STFT are off by 20%.....ideas??

[0mineralgrey3]

Here is my issue. This is a 2014 GT500...mods in sig. Car runs great. It's been 10.30 in 100 degree heat, short shifting, and a bad launch (1.82 normally in the 1.5's). The MPH was low on the passes....low 130's. It has had a drivability issue since it was tune ie: surging under 1/2 throttle. I decided to call Lund and get him to do a remote tune. We have been working together the past few days to get her on the right track. I put some ID1000's in and bought some division X rails from lethal. I also put the new JMS plug and play boost a pump in. I did the initial logs for John and he noticed my stft's are about 20% apart at idle. As you increase RPMS they almost mirror each other....just at idle are they all apart. I removed the division X rails and randomly put the injectors back in. Also discovered the vacuum line for my boost gauge had a hole in it which was T'd in line with FPR sensor. Fixed all that and made a log. STFT's are still off by almost 20%.

I checked for other vacuum leaks, no exhaust leaks...02's are new. I've heard a few people say cams could be out of time, but the car runs great. idles wonderful...starts great...no popping or anything to suspect the cams are out of time....besides the lack of MPH. I'm thinkin the MPH was down due to vacuum leak at the FRPS.

 

[Mike Dj]

Did this just come out of no where or after a new bolt on part?

 

[0mineralgrey3]

Honestly not sure. I'm having a remote tune done and this was discovered. Not sure if it's been an ongoing issue, but most likely wasn't there the first time it was tuned.

 

[Mike Dj]

Have you tried changing the FRPS with a known good one? The same with the O2 sensors. I only say this about the 02s because I work at a high performance shop with in house Dyno and have installed new O2s that were bad from the git or just acted in so many words stupid. One other thing check the 02 extensions for any visual problems check the connectors to see if the terminals have not pushed out. Lastly use a multimeter and set it to OHMs and check each wire in the extensions they should all show about the same amount of OHMs.

 

[0mineralgrey3]

I am not using extensions. The 02 sensors are relatively new, but im going to order new ones. The fuel injectors are new id1000s. I will check plug puns as well

 

[01yellercobra]

I would think a blown FRPS would cause other issues. Namely the car running rich and throwing a code.

Is it a deal where one side is reading correctly and the other is showing lean or rich?

 

[0mineralgrey3]

Yes....it's just a one bank deal. I've even switched 02 sensors bank to bank.

 

[Mike Dj]

slo984now is correct about the FRPS it will affect both banks if the diaphragm is damaged. On that note that was just a suggestion to eliminate any possible sensors that might be subject. I now buying factory 02s is expensive but in the 20 years of working/building Mustangs I have had more problems with aftermarket 02s even denso. If you have a wideband installed get another 02 bung welded in the other side of the exhaust before the X and as close to the collector as possible. See if the readings are the same or if the one bank has a lot of fluctuation if not I would assume the 02 is going bad.

 

[Wiseguy]

if you switched 02's and the same thing sf trims on that bank.... I would look at cam timing, I doubt the i.d injectors would have bank to bank issues new. See if your compression readings are alittle higher or lower on the questionable bank compared to other side.

 

[0mineralgrey3]

Driver side cam out of time. Some how it jumped a tooth. I did a compression check and I was about 10-15 psi down on the entire driver half of the motor.