99 Subaru Impreza Intermittent Trouble Accelerating

[ddeadserious]

99 Impreza Wagon L, 2.2L, Auto, AWD, 145K, no mods.

Started doing it last night, so this is not a long term issue, but it is concerning me, since I've owned the car less than a week.

From a stop, in drive, when I put my foot on the gas, I have to push and the car will move forward at idle speed/RPMs for about 1-2 seconds, the harder I push, the boggier it sounds, then(since I was gradually increasing pedal pressure), it will just go, generally with high RPMs because I had the pedal pushed down a fair amount.

Once I'm moving, it will shift/downshift properly, no lag, no issues, the issue is only from a stop.

Drove it home from my girls place last night - 5 minute drive.
Drove it to work this morning - 15 minute drive.
Drove it home from work - 15 minute drive.

It did it all the way home from work. I stopped, put it in Park, popped the hood and stared at the running engine for a minute(no particular reason). Got back in and drove another 20 minutes(NAPA, gas station) and it had absolutely no issues on that trip. I added a bottle of Lucas fuel injector cleaner because it was sitting in our garage, doubtful it will do anything though.

Anyways... Kind of seemed like a sticky throttle cable to me, but when I revved it in Park, it didn't bog down. Does it sound like a trans problem(praying it's not)? Any other ideas? Thanks in advance.

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[ddeadserious]

Sort of feels like it's misfiring.

Could it be a TPS?

[RaceFaceXC]

could be lots of things. Any CEL? Not a bad idea to have it scanned even if the light is not illuminated because stored codes and the problem causing them that have been cleared can take a while to re-trigger the light but the code will be in the computer and should show up on a scan. also, i have personally seen the CEL bulb fail on a vehicle so even if a DTC triggers the light, it wont illuminate.

[ddeadserious]

No CEL. Had one over the weekend, P0440 Evap Emissions Control System Failure, loose gas cap. Cleared the code, addressed the issue and it was good.

I will get it scanned tomorrow.

Any other, more specific ideas?

[ddeadserious]

Anybody else, it's driving like total crap, no accelerating at all properly, even at speed.

[sachilles]

How are the plugs and wires? Get a look at them and switch out at needed.

[RaineMan]

Yes, replace those plugs and wires if it hasn't been done. Won't cost much and the car will be a lot happier.

[yarrgh]

what kind of regular maintenance has been done? You say you've had it for a week, did previous owner say anything about that? If you don't know the history, then assume it hasn't been done. When done, reset the ECU and see if it acts better.

[ddeadserious]

Originally Posted by sachilles

How are the plugs and wires? Get a look at them and switch out at needed.

I see how the wires pull out of the side of the engine, but where the hell are the plugs?

Originally Posted by RaineMan

Yes, replace those plugs and wires if it hasn't been done. Won't cost much and the car will be a lot happier.

Sounds good. Where should I get the parts from? Any brand recommendations?

Originally Posted by yarrgh

what kind of regular maintenance has been done? You say you've had it for a week, did previous owner say anything about that? If you don't know the history, then assume it hasn't been done. When done, reset the ECU and see if it acts better.

Owner replaced the timing belt and water pump last year. No records or other mentioned maintenance other than oil changes.

I planned on getting the stuff to do a tune up and getting an oil change tomorrow(pay day). Figured I'd change the trans fluid and filter and diff(s) all at once, probably within the next couple weeks. Tires are good and the car doesn't make any strange noise, so I couldn't think of anything else on the immediate list of things to do.

How do I reset the ECU?

[eppoh]

I would suspect a vacuum leak, if it was running okay a week ago.

Start by inspecting and gently wiggling all the vacuum lines on the engine you can find.

Did you buy it from a dealer where they power wash the motor?

I had a similar problem on a Legacy, where the large breather hose was loose from the airbox. It is on the underside of the snorkel on my 97 legacy,.

[ddeadserious]

Bought from a private seller. Vacuum leak would make a ton of sense since I was wiggling the big air box at the throttle body the day before yesterday trying to change the filter. If there's a hose on the bottom of it, it'd be very possible it worked it's way the rest of the way off. Thanks alot, I'll inspect everything closely after class tonight.

[ddeadserious]

Just went out on break and looked all around for 10 min and couldn't find anything awry I was really hoping to find something. I see three small hoses attached to the sides of the airbox, and they're all connected, but I can't see/feel anything underneath.

[Tricky [RCAF]]

My car was acting like that recently, the dealer did a leakdown test and advised me I had a bad exhaust valve on cylinder 2.

[ddeadserious]

Just spent 30 minutes outside with some heater tube, a stethoscope, some propane, and a can of starting fluid trying to find a vacuum leak(I can hear some kind of hissing when I stick my head under the hood, but I can't pinpoint it).. It idles very nicely with no issues and I sprayed a bunch of startin fluid and propane on every hose I could find and could not cause any rpm spikes. This is so frustrating and I really don't have the cash to pay a mechanic or stearlership to diagnose a problem, especially if it'll be more to fix it.

[ddeadserious]

Had a suggestion to unplug the MAF and see if it changed the symptoms, and if so, to clean it.

I had it unplugged earlier(I don't remember why) and it would stumble and fall all over itself at idle and then stall out. Additionally, the "AT OIL TEMP" light flashes and my CEL came on.

I just went out and unplugged it and it ran well, so I took it for a drive(despite the flashing at oil light and cel), and it drove perfect. Will be cleaning it first thing in the morning, hopefully it does the trick and I won't have to replace it.

Will update this thread with a resolution.

[eppoh]

If it is idling smooth it is probably not a vacuum leak.

Be very careful cleaning that MAF. They are pretty fragile and break easy. Do not use high pressure air to blow them off.

The only other thing I can think of is fuel contamination. Changing the fuel filter is very easy and pretty cheap.

[Matt Monson]

My money is on the front O2 sensor...

[ddeadserious]

Cleaned the MAF yesterday morning(which looked nothing like the one I've seen in writeups). Drove really well all day(drove around a crowded city, stop-go, and then and an hour and half of freeway driving. Gave me no issues whatsoever.

By night time, it started doing it again.

So I decided to fill a jar with MAF cleaner and soak the sensor in it for a bit, let it dry and reinstalled it last night. Hasn't given me any issues today.

If it starts doing it again, I'll clean it maybe one more time, then I will likely just go get a new one.

[bangedlegacywagon97]

Highly unlikely but try this. Use a voltmeter they are like 3 bucks at HF and check the voltage at the battery. Before start. Cranking and running at around 3k rpm. At 3K rpm it should read 12.5 or above if the alternator is doing its job.
I had the exact same symptoms and it was the alternator which was on its way out, partially working at certain rpm ranges only. The battery light was not on in the dash either

[esad_b]

I have the exam same car and same issues as you... 99, 2.2L, 207,xxxkm, auto trans

Its if i hit the freeway its fine. But if i come to a stop or slow down and let it down shift (automatic) to 1st gear, and then try to accelerate again it just seems to slowly accelerate or 'choke' i just dont really know how to describe it.

[ddeadserious]

Started doing it last Friday, tried to clean the MAF but broke it, so I bought a new one from O'Reily's for an insane amount of money. Still was doing it. Sunday, I disconnected the battery, cleaned the battery terminals and alternator terminal and it ran great until last night(so 4 days of running good).

Started doing it again last night. Not as bad as before, but irritating, nonetheless.

Decided to disconnect the battery overnight just to see...

Drives fine now.

Any ideas why disconnecting the battery(i.e. resetting the system) makes it drive great for a few days?

I will check the voltage at the alternator to see if that may be the culprit.

[esad_b]

Originally Posted by ddeadserious

Started doing it last Friday, tried to clean the MAF but broke it, so I bought a new one from O'Reily's for an insane amount of money. Still was doing it. Sunday, I disconnected the battery, cleaned the battery terminals and alternator terminal and it ran great until last night(so 4 days of running good).

Started doing it again last night. Not as bad as before, but irritating, nonetheless.

Decided to disconnect the battery overnight just to see...

Drives fine now.

Any ideas why disconnecting the battery(i.e. resetting the system) makes it drive great for a few days?

I will check the voltage at the alternator to see if that may be the culprit.

Because you reset the system and it has no information in it.. and it takes a few runs/miles to let the system read/diagnose everything again and that's when it starts acting up.

Btw, I fixed my issue it turned out to be my knock sensor ~$130. It was a 5minute swap after that the car has been running A1! It was throwing the code for it tho I don't know if yours is or not but it might be worthwhile checking as it had exact same symptoms as you describe.

[ddeadserious]

Where is the knock sensor located at? I wouldn't want to buy a new one shooting in the dark, but I could check some junkyards. Thanks!

[esad_b]

its bolted to the top of the engine block, not on the head, its in the back almost directly under in the intake manfold, more towards the driver side.

its fairly simple to get at. You can try removing it and cleaning it out mine had a fair amount of junk there..