today i had a problem creep up on my Bravada. im experiencing a hard start. at first i though it was the fuel pump even though i replaced it in October of 2014, but i tested any way KOEO i got about 55 psi, on leak down the pressure actually started climbing to 60. engine running pressure was 55.

i can get her to start with accelerator, slowly accelerating is fine but if i quickly floor it it stumbles. i have also noticed a lack of power.

i have a scanner and have no codes,i can also see live data and nothing looked weird except TPS, it read 0.0 with my foot off the gas. is this normal? i thought the TPS would register some volts without accelerator. in December of 2015 i did a full tuneup and distributor. a year before that i did the fuel pump, ignition coil, and FPR the spider injectors looked good what else could mi check? does it sound like air, fuel, or spark related

 

The TPS on these trucks will read 0 at idle. this is because these trucks have a Idle Air Control (IAC) valve to control idle so the throttle is completely closed at idle. On newer vehicles that have fly by wire throttle the TPS will not read 0 at idle because the computer uses the throttle vane to control the idle.

Have you tried unplugging the MAF sensor and seeing how it runs?

 

That makes sense, no i didnt try that ill give it a shot but wont that stall the engine out altogether? Or make it not start at all

 

ok so i unplugged the MAF and the engine still started and ran, however there was no change in how she ran. plugged it back in, started engine again, and unplugged again and still ran same

i sprayed some starting fluid into the throttle body and was still hard to start, so i think i can rule out fuel issue?

the engine idles on all 6 cylinders but if i rev the engine it stumbles and misses, and feels lacking on power. when starting she cranks and cranks. could it be electrical?

just checked the IAC and it works, passages are all clear too

 

if it is still hard to start after spraying starting fluid into the intake, that definitely sound like a spark or ignition issue.
i would just start checking things one by one. starting with everything thats free and simple to rule out. you can pull the distributor cap and see if there is any corrosion on the contacts inside. The distributor rotor has a little spring loaded tab that contacts the center coil point on the distributor cap and will sometimes get corroded and stick causing issues.

 

well looks like a cap and rotor will definitely help.....thing is i replaced it in December of 2015. not much life out of a cap and rotor

 

Wow that thing has some serious corrosion. Its kinda sad how cheap stuff is made anymore.
Let us know if that fixes the issue.

 

Will do, i had to order a kit from AZ. In the mean time i got my Dremel out and wire wheel and attempted to clean the points to see if she would run better. Now she wont fire at all just cranks. I checked firing order, wires reinstalled correct, no broken points. I come to the conclusion the points are no longer contacting the rotor, so hopefully the new kit will male her run again at least

 

Sky blazer, it is often said on this forum that it is critical to use AC Delco or Delphi cap and rotors for the ignition. Others don't seem to hold up well. I am not sure it was said here on this thread. Use dielectric compound to seal the s/p wires to the cap.

 

That fixed it, running great now. I got a po122 which is TPS cleared it and have not seen the code again. Got that code after i put throttle body back on