This seems to be a common issue but wondering if anyone has advice on what steps to take. I've had this car a couple months and haven't driven it a ton. It seems to be in good overall condition, has 160k miles. Had a power steering leak that eventually got resolved with a new hose and relay. Other than that has been driving fine.

Last night after driving about ten minutes, it stalled at a red light. Started right up, went a few blocks and stalled again. Kept happening and getting worse, so I parked it and got a ride. Came back today, unhooked the battery for a minute (read about resetting ecu), it started and drove fine for 20+ minutes.

It makes me nervous to drive around a car that may stall at any point, so want to address possible causes. Couple things that probably aren't related but I'll mention: this was the first time driving it after replacing the stereo, also it had been raining all day.

Was thinking of changing the fuel filter, maybe the fuel pump, maybe recapping the ECU. Some other causes people have cited here are shift selector switch, torque converter locked up, air flow meter, idle air control valve.

Oh also, seems like the RPMs might be too low when stopped at a light or coasting, around 400 or even less sometimes.

Open to suggestions as to where to start - thanks!

 

If fuel pump and fuel filter(s) original, then it's time.

After 30 years the capacitors in ECU are toast. Start there.

 

i second the ECU caps as well!

the low idle is the likely contributor to your stalling condition, so while you wait to get the caps done do some routine maintenance like replace the air filter, clean throttle body and MAF (only use compressed air, no cleaners at all!), and potentially spark plugs.

also there is an idle valve that could be a culprit of low idle as well:
https://planetsoarer.com/IAC/iac.htm

 

thanks, these sound like good places to start. ordering caps now. should be able to handle that and the filters, not sure about the fuel pump or anything too mechanically advanced. will do some searches on the MAF and throttle body.

 

i'd much rather do a fuel pump than the ECU caps but hey everyone has different skills!

be careful of the ECU caps. if you're not familiar with PCB board soldering i would take it to the pros that can.

 

i have some experience soldering so should be okay. could maybe do the fuel pump. are there any brands of fuel pump that are recommended or to avoid?

 

Experienced technicians find this board challenging to work on...

​​​​​​Oftentimes leaking capacitors damage circuit boards, select a technician proficient with repairing circuit board lands and traces ...

 

it is definitely challenging! when i opened it up the ecu, it looked very clean. also it says "remanufactured by denso" on the outside. i wonder if it had been replaced at some point. i had already ordered the caps so figured i might as well install them. well, after one i decided to give up. the circuit board holes are tiny! i'll have to find someone else to do this but seems silly to pay $300 for someone to replace 7 caps. though of course there might be something else wrong with it. or maybe it's fine!

the air filter was pretty dirty, and the cabin filter was VERY dirty

 

Did you find the rodent that was living in with your cabin filter? There's no way that much insulation could get in there unless something put it there. That is one of the dirtiest I've seen in any car.
Is there a date on the ECU when it was "remanufactured"? My old 94 used to stall like that after driving 15-20 minutes and then finally wouldn't start at all. When I took out the ECU, one of the caps was burnt right off the board and was just rolling around inside. I put in another good ECU and it was fine. (Til that ECU went bad) Might want to have a professional take a look at it.

 

ha i wasn't sure if that was dog hair or insulation!

there's no date on it, but it looks pretty clean inside, no burns or anything. i'll search but let me know if there are recommended places to get them rebuild, or buy a new one. thanks

 

A smart guy would check ECU capacitors just seeing ID marks as is shown here. If those are marked PF(M) or PR(M), replace them unconditionally. Those don't follow the Arrhenius equation and wear faster than conventional electrolytic capacitors. It is needed to use a measuring equipment such as an ESR meter or an impedance analyzer for the precise judgement. But there is a way to judge only using human's eyes. It is to read the ID mark.

Denso hadn't been noticing the fact that those QAS capacitors fail prematurely until the end of the last Century and many remanufactured ECUs by Denso had been still used those capacitors.

 

thanks will look at that. i don't remember if they had that written on them. they are brown nichicons.

 

Not only are they brown, but bad.

If not caught in time, they leak acid onto circuit traces...and ruins the circuit board.

Obtain capacitors specified in ECU capacitor post.

Do not delay in this regard

 

I know you are helping people a lot. But I have to correct just some.

Those Nichicon QAS capacitors are all coloured brown with letters PR(M) or PF(M). The liquid is not acid but strong alkali. It eats copper traces, through holes and inner traces. Once the QAS liquid is leaked out, it is not easy to fix the board completely. Especially the QAS liquid leaked into the inner layer damages inner traces and it is almost impossible to fix. QAS capacitors don't follow the Arrhenius equation and you can't calculate the lifespan easily.

 

I've replaced the air filter, fuel filter, cleaned throttle body and replaced gasket which was missing a piece, repaired a few vacuum leaks. Thought it was better but then it stalled again.

Realized the check engine bulb had burnt out. Replaced it and got these codes:
15 ignition 2
21 main ox sensor left bank
24 intake air temp sensor
31 air flow meter

So I unplugged the MAF sensor and really thought it was better because it felt like it had more power. I drove it a fair amount like that and thought I was good, but it stalled again today. Unhooked battery for a minute, and was still stalling on the way home.

I guess I will replace the ignition coil and left main oxygen sensor next. MAF sensor too, though I'm not sure if I should order one of the $40 aftermarket ones or find a used one.

And I suppose I should deal with the ECU even though it looks ok. SIA Electronics repairs them for $180 which is the cheapest I've found. This is all adding up!