7.4L MAF Issue?

[Tom P]

The tech said they tested all the circuits and that was where the fault was. He was very confident. That still doesn't solve my lack of power issue, however. But the funny thing is, something similar happened a couple of weeks ago. And it was under very similar circumstances. Pulling a heavy trailer and then heavy breaking causing the truck to die. Only the first time it happened the truck came right back to life so it never clicked that these two instances. It's probably of my own doing because I keep a rather healthy key chain weight so probably when I hit the brakes, the keys swing forward and put a different kind of stress on the switch. I've heard of this issue before

 

[Supercharged111]

On my 88, the ignition tumbler's rotation actuated a pushrod and the switch itself was closer to the bottom of the column. I can't imagine much changed, but you never know.

 

[Tom P]

Well I won't know for sure until Monday now. And of course my scanner shows up yesterday just in time for the truck to make it to the shop. Thousand dollar question is, do I let the guys hook it up to their big boy scanners and let them find the problem or do I take it home and try to continue cobbling it myself...?

 

[Supercharged111]

For the ABS ****? Might be best for them if yours only reads PCM. I still haven't clicked to see which you ordered. . .

 

[Tom P]

For the ABS ****? Might be best for them if yours only reads PCM. I still haven't clicked to see which you ordered. . .

No I ordered the scanner to diagnose my lack of power issue. Just so happened that right before the scanner showed up the truck died of a completely unrelated issue. No ABS issues that I know of

 

[Tom P]

For the ABS ****? Might be best for them if yours only reads PCM. I still haven't clicked to see which you ordered. . .

I ordered the Foxwell Nt201. Seems to be a decent unit. Plugged it into the wife's Denali and had it run the live data.

So I can assume that I'll be looking for a bad value in the O2 sensor banks to confirm that diagnosis. The Denali read .46 volts average while the Key was on but not running and then after it warmed up it was reading .75 volts while running warm. I believe Christian said we were looking for either a 0 or .999 to confirm that. It also gave MAF readings and MAP data. I'll use the Denali as more or less of a baseline for the truck when I get it back tomorrow. I know the Denali is a different Generation of engine (2006 w/ 6.0) but the values should at least be in the same ball park

 

[Supercharged111]

Should be the same pretty much.

 

[Tom P]

Getting back to the run issue, I've had a couple of our techs here (work at a tractor dealership) suggest taking a closer look at Cam and Crank pos sensors. My symptoms don't seem to fit the crank sensor issue but what about cam sensor/ distributor? I know the distributors on these trucks are common failure parts but replacing them isn't exactly as strait forward as the old style, right? Pretty much need the techII scanner to set it up?

 

[Christian Steffen]

Getting back to the run issue, I've had a couple of our techs here (work at a tractor dealership) suggest taking a closer look at Cam and Crank pos sensors. My symptoms don't seem to fit the crank sensor issue but what about cam sensor/ distributor? I know the distributors on these trucks are common failure parts but replacing them isn't exactly as strait forward as the old style, right? Pretty much need the techII scanner to set it up?

Your scanner may be able to read cmp retard. I have an app that can do it through a Bluetooth adapter. Just need to get it at +/- 2 degrees

 

[Supercharged111]

I've had mine as far as 90 degrees off and it still never did what the OP is describing. It was 29 off when I did the distributor gear, dually is 11 off and not sure where the blue truck is since putting the intake on. Not discounting the importance of setting it correctly, just thinking from a troubleshooting point of view. Then again if he's 120 off who knows.