Bucking in 4@5 gear @65mph changed plugs /wires and tps ok few days replaced air filter ,fuelfilter and put in newer used fuel pump again ok for few days ???goes to red line in1,2,3,gear bucks 4,5,gear around 65mph
Look up check for clogged cat on youtube. Could be a coil braking down.. could be a egr problem.. could be IGN Module.. DO not replace these things.. there are tests that can be run.. Orellys auto parts can test them for you.. If the "bucking" is ign related it should set a code for engine missfire. A long shhot is grounds for the fuel injectors..each injector has 2 wires.. one power from the computer and one ground.. there usually grounded somewhere on the intake manifold or firewall.
SOURCE: 99 gmc no power when passing or climbing
It could be the cat. it sounds like this could be your problem
SOURCE: 2000 Gmc Yukon Denali wont start i changed fuel pump and filter
your getting too much air in chamber on igintion probly cause by a faulty intake and or a faulty tps (throttle positioning sensor) sounds like intake is sucking more air that fuel which is giving a bad air fuel mix in chamber also try checking your mass air could be faulty as well
SOURCE: 1992 gmc chevy 350 wont idle when warm
This could be a number of things but i think that your problem sounds like a vacuum leak or an EGR problem. Try listening for leaks and try un-plugging the EGR solenoid valve one time.
SOURCE: my son's gmc 4.3l hesitates upon acceleration. I
do you have any check engine lights on? If you do, that is the first thing I would have checked. It does sound like plugged EGR, vacuum leak, or bad TPS
SOURCE: 98 gmc jimmy loses power to a stop
the fuel pump could actually be malfunctioning. and the reason that you are able to restart and drive again is because when you turn the key on it is allowing the fuel pump to pressureize your system. but while the fuel pump is continuasly running it is loosing the fuel pressure. this is common on the cheap fuel pumps. i am not sure about were you got the fuel pump from but in all of my experiances with this problem i find that the fuel pumps have been boughten at a napa store.
i hope this helps you out.
and you could attach a fuel pressure gauge on to the fuel rail and start the car and watch the pressure to see if it is droping.
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Hi mark wellman, I want to help you with your problem, but I need more information from you. Can you please add details in the comment box?
2.2l flexruns good 1,2,3gear b fuel approx mileage245000. miles
why cat doesnt do it in all gears
how can we prove its cat??
there is one code small evaporator leak but thats been there for ever
Hi Mark, I had a chevy 2.2l in a s10, nice motor, all the other solutions posted are definitely something to look into. By all means take advantage of the free testing offered by some of the autoparts stores or you can purchase your own OBD2 code scanner. What kind of transmission does your truck have?
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