99 silverado LTFT, U7198

[Wireman134]

Maf Translator for LS1 based engines new here http://www.fullthrottlespeed.com/ItemDe ... 50LS1TRANS

I found mine used on LS1tech.com in 06' for $75 There was a web page back then that showed how to splice it in the truck harness. If you get one I'd try to get a used one. I can go over the colors with you if you want. There are allot of these being removed for custom tunes if you are patent you may pay less than I did. You just have to monitor the LS1/Corvette forms out there. Ebay has had some too.. http://cgi.ebay.com/ebaymotors/ws/eBayI ... 3348382634

[jackd]

Are you saying that 13.2:1 is going to be the best WOT AFR? My 01 is at 12.7:1 and the O2's are reading about 850-860mv. I just watched the playback on dataviewer.

[Wireman134]

Just a ballpark, every engine is different and the conversion seems to vary from mv to AFR with different devices and exhaust temps. Seems to be a narrow band in image. accurate from .800v-.400v

http://robertisaar.co.cc/web_images/afr ... age_nb.jpg

[jackd]

Should it be safe to use the same range from my 2001? I just spent some time working with it and came up with -17 on the LTFT and -6 on the PE Enrichment. This put the mv in the same range as my 2001.

[jackd]

I am enjoying this learning experience so I hope everyone doesn't get tired of me posting. I have been messing with cars and trucks all my life, but this type of tuning is new to me.

I noticed a difference in the logs for my 2001 compared to the logs for my 1999. At idle, my 2001 will go -1 to -2 on the LTFTs which makes sense because the throttle plate is closed causing less air flow. On the 1999 at idle, the LTFTs will go +5 to +7. Both have been tuned to "0" at cruise speeds.

Now I am thinking there has to be some type of small vacuum leak somewhere that is causing it to lean out at idle, but the truck runs incredibly strong and smooth. 06MonteSS, Go ahead and say "I told you so"!

Does anyone know of any problem areas for the 5.3L engine? I am not sure where to start looking. I am considering removing the intake and inspecting for cracks and replacing all gaskets. While I may not gain any more power, I am sure this is affecting fuel mileage.

[06MonteSS]

[jackd]

You know that's not cool!

[BC_Leadfoot]

One problem I ran into with my 01 Sierra is over oiling the K&N. The filter oil sucked in and wiped out my mass airflow sensor. I tried cleaning it but it never ran right until I replaced it.

[jackd]

Well I found out that a friend of mine who owns a shop has a smoke machine. I took the truck by today and we checked it out. I found a very small vacuum leak in the line to the fuel pressure regulator and a larger leak coming from underneath the intake. So, I hate to say it, but 06MonteSS was correct.

[06MonteSS]

ok, NOW I'll say it... told ya

and why would you hate to say it?? I was trying to help you out, letting you know something was up with your vehicle... been doin this stuff a long time man, thousands and thousands of data logs... I know the symptoms...

seriously tho... glad you found it... good thinkin with the smoke machine...

[jackd]

I appreciate the help. I'll keep you posted on the repair. It will probably be this weekend when I get it fixed. Thanks again.

[jackd]

I have replaced the intake gaskets and cleaned a badly gunked up throttle body and intake, replaced PCV valve and hose, and replaced other vacuum hoses. The vacuum leaks are obviously fixed now as the LTFT's act much more like my 2001. At idle now, the LTFT's are hanging around 0 to -2.

But, my LTFT adjustment is still the same. I reinstalled the factory tune, drove a few miles, upgraded to 9r17, reinstalled the 87 octane tune, drove a few miles, ran a log, and adjusted to -18. I believe I will end up back at -17. I even disconnected the EGR valve and it only made +2 difference.

Strangely, the PE does not appear to need any adjustment now.

I do not have any exhaust leaks.

Anyone have any new ideas or am I now in need of either a MAF translator or a custom tune?

Thanks.

[jackd]

Anyone?

[Wireman134]

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