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Discussion Starter · #1 ·
87' VG30I

I recently tore apart my throttle body to have the injectors rebuilt. Despite the other problem it created I have noticed much better throttle response and more overall power. However, it seems as thought I put something back together wrong.

If I'm not mistaken the Mass Air Flow sensor is the black plastic case with two diodes sticking out that is held onto the upper throttle body by three screws. I removed this and all other components before soaking the upper throttle body in parts cleaner for 7 days.

After I cleaned everything up and added new gaskets I noticed that my motor now bucks like a 383 stroker engine at 300 rpm. It also isn't quite what it used to be as far as power goes, much better than with better injectors, but not like it should be.

Upon checking the ECU it gave a code 12, Mass Air Flow sensor. I know I didn't break it when I took it out, I know they are expensive so I was careful with it. All I can think of is that maybe the wire harness is corroded enough to where its not fully functioning.

Any ideas? Has anyone else ever had this problem?
 

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Discussion Starter · #5 ·
Ochno- I'm not sure what you're talking about. I think you are elaborating on some mechanical/electrical component that adjusts idle based on butterfly position? This component was not dunked, see below.

88pathoffroad- All passages were clear because I probed them with a pipe cleaner.

Kaizen- Your VG30 engine has multi port fuel injection and is different than mine, these guys would be able to tell you more though. Use the search function to find out more.

All components were removed from the upper throttle body before soaking. I took a lot of attention to detail and removed all o-rings and gaskets. It was a combination of bare metal and rust going into the bath. My HB has the nickname Mud Doctor for a reason. I have had it in so many creeks and ponds the throttle body had a nice thick coat of rust where the injectors go. Thats why it took 7 days and 7 nights to clean. Thanks for the suggestions guys.

I cleaned up my contacts for the wire harness last night. It seemed to idle better as I pulled into work this morning but I haven't checked the ECU, I'll take care of it at lunch.
 

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Discussion Starter · #6 ·
I cleaned all the contacts, shot everything with electrical cleaner, and put it back together. I'm still getting a code 12. The MAF is working to some extent, when I unplug it the engine stops running. It has two filaments, I was thinking that maybe one side is working but not the other? Possibly it has a bad connection?

If you order a new MAF does it come with a new female harness as well? What is the best method to clean the inside of the female harness? I tried using a really small drill bit to score the surface, but that didn't help much either.
 

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Discussion Starter · #10 ·
Thanks for your correspondence. I checked the circuits for the MAF sensor. It is getting power on the Black wire with a white stripe. This is also true for the ECU signal, therefore the circuits match. There is a green/yellow, green/black, and black that do not have any fire out of the computer.

However, in doing this, I seemed to have completely ruined the sensor. I remember doing a trial where I ran the truck with the MAF unplugged to see which effect it would have. The effect is the same as what it is doing now, refusing to idle.

So it was working for a little bit, and now its not working at all.

But from what I'm thinking, the black/white and black wires going into the maf should both be hot, because there are two hot wires inside the maf. Just logic I guess, I may be wrong. The manual doesn't say anything about which wires should be hot and which should not.

If it were another sensor, wouldn't it pop up on the ecu?

Another problem developed as I poked around on the computer, the coolant temperature sensor flipped as well. Its a code 13, not sure how it happened but it did.

This thing is quickly becoming a mess! :lame:
 
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