2007 Yukon Denali Intermittent Crank No Start

[Maxpower_454]

What if any type of scanner are you using?

Just a generic little obdii to read codes but I have hptuners. I'll try hooking that up to see if I can find anything else.

I'm going to go over all the grounds on it to make sure theyre good.

 

[Maxpower_454]

Just remembered that one day while driving it was acting like it had no power. It kept running and driving but I slmost had my foot to the floor just to go up a little hill. It didn't die on me that day but definitely wasn't right.

Could a very dirty fuel filter cause this? I never replaced it. previous owner said it was replaced but looks old / factory.

 

[Doubeleive]

Just remembered that one day while driving it was acting like it had no power. It kept running and driving but I slmost had my foot to the floor just to go up a little hill. It didn't die on me that day but definitely wasn't right.

Could a very dirty fuel filter cause this? I never replaced it. previous owner said it was replaced but looks old / factory.

how many miles are on this thing and what maintenance has been done besides a fuel pump and cam sensor?
I really have no direct clue at the moment but this makes me wonder if it is your torque converter, what does the transmission fluid look like?
clogged cat's can cause no power, so can the tc plus it can make the idle rough and might make starting hard.
not trying to send you down a rabbit hole but could be something to consider if nothing else makes sense.
seems like either one would be more consistent though

 

[rdezs]

That sounds like the catalytic converters could be plugged.

I think the 2007 should only have the filter sock in the tank at the pickup. Not really a filter per se. But if you do have the inline filter definitely replace it

 

[Maxpower_454]

That sounds like the catalytic converters could be plugged.

I think the 2007 should only have the filter sock in the tank at the pickup. Not really a filter per se. But if you do have the inline filter definitely replace it

You're correct - no fuel filter. Definitely not a clogged cat. No codes for inefficiency and it has tons of power when driving. It was only that one time it acted up while driving. Didn't act like a clogged cat or obstructed exhaust. almost like a ground or something was weakly holding on

 

[Maxpower_454]

how many miles are on this thing and what maintenance has been done besides a fuel pump and cam sensor?
I really have no direct clue at the moment but this makes me wonder if it is your torque converter, what does the transmission fluid look like?
clogged cat's can cause no power, so can the tc plus it can make the idle rough and might make starting hard.
not trying to send you down a rabbit hole but could be something to consider if nothing else makes sense.
seems like either one would be more consistent though

Whats a TC? I'm thinking about replacing the throttle body but I'd hate to replace yet another part that doesn't need replaced

 

[donjetman]

transmission torque converter

 

[Doubeleive]

Whats a TC? I'm thinking about replacing the throttle body but I'd hate to replace yet another part that doesn't need replaced

(TC) torque converter
I wouldn't just replace parts, perhaps more troubleshooting is needed
if you are driving and it is seemingly running fine but has no power under a heavy load then it might be something more physical like clogged cats
mine was clogged and it drove fine if you drove like gramma (to me most people drive like gramma) but as soon as you went to do anything over like 70mph, high rpm heavy load like wide open throttle it had no guts, no power, may as well have been a lawn mower. If I pushed it real hard I would get missfires, yet idling and driving around town seemingly nothing was wrong in any way, you could have driven it like a normal person and never known the difference.
a back pressure test finally revealed the problem, mine should have had like 2.5psi max, mine had 5 at idle and 10 under throttle.
it doesn't explain a no start though.
have you cleaned the throttle body? does the butterfly move smooth? or does it feel sticky and not return quickly to almost closed position?
no answer on miles? previous maintenance?

 

[Maxpower_454]

(TC) torque converter
I wouldn't just replace parts, perhaps more troubleshooting is needed
if you are driving and it is seemingly running fine but has no power under a heavy load then it might be something more physical like clogged cats
mine was clogged and it drove fine if you drove like gramma (to me most people drive like gramma) but as soon as you went to do anything over like 70mph, high rpm heavy load like wide open throttle it had no guts, no power, may as well have been a lawn mower. If I pushed it real hard I would get missfires, yet idling and driving around town seemingly nothing was wrong in any way, you could have driven it like a normal person and never known the difference.
a back pressure test finally revealed the problem, mine should have had like 2.5psi max, mine had 5 at idle and 10 under throttle.
it doesn't explain a no start though.
have you cleaned the throttle body? does the butterfly move smooth? or does it feel sticky and not return quickly to almost closed position?
no answer on miles? previous maintenance?

No, I never cleaned the throttle body. Has 220k miles on it. Should I clean or replace? Whats the goal with cleaning and could it cause a crank but no start condition?

 

[Maxpower_454]

transmission torque converter

Definitely not giving me torque converter symptoms.

Is there a diagram showing all the grounds on a 07 yukon denali? I found the one on the firewall. That was broken when I bought it so I replaced it. That was before these crank/no start experiences.

What other grounds should I find and clean?

 

[Doubeleive]

No, I never cleaned the throttle body. Has 220k miles on it. Should I clean or replace? Whats the goal with cleaning and could it cause a crank but no start condition?

definitely clean it....and the maf and a new air filter

 

[rdezs]

are we confusing cam with crank sensor? he replaced cam sensor but these will run without a cam sensor. they won't run without a crank sensor?

I'm a bit lost lol

Aftermarket camshaft position sensors are notorious for a crank no start symptom, with no codes thrown. The last time I run into that was with a Wells brand. Tech 2 said it was getting the signal.... Swapped it out for an oem ACDelco, and it fired right up. Personally, I would look no further until I replaced the camshaft position sensor with an oem unit followed by a CASE relearn.

 

[donjetman]

no need for CASE relearn after a CAM position sensor change. I changed mine last summer.

 

[rdezs]

It will run forever without doing the relearn.... But it just won't be as efficient as it's capable of without it

 

[donjetman]

It will run forever without doing the relearn.... But it just won't be as efficient as it's capable of without it

my Yukons efficiency/mpg stayed good without a relearn.

 

[rdezs]

The mpg is probably a pretty good indicator that it's right on.

I was thinking it's a lot like when I was working on my first small block Chevy, setting the point gap and the dwell. It would fire up and run okay. Put a dwell meter on it, and realize I only got it close.... Was off maybe 10° on the dwell. Just like setting the distributor to get the engine to fire up. Always follow up with a timing light to get it perfect. There's nothing better than absolutely knowing it's on the money. (Sort of like checking the push rod length)

But yeah, if fuel mileage is staying the same, that's probably the best measurement overall

 

[Maxpower_454]

It was an oem camshaft sensor. Thars not the issue.

No info on grounds?

 

[rdezs]

The important ground is where your negative battery cable goes down to just above the oil pan on the driver side. Don't just clean and reattach.... Check the resistance of the negative cable to make sure it's serviceable. Then the ground strap from the back of the engine up to the firewall. Depending on the year, you'll probably find another ring connector where the battery cable attaches to the block. Normally that is routed to near the front of the frame rail on the driver's side. Don't forget to also check the resistance of the positive battery cable.

 

[Maxpower_454]

The important ground is where your negative battery cable goes down to just above the oil pan on the driver side. Don't just clean and reattach.... Check the resistance of the negative cable to make sure it's serviceable. Then the ground strap from the back of the engine up to the firewall. Depending on the year, you'll probably find another ring connector where the battery cable attaches to the block. Normally that is routed to near the front of the frame rail on the driver's side. Don't forget to also check the resistance of the positive battery cable.

Thank you! I'll work on all of this

 

[Maxpower_454]

Ok so I cleaned the front pass ground and tested the negative cable. All good.

It just died again on me last night. The problem appears to be more frequent now. It'll start idling lower and lower struggling to stay running at stops. Then the next tine I stop, it dies and won't start. Could it be throttle body and/or MAF sensor?