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94 gmc problem

surging problem

94 gmc problem

Postby lowrunner [OP] » Mar 14 2011, 4:38am

hey guys i have a 94 gmc sierra 1500 4wd Pu 5.7 liter AT. the problem im having is at low rpm it feels like its surging slightly, going up over a pass its shifting down more often then it should. it also is now getting extreamly bad gas mileage. i replaced cap, rotor,plugs and wires. the tranny does not slip and shifts fine, the transfer case works fine also. no whinning sound. all gears seem to work fine in trans auto or when i manualy shift it. no code is shown.i havent changed the fuel filter in the frame yet. could it be the cataletic converter ? i put my hand over the exaust pipe and it does not feel like theres very much pressure coming out. i seem to get more pressure out of my geo exaust than my trk. it feels like its being restricted going down highway like im got some power loss. 94 GMC cierra P/U 4X4 C1500 SLE, 5.7L, TBFI, A/T. approx 150,000 Miles.
im getting a slight surging when traveling down the highway, transmission down-shifting more than normal,bad gas milage,feels like im driving against a head wind.runs fine at a idle. when in gear, stopped on a hill, when barely throttling the engine up (just before the truck starts to move) it starts sputtering bad then smooths out, keeps doing it over and over. in netual i stomp the throttle down and it will sometimes pop. i have replaced: Cap,Rotor,Plugs,Wires,Caytiletic Converter and O2 Censor. which all but 02 censor needed replacing. i have no check engine code showing anything. hve checked throttle position censor it checks good. any ideas????????? thank youany ideas or help would be much appreciated

sorry but i moved this post from drive train and added to it.
Original Poster
lowrunner
Firing on 1 cylinder [L1]
Firing on 1 cylinder [L1]
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Re: 94 gmc problem

Postby lzn197 » Mar 14 2011, 1:10pm

I believe you have a spark plug or ignition wire problem. I know you changed them but.........Ever changed the air filter?
Gordon
2004 Chevrolet Silverado Extended Cab Z71
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Re: 94 gmc problem

Postby lowrunner [OP] » Mar 18 2011, 3:28am

yes on the air filter! but i will double check and test every plug and wire, ill let you know. thanks
Original Poster
lowrunner
Firing on 1 cylinder [L1]
Firing on 1 cylinder [L1]
Posts: 11
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Year: 1994
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Re: 94 gmc problem

Postby lowrunner [OP] » Mar 19 2011, 1:00am

ok guys , i changed cap,rotor,wires and plugs again runs better but still has the low rpm sputter and choking when in gear holding itself on a hill in drive. so when in park i reved the engine and held it approx 50+ % of throttle the engine would run fine for about 2 to 4 seconds then cough. then engine then pick back up. it will do that consistantly. as if 1 cylinder keeps missing. at idle and in park it runs fine. does that sound like a valve ? i havent done a compression check yet
Original Poster
lowrunner
Firing on 1 cylinder [L1]
Firing on 1 cylinder [L1]
Posts: 11
Topics: 3
Joined: Aug 08 2010, 2:29am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Year: 1994
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Re: 94 gmc problem

Postby Ready 4 a Ford » Jan 12 2014, 4:38pm

Did you ever figure this out? I'm having same exact issue with my 2500. I replaced Throttle position sensor and swapped egr from another truck but still same problem.
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Re: 94 gmc problem

Postby lowrunner [OP] » Jan 12 2014, 4:50pm

sorry not getting back but replaced egr with new one along with the sensor and that seemed to do it
Original Poster
lowrunner
Firing on 1 cylinder [L1]
Firing on 1 cylinder [L1]
Posts: 11
Topics: 3
Joined: Aug 08 2010, 2:29am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Year: 1994
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Re: 94 gmc problem

Postby Ready 4 a Ford » Jan 12 2014, 5:02pm

Map Sensor? Thanks for the quick reply!!
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Re: 94 gmc problem

Postby lowrunner [OP] » Jan 12 2014, 7:54pm

im not sure that might be what it was it was a while ago and I was changing just about every sensor ther was even if they checked out good with my tester I figured if I could afford it I would cause I got no sign from the computer for my egr valve but when changed it sure ran better so I personally dont trust the computers completely, although if it does tell me theres a problem with something I do replace that
Original Poster
lowrunner
Firing on 1 cylinder [L1]
Firing on 1 cylinder [L1]
Posts: 11
Topics: 3
Joined: Aug 08 2010, 2:29am
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Year: 1994
Make/Model: GMC Sierra
Group Membership:
Registered users

Re: 94 gmc problem

Postby Ready 4 a Ford » Jan 12 2014, 11:53pm

I had a 91 1500 with a 4.3l 5 speed and 4wd. Loved it, cold AC and got like 18mpg. The truck only had 130-140k on it and it started missing and running terrible. We replaced everything, even the computer and couldn't figure it out. Finally had the junkyard haul it away for scrap....now this one seems to be headed down the same path.....hence my username...lol
Ready 4 a Ford
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Re: 94 gmc problem

Postby lzn197 » Jan 13 2014, 4:23am

Ready 4 a Ford wrote:I had a 91 1500 with a 4.3l 5 speed and 4wd. Loved it, cold AC and got like 18mpg. The truck only had 130-140k on it and it started missing and running terrible. We replaced everything, even the computer and couldn't figure it out. Finally had the junkyard haul it away for scrap....now this one seems to be headed down the same path.....hence my username...lol


I fixed a ton of these. Most has a weak magnet star wheel on the distributor shaft. Replace the distributor shaft and the problem is fixed.
Gordon
2004 Chevrolet Silverado Extended Cab Z71
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