I posted the following question in the PCM Diagnostics & Tuning forum and it was suggested that I post it in the internal forum. So here I am.

https://ls1tech.com/threads/showflat...14&fpart=1

If anyone has any ideas about what could be wrong, please feel free to comment.

Thanks,

Jim

 

O.K., Obviously I don't know how to attach a link. So here's the original question:

Last year I ran 13.48 @ 106.41 mph with a 2.21 60'. Yesterday I ran 13.7 @ 104.2 mph with a 2.28 60'. Between the two runs I tuned the car with a MAFT to 13.2 a/f (that equated to 0.93 on the 02 sensor, previously it read 0.98). In addition, I descreened my MAF, removed both baffles in my hood, installed NGK TR55s, Pro 5.0 shifter, and ployurethane trans and motor mounts. Now my e.t. is 2/10 slower and I trapped 2.2 mph less.

My SES light is not on, but the car is running rough. Prior to going to the track I though that I was just feeling additional vibration due to the polyurethane. Now I think I must have hurt the engine some how between the two track outings and the polyurethane made the problem more obvious. Unfortunately, I did have a 3rd gear to 2nd gear shift at about 100 mph (before the Pro 5.0 and between the two track outings). I thought I caught it in time and pushed the clutch back in. Could I have possibly broken a spring or bent a push rod and not realized it until I put the motor mounts in? Is there any was to check with Atap? Or does anyone have an idea of what might be wrong?

Here's some additional info from that link:

if I hold the engine at 1300 rpm's it vibrates the steering wheel pretty good. Once I bring it up to about 1500 rpm's it smooths out considerably. However, once I get into the higher rpm's (say above 3000) it starts to vibrate again. This is kind of confusing me. I definitely feel that there is something wrong with the car, I just don't know what or where to start looking.

Well I just disconnected the MAFT and logged a couple WOT runs. The only thing that I found unusual is: O2 Sensor (B1S1) = 0.956 and O2 Sensor (B2S1) = 0.919

It seems the drivers side bank is running a lot richer than the passenger side. Any other time I logged WOT runs (either with or without the MAFT) the drivers side and passengers side O2s were always close to each other. I don't know if this means anything, but I found it unusual.

Sorry for all the cutting and pasting but I couldn't figure out how to attach the original link.

Any comments would be appreciated!!

Thanks,

Jim

 

I'm no expert, but I seem to hear alot about how de-screening the MAF can cause problems as well as be beneficial. When I was having my car tuned, Speed inc put stock ends (with screen) back on my car 'cause they said my de-screened ends would f/u the tune and that the 02's would end up all over the place. Do you have stock ends you can put back on to try?

 

Thanks for the reply.

Actually, I never removed the stock ends. The only modification that I did to the MAF was removed the screen. The screen got damaged when I removed it, so I can't put it back on. The only option is to buy a new MAF.