1998 Subaru Outback: replacing MAF makes stalling worse!

[latitude xt]

Hello again,

It's been a few weeks since my original pleas for assistance.
Yesterday, my husband installed the eBay MAF, hoping to solve the
problem of frequent stalling when idling, especially after a long-ish
drive. This is what he did:

- disconnected power cable
- unscrewed clamp from right side
- unscrewed 4 bolts from left side
- pulled out old MAF
- reversed procedure to put in new

(BTW, I'm very impressed with husband. He's not mechanically inclined,
but approached this job with gusto, even when several nuts and bolts
dropped into the air filter or through the car to an unreachable spot
beneath the car. He was feeling pretty good until...)

Unfortunately, the stalling is much worse now. The car starts up fine,
but only runs if we rev it up. The moment you take your foot off the
accelerator, the RPMs slide down to zero and it stalls out. In youse
guys' original suggestions, the IAC and plug wires were also
mentioned. Looks like an IAC on eBay is about $60... should we keep
going??

But why did replacing the MAF make it worse? Of course, the used MAF
might have been worse than the original, but it seems weird...

Thanks for any ideas!

--Emily

 

[johninky]

Hello again,

It's been a few weeks since my original pleas for assistance.
Yesterday, my husband installed the eBay MAF, hoping to solve the
problem of frequent stalling when idling, especially after a long-ish
drive. This is what he did:

- disconnected power cable
- unscrewed clamp from right side
- unscrewed 4 bolts from left side
- pulled out old MAF
- reversed procedure to put in new

(BTW, I'm very impressed with husband. He's not mechanically inclined,
but approached this job with gusto, even when several nuts and bolts
dropped into the air filter or through the car to an unreachable spot
beneath the car. He was feeling pretty good until...)

Unfortunately, the stalling is much worse now. The car starts up fine,
but only runs if we rev it up. The moment you take your foot off the
accelerator, the RPMs slide down to zero and it stalls out. In youse
guys' original suggestions, the IAC and plug wires were also
mentioned. Looks like an IAC on eBay is about $60... should we keep
going??

But why did replacing the MAF make it worse? Of course, the used MAF
might have been worse than the original, but it seems weird...

Thanks for any ideas!

--Emily

Check the hose between the throttle body and MAF. Good chance one of
the smaller hoses that attach to it came disconnected. Make sure the
hose clamps are tight and just verify everything unplugged got plugged
in. The IAC can be cleaned. Often the problem is there is a build up
of crud inside it. Whatever stuff you use to dissolve it, apply it in
a way that none ends up in the little motor.

 

[S]

Hi Emily!

In addition to what John has said, swap back in the original AFM. (I
know, it's a pain in the a__; it'll be way easier the second time
thru, hubby's _the expert_ now ;-) If the idle improves back to where
it was, I'd be having conversation with my trading partner.

Sounds electrical to me, tho; be sure the electrical plug is fully
mated.

If, OTOH, the original AFM does the same thing, and you've verified
that everything is hooked up as should be (Check to be sure the lip of
one of the rubber air intake hoses didn't get turned under during
reassembly, it's easy to do.), this could be a sign that the idle
control valve has finally stuck closed. If the engine will idle with a
bit of pressure on the accelerometer, but stalls as soon as you lift
your foot off, good bet that that is what has happened.

They're not a whole lot more trouble than the AFM to replace, as I
recall; two, or maybe four screws, out with the old, in with the new.

If it will help, I can send you the appropriate sections from a '98
Forester service manual. It probably will not be exactly the same, but
it will likely be very similar.

ByeBye! S.

Hello again,

It's been a few weeks since my original pleas for assistance.
Yesterday, my husband installed the eBay MAF, hoping to solve the
problem of frequent stalling when idling, especially after a long-ish
drive. This is what he did:

- disconnected power cable
- unscrewed clamp from right side
- unscrewed 4 bolts from left side
- pulled out old MAF
- reversed procedure to put in new

(BTW, I'm very impressed with husband. He's not mechanically inclined,
but approached this job with gusto, even when several nuts and bolts
dropped into the air filter or through the car to an unreachable spot
beneath the car. He was feeling pretty good until...)

Unfortunately, the stalling is much worse now. The car starts up fine,
but only runs if we rev it up. The moment you take your foot off the
accelerator, the RPMs slide down to zero and it stalls out. In youse
guys' original suggestions, the IAC and plug wires were also
mentioned. Looks like an IAC on eBay is about $60... should we keep
going??

But why did replacing the MAF make it worse? Of course, the used MAF
might have been worse than the original, but it seems weird...

Thanks for any ideas!

--Emily

Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

 

[GeoDoc]

98 Outback Stalling - Resolved!

Have had problems with my 98 outback (2.5) - manual, stalling during deceleration. Needed to turn key off and restart then OK. If I decelerated in neutral it was OK, If I downshifted and coasted to a stop then it would stall. Was bound and determined to troubleshoot this myself. It through a bunch of codes so I started replacing parts....

Parts that I replaced but did not help....

Idle control valve
Mass airflow sensor
Upstream O2 sensor
Vehicle speed sensor
also tightened screws on back of speedo

Came across thread that talked about cleaning the throttle body Butterfly valve where air enters the engine. There was lots of discussion about how to and how not to, but long story short I removed the plastic air intake, sprayed some carb cleaner in a clean rag, manually opened the valve and wiped out all the varnish in the throat and the valve edges.
Took me all of 10mins. While I did this the neg. lead was removed from battery. I then turned the key to the ON position for 5 min. and then started it and let it idle (no revving) for the ECU to "Learn to Idle". It worked!!

Apparently the gunk was preventing the throttle valve from closing properly. As I understand it, sometimes the valve would fully close and sometimes it wouldn't and the result is that the ECU would get all sorts of errors.

So, before you start replacing expensive parts, consider cleaning the throttle valve -- you might just get lucky!