99 K1500 Suburban 5.7l No Top End Power/wont Rev Past 4200rpm

Tugzy · January 3, 2010

Yesterday driving my suburban i noticed that when driving @ 60-80mph when in 4th gear, as i put load on the engine I feel a bump in the acceleration and it goes away (kinda hard to explain)...it feels like when the torque converter locks it BUMPS....

next when i step on the throttle i notice that the engine wont rev past 4200rpm and theres no top end power, low end acceleration is ok.

When im in Park or Neutral, the same goes...it wont rev past 4200 rpm and the idle is a bit rough.... plugs were changed last month, cap and rotor last year....I might try changing the wires and cap and rotor and o2 sensors. I did have an intermittant check engine light last month that went away. My tech said that the o2 sensors were at the border line of the range. Since he cleared the codes the light hasnt come on.

Could it be the fuel pump ready to go? Im in Toronto and the temperatures are very cold -10 to -20dec C..

thanks for the input

[email protected] · January 5, 2010

my fuel pumps have always went out at a pace that i couldn't even reach a speed of 30-35mph , with heavy surging, and nowhere near 4000+RPM's were attainable then they just quit...

kundog · January 7, 2010

Start with a fuel pressure test...55-62 psi at least or what service manual specifies. Then move along accordingly replacing the simpler things first.

Tugzy · January 3, 2010

rodram · January 7, 2010

... definitely get your fuel pressure measured.... service manual spec will say 61 to 66 psi for your Vortec Sequential Central Fuel Injection system... I understand that the injectors may still function ok down to about 58 psi or so.... but when fuel pressure starts to crap out on a Vortec engine like yours, the first sign is usually a gradually more difficult time actually starting the engine... then runs OK after started....

... personally I really do not have experience running my truck at engine speeds up around 4200 rpm... I'll check tomorrow again when I'm driving to work .. but I believe that I really just don't do that...

.. so if the fuel pump pressure is OK, then I believe your culprit will be your cat convertor and/or O2 sensors ... this will cause the engine to bog down.. and as they get worse the engine will just run out of power totally.....