Stalling issue

[subster]

Well, it's been a while since I've posted, how are y'all?

I have a 1995 SVX Ls, swapped with a WRX 5mt (done myself, with all of your help) and now I'm looking for some more help.

It's run swell since the swap (around 3 years ago) and have just had to do basic maintenance until recently.

As it got colder here in Minnesota last fall, the car ran a bit rough on start up. I would give her some revs, and she would mellow out, I'd be on my way.

Then, it was rough until it warmed up to operating temp or nearly there, and once I got her going, she'd purr just fine.

I figured, ok, she's getting old and doesn't like the cold.
Then, one very cold day, after work she wouldn't start.
I noticed two things:
1) She wouldn't turn over. duh
2) the radiator fans would come on right away.
So, to solve the no start thing on a very weak battery, I disconnected the radiator fans temporarily to avoid that drain to get her started. That worked thankfully, and I went to the auto parts store and bought a new redtop to replace the cheap one I had in there. Though, the fans on start up seemed very odd. Coolant temp sensor? I thought, but was just happy to have it get me home for the time being.

A few days later, she wouldn't start in the morning. She would turn over, and poof, not fire up.

I checked the CEL which was thrown and counted up to a knock sensor (95 so not OBDII) with the flashes on the dash. I figured that was part of the problem, but couldn't change the darn thing, (and it was darn cold) so had her towed to our mechanic who finished installing the new knock sensor (driver's side) ran some diagnostics and tried to get it going again. He checked the following:
1) Fuel pressure
2) CEL (codes were coolant temp sensor, EGR, knock sensor)
3) Spark
4) Alternator (after he got it started)
5) Battery
6) Signal to plugs and injectors
All were OK.

He couldn't get it started and said all systems seem to be working fine (aside from the whole not starting thing) so asked me the "how much money do you want to spend on this old beast" question. I said, try a couple more hours and I'll take it back from you. He ended up calling me back and said he got it started, but not exactly sure why. haha. He said he unplugged the ECU and replugged it in, after that it fired right up.

So, I took it back home and for a while it was running fine again. The CEL would come on everyonce in a while while driving, but would go back off.

Then, the rough running on start came back, but lasted longer and wouldn't go away until a mile or two down the highway. By rough, I also mean I would have to keep giving it revs because it seemed to want to stall. It still got me point A-B so I wasn't too concerned.

Then, one day after work, it ran very rough, even giving it revs, it would want to stall, I had to keep it on boil in rush hour traffic just to get her home and she still stalled a few times on the way home.


THE biggest part that I can call out of note is that if I start it up, she idles OK for a few moments, then RPMs drop and if I let it, it will stall. If I tap the throttle, revs increase again. BUT, if I hold the throttle down about half way, where it would probably be at around 4-5k RPMs, it will rev up to there and sound fine, but if I don't change position of the throttle, (e.g. keep it halfway to the floor) it will start dropping revs as if I'm not pressing the throttle. It's as if it "forgets" that I am giving it that signal. Then if I oscillate the throttle at all, it responds again. SO annoying and strange.

That's why I'm here today, I've tried to solve this issue but to no avail. She sits in my garage and I am a sad SVX owner.

Here's what I've tried since limping her home.
1) Replaced the other knock sensor (passenger side)
2) Replaced the coolant temp sensor
3) Cleaned the Exhaust Gas temp sensor (that was caked with carbon)
4) Replaced both O2 sensors (Helped SLIGHTLY)
5) Cleaned the intake and throttle bodies
6) Changed the engine oil and filter
7) Cleaned the Idle Air Control Valve (IACV) That was sticking. (Helped SLIGHTLY)
8) Checked the voltage on the Throttle Position Sensor (TPS) and it reads correct at .5v
10) Cleaned the MAF with MAF cleaner
11) Unplug the MAF and start it (no difference)
12) Cried and kicked and screamed and cried some more

Other recent maintenance was replacing the camshaft seals which were leaking and changing the timing belt and timing belt idler pulley while I was in there. That was this summer and it ran fine after that, so I don't see that as being a contributing factor.

Thanks for reading my novel, I figure the more information the better when trying to diagnose.

[92snowmachine]

did you just check the throttle closed voltage at the tps or did you monitor it while sweeping the throttle to check the curve?

[icingdeath88]

Maybe the fuel pump?

[Tapani]

You guys are gonna hate me soon, but here's my line again: Get a diagnostic interface (like the ECUTuner) to see what's going on. And no, Mike is not paying me to advertize this. It just makes life so much easier to see in real time.

Tapani

[subster]

Jeez, I feel like a jerk asking for help and then disappearing. It was an act of desperation last spring, but I solved the issue.

After all that, I called a friend who's very knowledgeable about Subarus who said it sounds like a MAF. So, I found one on ebay, replaced it and viola! It fixed the issue. So, at least I changed all those sensors and cleaned all that stuff. She's been running well since.

Thanks for the help and input, sorry I didn't get back on here to respond.

Noah