CHarris

iTrader: (5)

I had an interesting issue pop up since the install of the cam and the 2.75 pulley.

I was running around super rich in PE mode and decided to fix that the other day. When I hooked up the wideband I could see that I was in the 10.8-10.9 AFR range and wanted to tune it back up into the the 11.5 to 1 AFR range across the band. When I started taking away top end fuel I had a crazy lean condition happen somewhere in the 4600 rpm and up range. I took out 1% fuel in the upper range and all of a sudden the truck would stop pulling and AFR shot up to 17.x to 1 on the wideband. Needless to say I got out of it VERY quickly.

I was very perplexed by this... If I put the 1% back in it would run 10.9 to 1 AFR again. In no way should 1% fuel change from 10.9 to 18 to 1. Finally, today I was testing again trying to find the solution and it came to me in the form of an SES code...

The P0101 code tripped twice and set the SES light. When I looked it up I saw that this was the MAF failure code and then realized that when this tripped even once it was making the truck fuel according to the open loop fuel table which was commanding a 14.7 to 1 AFR. Well, a commanded 14.7 to 1 with 8 psi boost ended up at about 17-18 to 1 AFR.

To solve the issue I turned off the code so it will not set and, as extra insurance, I set the open loop fueling table to a 25% richer setting at 100 kpa. This will never happen again now.

As near as I can tell, when I leaned it out a little (remember it was a 1% change that started this issue) I guess I made it max out the MAF just a little sooner and it was enough to freak the whole thing out. If I had not been watching the AFR on the wideband I would have burned this engine. The truck just nosed over hard and kept reving... no pinging was adible or anything.

Word to the wise... if you truck stops pulling under hard acceleration get it looked at quick I can't stress the value of a wideband enough!

Hope this helps someone else... in my case the disaster was narrowly averted.

BeefTip

glad you caught that, im surprised that the maf is already maxed out though. Have others had this prob at this boost level.

BeefTip

awesome rides by the way

greentahoe

iTrader: (2)

I really hope you are compiling a list of issues you faced and what you did to correct them. I havent spent more than a couple hours total with my HPTuners... Where you logging this on the laptop or do you have an A/F gauge as well?

CHarris

iTrader: (5)

I post everything back in here on this forum. I know the p101 issue came up before somewhere. I couldn't find it when I looked this time around so I made sure to post mine up to better the chances of the info reaching the next guy.

Its important to keep in mind that mine only tripped a SES light the 7th or 8th time it happened. So if any of this sounds familiar to your situation it could be the problem.

I could feel the power loss when it happened. The Dynojet Wideband Commander gave me a visual reference for what was happening. If a person only had the scanning software they could see it as the O2 voltages dropping way down (going very lean). The best tool is the wideband, though.

02sierraz71_5.3

iTrader: (2)

have you tryed running in SD?

just out of curiosity I see youve got 60lbers what is the injector duty cycle whenever you start having fueling problems

02sierraz71_5.3

iTrader: (2)

have you tried running in SD?

just out of curiosity I see youve got 60lbers what is the injector duty cycle whenever you start having fueling problems

CHarris

iTrader: (5)

SD... yes I have run there for initial tuning but its always better to run the MAF if possible. ESPECIALLY in a truck so heavy (think high load all the time...). Honestly, I think that SD is only good for tuning your VE tables in the non-boost region.

60lbers... I seriously hope you're not suggesting that they aren't big enough and second guessing the info I stated in the first post. The problem was the code and what I did and wrote solved it. The injector constant is in the 2.0-2.2 ms range at idle now and is in the 13.4-14 ms range at 6000 or so RPM. Lots of injector left.