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Working on a 98 Z28 thats stock as far as I can tell. There are only 2 codes P137 and P157, that appear to be the rear O2 sensors. The car has 167,000 miles on the orignal engine and is starting to drop in power compared to a year or two ago. Even has a hick up once in a while while idling but not all the time. Can the codes cause the performane issues or are they only to monitor the cats? What would you do to check or test, replace of whatever?
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1994 Z-28 LT1 A4, Supercharger 6 psi, 3.73 Gears, GMPP 1.6 Rockers, LT4 Springs, 42LB Bosch injectors, PCMFORLESS tune, All MSD ignition, Inline fuel pump, SLP sub frames, Panhard Bar, strut bar and rear control arms & LCA relocation, 1LE sway bar, Mid pacesetter's. 3" exhaust to Jegs electric cutout. Nitto NT555R Extreme Drag Radial 275/40R17
The PCM does not take any actions that would affect engine power, when those codes set.
But, the 1998 factory manual indicates the codes could be the result of:
-low fuel pressure
-vacuum or crankcase leaks
Those could affect engine power. I'm not sure why the lean condition wouldn't also show up in the pre-cat sensors, but this is what the manual shows.
Have you checked the fuel pressure? Are the long term fuel trims elevated?
The car was parked for a year while he was in Afghanistan. So hoping fresh fuel and driving it will help. Will check fuel pressure also. Is it the same way as my LT1, with the schrader valve that can be hooked up to and ran up thru the cowl? so you can monitor while driving.
I think it's interesting to note that the manual also states that the pcm will set these codes when the car runs out of fuel.
Also, you might want to check to see if the O2 sensors have any extensions attached to fool the pcm into thinking the cats are ok. That might keep the outputs low.
1998 Trans Am, LS1, Automatic, stock all the way.
Ran fuel through it and it definitely helped a lot but still has a hic up while idling and at triple digits I smelt rotten eggs. I have a cutout so would that keep the cat codes from tripping? I'm going ahead and trying to replace the cats, I want to find some good high flow ones but don't need to pass emissions so I was also thinking just long tube headers and straight pipe with no cats?
I figured cats wouldn't give it a hic up at idle, only higher rpms? For new injectors what would you recommend? Its up there in mileage and I havn't been kind to her on the street. I did the basics (plugs, wires, intake, cleaned maf, etc) What would be some other maintenance needed at this point in the game? fuel filter, injectors, etc?
98 Camaro Z28/SS Clone, SLP lid, Throttle body spacer, Electric Exhaust cutout, Front strut bar, K&N Air filter, poly sway bar bushings, synthetic, Auto
2000 Silverado 1500 5.3 Vortec, 6in lift, mudding rims and tires