Air flow meter: Fix or replace?

clay1g · clay1g's Garage

It's looking like the problem with the hesitation problem in my 87 coupe was caused by the air flow meter. Ryland's in Marietta,GA is running a few more tests to make sure it isn't something else. They said the cost to replace the AFM is about $1000. Is that a competitive price? And is it possible to fix an AFM depending on what the problem is? Or when they go bad, are they just replaced?
Thanks

Kurt B · 11-11-2002, 09:04 AM

1000$. Ask him if he's on crack.
I got a new one and they put it in my car for just more than half that...I think 550$.
They're easy to install anyway.
They need to be replaced if broken, I think. You can take them apart (as I did) and screw around with the armature and things, but it didn't work form me.
My car simply ran rich and wouldn't pass smog. But I'm sure there are a lot of things that can go wrong with it. Hesitation is usually fuel/timing/spark related. I doubt your car is hesitating because of the AFM. I"m sure someone will correct me on this one.

JWest · 11-11-2002, 09:06 AM

http://www.pelicanparts.com/catalog/shopcart/911M/por_911M_FUELMO_main.htm

Here ya go - $355

Milu · 11-11-2002, 09:12 AM

If you have to replace AFM anyway, it's the ideal moment to fit a hot film kit.

Rick Lee · Rick Lee's Garage

What are some other symptoms of a bad AFM? My car is running rich and I've tried just about everything to fix it. A new O2 sensor helped, but it's still rich. I have no hesitation at all though.

marcesq · marcesq's Garage

Once the AFM is shot, the module with the reostat (potentiometer or something like that) has to be replaced ie buy a new one.

Like Kurt, I have been inside one of those things and there is no way to fix them with any acuracy.

Richard:

If the barn door and the potentiometer are not in sync the DME might be seeing the wrong door position and therefore not adjusting the mixture properly.

eurocarrera · 11-11-2002, 09:43 AM

What are you nuts!!! I got mine rebuilt for $150 bucks. There is some guy in Los Angeles that does it for a living.

If you want I can call my mechanic and ask for his name and address.

Milu · 11-11-2002, 10:51 AM

A symptom I've had on two different cars was the car stalling when moving off unless you kept revs up. In one case I sorted it by cleaning it up, the other I had to replace. If you take a look at it, it seems even more expensive and overpriced to fix or replace.

Brian Olsen · 11-11-2002, 10:51 AM

Clay,
As noted, you can get a replacement air flow meter for $355. You can replace yours in an hour with basic tools. Easy job. I don't know whether your hesitation is due to the air flow meter. As Milu mentioned, you could also replace the stock air box/meter with a MAF. I did this over the weekend, with a total cost of $690. A pretty easy two hour job. No special tools required. Richard, the kit I installed has two pots for air-fuel ratio adjustment (injector duty cycle) at both idle and WOT. With a digital multimeter, you can adjust AFR to whatever you choose. Lean it out to pass emissions, then revert to your favored settings, easy as pie. If you guys would like more info, let me know.

Regards.

Brian Olsen
bolsen@mc.com

marcesq · marcesq's Garage

Brian:

I would be interested in the particulars of the MAF you mentioned.

Thanks.

Brian Olsen · 11-12-2002, 05:59 AM

Marc,
I got the kit from an outfit named Pro-M. Their web site is www.pro-flow.com. They are primarily oriented toward Ford applications. They are the company that makes the MAF sensor sold by Autothority. I've heard it said the Huntley unit is also made by Pro-M, although I can't say for sure. Both the Autothority and Huntley units are a little different, and it's the proprietary intellectual work that they charge the long dollar for. On the Pro-M home page, follow the "Import Meters" hyperlink for a description of their kit. The kit consists of a cone filter, the 75mm MAF bullet sensor (hot wire), and the adaptor box. Cost is $690. It comes with everything you need to install and run. It takes about two hours to install, and an hour to get to run right. You probably want to install an air-fuel ratio meter, or go to a shop with one, just to make sure you're not running lean. Lean condition at WOT can be disastrous to your engine.
For the ~$1000 you'll save, you'll need to do a little extra work. Like I said, get the AFR checked for optimal performance and safety. Also, you'll need (and I still do) to create a bracket or some other method of bracing the MAF/filter. Currently, mine are being supported by the rubber boot, which is sagging a bit. It works fine, but isn't a nice permanent setup. You'll need to wire in four crimp-fit male spade connectors into the wiring plug for the original air meter. Also you'll need to come up with an acceptable connector scheme for secure connection, and water-proofing. The bare spade connectors are neither. You'll need to use a digital multimeter to set AFR (injector duty cycle) at idle and WOT. The adaptor box has two screwdriver-adjustable trim pots to do this adjustment. The idle adjust is pretty intuitive - adjust for best idle at 800 rpm. If it's too rich, it'll stall. The instructions contain guidelines for setting the WOT adjustment, and doing test runs. I set mine a little on the rich side for a safery margin. Finally, you'll need to find an acceptable mounting location and scheme for the adaptor box. None of these should be show-stoppers. The kit does come with accurate and complete instructions. Their tech. support wasn't great, but I did recieve some good info from fellow Pelicans and Rennlisters. I'd be glad to offer whatever info I can. If you have more specific questions, feel free to get in touch.

I'm also including below a setup/running report I sent to some of the guys who've been helpful.

Regards. Brian

Guys,

Well, the MAF went in on Saturday. Thanks for all the info and pointers you guys provided. The install was pretty uneventful. It did take a while to adjust the idle properly, but the baseline settings are apparently pretty close. I set the WOT pot. to a little rich, just to have a safety margin against running lean. I might go to a shop with a precision AFRM, just to get things properly dialed in, and to make sure it's not running lean. The only remaining items are to clean up the wiring, make a mounting bracket to stabilize the MAF, and finalize the location of the adapter box in the engine compartment. Pro-M supplies crimp-type male spade connectors to connect to the stock air meter wiring connector. Right now, they're just held in by insertion force. I'd like to find a better way. One that will be more stable, and water-proof. Likewise, I've temporarily mounted the adaptor box on the plastic heater duct to the heater blower. This will have to be moved back, out of the way of rain. What type of mounting bracket are you guys using to stabilize the MAF/filter assembly? Right now, mine's just hanging, and the rubber boot is sagging a bit. So, a bit of finish work is left to be done. The total cost of the Pro-M kit is $690, and everything is there to get up-and-running. It's not a simple plug-and-play like Autothority, but for $1000+, I'm willing to do a little extra work.

I did get a few surprises along the way. First, my stock air box was cracked. Second, an annoying rattle I've been unsuccessfully chasing for three years went away. It sounded like it was coming from the rear passenger speaker. I removed the rear deck assembly, and found nothing. So, apparently this rattle was somehow associated with the stock airbox. Puzzling. Third, the car now starts and goes to a strong, stable idle immediately. Previously, the car would hunt for idle, and just generally act very "groggy" for the first 30 secs. or so, when idling. This was even after replacing the idle stabilizer valve, O2 sensor, DME relay, and cylinder head temp. sensor.

So, how does it run? I wouldn't characterize the change as dramatic, but it does run strong and smooth, all the way up to 6k. It does sound a little nastier. It doesn't pop on deceleration as much as it used to. I'd have to do before-and-after dyno runs to quantify any performance improvement, so I really don't know. Worth it? Yup, I'd do it again. Just fixing the funky idle at startup was worth it. Once at work, a guy walked up to my car after I'd started it (cold), and said "man, this thing sounds like ****". Kinda ticked me off.

Again, thanks guys for the helpful info you shared with me. If I can ever be of assistance, feel free to get in touch.

Dan Owens · 11-12-2002, 07:30 AM

You can buy a rebuilt unit from **********.Com for about $150 and install it yourself in about 30 to 40 minutes. It comes with a warranty too.

Dan O.

eurocarrera · 11-12-2002, 11:24 AM

I just heard back from my mechanic. He will do one off rebuilds if they are sent to his shop in Livermore California. But based on the last reply from Dan Owens, it looks like the best way to go would be to send it as a core to Vertex. If you send it to Detlev (my mechanic), he will trun around and send it to his German Buddy in Los Angeles who rebuilds them at wholesale, and sells them to palces liek Vertex, so it is the same thing.