Intermitent crappy idle/acceleration. Possible causes???

[Imprezive]

Ok here it goes.... I bought my 1992 SS in October of 2006. When I bought it, it had a bad Knock Sensor that had to be replaced, a rough idle, and threw 2 CEL codes (knock sensor and water temp sensor) The knock sensor code cause is obvious, and the water temp sensor code was because the water line traveling from the coolant reservoir to the turbo had burst.

So I fixed both of those problems, and in an attempt to fix the rough idle I replaced the spark plugs with NGK V-powers and the Plug Wires with NGK wires, flushed the engine oil and replaced it with synthetic blend. That seemed to clean up the idle a bit but not completely. I then unplugged the battery for a night and in the morning the CEL was back on but just kept flashing. I tried both ECU reset techiniques and neither worked. So now my CEL just flashes for some unknown reason.

Now for the nitty-gritty: A few weeks after driving the car around daily I started noticing that sometimes under acceleration the car wasn't pulling nearly as hard as it should be, whether I was under full boost or just 5psi. Lets just say it was about as slow as my girlfriend's Toyota Corolla Sport when not running right. Along with the intermittent weak acceleration I just described, the rate at which the RPM's drop during shifting or just revving the car would slow, almost to the speed of when you first start the car and its running slightly rich. Know what I mean? That kind of made me think it was running rich sometimes.

I have also discovered that the idle quality will get worse when the car is started, driven for a while, and turned off more than once or twice. (Example: Leaving school and stopping by the bank, then leaving the bank and getting lunch, then from lunch going to work. - By the time I get to work the idle is pretty choppy)

So to recap, here are my symtoms:

Bad Idle (But only if it is left idling for about 10+ seconds. To describe the bad idle I'd say it idles at about 900rpm, stumbles down to as low as ~400 or so, bumps back of to around 900rpm, stumbles, sits at around 500rpm for a few seconds and so on...)

Weak Acceleration Not only on the bottom end or top end of rpm range. Sometimes it lasts a whole day, sometimes only a couple minutes. Sometimes it goes away, comes back, goes away etc...

CEL flashing for no obvious reason, no code to pull, nothing. Just flashing.

And here is what I've replaced/cleaned so far:

Spark Plugs

Spark Plug Wires

Engine Oil (obviously several times since I've owned the car)

o2 sensor (I don't know if the old one was bad but I had a new one so I put it on)

Helix TBE (no cats)

PCV valve

Cleaned the MAF



My knowledge isn't vast, and I am thinking its either the IAC, the TPS, or maybe the computer is pulling timing for some reason??? I haven't messed with anything just yet and I need some advice before I do. Oh and the only aftermarket item on my car is a Helix turbo back exhaust which shouldn't have anything to do with it.

Thanks for your guys' help!

[Soul Shinobi]

Every once in a while my idle bounces like that too. I used to happen a lot when I got the car, but much less often now. It worries me because sometimes the car nearly stalls.

I don't know how good my acceleration is compared to what it should be, this is the first car I've ever owned.

[Radial GT1]

My car has the exact same problems. Also had to replace all of the same sensors. That is weird.

Any-who here is a thread I had on the same deal, almost identical problems.

http://bbs.legacycentral.org/viewtopic. ... celeration

It boiled down to what I believe is wrong is the TPS. I have a new one sitting at my house right now waiting to be put in. I am in Iraq fighting the good fight right now, and will be installing it in about 2 weeks. That is when I get home.

I found a used TB with a known good sensor on it. Others have said that it fixxed a simular problem.

[Imprezive]

Hmmm, well maybe I should try testing mine. Let me know if the TPS fixes the problem.

[Soul Shinobi]

Do excuse my ignorance, but what's a TPS? A something-something Sensor I presume, and I'm sure it's not Tire Pressure...

[Subaru for Life]

Throttle position sensor, I think.

Subaru_for_Life

Do excuse my ignorance, but what's a TPS? A something-something Sensor I presume, and I'm sure it's not Tire Pressure...

[Radial GT1]

TPS- Throttle Position sensor. On the passenger side of the Throttle body. Had 3 or 4 wires on it, depending on year.

[Radial GT1]

TPS- Throttle Position sensor. On the passenger side of the Throttle body. Had 3 or 4 wires on it, depending on year.