Myron37

Hey Guys,

What a nightmare this POS has been!

98 Camaro SS 243 ported heads,Cam, bigmouth 102, MSD coil pacs, headers. NO CATs.... 2x O2 sensors

I have an intermittent problem that the engine will slowly (30 seconds) ramp up to a runs like **** mode!.. In 6th gear at low RPM it runs so rough that motor shakes like hell.. I have to downshift and run it for a while, then it smooths back out...

IT puts down 411 when running good.. maybe 370 when bad...

It has been to Lethal Performance near San Antonio twice.. they say they tweeked the tune (STFT was WAY off) but on my way home today it did the same thing... It constantly dies when you let off the gas in neutral and coast to a stop.... Total intermittent problem.. I just changed the plugs and wires.. Any ideas what to look at? Can the computer be easily swapped out? maybe the O2's?? HP tuners software didnt indicate that the O2's were bad or out of range....

Thanks,

Myron

LSX Power Tuning

iTrader: (4)

I would put a fuel pressure gauge on it and see what its doing when it changes how it runs.

Myron37

55 lbs under the hood I cant check while driving.

LSX Power Tuning

iTrader: (4)

I have run the fuel pressure gauge out and taped to the windshield before in a bind. I now just put it on the dyno and check it on there.

Myron37

Well, its condition seems to be running super fat... I got a whopping 148 miles out of 11 gallons of gas so I'm thinking its not starving.... its choking! I have two O2 sensors in it and the computer looks for 4... I wondering if that is causing it to freak out... I would hope that the two different shops that "dyno tuned" it would make sure that the ECU is set up properly...

2xLS1

iTrader: (25)

You would hope but sadly that is not always the case. Pretty much have to be data logging it when it acts up to figure out what is going on. Unfortunately that is where a lot of shops lack. The ability to diagnose. And the lack of after cat O2s should have no effect on your problem.

Myron37

I did the data logging with a friend that only does road tuning.. At the time we were just looking to see what was going on.. the Short term fuel trim was pushing 20-40% and I he told me its supposed to be single digits.. Its knock was way off too... Those were the biggies... since I already paid Lethal performance to tune it, I took it back to them.. they said it was acting up when they were logging it and they tweeked the STFT... Other than that they said it had an intermittent problem.... they said that it was fine this morning so I went and got it.... It ran like **** most of the way home.

LSX Power Tuning

iTrader: (4)

I see that almost everyday. We constantly get cars in that have been to several "big" shops and it ends up being something simple that was missed because they either didnt look or just cheated a few tables to get a dyno number and sent it on its way.

Normally I shoot for +-3% on fuel trims when tuning. Your car being a 98 makes it a little more of a pain to tune but it is tunable just takes alittle more time. I had a 98 408 blown vette fight me almost all day today just over idle, if it was a 99 it wouldnt have even been an issue. Some combo's can just be a pain sometimes.
Without you posting your tune and a log no one can really help besides just guessing

Myron37

I called them this morning and told them I wanted them to email all the log files and tune file over to me. I highly doubt they will as they are busy posting videos of their 1200HP TT/E85 cars. I know I paid the same shop rate for the work they did do, but the guys spending 20K or more get all the service.

Is it possible the computer is bad? And can the computer be swapped out just for testing or does it have to be calibrated to my chassis first? I just cant understand why one minute it runs OK than like **** the next.... Is there a way to test the O2's? and MAF with an ohm meter or something?

Myron37

As I suspected... Lethal Performance actually made the "Tune" WORSE... Car ran like **** when I dropped off but it would at least start and idle when it was cold... Now you hit the key and it snaps to life only to drop dead right after.. then you gotta crank the **** out of it to get it to start and only way to keep it running is to massage the throttle and keep the RPM high.... Is it possible to easily swap the ECU without having to match the vin or keys or body control module?