MAF - Parts Cannon Story - Paying it Forward

[OBS_Trash]

1996 Chevy 5.7

300,000 High mile truck, nice truck, nothing crazy on mods, (long tube headers, straight pipe) sounds and looks great, lots of miles though.

I clean up the interior, replaced carpet, new dash skin, basic tune up (plugs, wires, oil, air filter, etc)
I Do a 4/6 drop with spindles, flip kit, C-Notch
Replace all suspension items (Bushings, Pitman, IdleArm, TieRods)

After about 6 months of owning it it starts to backfire at 60mph coasting, intermittent rough idle. Code reader says EGR ISSUE. Replace EGR, problem persist and grows to MAF. Replace MAF myself and issue still there. Return MAF since it didn’t fix, Decide before this grows, take to shop and let them tell me what it is.

MAF and Fuel injector cleaning is what is quoted.

So I agree to repairs and and get it back, same issue (intermittent) runs good in cold weather, bad the warmer and humid it’s gets (I’m in Houston Area).

So I start replacing things myself that may cause these issues/codes to happen. (I know, I’ve been chewed out already in another post) but she has 300k plus so replacing parts makes sense and most likely need to be replaced. So I will not go into suuppeerr detail but here she goes.

I fell victim to parts cannon 101. Thinking one more (not that expensive part) could be it. (Mistake I know) but you can Monday morning quarterback all you want. At the time it made sense.

I know I should have checked electrical, I was not familiar with electrical stuff so I postponed, did some learning thanks to replies, learned, bought tools and started later on.

Troubleshooting phases FYI

Replace Parts in order:
Before issue and ran great for months-Plugs, wires, air filter, oil, at Time of purchase

After issue started:
•EGR (first code, replaced twice)
•MAF, (Code) after EGR Cleared
•O2 sensors (Code)
•Vacuum leak check via propane(none found)
•PCV, TPS, IAC, Crank shaft PS
•Ignition Coil
•New Cap and Rotor
•CWT Sensor

I had to lend my work travel car to my sister, so I was forced to drive the truck everyday with issues(Rich, can’t go over 55mpg or backfire)

More time at same shop (5days), I suggested possibly fuel pump, they said fuel pump was good. They sent to another shop that works on older trucks.They said either needs a tune or a new VCM.(I’m thinking he mentioned the straight pipe long tube headers) and ASSUMED it needs a tune.

I figured it ran fine so a tune was not it, ok possibly VCM, but now it’s time to learn to troubleshoot electrical. Thank you YouTube. After many videos….

More repairs:
•Replace harness on crankshaft PS due to Oily exposed wires at harness
•ground straps
•Harness at ERG (bad condition)
• verified MAF harness good (12v, 5v, Ground good) it’s had 2 new MAF’s
• Spider Fuel Injection Assembly
• Fuel pump Assembly
——-bought new distributor but held off…….

basic OBD2 Code reader.
I Clear the 15 codes, 2 codes pop up. And it’s some of the first codes
MAF - Low Circuit (P0102)
O2 - B2S1 Low Voltage

Now what?

So I think, ok been running rich, like crap for some time now, maybe I fried the O2 sensor and Plugs with the bad conditions, bad coke from tail pipe, water/carbon mixture.

Forum discussion (and ass chewing) leads me to download the service Manual for my truck and Order a better scan tool. (Which I thought was like 2k dollars) thank you to the team members for setting me straight.

$50 got a Bluetooth OBD2 and an iOS APP called DashCommand ($10 for app, $10 for 1996 PID) and checked all misfires and MAF g/s P0102 steps.

I check the MAF connection and it dosnt fit great. Service manual says Key on/Engine off needs to be 2 g/s. Mine read 11 g/s. I went and checked connection. Seemed loose, so in made tight, taped up. New reading is…2 g/s. Still drove like **** though.

Decided to get new plugs and O2 sensor since they are probably ****:

You must be registered for see images attach

#7 had the most misfires and the plug looked the worst terrible. Other plugs not so much but still bad for how new they were (or course they bad, drive rich for who knows how long)

I changed back to OEM plugs, not the new enhanced whatever metals for $12 bucks a plug. Bought the $4.50 OG copper ACD plugs.

Start her up, put her in gear and she lopes terrible and dies……..dies! WTF? That didn’t happen before?????

So i take a step back and say (well, if this was day 1 what would I do?)

I unplug the MAF and whaaalaa…..she idles like a champ. Take her for a spin, she runs great! Best ever like day 1.

Finalization:

•Is it possible that the MAF failed and the 2….2!! Replacements were both faulty?? This happened to scannerdanner, seems very unlikely but F-Me if that’s it.

• VCM might be the issue and it can’t read the MAF properly.

• (thanks to a buddy) Is it possible That the truck has a TUNE (it had long tube headers Nd no cats), and when the MAF went out, I replaced it. But the new MAF isn’t tuned, or doesn’t match the tune, or whatever the tune did is causing the VCM not to read the new MAF correct and she needs a new tune???

That’s where I’m at.

Be gentle, I know I couldShouldaWoulda, but that’s what happened. I’ll post an update when i get more info, learn more **** or verify the root cause.

Just hoping this story might help anyone in the future, or someone can learn from my mistakes.

 

[L31MaxExpress]

Check power and ground to the MAF. Also check the fuse for the MAF, forget if it is ECM 1 or 2. It possibly blew the fuse when the first MAF failed which will not keep the engine from starting and running. It will run like crap until it sets the P0102 code though. Ask me how I know this.

Possibility 2 is the MAFs are junk you have bought. I will only buy Delphi or Hitachi myself.

 

[L31MaxExpress]

Double checked, 96 should power the MAF through fuse #15 in the underhood fuse block, labeled Eng1.

 

[movietvet]

Have you considered a compression check? Two reasons: #7 plug condition and mileage?

My reasoning is that, if you have mechanical problems, why throw money/parts at an engine.

 

[Pinger]

Double checked, 96 should power the MAF through fuse #15 in the underhood fuse block, labeled Eng1.

It also supplies the heating elements in O2 sensors and the EVAP system.

 

[OBS_Trash]

Replaced all fuses before the last unplug
, power to MAF is good (Signal 5v, Power 11.8v, ground good) Bought new grounding straps, all original but seemed ok. Cheap stuff so bought anyway.

MAF - Bought the first one AutoZone good quality (returned it), as for the shop, don’t know what they put in. I’m going to buy another one to test the theory.

Compression test - I haven’t, however, once I unplugged the MAF she runs great, no misfires, no soot mixture from tail pipe. All issues cleared up. I will do one anyway just to verify its condition but don’t think it’s driving this particular issue.

 

[l1lartur0]

Probably wouldn't hurt to check the wiring again, not just grounds and around the connectors. If you haven't done so already, check at the sections of wiring that come into contact with anything that it could rub against, which may wear away its jacket and shielding over time and expose the wire itself. I am finding this issue during my own quest of hunting down electrical gremlins. Good luck!

 

[someotherguy]

Replaced all fuses before the last unplug
, power to MAF is good (Signal 5v, Power 11.8v, ground good) Bought new grounding straps, all original but seemed ok. Cheap stuff so bought anyway.

MAF - Bought the first one AutoZone good quality (returned it), as for the shop, don’t know what they put in. I’m going to buy another one to test the theory.

Compression test - I haven’t, however, once I unplugged the MAF she runs great, no misfires, no soot mixture from tail pipe. All issues cleared up. I will do one anyway just to verify its condition but don’t think it’s driving this particular issue.

IMO very little from Autozone is "good" quality. Their biggest sellers are "lifetime warranty" parts that you might replace a couple times on their dime but your labor, until you get sick of messing with it then sell the vehicle along to someone else that will buy new parts because they didn't know they were lifetime warranty parts.

Richard

 

[Pinger]

Re MAF sensor. When I had mine non-functioning (missing fuse) the upshifts were hard. Apparently, the PCM reads from the MAF sensor to set line pressure in the trans. No signal and it resorts to maximum line pressure hence hard upshifts.
The quality of your upshifts may shed light on how well your MAF sensor is functioning.

 

[OBS_Trash]

IMO very little from Autozone is "good" quality. Their biggest sellers are "lifetime warranty" parts that you might replace a couple times on their dime but your labor, until you get sick of messing with it then sell the vehicle along to someone else that will buy new parts because they didn't know they were lifetime warranty parts.

Richard

I agree completely. What I meant is it wasn’t a $40 Amazon special, no it wasn’t the 180$ ACD, they didn’t stock it, it was a Duralast $111, which I guess I consider “good” not best or preferred.

The scan tool showed it reading 11g/s not running. (Should read 2 g/s). So I played with wiring and noticed it had play, fixed it up tight. Then got the 2 g/s reading like the service manual says. I just picked up another (3rd) MAF (Dura ) but I wasn’t waiting for ACD. I’ll take it back if my issue stays. If it changes I’ll take it back and order an ACD. I just need it to troubleshoot today.

Question for group: Can anyone confirm or object to the idea of if it had a tune, a new Functioning MAF would interfere with that tune? I am not familiar with tunes. In my head I would think the Process Variable the MAF is sending is the same. The tune would take that PV and do its thing to tell other things to do certain things or change the valuebtk do what ever. It since the airflow is the same (not a motor fan or a pump) the air flow is flow that is not increased. But like I said I am not familiar with what the tune does to the VCM. Is it possible a new MAF means I need a re-tune? If it even has one, don’t know how to check that either.