lots of knock

[cldturbo]

Hi guys,

I recently picked up a totally stock 87 GN with 65,000 miles. I did a full spring cleaning as suggested on gnttype.org. Car runs significantly better, but after getting my scanmaster hooked up, it looks VERY lean, and I'm getting 8-9 degrees of knock at WOT. I know that is bad news. Stock boost levels, stock chip, upgraded fuel pump, adjustable regulator, K&N, stock style exhaust (has been replaced recently though). New o2 sensor, new plugs, wires, cleaned intercooler, all vacuum hoses replaced, header crack welded up, I suspect the aftermarket stock style MAF that was replaced at some time may be the culprit. I had to crank the fuel pressure up to 46 line-off to get it running well, It still acts lean at WOT though. I hooked up a good fuel pressure gauge and watched it at WOT, pressure held steady at 65ish

IDLE:
BLM 150
INT 150
TPS .44
IAC 34
AF 3-4
02 50-850
idle 625
coolant 190

WOT:
O2s start around 780's and dropping
knock gets worse, so it isn't false
AF 174 initially, then dropped to 140s, slowly climbing

driving around BLM around 128 and Int jumps 120s to 140s

Any suggestions? Anybody in Austin with a good MAF I can try?

Any help greatly appreciated

 

[Jbenn911]

By far no expert, but I'd say you have a serious vac leak somewhere with INT and BLM's at 150...Also I believe I've read that 5-6 is normal idle MAF reading.. How are you judging the stock boost level ? If you're relying on the stock gauge, forget it!!..Check for leaks elsewhere, like vacuum block on the TB, leaky exhaust to block, crossover, etc etc..Back to MAF, I had nothing but bad luck with them, ended up with LT1 and Translator, no problems since. I've read on this site and others that the aftermarket ones are not always calibrated correctly for our cars.....Might also want to think about a new chip...

Just my $ .02 :wink:

 

[cldturbo]

Lean

I've spent some time looking for vaccum leaks with a spray bottle, no luck. I've replaced the intercooler hoses, all vaccum lines, vaccum block gasket, replaced the PCV valve with a check valve, inspected the MAF tube, everything looks good. I agree, it looks like a vaccum leak or exhaust leak, but I'm not finding any. I have a set of 50lb injectors and a new chip, I was hoping to resolve this before starting the mods, though.

Thanks for the suggestions