Idling and Shifting Weirdly

So I have a quick question and I think I know the answer already but I want opinions before I go buying parts.

 

So the car occasionally idles like crap, it seems random but sometimes its fine and sometimes it does stuff like; I pull into a parking spot, put it in park and it goes from 700rpm up to 1500rpm until I shut it off. Then once I restart it, it does up to 2000rpm as if the engine is in a warm up sequence.

Also, when coasting at low speeds, such as when driving through the neighborhood, it gets bipolar with which gear to be in, so sometimes it holds 1st for too long or won't switch out of 2nd when accelerating or decelerating.

 

Info on the car, 96 2.2L Auto

 

Also, if you've read my threads, you would know that nearly everything on the car is new and/or cleaned. The only parts I cleaned instead of replacing during the engine rebuild was the MAF, IACV, EGR and throttle body. All of the servicing was done about 12k ago, so most of the stuff on the car is less then 30k old.

I pulled the IACV and cleaned the crap out of it. When I first pulled it, you could manually move the little valve in it but it'd stay in the position you left it in which isn't right. I used a whole can of gumcutter/carb cleaner and a ton of q-tips, and now the valve moves fluidly and returns to it's rest position. I haven't driven the car much yet aside from pulling it out of the garage, but I'm pretty sure that was the problem.

If this doesn't work then I may just buy a new IACV but the dealer one is $250 ish :/

Just an update: The problem still exists but is definitely better then it was but being that the symptoms changed and still exists means it is the IACV or a related part, so I ordered a new OEM IACV and I'll be putting that in shortly. Fingers crossed it fixes it.

Dang, I hope so.

Short update

I daily the car about 50 miles a day and since most of it is stop and go traffic, the symptoms are very noticeable. But the last two times I filled the tank, I went with 92/93 whatever he highest readily available octane is, and also put in a full can of seafoam, and so far the symptoms still happen but they are now happen less frequently. I normally run the mid grade octane so it's not a big of a difference, but I just wanted to see if anything changed.

The IACV should be here today or tomorrow and I plan to put it in this weekend, so we'll see if that fixes the problem.

I hope you are not having the same issues I'm having with the GT (see my updated post). I've tried 2 other IACV's on mine and the fluctuating idle seems to return. Mine cold starts at 2500 RPM, drops rather quickly to 1000- 1200 RPM, then will fluctuate a some, with less fluctuation when warm.

I finally got around to installing the new IACV and while doing so I reset the ECU and so far so good. I haven't driven in my typical commute traffic yet, which is where the symptoms are most pronounced but I'll give an update in a few days once I'd had time to drive it. If this doesn't work, I'm thinking it may be a crank sensor, even though I have no CEL, it occasionally starts super quickly and sometimes it's normal, so I'm thinking maybe it's reading slightly inaccurately.

When my left cam slipped a few teeth compared to the crank I never got a code about either the cam or the crank. Mine was far enough out to cause misfires at idle. I sometimes got codes for that.

After a day of driving, the symptoms are still kind of there. In stop and go traffic it's not nearly as bad as it used to be, and for the most part the symptoms are gone. However, after shutting the car off and restarting it, the rpms jump up to 2k and then gradually drop as if it's in warmup. And then moving around a parking lot, it wants to idle at 1500rpm or so. For now the symptoms are tolerable and I'm just going to ignore it until I have time to pull off the timing cover to look at everything. I may just buy a new crank sensor and if it ends up not being the problem then the old crank sensor and IACV will go onto the new subaru.

The car FINALLY threw a CEL which was P0121 which comes up as Throttle Position sensor and that makes a lot of sense, it's the last original sensor on the car, so I'm ordering one now and fingers crossed it fixes the issues. It's getting kind of annoying...

The Hitachi/OEM TPS came in yesterday and I installed it along with an optima battery (freebie from work) and so far the idling and shifting problem is fully gone. I had to twist the position of the tps a little to get it to idle at a normal rpm instead of 2k+ but other then that, the issue seems to be resolved. Now just have to drive it in traffic to know for sure

Nice, glad you were able to get to the bottom of it!

I wonder if a new TPS would help the '97 GT. The replacement ECU got rid of the misfire, but the idle is still way too high at start up and fluctuates a lot when cold.

I wonder if a new TPS would help the '97 GT. The replacement ECU got rid of the misfire, but the idle is still way too high at start up and fluctuates a lot when cold.

 

I would definitely consider it, or at minimum, loosen the sensor and rotate it with the car running, then just tighten the sensor in place once it idles where you want it.

I would definitely consider it, or at minimum, loosen the sensor and rotate it with the car running, then just tighten the sensor in place once it idles where you want it.

 

I did move it some when I was having the idle issues, it would speed up the idle a bit, then the ECU would adjust it again. Maybe I should pick up a spare since they don't seem that expensive, give I think it would fit any of our three 2nd gens

Yeah and being that it's just a variable resistor, it's understandable that it can wear out in time. The aftermarket ones are $25-35 and then the OEM one which is Hitachi is $50. I would suspect that it's the same sensor across all of the same gen motors.