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2000 Astro, 4.3L shakes and surges at idle while in gear...

jonrpick

jonrpick

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Title says it all. I got the Astro as a cheap DD / work / gigging vehicle. I bought the only "work" Astro I could find in town.

Anyway, when in gear, sitting at a red light, it shakes. It's annoying enough that I usually take it out of gear while not moving. When I do, the oil pressure gauge needle jumps around violently, even though the van itself does not while in neutral.

Years ago, my Dad's Saab had a similar problem, and IIRC, it was a TPS.

Ideas? I need to go through it and do the usual tune-up process... plugs, wires, filters, thermostat, oil, etc...

Another thing I just thought I'd throw out there. It'll probably be fuel pump time soon. It whines pretty good. The thermostat needs replacement. It runs cold and the heater output sucks...

Thanks... ;-)
 
does it feel like a miss? If it is not a missfire, pull the egr valve and see if it is stuck open. big chunks of carbon will get stuck, and hold the valve open enough to make them idle really bad.

If it is carbon in the egr valve, they make an updated gasket that has a screen to keep this from happening.
 
How in the heck do you go Gigging with a...........

Oh, you mean music gigs, not flounder.........

Sorry, been living on the coast too many years.

Does the motor seem to be surging or running strange when the oil pressure needle is moving?
Any other instruments acting weird?

I wondering if the computer or some engine electrical part has a loose connection causing an intermittent misfire.
 
All 3 of mine did that at some point. Bad dist. cap was the issue on all 3. The slight miss was there at RPM. Just could not feel it as much. If you are going to put any milage on it. Do the full tune up thing. You will be surprised at how well it will run. Do the EGR valve also. Get a Delco brand. The others are crap for some reason. I was getting 21 MPG out of all 3 loaded all the time. Mostly city driving.
 
black dawg said:
does it feel like a miss? If it is not a missfire, pull the egr valve and see if it is stuck open. big chunks of carbon will get stuck, and hold the valve open enough to make them idle really bad.

If it is carbon in the egr valve, they make an updated gasket that has a screen to keep this from happening.
Click to expand...

At certain constant speeds, yes, it feels like there's a miss. Above 70mph+ on the interstate, it's fine. Around 60mph, it feels like it's missing some. EGR valve is cheap. I'll just add that to the tune-up list.




Fordum said:
Does the motor seem to be surging or running strange when the oil pressure needle is moving?
Any other instruments acting weird?

I wondering if the computer or some engine electrical part has a loose connection causing an intermittent misfire.
Click to expand...

No... when the needle is jumping, it's in neutral. It's fairly steady in gear, especially while moving.

Another thing... I'm pretty sure this van sat for a while before I got it. Like I said, I suspect the fuel pump is on the way out. That and an old fuel filter could be not supplying enough fuel, causing the aforementioned miss.

In spite of all this, this Astro will flat-out haul ass compared to what the K5 ever did on its best day. I believe it'll out-accelerate the wife's Yukon XL with the 5.3L and 3.73 gears, EASILY... :-o
 
I used to pass cars on a very curvy mountain road in mine. Always wanted to put nitrous on it. Just was never sure I was going to make it. Drag raced my wife trailblazer. Smoked it to 65. But the V6 was screaming.
 
ktmoutfront said:
I used to pass cars on a very curvy mountain road in mine. Always wanted to put nitrous on it. Just was never sure I was going to make it. Drag raced my wife trailblazer. Smoked it to 65. But the V6 was screaming.
Click to expand...

Everyone I know who has a Vortec 4.3L is really impressed by them.
 
ktmoutfront said:
All 3 of mine did that at some point. Bad dist. cap was the issue on all 3. The slight miss was there at RPM. Just could not feel it as much. If you are going to put any milage on it. Do the full tune up thing. You will be surprised at how well it will run. Do the EGR valve also. Get a Delco brand. The others are crap for some reason. I was getting 21 MPG out of all 3 loaded all the time. Mostly city driving.
Click to expand...

Just saw this post. Tapatalk didn't refresh...

I'll look into that as well. Good thing is, most of this stuff is driveway stuff except the fuel pump, though I've read about guys loosening the tank and doing it that way.

I'm personally thinking about getting some scrap sheet metal and making an access panel over the tank for future servicing needs.

I do plan on driving it quite a bit, though for now I drive a company van for work and bring it home, so I don't drive it much. It has shelving that I need to remove. It had a partition, which someone removed. I bought a used one for $50 that I need to strip and repaint.
 
I just added up the vehicles I have owned with 4.3s. 9 of them. All but one went to 200k before I got rid of them. Only one needed a trans. All other stuff was regular maintenance.
 
I chose an Astro specifically over other vehicles in its class because of the drive train being so similar to a FSC truck. Same engine / tranny / rear axle, plus everything else. I think every other small van is FWD, and I didn't want to deal with that mess.
 
I will say, would've been cool to get the AWD version... I saw one, but it wasn't a work van and was a LOT more money. When this is done, I hope to have a bunk in the back to sleep in so I can avoid hotels when traveling for gigs.
 
jonrpick said:
True...
Click to expand...

I had an S10 Blazer come through my shop once that was behaving similarly. There were no codes, shook in gear but took off alright. It held it's gears though, which I felt was weird.

Problem was a failed MAF sensor. It was reading, but not the correct volume. Cleaning didn't help, but a new sensor had the truck behaving just like brand new again. I changed all the plugs, wires, coil pack, cap & rotor anyways though, they were factory originals with quite a few more miles than they should have gone :haha:
 
If the thermostat isn't letting it get up to 195 degrees,the coolant temp sensor wont let it go into closed loop and it'll run crappy too!....just a few PSI under specs on the fuel pump can cause issues like this too...
 
diesel4me said:
If the thermostat isn't letting it get up to 195 degrees,the coolant temp sensor wont let it go into closed loop and it'll run crappy too!....just a few PSI under specs on the fuel pump can cause issues like this too...
Click to expand...

Good call. The fuel economy definitely isn't what it should be for this vehicle.

This week, I'll start swapping out parts as part of the overall tuneup process. Gonna research the easiest way to DIY a fuel-pump change without a lift.
 
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