tri-Ax Shifter Full Boar turbo mufflers Hi-speed fan switch

255/60R-15 rear tires

Reply to
<memset

then use Auto-lite in your Ferd

Reply to
TranSurgeon

I'll stick with NGK Iridium, thanks though :P

-Mike

-- A happy kid behind the wheel of a 98 Mustang GT Cold air intake FRPP 3.73 gears Steeda Tri-Ax Shifter Full Boar turbo mufflers Hi-speed fan switch

255/60R-15 rear tires

Reply to
<memset
*BARF* Gary... I'll thank you not to mention ANY type of Allied-Signal crap within my presence ;-)

I don't use anything but the plain old black base AC-Delco plugs in GM engines. All those dual and quad electrode plugs do is drain your wallet. I've never even heard of NGK Iridium plugs, but for $7-8 a pop, they better give me a 40-50 HP increase... otherwise there's no way that's worth it. ;-)

Back to the topic of the truck... I definately know that the problem is fuel related, since the truck acts just like a carbureted engine that just got started up in -20 degree weather ;-) It also wants to die the very first time it's started after sitting overnight. Runs for a couple seconds and dies, unless you give it some gas.

I haven't changed the fuel filter yet, so I'll try that. If that is no help, then looks like I'll have to take it down the road to the local shop and have them test the fuel pressure. I'm not looking forward to dropping the fuel tank on that thing :-(

Tony

Reply to
Tony Kimmell

another suggestion on your truck........loosen and re-tighten any bolt or nut with a wiring harness ground under it

Reply to
TranSurgeon

Save yourself the time and effort and go with rubber lines and hose clamps. She's only putting out 9-13 psi and they'll hold fine. When I bought mine (88' C1500) the lines were rusted so bad that they twisted off whilst trying to remove the filter.

I just cut through the steel lines 4" on either side of the filter and installed a compression-to-hose barb union on the pump side, and a barb-to-barb union on the engine side. If you wrap the braided stainless line with duct tape before you slice it it won't fray. Then a few short lengths of hose to a Deutch (AutoZoo's brand) FF507 which is a nipple-type filter as opposed to nut fittings. I've never had a leak, and never had a problem getting the damn thing off since!

Not fun.

If you decide to go with steel lines, compression fittings should do the trick. On a newer MPFI truck pumping 60-66 psi I'd use flare, but on a TBI compression fittings will do the trick.

Doc

Reply to
"Doc"

That was the point, he he he. Poor fella's like a silly little puppet...................it's too easy to get him going.

Doc

Reply to
"Doc"

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