2010 silverado 1500 need help

nick gorske · February 20, 2020

Ok I bought a 2010 silverado 1500 LT around August/September. The truck has 192k on the body, but the engine was recently rebuilt before I bought it. Truck has engine work done, from what i was told it had and feel/hear it has a lot beefier cam in it, full exhaust with headers, haven't really gotten to into looking around cause there was never any need to pop the hood and inspect anything. (Didnt wanna jinx myself). When I first got it the truck was amazing, ran like a beast, never any issues, best running vehicle I've had in a long time. Since the colder months have set in the truck hasn't been running right. I go out to start it and if the engine is cold it'll either catch and shut right back down, or kind of catch and just keep turning over until I feather the throttle. After it starts I have to stay on the throttle for a few minutes so it'll stay running. Sometimes when I put it in gear it'll hesitate then putt putt stall. It's worse if it's really cold out. If its say above 45° it's not that bad. While I'm driving it i brake to fast it might stall or when I stop it's almost like it starts surging and if I'm not heavy on the brake pedal it'll lung forward. This is my first chevy with a not so stock engine so I'm seeking out help. I've had a few mustang's that when having similar issues it needed a tune-up, which I'll be doing this weekend regardless. But I just wanna know if it's something other than just a tune-up I'll be going after. Any and all help is much appreciated. Thank you.

Also there is no CEL on.

swathdiver · February 20, 2020

1 hour ago, nick gorske said:

Ok I bought a 2010 silverado 1500 LT around August/September. The truck has 192k on the body, but the engine was recently rebuilt before I bought it. Truck has engine work done, from what i was told it had and feel/hear it has a lot beefier cam in it, full exhaust with headers, haven't really gotten to into looking around cause there was never any need to pop the hood and inspect anything. (Didnt wanna jinx myself). When I first got it the truck was amazing, ran like a beast, never any issues, best running vehicle I've had in a long time. Since the colder months have set in the truck hasn't been running right. I go out to start it and if the engine is cold it'll either catch and shut right back down, or kind of catch and just keep turning over until I feather the throttle. After it starts I have to stay on the throttle for a few minutes so it'll stay running. Sometimes when I put it in gear it'll hesitate then putt putt stall. It's worse if it's really cold out. If its say above 45° it's not that bad. While I'm driving it i brake to fast it might stall or when I stop it's almost like it starts surging and if I'm not heavy on the brake pedal it'll lung forward. This is my first chevy with a not so stock engine so I'm seeking out help. I've had a few mustang's that when having similar issues it needed a tune-up, which I'll be doing this weekend regardless. But I just wanna know if it's something other than just a tune-up I'll be going after. Any and all help is much appreciated. Thank you.

Also there is no CEL on.

Nick, I would say your truck needs a tune by a tuner. You can over the basics like plugs and wires and cleaning the throttle body and inspecting for leaks first. You might also endeavor to find out what exactly was done to the motor, was AFM deleted for example? In order to properly and quickly diagnose these trucks, you need a good scan tool that can read and graph the O2 sensors, Fuel Trims, etc.

nick gorske · February 20, 2020

Ok, thank you. I'll be bringing it to the local speed shop to have it checked out. I appreciate the input

It's Tim · February 20, 2020

2 hours ago, nick gorske said:

feel/hear it has a lot beefier cam in it,

Could have one or more dead cylinders.

nick gorske · February 20, 2020

2 hours ago, It's Tim said:

Could have one or more dead cylinders.

It runs strong other than starting from cold, and the stalling when braking hard. If it had a dead cylinder it would run like crap all the time.

nick gorske · February 20, 2020

4 hours ago, swathdiver said:

Nick, I would say your truck needs a tune by a tuner. You can over the basics like plugs and wires and cleaning the throttle body and inspecting for leaks first. You might also endeavor to find out what exactly was done to the motor, was AFM deleted for example? In order to properly and quickly diagnose these trucks, you need a good scan tool that can read and graph the O2 sensors, Fuel Trims, etc.

quick question before I go and spend $200 an hour at the speed shop, if it needed to be tuned would that cause it to act the way it does on a cold start, dying out when braking hard and the whole lunging bit. It lunges when the rpms drop like its gonna stall then come back up quick. Almost like I'm hitting the throttle. I figured if there was an issue with the o2 sensors it would throw a code. Just wanna make sure I'm not dumping a good $600 at the shop if I really dont need too.

It's Tim · February 20, 2020

20 minutes ago, nick gorske said:

it would run like crap all the time.

From your description it sounds like it does.

Someone could have pulled the bulb for the check engine lamp have it scanned for codes.

What is the fuel pressure in psi?

nick gorske · February 20, 2020

14 minutes ago, It's Tim said:

From your description it sounds like it does.

Someone could have pulled the bulb for the check engine lamp have it scanned for codes.

What is the fuel pressure in psi?

I will throw my scanner on it when I get home and see. I'm not to sure on the fuel pressure. I dont have an adjustable regulator. Also the truck just passed emissions 2 weeks ago

It's Tim · February 20, 2020

2 minutes ago, nick gorske said:

I will throw my scanner on it when I get home and see. I'm not to sure on the fuel pressure. I dont have an adjustable regulator. Also the truck just passed emissions 2 weeks ago

You can borrow a fuel pressure test gauge from autozone for free.

sefiroxx · February 21, 2020

Clean your throttle / butterfly.

Use a scanner to check if it is in closed loop (too soon). Also check ithrottle angle (tps). Manually open the throttle while monitoring too verify smooth movement , if not, replace tos or while throttle body.

Monitor tos when cold idle and warm idle. It should be open more on cold idle (to achieve higher rpms on cold start). If not, then throttle body/motor needs replacement.

nick gorske · February 21, 2020

4 hours ago, sefiroxx said:

Clean your throttle / butterfly.

Use a scanner to check if it is in closed loop (too soon). Also check ithrottle angle (tps). Manually open the throttle while monitoring too verify smooth movement , if not, replace tos or while throttle body.

Monitor tos when cold idle and warm idle. It should be open more on cold idle (to achieve higher rpms on cold start). If not, then throttle body/motor needs replacement.

I'm gonna get into it today after I drop my son off at school. I have 1 of those cheap scanners that just gives you the codes and there's none that popped. I'll be back later with an update. I appreciate it.

swathdiver · February 21, 2020

17 hours ago, nick gorske said:

quick question before I go and spend $200 an hour at the speed shop, if it needed to be tuned would that cause it to act the way it does on a cold start, dying out when braking hard and the whole lunging bit. It lunges when the rpms drop like its gonna stall then come back up quick. Almost like I'm hitting the throttle. I figured if there was an issue with the o2 sensors it would throw a code. Just wanna make sure I'm not dumping a good $600 at the shop if I really dont need too.

Well, the new camshaft grind may not be compatible with the current tune, whatever that might be. You have a lot of unkowns under the hood and the tuner can help sort them out. Might not be the tune at all, could be a bad MAP sensor or MAF sensor or throttle body or a vacuum leak...

nick gorske · February 21, 2020

3 hours ago, swathdiver said:

Well, the new camshaft grind may not be compatible with the current tune, whatever that might be. You have a lot of unkowns under the hood and the tuner can help sort them out. Might not be the tune at all, could be a bad MAP sensor or MAF sensor or throttle body or a vacuum leak...

Ok I pulled the first plug on the driver side and it has very little oil just past the nut. I'm gonna pull the rest and see where I'm at

nick gorske · February 21, 2020

3 hours ago, swathdiver said:

Well, the new camshaft grind may not be compatible with the current tune, whatever that might be. You have a lot of unkowns under the hood and the tuner can help sort them out. Might not be the tune at all, could be a bad MAP sensor or MAF sensor or throttle body or a vacuum leak...

Ok I pulled the first plug on the driver side and it has very little oil just past the nut. I'm gonna pull the rest and see where I'm at. Or I'm hoping it's just a leak down from the valve cover.