2000 V70 stalls when stopping after battery swap

Post by **FireFox31** » 29 Dec 2009, 10:51

Hello, my 2000 V70 manual is experiencing very low rpms and often stalling as I coast to a stop in neutral. Once fully stopped, idle rpms return to normal. In the past, a dirty throttle body caused this, and the ETM recall fixed it permanently. Now, this problem resumed after I had my battery disconnected for three weeks, and after installing my snow tires.

In November, I had a 102k mile used engine swapped in to replace my 160k mile engine which had blown. With the replacement engine, I drove the car a few times over a three week period and everything was fine. I then took out the battery to test and charge it, which took three weeks. After reinstalling the old battery and my snow tires, this low idle and stalling problem began. I cleaned the battery cables and installed a new battery, but the low idle still happens. I've only driven 65 miles (two trips) with this problem and won't drive again until it's fixed.

Does anyone know what would bring about this rough idling in neutral, only between 1 mph and 30 mph? Battery disconnection, snow tires, computer lost its adaptive settings, or worse?

Detailed diagnosis from a 30 mile drive:
The low idle is not as bad when the engine is cold.

When coasting in neutral, engine rpms drop relative to speed, beginning at 30 mph. ie: 24 mph = 700 rpm. 12 mph = 200 rpm.
While in gear between 0 and 30 mph, there's a slight engine strain.
While in gear above 30 mph, everything is fine.

When rolling to a stop, drop into neutral or press in the clutch, and the engine rpms drop to 200 or worse. Sometimes, the engine will rev on its own up to 1000, but fall right back to 200. Often, rpms drop to 0 and it stalls.

How could engine rpms be directly related to speed while in neutral? Doesn't neutral separate the engine from the tires entirely?

Post by **jblackburn** » 29 Dec 2009, 11:11

The couple times I have killed my battery, it took my car awhile to learn how to idle again. For the first couple drives, the revs would dip down below 500 and it would almost die when coming to a stop. It never outright died like yours is, but it felt like it was going to.

I'd say go through a couple drive cycles, and it should "re-learn" itself. Take it around town, and "clutch brake" to a stop if you know what I mean, downshifting through the gears until you reach a stop to avoid stalling. The rpms dropping while in neutral with speed though is just...strange. I can't explain that.

You may also try cleaning the MAF sensor or taking it on a drive without it plugged in and see if it can idle any better, I don't know if you replaced that or not when you swapped your engine.

Post by **misha** » 29 Dec 2009, 18:07

Disconnected battery could cause this,but it looks like your iac valve and maf sensor needs cleaning.
Try first with relearning procedure it could last for a few days.
Relearning procedure:

Post by **FireFox31** » 30 Dec 2009, 07:51

Thanks for the helpful information and fact sheet.

I use engine breaking by downshifting all the time, but very rarely doing a 2-1 shift right before stopping. I tried the 2-1 with this stalling condition, and pushing the clutch in to perform the shift would drop the idle so quickly that I had to slam it in first and dump the clutch faster than I'd like. Coming to a stop at 750 rpm in 2nd (that's almost legitimately stalling) is more comforting. If the car is trying to relearn my driving habits, these "survival techniques" aren't them.

Are the MAF and IAC valve permanently on the engine? In other words, when I got a replacement engine, did I get that engine's MAF and IAC valve?

I'm working to learn what components I got with the replacement engine, to know what problems I inherited from the engine's former owner. Thanks again, I will do what you've recommended.

Post by **jblackburn** » 30 Dec 2009, 14:53

Are the MAF and IAC valve permanently on the engine? In other words, when I got a replacement engine, did I get that engine's MAF and IAC valve?

Most likely not. At least I wouldn't think so. Those are both on top of the engine, the IAC under the black cover and the MAF attached right next to the airbox, not integrated into the block anywhere. At least if I were doing the engine swap, I would have kept both of them in there.

Try cleaning both of them as suggested and see if your predicament improves. If cleaning makes no difference, try running with the MAF unplugged and see if the car can figure out how to idle any better.

Post by **FireFox31** » 02 Jan 2010, 23:46

I wonder if my exhaust problems are contributing. During the engine swap, a leak was created in my exhaust before the cat (which I'm assuming is the huge thing very near the end of the tail pipe). Perhaps the O2 sensor (in the cat, right?) is sensing a lean mixture since some exhaust is leaking out beforehand, thus making the car run richer. The exhaust smells pretty bad, supporting this idea.

But why would running rich make it stall? Or maybe it's running lean; I don't know what that smells like.

Regardless, I'm going to get that pipe fixed before I drive too much more. After that, I'll try disconnecting the MAF, then visually inspecting it, then cleaning it if necessary. Thanks again.

9394volvo850s · Post by **9394volvo850s** » 03 Jan 2010, 10:18

FireFox31 wrote:I wonder if my exhaust problems are contributing. During the engine swap, a leak was created in my exhaust before the cat (which I'm assuming is the huge thing very near the end of the tail pipe). Perhaps the O2 sensor (in the cat, right?) is sensing a lean mixture since some exhaust is leaking out beforehand, thus making the car run richer. The exhaust smells pretty bad, supporting this idea.

But why would running rich make it stall? Or maybe it's running lean; I don't know what that smells like.

Regardless, I'm going to get that pipe fixed before I drive too much more. After that, I'll try disconnecting the MAF, then visually inspecting it, then cleaning it if necessary. Thanks again.

no thet huge thing at the end of the exhaust is a muffler and there are no sensors in it. the cat is all the way up in the front about 24" from the motor, it needs the exhaust gasses to be hot to do its job. get some maf cleaner also.

Post by **FireFox31** » 03 Jan 2010, 23:22

Thanks for the tip. I do plan to clean the MAF with proper cleaner.

The stalling may be getting better by "just driving". After driving 100 miles, it's not idling as violently as I come to a stop, but it's still too low. I disconnected the MAF but that didn't make much difference.

Oddly, disconnecting the MAF hurt my door locks. When I unlock the door from the outside using the key, the dome light doesn't come on, and opening the door causes the alarm to go off. When exiting the car, I the "lock all doors" button did not work. Instead of risking an alarm again, I just left the car open.

And the electrical system seems weaker. While driving 65 on the highway, I turned the cabin fans from off to auto, and the headlights dimmed for a moment. That's never happened before.

And it smells pretty bad under the hood and from the tailpipe. I hope this car isn't decaying right under my nose... It must be something simple....

Post by **jblackburn** » 04 Jan 2010, 07:31

Strange indeed. I wonder if there's just little gremlins living in your car going around and breaking stuff.

In all seriousness though, I'd take a look at your battery cables, both the ground connection and the wire into the fusebox. What kind of voltage are you getting at the battery with the car idling?

Something as insignificant as that could be the cause of all your electrical problems.

And as far as your exhaust leaks, I wonder if they crimped the exhaust manifold gasket putting the new engine in? That would confuse the O2 sensor...a leak further down the pipe under the car, however, would not. It just makes it make a lot of noise

Post by **FireFox31** » 04 Jan 2010, 16:13

CORRECTION: My door lock, dome light and alarm confusion was caused by the front passenger door "lock all" button being partially stuck down. Pushing it a few more times resolved that. I'm going to double check the fan's affect on the headlights with this stuck button resolved - maybe it was putting a parasitic load on the battery.

jablackburn: The exhaust leak is between the cat and the muffler, and the shop made a decent attempt to seal it with a clamp and some goop. I trust that the bad smell is its worse symptom.

The car is now idling better, and I attribute it to simply driving it enough for the computer to relearn the adaptive settings. After 150 miles, the idle while rolling to a stop in neutral dropped down only to 600 rpm, hardly hurting the car. After 200 miles, the idle while stopping only drops to 750 and quickly returns to 900, which is perfectly normal.

Bottom line is: In the 2000 V70 5-speed, after removing the battery for long enough to erase the computer adaptive settings, it must be driven 200 miles under normal conditions to fully remove rough idling while rolling to a stop in neutral. For those first 100 miles, to avoid stalling while rolling to a stop, shift through 3rd than 2nd than 1st, using engine breaking to keep the revs up (since double clutching 2-1 is a safety hazard). Only press down the clutch pedal or drop into neutral as late as possible to minimize the time you're rolling slowly while not in gear, which causes the rough idle.

Thanks again for your tips!