1988 Silverado k1500 - runs great, for a few minutes.

rkrizan · 03-26-2007, 12:46 PM

I have a problem with my pickup. It has a relatively fresh motor, with only 30,000 on a crate engine. It ran great for about 2 years of use. The other day, I started it up to do some hauling and I left it to idle for about 5 minutes before I moved it, which I normally do, however, it started idling higher and higher and the check engine light came on. I figured the automatic choke was stuck or something, and at this point the engine was at proper operating temperature anyhow so I tapped the throttle to bring it back down. The truck starting choking and it died, and would not restart. It wouldn't kick at all, as if it was starving for fuel. So I checked the plugs, they had a little carbon on them, so I replaced them, along with the cap, router and wires. Of course by this time the engine was cool again, so it fired right up. I again let it sit for a few minutes, and it did the same thing. I let it cool for a couple hours, pulled the oxygen sensor, cleaned it off a bit, changed the air filter, checked the map sensor plug, and even tested the map sensor, all seemed fine.

This time, when the engine was cool, I started it up, and immediately took it out on the road and opened her out, thinking maybe she needed her throat cleared, ran great, until it got to proper temp again. Got it back to the yard, she died, refused to start. I'm kind of lost, as I've tried tracing down any electrical problems, replaced several parts, etc. Any of you know what I might be missing? I know chevy engines like the back of my hand, so any help would be much appreciated. The only thing I haven't checked is the computer, however from what I'm told once a computer goes, it goes.

I've just recently replaced the fuel filter, and pump as well.

Thanks

75K30 · 03-26-2007, 01:03 PM

How about the coil? Coils can overheat an open causing the loss of fire, and when cooled they will close again and run fine. I know it sounds like a long shot, but this is where I would look first.

rkrizan · 03-26-2007, 01:12 PM

Sorry, I should have stated I checked that too. I've checked it both hot and cold, seems to have great spark. I'm leaning toward the oxygen sensor, although its not that old. I replaced it when I dropped in the crate engine. It had a little carbon buildup on it, which I cleaned with a wire brush before I put it back.

75K30 · 03-26-2007, 01:23 PM

So much for the easy fix. How hot is hot? is it true normal operating temp? Could the fuel line be up against the exhaust or something, and causing a vapor lock issue?

rkrizan · 03-26-2007, 01:29 PM

This engine operates at about 195-200 degrees normally, and thats right when the engine starts running badly and the check engine light comes on. The fuel lines are away from any heat. Could the map sensor be going bad on me again?

I should add this as well.. Since I've owned the truck, even with the old engine, it would drive great, however, whenever I was running light, without any weight in the truck other than myself, and I jumped on the throttle either to pass someone, or for any various number of reasons why I wanted to hot-rod the truck a little, it would hesitate just very very little, the engine engine light would come on, and I would feel a slight improvement in performance. The check engine light would stay on until I shut the truck off and restarted. However, I would lose gas milage if I ran the truck with the check engine light still on. I'm assuming that the ignition would change into limp home mode, not sure on that. Might be related somehow?

bradrhale · 03-26-2007, 02:13 PM

long shot but what code does it pull up??

rkrizan · 03-26-2007, 02:15 PM

I dont have a code tester, and I've never ran diagnostics on a vehicle before. Is there a tool I need to run? I have both Hanes and Chilton books, I could probably see how to do a test from there..

bradrhale · 03-26-2007, 02:19 PM

http://www.troublecodes.net/GM/
check out this site to read codes on OBD1 ports.

rkrizan · 03-26-2007, 02:43 PM

Thanks very much.

pit_boss · 03-26-2007, 05:54 PM

You said you replaced the fuel pump, Iam not familiar with th 88, but if it has a mechanical pump I would suspect a faulty diaphram.

03-26-2007, 12:46 PM	#1
rkrizan Junior Member Join Date: Mar 2007 Posts: 9	1988 Silverado k1500 - runs great, for a few minutes. I have a problem with my pickup. It has a relatively fresh motor, with only 30,000 on a crate engine. It ran great for about 2 years of use. The other day, I started it up to do some hauling and I left it to idle for about 5 minutes before I moved it, which I normally do, however, it started idling higher and higher and the check engine light came on. I figured the automatic choke was stuck or something, and at this point the engine was at proper operating temperature anyhow so I tapped the throttle to bring it back down. The truck starting choking and it died, and would not restart. It wouldn't kick at all, as if it was starving for fuel. So I checked the plugs, they had a little carbon on them, so I replaced them, along with the cap, router and wires. Of course by this time the engine was cool again, so it fired right up. I again let it sit for a few minutes, and it did the same thing. I let it cool for a couple hours, pulled the oxygen sensor, cleaned it off a bit, changed the air filter, checked the map sensor plug, and even tested the map sensor, all seemed fine. This time, when the engine was cool, I started it up, and immediately took it out on the road and opened her out, thinking maybe she needed her throat cleared, ran great, until it got to proper temp again. Got it back to the yard, she died, refused to start. I'm kind of lost, as I've tried tracing down any electrical problems, replaced several parts, etc. Any of you know what I might be missing? I know chevy engines like the back of my hand, so any help would be much appreciated. The only thing I haven't checked is the computer, however from what I'm told once a computer goes, it goes. I've just recently replaced the fuel filter, and pump as well. Thanks

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03-26-2007, 01:03 PM	#2
75K30 Senior Member Join Date: Jul 2006 Posts: 2,636	How about the coil? Coils can overheat an open causing the loss of fire, and when cooled they will close again and run fine. I know it sounds like a long shot, but this is where I would look first.

03-26-2007, 01:12 PM	#3
rkrizan Junior Member Join Date: Mar 2007 Posts: 9	Sorry, I should have stated I checked that too. I've checked it both hot and cold, seems to have great spark. I'm leaning toward the oxygen sensor, although its not that old. I replaced it when I dropped in the crate engine. It had a little carbon buildup on it, which I cleaned with a wire brush before I put it back.

03-26-2007, 01:23 PM	#4
75K30 Senior Member Join Date: Jul 2006 Posts: 2,636	So much for the easy fix. How hot is hot? is it true normal operating temp? Could the fuel line be up against the exhaust or something, and causing a vapor lock issue?

03-26-2007, 01:29 PM	#5
rkrizan Junior Member Join Date: Mar 2007 Posts: 9	This engine operates at about 195-200 degrees normally, and thats right when the engine starts running badly and the check engine light comes on. The fuel lines are away from any heat. Could the map sensor be going bad on me again? I should add this as well.. Since I've owned the truck, even with the old engine, it would drive great, however, whenever I was running light, without any weight in the truck other than myself, and I jumped on the throttle either to pass someone, or for any various number of reasons why I wanted to hot-rod the truck a little, it would hesitate just very very little, the engine engine light would come on, and I would feel a slight improvement in performance. The check engine light would stay on until I shut the truck off and restarted. However, I would lose gas milage if I ran the truck with the check engine light still on. I'm assuming that the ignition would change into limp home mode, not sure on that. Might be related somehow?

03-26-2007, 02:13 PM	#6
bradrhale Moderator Join Date: Apr 2006 Location: Texas Posts: 3,619	long shot but what code does it pull up??

03-26-2007, 02:15 PM	#7
rkrizan Junior Member Join Date: Mar 2007 Posts: 9	I dont have a code tester, and I've never ran diagnostics on a vehicle before. Is there a tool I need to run? I have both Hanes and Chilton books, I could probably see how to do a test from there..

03-26-2007, 02:19 PM	#8
bradrhale Moderator Join Date: Apr 2006 Location: Texas Posts: 3,619	http://www.troublecodes.net/GM/ check out this site to read codes on OBD1 ports.

03-26-2007, 02:43 PM	#9
rkrizan Junior Member Join Date: Mar 2007 Posts: 9	Thanks very much.

03-26-2007, 05:54 PM	#10
pit_boss Full Member Join Date: Dec 2006 Location: Hartland,Minnesota Posts: 25	You said you replaced the fuel pump, Iam not familiar with th 88, but if it has a mechanical pump I would suspect a faulty diaphram.