Crusty Rusty Leaky Squeaky 67 Step

[Jason7121]

Try unplugging the mass airflow sensor and take it for a drive see if it makes a change

[Jason7121]

If your filter is a type that requires oil sometimes that oil will get on the mass airflow sensor and skew the reading you can also try cleaning the mass airflow sensor with brake cleaner and Shop air

[Vic1947]

Originally Posted by Jason7121

Try unplugging the mass airflow sensor and take it for a drive see if it makes a change

Originally Posted by Jason7121

If your filter is a type that requires oil sometimes that oil will get on the mass airflow sensor and skew the reading you can also try cleaning the mass airflow sensor with brake cleaner and Shop air

The MAF looks like it did the day I installed it, clean as a whistle. However, unplugging it made a huge difference. It smoothed out at idle immediately and I was able to drive the short distance back home with no popping and banging. Do you believe this is due to a bad sensor or could it still be something in the tune?

I'm going to make another run and record data with the MAF unplugged. With it plugged in, STFT's were 25% on B1 and 28.1% on B2. Timing looked stupid too.

[Ol Blue K20]

I sure hope it's something simple.....all this computer stuff is beyond me.

[Jason7121]

I think the majority of your issue is with the tuning. I would still clean the mass airflow sensor and blow it out there I don't think you have a bad sensor

[duke_lbz]

what size is the intake tube? The tune needs to be modified if it is larger than stock size.

[Vic1947]

Originally Posted by Ol Blue K20

I sure hope it's something simple.....all this computer stuff is beyond me.

Me too!

Originally Posted by Jason7121

I think the majority of your issue is with the tuning. I would still clean the mass airflow sensor and blow it out there I don't think you have a bad sensor

I'll give that a try. I think it would be surprising if the MAF became unstable with so few miles on it.

Originally Posted by duke_lbz

what size is the intake tube? The tune needs to be modified if it is larger than stock size.

The 4" aluminum tube is from a kit made by Spectre. I modified it slightly with a 45 degree bend to relocate the filter, but the inside has been smoothed with a die grinder and cartridge rolls in the vicinity of the weld. I think it meets all the criteria WRT the placement of the MAF.

The second test drive with the MAF disconnected predictably set a DTC and the CEL was on the entire time but the truck drove great at all speeds and conditions. The trip to the tuner is 33 miles. I was planning to drive there if the truck would cooperate. Is there a downside to driving it without the MAF connected?

[Jason7121]

No it will be fine driving it. The ecm will compensate for lost signal as you can see with the fuel trim. It sounds like it runs to lean with maf connected. Keep us posted on the tune.

[Low Elco]

Not for nuthin- but it seems theres a bit of a block to the mount could it be the actual sensor isnt out in the airflow enough? Just a WAG from the peanut gallery

[Vic1947]

Originally Posted by Jason7121

No it will be fine driving it. The ecm will compensate for lost signal as you can see with the fuel trim. It sounds like it runs to lean with maf connected. Keep us posted on the tune.

Thanks, Jason, you've been a lifesaver!

Originally Posted by Low Elco

Not for nuthin- but it seems theres a bit of a block to the mount could it be the actual sensor isnt out in the airflow enough? Just a WAG from the peanut gallery

I'm not sure, Chip. The tube came as a kit from Spectre. The MAF mounting pad was already welded to the tube. I didn't make any changes other than cutting the tube and welding the halves back together 180 from stock so the MAF plug would be facing the engine. As you would surmise, I carefully ground the inside of the tube to be nice and smooth to avoid any turbulence. Should not have mattered, as that close to the wall it would be boundary layer anyway. But you know how OCD afflicted people are.

However, if that were a contributing factor, my mill could easily shorten up that pad. I'll see what Bryan has to say next week.

[Low Elco]

If it won't fit in the vise, I have one it will. Holler if you need anything.

Also, there's a related reply in my Big Black thread- http://67-72chevytrucks.com/vboard/s...d.php?t=767247

hope it helps.

[knomadd]

Since you're talking about it, and I had a different but slightly similar issue when I first got my swap running, I'll throw this out there for you.

My STFT (short term fuel trims) were WAY off. I mean WAY WAY WAY off. They stored a 30-34 through all cells of my LTFT just to get my STFT in the 24-28 range. This is showing a severely lean condition. BUT... It smelled super rich. All things pointed to a vacuum leak, a bad connection to the O2 sensors, bad O2 sensors, or a bad MAF (although I could only fine one reference to a MAF sensor issue).

I replaced the MAF and had no change. Cleaned the old one and again, no change. Couldn't find a vacuum leak anywhere either.

So, I talked with my tuner, told him I had a larger intake (3.5" tube) than the van the motor came from, and wondered if he could play with the MAF tables to get it working. His first attemt was to bump it by 20% (so he told me) and it changed, but still in the low 20s for STFTs. 4 more revised tunes and I'm now at a LTFT of -3 to +4 (most at 0 to +1) and STFT of -4 to +11, most at about -3 or +5, depending on load.

All of my research said if you have fuel trims beyond a +/- 15, there are some major issues. Now, that's not to say you can't drive it, but the longevity of the engine would be compromised, however slightly. Talking with a local hotrod shop, they told me as long as I had my STFT in the high teens or low 20s I'd be okay for a short period, but definitely get it checked out before your first oil change.

I say all of this because you may very well have a tuning issue where the intake is allowing more air into the engine than the MAF can register due to the parameters in the tune. You may just need a good tuner to make some adjustments to the MAF tables and it COULD fix your issues.

Good luck!

[Vic1947]

Thanks, Duane! I printed off a copy of your remarks and will add it to my list of topics to discuss with the tuner.

[Vic1947]

Took CRLS to have a new tune done at LSXkilr in Bonner Springs, KS this past Wednesday evening. During the Q&A before Brian got started, he speculated that the previous tune was problematic due to the fuel regulator issue. It was likely that the hard starts and other issues were traceable back to the adjustments made when the regulator was already under stress from the wrong size fuel pump. At least that was the working theory.

Brian hooked up the original MAF sensor and loaded a basic 2010 Camaro LS3 tune into the ECM and fired up the engine. It started on the first try and very quickly began to idle normally. He let it run at idle for a while so the ECM could run various diagnostics and begin learning. Ran it up to city speeds on the dyno and made some adjustments then did the first pull. Several more adjustments and three more pulls and we were done. He took it for a 20 minute test drive and I think maybe made some minor adjustments to the shift points and it was ready for me to take home. Drove like a dream with no popping and banging, surging or stalling.

The numbers weren't all that impressive partly because the IAT was above 140 degrees for the last two runs and the ECM was pulling about 10 degrees of timing out under load. Still it made 333HP@5400 rpm which is a tad better than the 325HP@5400 it made at Justune. Not sure if the comparison is valid since the equipment and conditions were different, but what the heck... it's a work truck. We're headed to a car show over by KS Speedway tomorrow, hoping the rain will hold off till late afternoon.

Just a couple of more things to do. Hook the AK pushbutton start back up and install the new billet door handles. Will post up when they're done.

Dyno Pull at LSXkilr - YouTube

[swamp rat]

Awesome news! Maybe next year you can drive CRLS to Washington for Goodguys!

Actually I thought your exhaust would be a bit louder but i'm sure it was muffled a bit by the dyno.

[sduckworth13]

That’s great to hear Vic!!

[Jason7121]

Great news and makes sense why first tuner was compensating for fuel delivery issues.

[Ol Blue K20]

Glad it's running good again. It sounds great.

[Low Elco]

Glad Bryan got you fixed up. He seems to be a good cat.

[knomadd]

Great news Vic. Hopefully it'll get even better as the ECM learns and you can just jump in and enjoy CRLS like you're meant to.

[Vic1947]

Originally Posted by swamp rat

Awesome news! Maybe next year you can drive CRLS to Washington for Goodguys!

Actually I thought your exhaust would be a bit louder but i'm sure it was muffled a bit by the dyno.

I think before we do another long trip, Mike, we're going to make a lot of local excursions to make sure nothing else is lurking! I did ask Brian about making a pull with the exhaust open, but he said the only reason it would make more power that way was if the exhaust was severely restricted, so we didn't bring on the noise.

Originally Posted by sduckworth13

That’s great to hear Vic!!

Thanks, Scott!

Originally Posted by Jason7121

Great news and makes sense why first tuner was compensating for fuel delivery issues.

I thinks so too, Jason. Plugging in a new base tune made a huge difference right off the bat, so there was obviously something really wrong with the existing one. Probably no way it would have wound up that way without some underlying issue.

Originally Posted by Ol Blue K20

Glad it's running good again. It sounds great.

Thanks, Dale!

Originally Posted by Low Elco

Glad Bryan got you fixed up. He seems to be a good cat.

Yes he does, Chip. He said more to me in the first couple of minutes than the first guy did the entire time I was in his shop. Main thing for me was that he seemed to really know his stuff and didn't get sidetracked by my theories.

Originally Posted by knomadd

Great news Vic. Hopefully it'll get even better as the ECM learns and you can just jump in and enjoy CRLS like you're meant to.

Thanks, Duane. Kathy and I took it to the car show over in Bonner Springs last Saturday and it ran like a champ all the way there and back home. We have some more cruise in's coming up and Kathy has some remodeling plans for the house so I'll take some snaps of it in the Lowe's parking lot.

[cornerstone]

Super pumped for you sir! That's what we all want when we go to such lengths of work. Glad you're able to enjoy the fruits of your labor man! Yall enjoy.

[builtbyKane]

Man I've been hanging by a thread every day to see what the fix was going to be. Sounds like you got it nailed down. The shake down miles are always the nerve racking ones.

[rustytruck50]

That's great news, Vic! I knew you'd get it sorted out and start really having fun!

[tune_1]

Glad to see you getting to enjoy the truck.

Dwight