2000 yukon denali idle issues

[socalyukon]

hey guys got a 2000 yukon denali 5.7 vortec motor and having some slightly rough idle when the engine is mostly warmed up. I will give you some background info, bought the truck with 99k miles and now it has 116k miles, a couple months back i noticed going uphills the engine would lose power and shake, and check engine light would flash and the code would always be random misfire p300 i think it was. So I replaced a shit ton of parts, crankshaft sensor, tune up complete using all AC delco delphi stuff, temp sensor, Idle air control valve, chevked the distrubtor gears, changed fuel pump, fuel filter, cleaned MAF sensor, and none of that fixed the problem, so i went ahead and did the upgrade AC delco spider fuel injection swap, at the same time I had lower intake gasket replced also since Ive read this is a very common problem. The spider upgrade definitely made a huge difference in power and throttle and havnt had the problem as bad. But now at idle when the truck warms up it has a noticable small miss. I have no idea what else to do. any6 help would be greatly appreciated.

 

[SunlitComet]

Was the old spider dumping fuel into the engine or was it starving it?

 

[socalyukon]

Was the old spider dumping fuel into the engine or was it starving it?

Before I swapped the spider, Going up a steep hill the engine would lose power from 70 mph quickyl down to 50mph and start shaking and the check engine light would flash and then stay on until i drove it about 50-100 miles after and go away, Everytime the code would be random misifre.

 

[SunlitComet]

Sounds like it was being starved then. Well in that case give your current plugs and other ignition parts a visual once over just in case something went a goof between the time of old other parts to new ones in case something has gotten fouled up. Another thing to look at is the cylinder misfire history. If the readings show zero then it is likely just a weak link in the ignition somewhere. But not enough to cause a complete misfire.

 

[socalyukon]

Sounds like it was being starved then. Well in that case give your current plugs and other ignition parts a visual once over just in case something went a goof between the time of old other parts to new ones in case something has gotten fouled up. Another thing to look at is the cylinder misfire history. If the readings show zero then it is likely just a weak link in the ignition somewhere. But not enough to cause a complete misfire.

already went bacK AND cleaned and rechecked the gaps on the new 2 month old ac delco plugs. You think a weak coil might cause this? Ive noticed driving today, sometimes stopped at the light it idles smooth and other times you can feel a little misfire, but when your driving down the road or on the freeway it runs perfect.

 

[2000tahoeZ71]

In my opinion, a coil def couldn't hurt. I had an instance where being on the interstate when it was raining and being behind semis, my engine compartment would get drenched. I had bad plug wires that would start jumping and it burned my coil up. I put a new one on after replacing my ingnition components and it pepped it up.

 

[SunlitComet]

Perhaps look for burn-thru on your wires then. Or one that may not be fully seated.

 

[socalyukon]

All the wires are good and seated perfectly. My mechanic says that the coil wouldnt cause something like this?? He says it might be a valve issue??? He did a compression test and all of them where 180 and 3 cylinders 2,7,8 where about 10 lower. Sometimes randomly it will shake more than usual and sometimes it will be smooth. I dont feel the idle being like this honestly before the spider swap, about a week after the spider swap did this start happeneing.

 

[SunlitComet]

Then remove inspect and re-seat the EFI body connector and ensure it is completely locked down and not just bottoming out on the surrounding intake.

 

[socalyukon]

Then remove inspect and re-seat the EFI body connector and ensure it is completely locked down and not just bottoming out on the surrounding intake.

yeha but ive already sprayed carb cleanre all around those areas looking for a leak and nothing, this motor is pissing me off already

---------- Post added at 11:08 PM ---------- Previous post was at 10:14 PM ----------

I read somewhere it could be the knock sensor? Another thing Ive noticed is rarely seomtimes when i turn the car off in a parking lot, come back to it withint 5-10 mins turn it back on and pull out the parking lot and step on the throtle a little the car gets confused, as if it doesnt know Im pressing the gas, and then all of a sudden its like it catches and then takes off.