bad MAF?

We just had gotten the LT1 swap running sweet and then it cut out on the road. Circumstances resulted in having it towed home.

Went though the usual diagnosis, good fuel pressure, checking all the values in the ignition related stuff. Could not pin anything down and I was just about to consider a failed opti. But then I randomly decided to unplug sensors one at a time to see if anything happened. Well, it starts and runs with the MAF unplugged. Plug the MAF back in with the engine running and it will die after a few seconds. It had not thrown any codes, but obviously there is now since I unplugged the MAF it's running in limp mode with MIL on and fans running, but no codes prior to point me in any direction.

So, is this good evidence the MAF is the actual culprit? Got 12v to the pink wire at the MAF connector with KOEO.

If it needs a MAF, should I stick with AC Delco or is there a better choice? I see Delphi too. Looks like the Delco units are reman and the Delphi are new.

unless you have badly torn the boot between the maf and throttle body, you probably have a dead maf or busted wire. you could probably just get another maf from an auto wrecker if you wanted a quality one

Quote:

---

Originally Posted by steveo

unless you have badly torn the boot between the maf and throttle body, you probably have a dead maf or busted wire. you could probably just get another maf from an auto wrecker if you wanted a quality one

---

Cool thanks. I just did some cross reference at Rock Auto and it looks like some other GM vehicles use the same MAF. B and F bodies pop up now and then in the yards near me but it looks like some of the GM trucks and SUV's use the same MAF. Tahoe, Suburan, Yukon, K trucks, C trucks, Express vans, this should be easy.

Edit: Just checked one local boneyard inventory online and they have 7 of these vehicles in stock. At least one is bound to have a Genuine GM MAF on it. I think they run about $25

there may be other mafs that fit but have different calibrations. if you've already tuned to the fbody maf thats what you should get. the bbody maf has a different calibration too.

Quote:

---

Originally Posted by steveo

there may be other mafs that fit but have different calibrations. if you've already tuned to the fbody maf thats what you should get. the bbody maf has a different calibration too.

---

Interesting. At Rock Auto they show cross reference to other vehicles that share the F body MAF part number and you are correct, the B body LT1 cars are not included in that list. But interestingly, Vortec, LT1 and LS engine equipped cars and trucks are included under the same part number. So, the MAF we just bought came from a 2001 GMC Savana van and its compatible with the 1994 Z28. Heres the listing at Rock Auto and if you click on the part # 2133457 on the AC Delco line you'll see the cross reference vehicles.

Even more interesting is this. We just went and got the used MAF before we took the suspected bad one out of the wagon. Low and behold we discovered the screen had caved in and shorted the sensor. Pulled the screen out and the thing fires up and runs like it should. So now I have a spare MAF which is just fine.

On the screen idea, I now have a screenedMAF and an unscreened MAF. Is there any benefit in running unscreened in my application? The only mods on this LT1 are 1.6 roller rockers, 52mm TB and long tube headers.

Here's the pic of the caved in screen. Damn I should have just checked that initially on the side of the road. Could have just driven home.

Quote:

---

But interestingly, Vortec, LT1 and LS engine equipped cars and trucks are included under the same part number.

---

just because a chinese knock off universal maf sensor says it works with 100 different vehicles, because their only qualifier is that it fits/starts/runs doesn't mean that all 100 vehicles actually have the same maf sensor with the same calibration curves.

rockauto is great for finding cheap parts but not necessarily the right way to ensure fitment of a critical sensor like a maf. they run cross reference chains to universal fit stuff and back in both directions to ensure the greatest amount of bottom-of-the-barrel cheap parts show up in the list.

a vortec or LS1 maf is definitely not the same with regards to airflow vs hz output and if this is a car you're actually tuning you need to totally recalibrate to that new maf

Quote:

---

Is there any benefit in running unscreened in my application?

---

no, but again, will throw off your calibration a bit. we've always figured that screen is probably there to reduce turbulance for more accurate readings (which doesn't make a huge difference in reality, but make sense from a design standpoint) and to stop crumbling peices of that air filter you haven't changed in 200,000 miles from ending up destroying your maf wires

Okay stevo thanks.

Actually it didn’t like the Savana MAF. It made the pcm add too much fuel and made it way rich. So I put the Camaro MAF back in without the screen. It didn’t like that either. Ran out of time for the moment but later I will remove the screen from the Savanna MAF and put it on the Camaro MAF. Then I’ll have the proper MAF with a good screen. I’ll post back if that finally fixes it.

it's' totally possible the fbody maf was damaged beyond repair when the screen contacted the wires. they're really sensitive. you could totally use the wrecker maf if you wanted to just recalibrate your maf table for it. you should also datalog and see what kind of AFGS you're getting when trying these maf sensors out. if you have an old datalog, you could easily compare aganist known good maf calibrations (you should get similar airflow for a particular MAP x RPM from a 'known good' log)

oh another thing you might not realize is that if you've been driving around without a maf, and you plug one back in, your BLMs are probably now trimming for your VE table and will take a bit to catch up and trim for MAF instead. it might be good to clear your BLMs when reconnecting the maf, before starting the car.

Back in business! Put the screen from the Savanna maf on to the Camaro maf and put it back on the car. Cleared the blm and drove it around for 30 mins running it through all the various driving conditions. In the beginning of the drive it was still acting up a bit but it gradually got better. It's now back to happy and running great. The camaro maf survived and it wasnt a waste getting the maf from the Savanna since we needed the screen anyway.

……..and I’ll keep the sensor portion of the Savanna MAF with consideration towards fiddling with its calibration. It’s good to know that’s possible. Thanks for the info Steveo

no problemo. you can pretty easily figure out a MAF calibration as the curve itself is pretty easy to find by hand once you've got a few good data points, it's the upper RPM ranges where you're pretty much going to be in power enrichment that are hard (unless you wideband tuned that thing) but again you can kind of guess the curve based on the other data.