Knock at 16lbs and 100 Octane

[CopGn]

12lbs of boost / 93 octane / 42 fuel presure = 820 o2 no knock.

16lbs of boost / 93 octane / 42 fuel presure = 770 o2 4 knock and a "pop" almost like a backfire. I think this is a mistake so make another run and this time o2 are at 247 and 5 knock and a "pop" again.

No loose wires. Checked coil pack and it is OK. I decide to make sure octane is not an issue and pump up octane to over a 100.

Take another run and still pop and knock.

What am I missing? My trans is going bad at full throttle and I am not getting hard shifts at wide open throttle. Could this be the source of the problem?

 

[efi-street]

Need more info. How old are your injectors, FP, FPR, plugs, wires, etc...
With the popping, I would think an ignition issue. The other symptoms would lead me to look at the fuel system.

 

[scottyb]

What he said.
What are your fuel system parts and ignition system parts?
The pop is typically ignition related. Was the 770 in 3rd gear? In addition to ignition, and assuming that the fuel delivery is sufficient, then bump the fuel pressure a bit.

 

[tyrod]

Originally posted by CopGn
12lbs of boost / 93 octane / 42 fuel presure = 820 o2 no knock.

16lbs of boost / 93 octane / 42 fuel presure = 770 o2 4 knock and a "pop" almost like a backfire. I think this is a mistake so make another run and this time o2 are at 247 and 5 knock and a "pop" again.

No loose wires. Checked coil pack and it is OK. I decide to make sure octane is not an issue and pump up octane to over a 100.

Take another run and still pop and knock.

What am I missing? My trans is going bad at full throttle and I am not getting hard shifts at wide open throttle. Could this be the source of the problem?

Copgn, I had similar problems last winter. My o2 sensor was bad. SOB didnt code through the service engine light. I also had a coilpack to go bad around the same time. Checking across the post (secondary) tested good. I also had a fuel pump relay that was mounted around the gas tank(Hot wire kit from some vendor on car when I bought it) started pulsing the fuel pump intermittenly going down the road. Crazy O2s. Yours sure reminds me of the coilpack. My car "hunted idle" while sitting still when the O2 was ailing. Hope this helps.

 

[CopGn]

Thanks guys for the help. Coil Pack was tested OK. Fuel delivery is not an issue as far as pump. As far as injectors they are still stock (have new setup going in) but they were cleaned. Everything else is new so the new setup is going in sooner than I thought. Knock came at the top of 2nd so came off. No problems on 93 and 12 to 14 pounds of boost. Also it still has an old Hypertech chip which can't help.

 

[77tech9]

Yours hearing pop noises also?

 

[galoush]

I would check the headers and crossover for cracks and leaks too , wont cost a dime to look . Especialy the driver side .

 

[1 RARE T]

That old Hypertech chip has tonnes of timing.

Time to upgrade officer.

 

[ronbuick]

Check your TPS voltage!!

Ron

 

[whitehot84]

What size and type of exhaust do you have. I had a similar problem several years ago and it turned out to be my "new" exhaust system. Bigger is better here.

 

[CopGn]

TPS is good and running a single 3" exhaust no cat.

 

[ThikStik]

My popping was caused by a dying exh. lobe. Damn thing had great smooth low end and even the compression/vacuum was perfect. (This never couldve happened with intake lobe).
Sounds like o2 in your case. Are these cars satan?

 

[turbowidow]

had a similar situation with my car last year, turned out the MAF was bad, wasn't coding but not showing the proper grams os airflow to the ecm. car spooled fine to 12psi then a loud pop( i stopped the car right there and looked for pieces, thought the motor came apart) good luck with your trouble shooting

 

[TurboJim]

I'd be looking at a lean cyl or a cam lobe dying. Pretty much the only things that will cause it to pop, aside from a bad voil pack which you say is known good