Tough car to tune for a newbie

[2FAST4U]

I cannot get KR out of my car. The weird thing is I don't know if it is legitimate KR because it sounds more like a miss and the car stutters when it happens. I wouldn't think KR would be so violent.

I can keep it from happening if I ease into the throttle gradually. If I am in drive I have to pull it back to 3rd to get the rpm's up before I try to accelerate, otherwise it will start to stutter and I feel something similar to a miss in the car.

One other thing... When the car is cold on startup (open loop) i can be MUCH more aggressive before the car will stutter.

This is killing me and to make it worse my 17yr old nephew wants to borrow the car for prom in a couple weeks to impress his girl and friends. Won't be very impressive like this!

This is my first post so I hope my attachment works. I'm not sure if it will give you much good info though. They show the tune I was using and the scan I took afterward. Thanks in advance for any help.

[Bill@HPTuners]

I'd like to see what your actual afr via wideband as well as your commanded afr...but commanding ~22-23* on a boosted motor is part of the problem I would think

[2FAST4U]

Thanks for your reply-
Of course I'm at work now (4-midnight) so I don't have my laptop with all my files on it . To tell you the embarassing truth, I don't know for sure what you mean by "commanded" A/F ratio or how to change it . I swear I have been reading like crazy and must have somehow missed that. If I get time at work I'll be researching it and I'm going to be jumping on my laptop as soon as I get home. Again, thanks!

[Bill@HPTuners]

commanded air fuel ratio...just like it sounds...its what the computer commands the a/f ratio to at wot. It looks like its only commanding 11.7:1 which on most stockish cars is ok but something modded its probably going lean in actuality.

[2FAST4U]

OK, I am starting from scratch... I tried making some changes but it got worse so I set the computer back to stock. I forgot to add in my signature before that I added 65# injectors so am trying to figure out how to configure those.... I am going to add updates in here as I go so please add any suggestions or comments...I'm dying to learn/understand this stuff.

Also, I've been told by more than 1 person that it will be nearly impossible to tune this car with the 9.5:1 pistons. Any truth to that? Thanks!

[2FAST4U]

Well, as far as the engine programming goes I have only changed the (Flow rate vs. KPA) to account for the larger injectors. The Mototron website says my injectors flow 60 lbs/hr at 43.5PSI. My fuel rail is at about 45PSI according to my pressure tester. So the Unit conversion calculator says my flow rate is 61.03lbs/hr. So does it look like my Flow rate vs KPA scale is OK? If so where do I go from here....VE table? MAF? Timing? HELP!!! I reset the fuel trims and took a spin...take a look.

[Russ K]

Looking at your scan, the O2 sensor goes to 900+ mv for long periods at a time.
Try replacing the O2. You need a wideband O2, then log air fuel ratio commanded low res and mass air flow hz. Then use the maf error histogram to check and scale your maf table. I would use 12.5 afr on your boosted engine.

Did you check the basics - spark plug wires, bad igntion coils carbon tracked spark plug? Your scan is not showing excessive spark knock.

Russ Kemp