hesitation and poor acceleration..

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Thread: hesitation and poor acceleration..

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    Walking
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    hesitation and poor acceleration..

    Hi all -- new to this forum because I have not had any problems with my Chevy van in tens of thousands of miles.
    Now, I am here because I have a problem -- it is an '89 Chevy G20 (3/4 ton) conversion van with a 5.7L TBI and 193k miles on her. Just within the last month, it has started to hesitate off the line when cold -- then runs ok when it warms and then it starts hesitating again when I have been driving for a longer period of time. When I am up to speed on the highway it is fine -- even though sometimes when I accelerate at hwy speeds, it does hesitate a hair. Also, sometimes it does want to act like it is going to stall after a long run on the hwy -- when I come to a stop. When it hesitates off the line, if I really feather the gas super quickly, she goes -- but I really have to feather the throttle a lot.
    I have recently done the fuel filter, plugs, wires, cap/rotor, and 02 sensor. I have not checked the fuel pressure (I am going to get the gauge and learn how soon if need be).
    I do have a stored error code 44 "lean exhaust" which says to check fuel pressure causing a lean running condition. My first thought is the fuel pressure regulator which I plan on installing this morning -- but wanted to ask you all b/c I hate just throwing things in it w/out some expert opinions first.
    Also, it usually will need a little throttle to start when at normal running temp (hot) -- which is what led me to the fuel pressure regulator as the possible culprit.
    Any help/thoughts here would be great and much appreciated.
    Thanks in advance!
    Last edited by paintguy; 04-13-2005 at 07:46 AM.

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  3. #2
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    Re: hesitation and poor acceleration..

    can't say I know anything about the magnets in the distributor main shaft -- how do I go about inspecting them?
    Thank you.

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    6.2 Liter LS3 V8 Premium Member T-Type's Avatar
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    Re: hesitation and poor acceleration..

    Your symptoms could also be a vacuum leak. Unmetered air entering the engine will also make it go lean. Check all your vacuum lines. Replace all that are hard or cracked.

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    Re: hesitation and poor acceleration..

    it has been doing it mainly when hot (when I have been driving it for a while) -- turn it off, then when I go to drive again, it hesitates really bad and even stalls in gear (auto trans) when I stop at a light. Refires when I try to start her again, only if I dont give it too much gas. Once up to hwy speed, she runs like a champ -- seems to run crappy again at low rpms in each gear and from a stop.

    only a little hesitation from a standing start when cold, but most of the hesitation and stalling symptoms are happening while hot.

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    Re: hesitation and poor acceleration..

    Quote Originally Posted by paintguy
    it has been doing it mainly when hot (when I have been driving it for a while) -- turn it off, then when I go to drive again, it hesitates really bad and even stalls in gear (auto trans) when I stop at a light. Refires when I try to start her again, only if I dont give it too much gas. Once up to hwy speed, she runs like a champ -- seems to run crappy again at low rpms in each gear and from a stop.

    only a little hesitation from a standing start when cold, but most of the hesitation and stalling symptoms are happening while hot.
    Sounds like a weak fuel pump to me.

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    Re: hesitation and poor acceleration..

    I have been pondering the thought that my fuel pump may be going also. I also think that my fuel tank may be contaminated causing poor flow. I guess I am going to have to drain the tank and lower it, clean it out, and replace the fuel pump -- anything else I should do while the tank is out?
    Thanks Lynch Mob.

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    Re: hesitation and poor acceleration..

    Quote Originally Posted by paintguy
    I have been pondering the thought that my fuel pump may be going also. I also think that my fuel tank may be contaminated causing poor flow. I guess I am going to have to drain the tank and lower it, clean it out, and replace the fuel pump -- anything else I should do while the tank is out?
    Thanks Lynch Mob.
    No problem

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    Re: hesitation and poor acceleration..

    could it possibly be my timing chain is in need of replacement?

    anyone please chime in if you can think of anything else before I break down and drop the tank. If it is a weak fuel pump, would it really act up when hot (been running her for a while, then turn her off and when I go to drive again she really acts up and I have to feather the crap out of the throttle to get her going)?

    I have replaced the fuel pressure reugulator, TPS, and O2 sensor and she runs noticably better except after I shut her down after a long run (20+ miles) and then when I start her up about ten minutes later she runs like crap until I get up to hwy. speed.??????????.

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    Re: hesitation and poor acceleration..

    Fuel pump.

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    Re: hesitation and poor acceleration..

    I did the fuel pump and it was the culprit! Thanks everyone for your help!!

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    Re: hesitation and poor acceleration..

    Quote Originally Posted by paintguy
    I did the fuel pump and it was the culprit! Thanks everyone for your help!!
    I had an Astro van give me the same problem.The TBI fuel systems are sometimes a little tricky because you still could have the correct pressure lets say 13 psi ,but you will not have enough volume.I am glad i could help.

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    Re: hesitation and poor acceleration..

    I am having the same problem with my 92 Chevy 1500 truck. 350 5.7liter 2wd. I have replaced the Coolant Temp Sensor, MAP Sensor, Fuel pump,filter,strainer. Also the O2sensor,TPS,IAC,Plugs,Wires,and EGR solenoid. After replacing the coolant temp sensor, and the fuel pump, it ran great for about 6 miles. Then as it idled the engine light came on with code 44. I get a surge then drop when it idles, and I have the same symptoms as painguy. Distributer is good, I just don't know what else is going on with it. Any help I would be greatfull for. Thanks

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    Re: hesitation and poor acceleration..

    On many of these year vehicles there is a plug in connection inside the tank at the top for the fuel pump. This can get corroded and charred, actually burned looking, and lose connection. When replacing the pump you move the wires enough to get a connection for a while, but it fails again. Check to see that the pump is actually running as it should before going any further.

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    Re: hesitation and poor acceleration..

    Quote Originally Posted by partygras
    I am having the same problem with my 92 Chevy 1500 truck. 350 5.7liter 2wd. I have replaced the Coolant Temp Sensor, MAP Sensor, Fuel pump,filter,strainer. Also the O2sensor,TPS,IAC,Plugs,Wires,and EGR solenoid. After replacing the coolant temp sensor, and the fuel pump, it ran great for about 6 miles. Then as it idled the engine light came on with code 44. I get a surge then drop when it idles, and I have the same symptoms as painguy. Distributer is good, I just don't know what else is going on with it. Any help I would be greatfull for. Thanks

    what about the EGR valve itself? try spraying carb cleaner in it.

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    Re: hesitation and poor acceleration..

    Those TBi small blocks were also known for bad distributor shafts, as the magnets would loosen up of crack....causing issue with the pick-up coil as well.

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