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Hesitation From A Dead Stop Only

dansierra

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dansierra Enthusiast

dansierra

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I'm having a problem with a stock 1989 GMC Sierra 1500 - 305 engine. It hesitates off the line intermittently. Sometimes it picks right up and goes and sometimes just drags along then takes off. It goes through all 3 gears though. I don't have any problem once it is going. Kick down the pedal on the highway and away we go, no problem. This problem only happens from a dead stop, occasionally. I've had several things changed but no results yet. (map sensor, oxygen sensor, shaft replaced in distributor, fuel filter, fuel pump, cat, muffler). My mechanic gave up and thinks it might be a partially locked up torque converter. Trany shops don't think so though. Trany guys say this 400 hyrdramatic trany does not have electric torque control, it's mechanic/hydraulic. I checked the governor as suggested and it's ok. Problem all started when I had the trany fluid and filter changed (may be a co-incidence). Any ideas much appreciated.

HotdogMB Enthusiast

HotdogMB

Posted
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I'm having a problem with a stock 1989 GMC Sierra 1500 - 305 engine. It hesitates off the line intermittently. Sometimes it picks right up and goes and sometimes just drags along then takes off. It goes through all 3 gears though. I don't have any problem once it is going. Kick down the pedal on the highway and away we go, no problem. This problem only happens from a dead stop, occasionally. I've had several things changed but no results yet. (map sensor, oxygen sensor, shaft replaced in distributor, fuel filter, fuel pump, cat, muffler). My mechanic gave up and thinks it might be a partially locked up torque converter. Trany shops don't think so though. Trany guys say this 400 hyrdramatic trany does not have electric torque control, it's mechanic/hydraulic. I checked the governor as suggested and it's ok. Problem all started when I had the trany fluid and filter changed (may be a co-incidence). Any ideas much appreciated.

check the adjustment on the TV cable. Might be way out and not be shifting all the way down to first as you stop.

dansierra Enthusiast

dansierra

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I'm having a problem with a stock 1989 GMC Sierra 1500 - 305 engine. It hesitates off the line intermittently. Sometimes it picks right up and goes and sometimes just drags along then takes off. It goes through all 3 gears though. I don't have any problem once it is going. Kick down the pedal on the highway and away we go, no problem. This problem only happens from a dead stop, occasionally. I've had several things changed but no results yet. (map sensor, oxygen sensor, shaft replaced in distributor, fuel filter, fuel pump, cat, muffler). My mechanic gave up and thinks it might be a partially locked up torque converter. Trany shops don't think so though. Trany guys say this 400 hyrdramatic trany does not have electric torque control, it's mechanic/hydraulic. I checked the governor as suggested and it's ok. Problem all started when I had the trany fluid and filter changed (may be a co-incidence). Any ideas much appreciated.

check the adjustment on the TV cable. Might be way out and not be shifting all the way down to first as you stop.

 

 

Thanks for the input. I spoke with the GM shop forman and he said that this 400 hydramatic is vacuum controlled and does not have a TV cable. He said if the vacuum didn't work either way, then it is designed to rev up and not show the symptoms I have.

Genuinefine409 Enthusiast

Genuinefine409

Posted
Posted
I'm having a problem with a stock 1989 GMC Sierra 1500 - 305 engine. It hesitates off the line intermittently. Sometimes it picks right up and goes and sometimes just drags along then takes off. It goes through all 3 gears though. I don't have any problem once it is going. Kick down the pedal on the highway and away we go, no problem. This problem only happens from a dead stop, occasionally. I've had several things changed but no results yet. (map sensor, oxygen sensor, shaft replaced in distributor, fuel filter, fuel pump, cat, muffler). My mechanic gave up and thinks it might be a partially locked up torque converter. Trany shops don't think so though. Trany guys say this 400 hyrdramatic trany does not have electric torque control, it's mechanic/hydraulic. I checked the governor as suggested and it's ok. Problem all started when I had the trany fluid and filter changed (may be a co-incidence). Any ideas much appreciated.

 

my cousin had a truck with the 305/th400 and he had a stumble on inital accelerating. it was his EGR valve messing up. it would open all the way and make the engine run rough and it almost sounded "cammed up" from the exhaust gasses making it choppy. did you replace the EGR valve?

dansierra Enthusiast

dansierra

Posted
  • Author
Posted
I'm having a problem with a stock 1989 GMC Sierra 1500 - 305 engine. It hesitates off the line intermittently. Sometimes it picks right up and goes and sometimes just drags along then takes off. It goes through all 3 gears though. I don't have any problem once it is going. Kick down the pedal on the highway and away we go, no problem. This problem only happens from a dead stop, occasionally. I've had several things changed but no results yet. (map sensor, oxygen sensor, shaft replaced in distributor, fuel filter, fuel pump, cat, muffler). My mechanic gave up and thinks it might be a partially locked up torque converter. Trany shops don't think so though. Trany guys say this 400 hyrdramatic trany does not have electric torque control, it's mechanic/hydraulic. I checked the governor as suggested and it's ok. Problem all started when I had the trany fluid and filter changed (may be a co-incidence). Any ideas much appreciated.

 

my cousin had a truck with the 305/th400 and he had a stumble on inital accelerating. it was his EGR valve messing up. it would open all the way and make the engine run rough and it almost sounded "cammed up" from the exhaust gasses making it choppy. did you replace the EGR valve?

 

 

Thanks for the input but what do you mean it sounded "cammed up". When my truck hesitates, it doesn't really make any special noise, it just kinda stops making noise and slowly starts reving up even though I'm putting the gas pedal full down. Like it's choking and not getting any gasoline. But mechanics have put a fuel flow meter on it and they say it's getting flow. Put new fuel filters and fuel pump on it.

dansierra Enthusiast

dansierra

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By cammed up he means it lopes like it has an oversized camshaft in it.

 

OK. My mechanic says I'm not explaining the symptom correctly. I guess the word "hesitation" is incorrect. My truck(intermittently) "JUST HAS NO POWER FROM A STOP!". It pulls away slow (not missing or stumbling) even though I've got the pedal right down. After it gets up to say 15-20 mph, it's ok then. This only does this from a stop and it is intermittent.

dansierra Enthusiast

dansierra

Posted
  • Author
Posted
I'm having a problem with a stock 1989 GMC Sierra 1500 - 305 engine. It hesitates off the line intermittently. Sometimes it picks right up and goes and sometimes just drags along then takes off. It goes through all 3 gears though. I don't have any problem once it is going. Kick down the pedal on the highway and away we go, no problem. This problem only happens from a dead stop, occasionally. I've had several things changed but no results yet. (map sensor, oxygen sensor, shaft replaced in distributor, fuel filter, fuel pump, cat, muffler). My mechanic gave up and thinks it might be a partially locked up torque converter. Trany shops don't think so though. Trany guys say this 400 hyrdramatic trany does not have electric torque control, it's mechanic/hydraulic. I checked the governor as suggested and it's ok. Problem all started when I had the trany fluid and filter changed (may be a co-incidence). Any ideas much appreciated.

 

my cousin had a truck with the 305/th400 and he had a stumble on inital accelerating. it was his EGR valve messing up. it would open all the way and make the engine run rough and it almost sounded "cammed up" from the exhaust gasses making it choppy. did you replace the EGR valve?

 

 

Thanks. My mechanic says I'm not explaining the symptom correctly. I guess the word "hesitation" is incorrect. My truck(intermittently) "JUST HAS NO POWER FROM A STOP!". It pulls away slow (not missing or stumbling) even though I've got the pedal right down. After it gets up to say 15-20 mph, it's ok then. This only does this from a stop and it is intermittent.

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