High Rpm Spark Knock

[biga72]

Hello everyone, newbie here, well to Chevys too. I have a problem with my 01 Silverado 4x4 5.3. Spark knocks under slight stress for example going up hills where the trans is required to downshift the SES light would flash and power would lack a bit... Its absolutly driving me crazy. I took it to a local part store and they hooked it up to one of thier cheapo generalized code readers and it said "misfire cylinder 3". So under the recomendation of the gentlemen who just wanted to sell me parts; I replaced the plugs, wires etc. And a general tune up as the truck does have 130k on the clock, it was needed. But the problem still exsists! Honestly seems abit worse.... But rather than throwing parts and senseless $$ at it, I come to pros. Please help! im pretty handy with cars/trucks so im no stranger to this stuff.. Its just foriegn to me(as i was a ford employee and driver of fords for MANY years).

[2COR517]

What did you put in for plugs, and what did you gap them? Your truck will be most happy on AC Delco platinums, gapped at .040.

[biga72]

What did you put in for plugs, and what did you gap them? Your truck will be most happy on AC Delco platinums, gapped at .040.

 

 

Thats exactly what I have in it, AC Delco platinums, Gapped @ .40. and OEM replacement wires... im just clueless here.. unfortunate part is i use my truck for work.. :-(

[biga72]

Update. Changed coil 3 as per P0303 code misfire on cylinder 3. As ive said before, all plugs, wires, and general tune up to include fuel filter has beed changed. Took it to local mech with a code reader because all of this did not fix the problem. Now its a P0300 misfire random multiple cylinders code. So after the run around from a few local shops about ALL the possibilities, ive been told the fuel pressure should be about 60psi on start-up and approx 50 at an idle. The idea was injector issues... So ive now had the fuel pressure checked and im 59-61 at start up and 48-50 at idle... which leads me to believe its not a fuel issue... yet ANOTHER idea or two were cam sensor/crank sensor or ECM?????????? Im so lost and need help desperatly. Engine light flashes continuously and truck has very little to no guts after 2000rpms and continues to spark knock under slight stress. PLEASE HELP!!

[biga72]

Been thinking.. Clogged cats? Just a thought.. Any ideas anybody?

[tobias]

What did you put in for plugs, and what did you gap them? Your truck will be most happy on AC Delco platinums, gapped at .040.

 

 

Thats exactly what I have in it, AC Delco platinums, Gapped @ .40. and OEM replacement wires... im just clueless here.. unfortunate part is i use my truck for work.. :-(

 

 

I do believe the Platinums are supposed to have a .060 gap and the Iridiums .040.

 

When you got your plugs, were they at .060 and you adjusted them or did they come at .040?

 

What is the part number for the plugs you used?

[biga72]

Been thinking.. Clogged cats? Just a thought.. Any ideas anybody?

 

sorry. hit wrong button.

[biga72]

Been thinking.. Clogged cats? Just a thought.. Any ideas anybody?

 

 

Thank you thank you thank you for paying attention to my post! I need help! and ur right the plugs i bought and installed ARE/WERE iridiums! they came gapped at .40 but of course i checked them and corrected a few..

 

part numbers on box are as follows:

ACDELCO Professional

8#41-985 and on the other end of the box, 12571164

 

any help u can offer is greatly appriciated!!!

[2COR517]

Whatever plug you run should have a .040 gap.

[biga72]

Whatever plug you run should have a .040 gap.

 

 

Any other ideas? is the fuel pres i was told correct and is mine fine?

i have to admit, im leaning on cats clogged... but still absolutly open to suggestion.

[tobias]

Whatever plug you run should have a .040 gap.

 

GM does not recommend .040 on the Platinum plugs, only the Iridiums.

 

OP, 2COR517 runs his Platinums at .040 and that's his choice, BUT... your owner's manual and the sticker under the hood AND the GM Parts Pros on this site all recommend .060 on the Platinum plugs. Just FYI

[2COR517]

Didn't we just go through this........

[txab]

[biga72]

Well now it has no guts at all. Zero. Rough idle and barly stays running. Out of patients.

 

This truck ran so well at first. Begining to think this was the worst purchase ive EVER made. Real nice.

[jf781]

I'd check your cats. Symptoms starting to sound more and more like it.