I scanned my sister's 99 Ford Escort and noticed that the MAF reading is flickering between zero and .32 lb/min on my AutoXray EZ Link scanner. Possible dirty filter or dirty MAF. LTFT is -4% and from what I've read a dirty MAF will generate LTFT of -12%.

I ran across this test: http://www.lindertech.com/newsletters/nwk11~99.pdf.

Of course you need a scope or a DMM that has a min/max recording like some Fluke meters do. I have a Fluke 189 and ran the test but got a bit of a low reading of 3.1v on my 97 Ford Ranger 4.0L. The MAF was cleaned three times just a couple months ago!

I also have a OTC DAT which can't catch this reading!

Anyone else ever ran this test? Hey, Ken??

 

For the low MAF reading I would try cleaning the MAF to see if you get an improvement. If that doesn't work I would run the pinpoint tests. Is this giving you a code or other problems?

Great link, I'll have to look at some of their newsletters.

I have never run that test. Are you sure you got a good reading, they said that you can get a low reading if you don't get a good "snap".

 

[updated:LAST EDITED ON 19-Aug-02 AT 08:12 PM (EST)]Ken:

That's why I'm asking! I think that I got a good snap.

The Escort isn't generating any DTCs. I just noticed the funny value for the MAF PID. If it doesn't rain on me Thrusday, I'll run that test and clean the MAF.

One thing about the test. They mention that a new MAF could give you 4v. In my manual a 3.9v is listed for max but that check is done at warm idle. Not sure if that's a max value for WOT.

I tried it again yesterday which was a bit cooler and barely got above 3v. One reason for the retry was that the OTC DAT has a Sensor function which has a MAF selection which I forgot about. That didn't work either plus it's dual screen is supposed to show frequency also. With my past tool-luck, it read zero! I'll have to contact OTC about this problem. Maybe I have a future in test equipment testing:P

I have to admit that the Fluke read the MAF frequency as a continuous varying value which might be too much for the DAT.

I tried the logging feature on the Fluke but I guess that it's a bit too fast for that feature to catch the max value. The analog bar graph only registers a high of around 2v. The DAT's bar graph doesn't get above 1v.

BTW: The Fluke 189 has the min/avg/max feature but also has a Fast min/avg/max feature which is supposed to catch 250 microsecond glitch. The standard feature is 100 milliseconds.

 

For the Escort I would clean the MAF and see if the value gets above 0.23v @ idle. If you still have a problem with it you might try running the pinpoint tests starting at DC2.

For the Ranger I couldn't find a max voltage in the reference tables for the MAF, were did you find the 3.9v reference. I did find a min/max reference in pinpoint test DC16, 0.23-4.60v. They also had 4.79v listed in the conversion tables. While I was digging around I also found a reference of 13-17gm/sec @ 2500rpm no load, sorry didn't have time to convert the value.

Since you did get a good "snap" then that value does bother me. Are you sure the Fluke is capturing the data accuratly? I would hate to spend $$$ on a MAF thats not needed. Maybe you could find one in the junkyard cheap just to try out. It will also be interesting to see how the Escort tests out.

If you do get that job testing equipment I'll be glad to help you test out any interesting ones.


Have to run, it's a very busy day, I'll keep thinking about this.

Ken

 

Ken:

In the pinpoint test(DC4) they say that the MAF voltage at idle should be between .39v and 3.9v.

The Ranger runs fine, MAF read .79v which is within specs with .32 lb/min air flow which is what I read on a 2002 Ranger 4.0L too.

I think that the Fluke is fast enough to capture the reading, if not I'll be testing a OTC Perception in a few days. I find this stuff very interesting but might have to start working overtime to pay for my toys I could start a automotive diagnostic business with the equipment that I will have right. I hope that I don't find anything wrong this unit!!

I tried to convert lb/min to gm/sec but it didn't make any sense at all.

 

We must have different versions of the Ford manual DC4 is check VPWR voltage to MAF sensor. In mine there is a section called reference values and it has a conversion table gms/sec to volts, if you want a copy let me know. It only gives 5 or 6 values and it doesn't seem to be linear. If the Ranger is running good then maybe wait on doing anything until you get a chance to do a "snap" on the Escort.

The way you are going you'll be able to open a top notch shop, all you need is a lift now.

 

Ken:

I wasn't planning anything for the Ranger, I just check my hook-up on it. I did connect to the Escort last week but seems like the wires didn't jive. If I remember right, the voltage increased on a wire with the wrong color. Red should be B+, black is ground, one stripped is signal return and the other is the MAF signal. It should have been on of the last two but wasn't. I was in a hurry, so I'll recheck that again.

I've got that chart also, I remember it. That's why i was trying to convert gm/sec to lb/min.

Actually, I've seen a portable lift but it might take the top off my garage

 

Ken:

Ran the snap-rev test on the Escort, got 3.44v before the cleaning and 3.88v after. That's better than my Ranger.

The only catch is the connector for a Escort is in my Ranger manual but no color codes for the wires. Comparing to my Ranger, the MAF signal should be on a Lt Blue/Red which is on both vehicles but I seem the get the proper voltage that increases with the throttle on a Brown/Black wire. Ah! I don't get the constantly changing frequency that I get on my Ranger on the wire. I get the changing frequency on the Blue/Red wire on the Escort but get a vary low voltage there.

I got the OTC Perception today but haven't opened the box yet but it's supposed to have a built in database for connections, etc. so maybe it'll clear the wire confusion issue.

 

[updated:LAST EDITED ON 22-Aug-02 AT 10:00 PM (EST)]Ken:

Yep, the Perception showed that I was on the right wire and they show that there are two different MAFs possible! One is High Freq. and the other is Low Freq. Maybe that's why I couldn't read a frequency on the right Escort MAF signal wire.

I'm sure glad that it came with a video because the manual is only a few pages :P

I forgot to mention the cleaning the MAF on the Escort didn't help the low Air Flow real time PID, still zero till the throttle is touched!

 

With the good "snap" reading after cleaning on the Escort you know you are doing the test properly. I see you still have the low reading at idle, how's the idle speed and the IAC cycle? If you want I can look at my other manual that covers all 96-03 vehicles this weekend for more information about the wiring, it's a DVD and I don't have a DVD drive at work. I didn't know they had two types of MAFs. If they both run OK I would just leave them unless a cheap MAF can my way. Have a good weekend and have fun playing with all your new toys.

 

Ken:

No need because the wiring is clear I believe.

Escort idle is 642-702rpm, IAC DC is 34%. Both normal.

The MAF flickering reading of 0/.32 lb/min is the realtime reading with the EZ Link but in capture mode I get .26/.28 lb/min. Capture mode takes a series of reading at a predefined and changable interval. It's set at default of 1000ms or 1 sec. I emailed AutoXray and asked what's the timing of the reading in realtime. I'm wondering if that might be causing the flickering values possibly tied to the high/low freq. MAF difference. Just a guess though!

My sister thinks that her car runs better, who knows

 

Well if you do need anything, feel free to ask.

Yep.

It might be due to that, it will be interesting to see what they say.

It's good that she's happy.

 

Ken:

Looks like this LabScope is going to be a steep learning curve I couldn't get anything that looked like a waveform with the built in set-ups without changing settings for the MAF or IAC and neither looked like reference waveforms in the unit. I'll have to watch the video a few more times!

I found a fast way to kill the engine while connect to the MAF! I was in the meter mode changing what to read and I think it was diode mode. It restarted with no DTCs. Must have sent a wild signal to the PCM.

I got the PC software also which will only download one of the four memory locations. A problem right from the get go

 

Sounds like you'll have plenty to do in your spare time. It always seems to be the same way when we get new laboratory equipment, takes us a few weeks to get all the bugs out. Good luck with your new toys and let me know what the name of your automotive repair shop is.

 

My 97 Ranger went electrically dead this morning, relays chattering, no all dash lights but some were dim, clock was out but door locks worked.

I tried the battery cables, no go. Voltage was good. I've seen this before on my last battery, it was stranger yet! Door locks opened and closed by themselves. Battery shorted I guess!

While waiting for a ride to the auto parts, I was looking at the manual. Ranger was blocking other cars.

I found in the book that the MAF is analog and after looking at the Perception video twice, I see that they have the same sensor list for all makes.