Jacob42

I have a 2001 with 196K and often when starting cold or after sitting for a couple of hours it will do the following: start, rev to about 1200 rpm, immediately fall to 200-300 rpm and acts like its going to stall but at the last minute it comes back and settles to a normal idle. I've cleaned the MAF and TB with no effect, it seems to be somewhat triggered by the cold as its been happening more as it gets colder. This is also sometimes accompanied with the oil light flashing on for a second or two when starting but that could just be from the cold?

maxiiiboy

Any codes?
At any rate, it looks like your IACV is not working properly. It may need cleaning or replacement (if never replaced). The document about ECU Failures (link in my signature, below) explains the IACV issues in detail.

Child_uv_KoRn

iTrader: (7)

I concur, doctor. Spray the IACV out with brake cleaner and lube. And coolant bypass before you have a terrible, horrible, no good, very bad, day.

Jacob42

It has a pending P1165 (Swirl Control Valve Control Vacuum Switch) but no CEL, I'm not sure if that's related in any way.
The IACV was replaced about a year ago after killing the ECU, and the coolant bypass is done. And just a suggestion, but I used a 5 amp fuse instead of the 7.5 when replacing the eng cont1 fuse and it has been fine, it just gives a bit more protection and hasn't blown. I can try cleaning the IACV but its almost brand new so I don't think it will make a big difference, maybe its just defective in some way? And if it is the IACV shouldn't it have consistent problems at idle? This only happens immediately on startup then it runs and drives normally. I don't know if that's a correct assumption but just thought I'd throw that out

MadMax07SL

That many miles, how old are the spark plugs?

Child_uv_KoRn

iTrader: (7)

Well, that's more interesting. TPS issue?

DennisMik

iTrader: (2)

check the ECTS. The oil light is coming on because of the low rpms.

Jacob42

Sorry its been a while, but I took it apart again and cleaned the IACV, and checked the connections while there, the TPS seems to be working normally, I plugged in a cheap scan tool and the data from it was normal, the only thing is it wouldn't go full open, with the accelerator pedal floored it read 90% on the scan tool, I don't know if that's normal but when my foots fully off it reads 0%, I tested the ECTS with the same tool, at night with the outside temp as 25*F (according to google) with the engine off it read 32*f as soon as I started it, it started climbing steadily and 4 minutes in it read 122 and I took it for a quick drive at low speed (less than 35mph) 10 minutes in it got to 185 and then stayed within +-5*F of 180*F after stopping and shutting it off it started slowly dropping. There weren't any abnormal spikes or drops. When cold the idle rpm was 1220 and when warm it was 750. After cleaning the IACV it does seem to happen less often but Its hard to say if that's from the cleaning or just a coincidence, it does still happen and I was able to catch it on video, see the links below. As for the spark plugs, I don't know when they were last changed but I took one out and it still looked in decent shape if a little rusty on the threads, I think I'll change them this summer
Abnormal startup
Normal startup

Child_uv_KoRn

iTrader: (7)

Jacob42

So just a quick update, it's been getting worse and has started stalling all the way sometimes, usually when it's especially cold or humid. And it can take several tries to get it to start, the last time I had to keep tapping the throttle to keep it from stalling for about 5 seconds before it started working. I was browsing the tsb and found one that describes a similar problem.
NHTSA ID629174
TSB IDNTB02010
I'm thinking it's probably the IACV, when it was last replaced they used an aftermarket one not oem. My plan right now is to get one from the junk yard and see if it fixes it.

MichMaxFan

It seems to me the iacv would affect every start-up the same. Either it works or it doesnt.

However, the maf is electrical and possibly giving faulty info based on air temp.??

I know you said you cleaned the TB....but....Mine idled like crap when cold at one time and a really good cleaning took care of it. Complete removal and engine cleaner throughout and reinstall. A small passage way in there may be clogged. It wasn't as severe a condition as yours but worth a try maybe.

Jacob42

Sorry, it's been a while, and thanks for all of the help. Its been a bit of a crazy week. But I was able to make a trip to the scrap yard and got a TPS, MAF, IACV, all from the same car. I replaced the MAF on mine with the junkyard one. It looked very different, it's much shorter but when I installed it, it worked fine. But the stalling issue persisted. So like you said I removed the entire TB and gave it a much more thorough cleaning, I was going to replace the IACV but after a closer inspection of the one from the junkyard, it looked like it had a coolant leak and I didn't want to risk it. Instead, I cleaned the one on it already as much as I could though it was already spotless, and followed the FSM for testing procedures and it seemed to be working normally. I also decided not to replace the TPS because I wasn't sure if it would mess up some calibration. After cleaning it seems to happen less / not as severely but it's still happening. At this point I'm kinda stumped, should I replace the TPS? It also sometimes has a slow/rough shift from 1st to 2nd and from 2nd to 3rd, I wonder if it's related? I read on another post that the TPS can sometimes cause strange things like that. I'm just a little hesitant to mess with it because it doesn't just bolt on, it has room to be adjusted, how would I not mess it up?

MadMax07SL

196k miles, have you ever replaced the spark plugs??? If not they are long overdue.

rodent_infested_03

Any update on this problems?

Jacob42

It seems to have gotten better after cleaning the TB and IACV but its still happening, just less frequently. I have also started turning the key to on and waiting for a while before starting. That seems to help as well, based on this I think the fuel pump is starting to get weaker or maybe the filter is clogging in conjunction with a possibly slow response from the IACV. As I mentioned before the IACV currently installed isn't an OEM Hitachi but does seem to be working more or less, perhaps just not as well as a genuine part. With turning the key on and waiting for about 5-10 seconds it hardly ever happens or happens much less severely (instead of dropping to 400rpm it goes to about 800rpm then 1100rpm)