Intermittent - no start, sputter and shunts or runs perfectly ~!?

[nimrod.sixty9]

GF's 99 Yukon has been developing a no start issue.

Motor comes to an abrupt halt, shudder and shunts when cranking. Sometimes complete stops then continues cranking.

Took off cap and rotor, both were dirty; cleaned points with a Dremel wire wheel. Fired right up multiple times, told girl she can drive the truck to work the following day. Comes back in in the morning and wakes to tell me it's once again doing the same thing. Then will run again, then wont, then......

Fuel pressure good, new CPS, terminals tight and clean. Changed over complete throttle body and coil/ICM from my Tahoe; same result and Tahoe has been running great for days.

Does not seem starter or short related. Itll either fire right up, or turn and turn then kick back, or turn and immediate kick back. Never just turns, turns, then starts. Pretty much can immediately tell if it will run or not. When it runs, it runs perfectly!

Turns out the spark plug tester was a waste; tons of wasted attempts (with it not running). So just decided to grab another plug and use jumper cables. Sparked without issue. And I just knew it would leave me on a hanger so I immediately decided to hook the wire back up and sure enough it fired right up! AHHHHHHH!

Cranked instantly next 10 times and runs perfectly... fkn figures. So now I have no idea if it was a valid test.

Lets assume its an intermittent no spark on start; what would cause this?`

Videos:
Start and shudder start;
https://www.youtube.com/watch?v=eRNbugWLztQ&feature=youtu.be

No start, and putter; with fuel pressure;
https://www.youtube.com/watch?v=W7XKROSdw68&feature=youtu.be

 

[Slammed]

Either replace cap and rotor or have injectors tested you might need new spider injectors

 

[nimrod.sixty9]

Either replace cap and rotor or have injectors tested you might need new spider injectors

I dont believe it to be fuel related. FP has same results in either running or not running condition.

Wouldnt bad cap cause it to run rough, not a no run and run perfectly scenario?

 

[Slammed]

OK then it sounds like the coil that would make more sense other than that you need to get a code to pop up

I dont believe it to be fuel related. FP has same results in either running or not running condition.

Wouldnt bad cap cause it to run rough, not a no run and run perfectly scenario?

 

[nimrod.sixty9]

OK then it sounds like the coil that would make more sense other than that you need to get a code to pop up

No codes and after testing today, I DO have spark during the no start situation. No codes atm.

Also, confirmed the noise is from the IAC.

If youre up for a long read;

http://tahoeyukonforum.com/forum/showthread.php?t=62501

 

[lesterl]

Looks like a timing issue....... Check that the CKP sensor is not damaged

 

[nimrod.sixty9]

Looks like a timing issue....... Check that the CKP sensor is not damaged

Crank sensor is new and old one was not damaged. Im going to check to see if the distro might be jumping timing.

 

[lesterl]

Check bottom of distributor gear for wear also.... Also have you replaced Cap and rotor with an aftermarket or an OEM unit?

 

[nimrod.sixty9]

https://www.youtube.com/watch?v=Ikaqkr8j7o8&feature=youtu.be

What do ya think? I could feel it come up slightly; riding the curvature of the teeth.

Going to see if I have warranty on cap and rotor and replace if so. Deff wasnt OEM. Dont see any cross spark.

 

[lesterl]

How many miles?

 

[nimrod.sixty9]

How many miles?

180K+ give or take

 

[lesterl]

Hmmmm..... When it is acting up, can you shoot some carb cleaner into the intake and get it to fire back up at least momentarily?

Does it smell of fuel when acting up ? (Exhaust)

MAF sensor been tested/ cleaned/ replaced?