Once again, my 157 comes back.

[cRaZySHO.]

A while ago, I had a problem with my 157-MAF signal too weak. And it now returns! Only this time, my car bucks at certain times, and idles like crap, and is running on the verge of dangerously lean.

I get no pinging at any throttle postion, but my AF gauge, at WOT is two lines away from the lean range. Normally at WOT I'm at the top section of Stoich, and have one green and one yellow LED.

And the bucking problem usually happens when I am holding a constant throttle. It has happened at all speeds, and in all gears. It feels as if the gas pedal is released, and then sharply stabbed again.

And my idle goes down to like 500rpms, and then jumps up to the normal 800-950rpms.

I took out my 73mm MAF and put in my stock unit. I then cleared the codes, and reset the EEC per SDPATT's directions. I then start the car, and go for a drive. The car seems fine, then the light returns, and it begins to buck.

The only other thing I can think of is to replace my MAF harness with a new one. I ran a search on this, and no one else had this problem except guys running the PRO M. And they don't have the same symptoms. They all have the bucking, but no one else reported the lean condition, or the rough idle.

I'm lost on this one. Another thing, what should my MAF voltage be at idle? And at WOT? I have my A'Pexi SAFC hooked up, and it reads sensor voltage, and it reads my MAF and O2's for me.

Also my 02's are both brand new, less than 5k on them. My ACT, and TPS are also brand new, less than 5k on them.

Sorry for the long post. Thanx in advance!

Cory

<small>[ January 14, 2003, 02:54 PM: Message edited by: crazySHO88 ]</small>

 

[Chrisssssssss]

With me, I had similar symptoms with the RPM's fluctuating, but not the car bucking like you say. I replaced my MAF with another one and it seemed to cure the problem. I would look at your IAB valve also and follow the cleaning procedures on www.shotimes.com and then reset the idle again when you reinstall it. See what happens. Just a thought.

 

[sdpatt]

You need to do the "wiggle" test of the wiring harness for the MAF. You replaced the MAF body, with the OEM, but used the same electronics. The electronics do not know what they are bolted to, only that they must send a current to the EEC. You may want to try sustituting a known good MAF MAF electronics box and see if you still get the error. If so, it is the black box. If not, it is in the wiring harness.

 

[cRaZySHO.]

Scott, maybe I should borrow CrizzaSHO's MAF and see if that cures the problem. His 94 MTX is in my driveway with blown diff. His MAF works fine. Trial and error I guess is my next step. And if it's not the black box, can I buy the harness? Or will I have to splice my own?

Also, Scott, do my symptoms sound like a direct MAF glitch?

 

[jthomas68]

It does sound like the MAF is getting bad readings,i had the same experience of bucking when my MAF came loose one day(don`t ask).Disconnect the MAF and see how it runs,you will get a CE light,but the computer won`t get bad readings and try to compensate for it.This should at least rule out the MAF itself.If you want to try an electronics box specifically,i have a spare box if you want to pay shipping to you and back.

 

[cRaZySHO.]

JT, thanx for the offer. I'm going to try Crizza'a MAF first. If it doesn't work, I'll let you know.

 

[sdpatt]

Easy things first. I would try wiggling your MAF wiring harness as far along the bundle as you can trace it while the engine is idling to determine if you can duplicate the symptoms. Also wiggle the throttle position sensor wiring since this could also cause similar problems. Next try unplugging the connector at the MAF to leave the EEC in open loop mode, bypassing the input from the MAF. If this does make a difference, then swap the sensor electronics with a known working sensor. You really only need to swap the black box portion of the sensor since the aluminum body does not cause the error you are seeing adn only requires a screwdriver. Be careful with the filaments on the bottom end of the sensor box.

Is the 157 the only code you are receiving? Any other information would be helpful.

 

[jthomas68]

No problem Cory,just let me know.I`d just let you have it,but i`d like to keep one as a spare,just in case.

Scott-it looks like you and i were on the same page here.One question though,unplugging it will smooth out the problem if the box is the problem,but how does un unplugged MAF affect a/f readings?I`m just wondering if will will run in "limp" mode,or cause a lean condition.

<small>[ January 14, 2003, 03:23 PM: Message edited by: jthomas68 ]</small>

 

[cRaZySHO.]

Hey guys, I just tryed to take Chris' MAF black box out, and his screws are stuck. I don't want to force it, because a torx head will round out easily. But I will try the wiggle test Scott.

And Scott the other code I almost always get, but doesn't throw a CEL is a 542- Fuel pump open relay not grounded, or something of the sort. I know it's a 542, but the description I don't remember. Thanx again guys.

The only thing that scares me is the extremely lean condition at WOT.

 

[cRaZySHO.]

OK, I found the problem. I unplugged the MAF, and all problems went away. How long can I drive like this with no damage to my motor? I only drove to the store earlier. And no bucking, no rough idle, and no lean condition. And my 02 voltage went back up to it's normal .7XX volts at WOT. And Scott, I did the wiggle test on the two sensors(TPS+MAF), but no dice. So I will now have to pick up an MAF. I think I just may spring for the ProM 75 unit. Thanx again guys!

Once again, the SHO Forum come through in the clutch!

 

[sdpatt]

You don't need a new MAF, but only the electronics. Check out a salvage yard or an A1 Cardone remanufactured on AutoZone.com for $76.

If you can't get the electronics off of your friend's, just swap the whole MAF sensor. Doh!

<small>[ January 14, 2003, 10:53 PM: Message edited by: sdpatt ]</small>