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Stumbling effect?

Tim Wurtz

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Tim Wurtz Enthusiast

Tim Wurtz

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Posted

This one has left me scratching my head, I have a 1995 Chevy K1500 with a 5.7L engine. The problem I am having is the truck is missing under a load. There are a couple areas where I notice this. It seems to always be worse when the truck is at operating at a warm temp. While driving down the road and in overdrive and you ease into the throttle the truck really starts missing bad, but when I manually shift it into 3rd to get the rpms up it don't do it then. I notice when I have extra passengers it seems to do it bad also. Sometimes at an idle I randomly feel a missing kinda like a jolt every once in awhile, and also sometimes while taking off from a stop it will miss a few beats too.

 

I would think it is not spark plugs, new or old didnt make a difference. The problem doesn't seem consistent with plugs or wires because this is an intermittent problem, and mostly seems to happen while under a load and while it is warmed up. but hen again what do I know cause I am asking you all, lol.

 

Any ideas out there on this one?

 

BTW this thruck only has 84,000 miles on it.

drumset5994 Enthusiast

drumset5994

Posted
Posted

I had the EXACT same problem on my old Chevy S-10...to an absolute "T" ...when under slight load in OD (you give it a lil gas) it would stumble, rumbling, jitter, etc. When it downshifted, it was fine.

 

I had the 4L60E in that truck...and found out later it was the Torque Converter going. Check into that to see if it might be the cause. I had changed everything on it (plugs, wires, sensors, coil packs) and it didnt change. Found out through my mechanic it was the torque converter that had gone bad.

Tim Wurtz Enthusiast

Tim Wurtz

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Hmmm, I hope it is not that, lol. I wonder if it would be the torque converter but it also does it once in awhile at idle as well only when it is really warmed up with it in gear, never really tried it in park to see. I seen a post on the net somewhere that a gm tech found a guy's problem like mine and it was a temp sensor sending a wrong signal back to the computer and in turn it was changing the spark timing and fuel signals among other things.

 

Suppose this could be my problem? I wouldnt know where to look for the temp sensor though.

snoman Senior Enthusiast

snoman

Posted
Posted
Hmmm, I hope it is not that, lol. I wonder if it would be the torque converter but it also does it once in awhile at idle as well only when it is really warmed up with it in gear, never really tried it in park to see. I seen a post on the net somewhere that a gm tech found a guy's problem like mine and it was a temp sensor sending a wrong signal back to the computer and in turn it was changing the spark timing and fuel signals among other things.

 

Suppose this could be my problem? I wouldnt know where to look for the temp sensor though.

 

 

 

 

 

How is mixture? Does it smelll rich when not missing? Also, when was the last time you changed plugs, wires and distributor cap?

Tim Wurtz Enthusiast

Tim Wurtz

Posted
  • Author
Posted
Hmmm, I hope it is not that, lol. I wonder if it would be the torque converter but it also does it once in awhile at idle as well only when it is really warmed up with it in gear, never really tried it in park to see. I seen a post on the net somewhere that a gm tech found a guy's problem like mine and it was a temp sensor sending a wrong signal back to the computer and in turn it was changing the spark timing and fuel signals among other things.

 

Suppose this could be my problem? I wouldnt know where to look for the temp sensor though.

 

 

 

 

 

How is mixture? Does it smelll rich when not missing? Also, when was the last time you changed plugs, wires and distributor cap?

 

 

 

 

 

I have noticed it smells rich, I recently changed the plugs but it didn't change anything, as far as the wires and cap I haven't changed them, I guess I should give that a try.

Goldburb Enthusiast

Goldburb

Posted
Posted

I have this same problem on my Suburban. I have a 2000 with the 5.3 in it and I have both the issues in OD and at idle while in gear. I've got about 118K on it and I've changed plugs, fuel filter, fuel pressure regulator and cleaned the throttle body. I'm still tying to get some answers here locally, but I'd be interested to hear what you ind out!

snoman Senior Enthusiast

snoman

Posted
Posted
Hmmm, I hope it is not that, lol. I wonder if it would be the torque converter but it also does it once in awhile at idle as well only when it is really warmed up with it in gear, never really tried it in park to see. I seen a post on the net somewhere that a gm tech found a guy's problem like mine and it was a temp sensor sending a wrong signal back to the computer and in turn it was changing the spark timing and fuel signals among other things.

 

Suppose this could be my problem? I wouldnt know where to look for the temp sensor though.

 

 

 

 

 

How is mixture? Does it smelll rich when not missing? Also, when was the last time you changed plugs, wires and distributor cap?

 

 

 

 

 

I have noticed it smells rich, I recently changed the plugs but it didn't change anything, as far as the wires and cap I haven't changed them, I guess I should give that a try.

 

 

 

 

 

My 89 4x4 burb with same engine did the same several years ago. New plugs, wires and cap cured it. (same engine family as yours)

Rolandd Enthusiast

Rolandd

Posted
Posted

Folks,

 

Remember that the engine in question has TBI. If you are having mixture issues you need to put it on a scope and see what the various sensors are reading. Sometimes two sensors can fail such that they are still in range but leave the ECU hunting for the correct program (e.g.: outside air temp is hot but the engine coolant is cold when in fact it is an average day and the truck is at operating temp). An ODBC-2 engine will have a completely different set of conditions to create the same symptoms, as will a carb'ed engine.

 

The torque converter is a possible culprit, however when set to "3" the truck should exhibit the same behavior at lower speeds as the converter locks and unlocks.

 

These kinds of issues can be very nasty to debug. Patience is one of the most needed tools in this process that may lead you to spend 50 hours to find a loose wire to an O-2 sensor.

 

Good luck

 

--Roland

Tim Wurtz Enthusiast

Tim Wurtz

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Posted

I noticed today that the truck is now missing quite a bit more as I was backing out of the garage and did it all the way to work. wasnt a heavy miss but you can tell it is not hitting all the cylinders evenly or something. I think I will go get new plug wires and a cap and see it it makes a difference. Dang I wished I could put my finger on this problem, lol.

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