Stalling when coming to a stop, need help

[abscate]

I had my girlfriend test the battery with a multimeter. It read only 9.86 V. I'll have her pick up the new battery tomorrow.

What could have killed the battery aside from age? My girlfriend recalled that the idle has had some slight fluctuation and running had some vibration for weeks. The alternator is a parts chain brand, but these symptoms don't match my experience with a non-charging alternator. Back in April 2022, the battery would die overnight, I never found a parasitic drain, and the dying stopped once the car was driven more.

My girlfriend was unable to pull the DTC codes because the OBD2 reader failed to connect. The ignition was in position 2, interior lights were on but a little dim. We'll try again with the new battery installed.

Thanks again for your input.

9.86v

Dead dead dead

I’m not even sure scot850 would buy that one.

[volvolugnut]

After installing new battery, have her check the voltage at battery with engine running. A good alternator should give back about 14 volts to the battery. Any less is bad alternator OR voltage loss in battery cables. An old alternator may need new brushes. I think these are replaceable if you can find a source of brushes.
A bad alternator could have killed the battery before it's time.
volvolugnut

[scot850]

You can replace just the voltage regulator and brushes, but careful, there are a lot of bogus 'Bosch' parts out there.

I talked to my friend who was a master mechanic and now shop manager for a Volvo dealer. He said on Volvos. 13.5V and up is good.

Neil.

[FireFox31]

The problem is bigger than the battery. With a new OEM battery, the car starts and drives, runs kind of rough, and randomly stalls at low speed. After stalling, it will start up and drive. My girlfriend recalled that the car has been idling and driving a little rough for the past few weeks, though no check engine light showed.

Current DTC codes and possible translations:
P1670 - Immobilizer ?
P0106 - Manifold absolute pressure sensor
P1119 - Manifold absolute temperature circuit ?
P0300 - Random / Multiple cylinder misfire detected

These suggest a bad MAP sensor or crumbled vacuum lines. Can I have my girlfriend diagnose the MAP such as driving it electrically disconnected? I'll have her check the vacuum line and see if the sensor hole is plugged.

Can anyone recommend a MAP vacuum line replacement available at Home Depot or Lowes? What material and inner diameter is it?

Worst case, FCP has a Vemo brand MAP sensor for $151. Is that aftermarket brand trustworthy? OEM is $295 from the dealership. Thanks for your input.

[abscate]

That MaP sensor won’t cause poor running like that.

How old are coils and plugs? IS wiring to the coils in good shape, and are all the coil grounds in place, tight and clean ( 2 m6 bolts that go into the head) as well as head to body grounds, qty 2?

[xHeart]

This is idle control issue. I will examine fresh air hose between air box and throttle body to rule out aging pipe -- suspect: a fine crack throws a monkey wrench as it warms.

[volvolugnut]

A small vacuum leak will have less and less running impact as the air flow increases with higher speeds. Bad coils, plugs would be expected to fade at higher speed.
Can GF spray some carb cleaner/ starter fluid on vacuum hoses and see if engine speed increases from idle? Could be a fire hazard if sprayed on hot parts. Speed increase would indicate a leak in that spray area.
volvolugnut

[FireFox31]

Vacuum or air leak is likely but finding it may test my girlfriend's patience. What are all the vacuum lines on a 2000 NA which would have to be tested/checked?

Those MAP codes seem like a strong indicator. She inspected the MAP hose but it's braided (not OEM?) which may be concealing a break. Another hose on the exhaust manifold was replaced with something crude. What are the inner diameter and material specs of vacuum hoses in case we need them from Home Depot?

The plugs are 2 years old. Three coils are original, one newer Volvo, one aftermarket; no code pointing to a specific one failing. Grounds to engine and body were redone decently by previous owners. The multi-strand red power cable to the fuse box is corroded at the fuse box end.

When idling roughly, the dash lights flicker slightly. I believe that's with the new battery in.

What about idling/driving with the MAF electrically disconnected to check for worse performance? I recently replaced the engine coolant temp sensor with Volvo due to non-starting. The ETM is 290k mile original (from my car, not neglected Geronimo). I removed the intake manifold, air box, etc to replace the PCV but that was six months ago.

[abscate]

The multi-strand red power cable to the fuse box is corroded at the fuse box end.

That’s a thing you need to address. It’s the same as a bad battery.

[volvolugnut]

The multi-strand red power cable to the fuse box is corroded at the fuse box end.

That’s a thing you need to address. It’s the same as a bad battery.

Yes. Voltage drop in cable equals voltage drop at all electronics.
volvolugnut