Advice needed after checking codes

[striknein]

I purchased a 94 Ex 2-3 months ago with the following symptoms. I get a rough/erratic idle, low mpg, and black soot from the tailpipe. I have so far replaced the catalytic converter and fuel regulator.

I purchased and hooked up a code reader today and got KOEO codes 157 (MAF Low Voltage fault), 158 (MAF High Voltage fault), 172 (O2 Lean), and 176 (O2 always lean). With the KOER test, I get a 998 failure with error code 157 (MAF failure).

So if I'm interpreting this right, my MAF and o2 sensor are shot, correct?

Also, in another thread it was stated that the 94 Explorers had two o2 sensors. I can only see one after the y-pipe. Where is the 2nd one? [EDIT]: Found it. Man that thing's in a tight spot!

 

[Positive Vibes]

Start with the easy stuff. I would clean the MAF with electronic cleaner first. Then check the PCV or IAC. Also look for loose vacuum lines. I'm sure some of the gurus will chime in here soon. Also try searching for your codes and syptoms on here. The search feature is your best friend.

 

[striknein]

The MAF was cleaned before performing the KOER test.

 

[Positive Vibes]

The MAF was cleaned before performing the KOER test.

And you did disconnect the battery when you did this correct??

 

[Jarubell]

Is it important to disconnect the battery before cleaning the MAF and should one clean it?

 

[striknein]

PV: No, I didn't clear the codes before I did the KOEO test. I did clear them after I finished running the KOER test and now I only get 157 (MAF Low Voltage). I'm guessing I didn't get any o2 sensor errors because I haven't run the car to operating temperature yet.

I just cleaned the IAC, the idle at start improved somewhat but after going to closed loop it starts getting lumpy again. The o2 sensors are definitely getting changed, unfortunately not by me.

 

[BrooklynBay]

It's possible that the MAF is defective, and the O2 sensors are doing their job detecting the wrong mixture which is caused by the defective MAF sensor.

 

[striknein]

It's possible that the MAF is defective, and the O2 sensors are doing their job detecting the wrong mixture which is caused by the defective MAF sensor.

Given that o2 sensors are considered a maintenance item anyway, would I be better off replacing them first? Or do you think it's more likely to be the MAF?

 

[striknein]

Is it important to disconnect the battery before cleaning the MAF and should one clean it?

Disconnecting the battery ensures that the ECU codes are cleared. Cleaning the MAF can improve a rough idle.

I took mine out and the leading edge of the filament was caked in crud. I can definitely see it causing an issue.

 

[BrooklynBay]

Disconnect the battery first, and see if the MAF code comes back. If so, replace the MAF, and disconnect the battery. If you see the O2 codes coming back (I think it might not), then go ahead and replace them.

 

[striknein]

Disconnect the battery first, and see if the MAF code comes back. If so, replace the MAF, and disconnect the battery. If you see the O2 codes coming back (I think it might not), then go ahead and replace them.

Thanks for the advice. Now, where should I look for a MAF sensor on the cheap? Is it possible to buy new or remanufactured for less than $300?

 

[Positive Vibes]

Given that o2 sensors are considered a maintenance item anyway, would I be better off replacing them first? Or do you think it's more likely to be the MAF?

Got a 177,000 miles on mine never had to replace one. YET!

 

[Positive Vibes]

Thanks for the advice. Now, where should I look for a MAF sensor on the cheap? Is it possible to buy new or remanufactured for less than $300?

For really cheap try the pick and pull. Could try ebay. Or just go buy one and check and see if it fixes it if it doesn't just return it.

 

[BrooklynBay]

Check the price on WWW.FastPartsNetwork.Com, and WWW.RockAuto.Com.

 

[a711112a]

replace the MAF. it is the first thing in the sequece of events that happen when you engine is running.
a bad MAF will give your o2 sensors a bad reading hence the codes 172 (O2 lean) and 176 (O2 always lean)

 

[striknein]

I ordered a new MAF from FastpartsNetwork. I'll keep you guys posted when it shows up.

Thanks for all the help.

 

[BrooklynBay]

How much was it with shipping? Is it new, or remanufactured? Do you have to send them your old one as a core?

 

[striknein]

How much was it with shipping? Is it new, or remanufactured? Do you have to send them your old one as a core?

$121.36 for the MAF, 75.00 core, and 9.50 for shipping. They didn't specify whether it was new or remanufactured.

It's worth the expense to get a known working part (hopefully), given that I don't actually know which part isn't functioning. I could have saved about 30 bucks through Rock Auto, but I didn't want to gamble with a cheaper part.

 

[BrooklynBay]

Let us know how everything works out.

 

[striknein]

After receiving a remanufactured MAF from FastPartsNetwork.com (whom I can't recommend enough) and clearing the codes, my rough idle and rich condition completely went away. I haven't driven it yet, but after a few minutes idling in the driveway the CEL stayed off and the idle never went lumpy. I'll let you guys know if the o2 sensors need changed as well.

Thanks to everyone for your advice, especially BrooklynBay and Positive Vibes. I'm definitely looking forward to driving her tonight!

EDIT: After about 15 minutes running, the CEL comes back on. Looks like it's time to change the o2 sensors... I'm taking it in to the shop to have them look over the brake system and fix whatever's causing my ABS light to turn on, I'm going to have them change the o2 sensors too. They're rust-welded into the exhaust, and 20 minutes with penetrating oil and a pair of vice grips couldn't bust 'em.