Subaru Forester Owners Forum banner

1 - 20 of 21 Posts

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #1
There seem to be a lot of people with similar issues to mine.

Still trying to figure out what is going on as there aren't any definitive codes thrown by the ECU. Does any one know if an IACV is on a 98 2.5 NT? Also, the engine begins to stall at the 5 min. point, almost to the second. Anyone know what is going on in the ECU that would bring a sensor or device into operation at this time?

This car is starting to really PMO.
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #2
Update: Tested the rear O2 sensor. 450mV out. Works fine amd throws a code when disconnected. Drove the car when disconnecected and still craps out. Found and disconnected the front O2 sensor. Tested it and found it only gives a 24 mV output. Likely fault. Tried to drive with it disconnected but still have the stalling issue. Waiting on a scan tool to log the symptoms and will update when the deed is done.
 

·
Registered
03X MT
Joined
·
846 Posts
I'm thinking that a failing/failed sensor "should" throw a code.

Some time back I had a stalling symptom (not at a precise time) like yours. On mine it would stall and then idle roughly and less power. It ended up being caused by a plugged filter.
 

·
Registered
04 Forester X, MT
Joined
·
1,039 Posts
fuel filter is easy and cheap to change on a 98. could also be crap in the tank.

IACV has a blue sticker and is mounted on top of throttle body with an electrical connector. if never cleaned out, this could be part of the problem especially with bad idle.

the engine computer will go from open-loop to closed-loop control when the engine gets warm and reduce fuel at idle. the timing of about 5 min could be related to this issue.
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #6
Been there, done that

fuel filter is easy and cheap to change on a 98. could also be crap in the tank.

IACV has a blue sticker and is mounted on top of throttle body with an electrical connector. if never cleaned out, this could be part of the problem especially with bad idle.

the engine computer will go from open-loop to closed-loop control when the engine gets warm and reduce fuel at idle. the timing of about 5 min could be related to this issue.
When the problem first manifested itself, I immediately thought of a fuel system issue.

Replaced the filter first. No change.

Did a fuel system pressure test according to Haynes. Pointed to a faulty fuel pump. Replaced that, no change.

Possible fuel pressure regulator fault? Replaced that, no change.

Fuel pump relay? Replaced that, no change.

Through out all of this, I constantly monitored for ECU codes but there were none shown other than the occasional misfire or low MAF which is what you would expect if the engine is gasping and running like crap......

I have purchased a new front O2, which I will install today. To top it off the alternator has pooched. I will install that today as well.

I also purchased a scan tool, so will log the results and share them.

Haven't yet had a peek at the IACV but will check that though the car runs and idles perfectly until it dies......

Progress will be posted, so stay tuned.
 

·
Registered
Joined
·
16 Posts
Try checking the timing belt and associated parts for slack, missing belt teeth, sticky tensioners and pulleys.

Try checking camshaft and crankshaft position sensors. Intermittent failure can cause stalling.

Perform throttle body service; clean iac valve.

Check ignition coil, spark plugs, wires.

Check egr valve; could be clogged.

Try changing gasoline brand. Too much water in the fuel? Clogged injectors?

Check harness wiring; check wiring at fuse box for corrosion.

Keep up the investigative work. You're doing well, and I do appreciate your methodical approach. Using a data logger to record live data while driving and up to point of car stalling is a good idea.
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #8
IF I had a hammer.....

Progress update.

I am happy to report changing an alternator is easy - peasy. Half hour max.

The front O2 sensor, not so much......The trick was to get at it. After determining that the cat was rusted in, but good, the next option was to remove the heat shield. Too bad the 10mm bolts looked like 6mm bolts. Nothing to put a wrench on, so using the angle grider to remove them was the best option. Once that was out of the way, at the 4 hour mark, torching the boss on the cat allowed the old O2 sensor to be removed easily.

As it says in the manual, re-assembly is the reverse. It doesn't mention going to a neighbors to borrow bolts because you don't happen to have the correct size and the stores are now closed......

All this to say the results were underwhelming. The car still stalls.

......as they say in Thailand....Phuket. I am going to bed.
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #9
Scan tested the engine

I scan tested the engine today, after getting a handle on how the software works. The car died at about the 3 minute mark. I noticed the Long Term fuel trim reduced the fuel by a large amount about 30 seconds prior to stalling. I would like to post the .csv file for analysis but need some guidance as to how and where.

Any suggestions?
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #12
almost sounds like a dieing maf
I thought of that too after all the parts replaced but the engine scan seems to show otherwise.

I removed the connector body from the MAF harness so I was able to measure directly at the pins. The voltage changes and moves like it is supposed to when the airflow changes, so I am not sure if it is the MAF.

I had a thought this morning that there would be a fuel trim related to engine temperature and air temperature. Which has more influence; the MAF or the engine coolant sensor?
 

·
Premium Member
2008 Forester X Premium 5MT
Joined
·
8,070 Posts
This board has seen many random stalling threads that have turned out to be a bad MAF. In those cases the it would seem that the MAF worked fine until it goofed up and the car stalled.

Thus it may read the correct voltage as flow changes but that doesn't mean crap if it randomly drops out and goes on vacation....
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #14
This board has seen many random stalling threads that have turned out to be a bad MAF. In those cases the it would seem that the MAF worked fine until it goofed up and the car stalled.

Thus it may read the correct voltage as flow changes but that doesn't mean crap if it randomly drops out and goes on vacation....
Finally got my internet connection back, a bit late but here goes.

Thanks for the insight flstffxe, but I have put over a grand into the car and I am hesitant about putting out another $400 for a MAF. $20 for the T-stat is do-able.

I looked at the log again. The onset of the problem starts at 2.33 minutes when the short term fuel trim chokes off flow and the long term fuel trim goes south. The MAF is working fine up to the point where the engines stalls out at 2.93 minutes.

The other thing that occurs is that the MAP goes lower which corresponds to the throttle valve closing and then comes up higher than previous readings in the next reading .48 seconds later until stall.

Not sure where to go from here, other than to push the car off a cliff after lighting it on fire. I believe in Vikings......
 

·
Registered
2003 Forester XT
Joined
·
500 Posts
Sounds like what I have. Cold starts it idles rough and then cuts out when I come to the end of the road to stop. Have to wait about 15 seconds before it will start again. I'm taking it to subaru next month to check it over as I have an oil leak I need fixing. Just fixed a crack in my radiator too! Can't really afford to buy a new maf only to find its not that. So hopefully subaru will be able to tell?
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #16
Sounds like what I have. Cold starts it idles rough and then cuts out when I come to the end of the road to stop. Have to wait about 15 seconds before it will start again. I'm taking it to subaru next month to check it over as I have an oil leak I need fixing. Just fixed a crack in my radiator too! Can't really afford to buy a new maf only to find its not that. So hopefully subaru will be able to tell?
Your problem is somewhat different. My car does not idle rough or run rough. It starts smooth and reaches operating temperature and then idles down to 800 with nary a hiccup. Then it stalls. Your issue sounds like an air leak or vacuum leak, so check all your tubing and connections. As well, is the CEL on?

I have found a MAF for $90 at a wrecker so I will get that but am going to order the coolant sensor since it's only $16....
 

·
Registered
1998 Forester
Joined
·
39 Posts
Discussion Starter #17 (Edited)
Last post hopefully. Finally got around to replacing the coolant sensor. Tested the old one and found it was intermittent but replacing it did not solve the stalling issue. I then subbed in the scavenged MAF and it seems to have solved the problem. It doesn't stall at the 3 minute mark or burp on the test drive......but in looking at the MAF readings they are exactly the same as the one I took out.......go figure.

If you want to buy my Sub, it's now for sale. Lots of new parts and guaranteed to pass an e-test. $2500 C$. Send me a PM.
 

·
Registered
1998 Forester
Joined
·
1 Posts
intermittent stalling at speed

I've got a '98 Forester L that has been stalling intermittently all winter. 3 hours from the nearest Subaru dealer, so have had two local shops troubleshooting - not solved yet (codes for MAF, TPS low volts, misfires, undoc code for MAF, P0102 for MAF low volts and P0106-MAF). Seems to be no pattern. Engine cold or warm, usually at highway speed, sometimes at idle, but only when part of a long series of stalls, restarts, when it doesn't want to run. At times like that, seems like shutting the engine off for several minutes, then restarting solves things temporarily. Occasionally just bucks once, or twice on longer trips (30-60kms). Have looked at everything from fuel and filter, fuel pump, ECM, sensor connections, MAF, other sensors (MAP, TPS, VSSV) etc, etc. Cleaned MAF. There are times during a 50km trip that it will stall repeatedly for the first 25kms, then run fine for the remainder. It has also been on 400 km trips, shortly thereafter when it runs fine, maybe only bucks once. Then recently it was on 1200km trip to Calgary and back. On the way, stalled dozens of times, on the return trip, only a few times. Very unpredictable. Looks like dharmashiv gave up on his - numerous other threads (and in other forums) have implicated the MAF, but I am not convinced. Several have replaced the MAF only to find it didn't solve the problem. Anyone looked into fuel pump relays?? Running out of ideas - thanks for any help.
 
1 - 20 of 21 Posts
Top