Volvo 850 1996 / Tranmission or PNP or what? Topic is solved

[BeerDeer]

Hello everyone,

I apologize for any inconvenience caused by my frequent posts. I am currently facing a new issue with my car and would greatly appreciate your assistance.

Today, I encountered a problem when starting my car. It was difficult to start, and I suspect it could be due to the PCV valve, relay pump, or another potential issue. After starting the car, I put it in reverse and it functioned normally. However, when I shifted into drive (D), the car stalled. I tried shifting back into reverse, and it worked again. However, when I shifted into drive (D) once more, the car stalled again. Interestingly, when I used the winter mode, the car was able to drive without any issues. I am concerned that there might be a problem with the transmission. I intend to flush the transmission fluid to see if that resolves the issue.

I would like to know if the issue could be related to a clogged PCV valve, a problem with the transmission, the PNP switch, or a vacuum leak. Any insights or suggestions you may have would be greatly appreciated.

Thank you for your attention to this matter.

[yanga001]

Probably not a transmission issue as that will not normally cause a car to stall out. I have not owned an 850 (v70 98) however how did you use winter mode without the car being in drive?

Is the starting difficulty an issue with weak cranking/turning over, the car sputtering/dying, or some other issue? Will the car idle in neutral and park smoothly? If you have a VagCom cable and VolFCR or some other OBD2 can you report the fuel trims and fuel pressure?

Reverse is usually the first gear you lose in a failing transmission. One of the cars i purchased (98 s70) had the flashing arrow but a really strong and smooth reverse gear. The car drove smoothly after replacing the transmission computer. The transmission is very mechanical in these cars so its unlikely that it is mechanically causing an issue.

How does the car die? Does it sputter or just cut out completely?

[BeerDeer]

Probably not a transmission issue as that will not normally cause a car to stall out. I have not owned an 850 (v70 98) however how did you use winter mode without the car being in drive?

Is the starting difficulty an issue with weak cranking/turning over, the car sputtering/dying, or some other issue? Will the car idle in neutral and park smoothly? If you have a VagCom cable and VolFCR or some other OBD2 can you report the fuel trims and fuel pressure?

Reverse is usually the first gear you lose in a failing transmission. One of the cars i purchased (98 s70) had the flashing arrow but a really strong and smooth reverse gear. The car drove smoothly after replacing the transmission computer. The transmission is very mechanical in these cars so its unlikely that it is mechanically causing an issue.

How does the car die? Does it sputter or just cut out completely?

Hi everyone,

I’ve attached a video showing the car when starting and idling. Currently, the car loses RPM when idling or in parking. I’m aware that my PCV system is clogged and plan to replace it this week. For now, I’ve kept the dipstick 4 cm out to help relieve pressure. Could this issue be entirely caused by the PCV system, or could it also involve the MAF sensor or IAC valve?

Transmission Issue:

When I shift into Reverse, the car doesn’t stall, and it operates as expected. If I use Winter Mode (bypassing gears 1 and 2), I can drive without issues (I drove 5km with Winter Mode). However, when I switch back to Drive (D) after using Winter Mode, the car stalls after moving about half a meter. The engine shuts off, and all dashboard lights come on.

Additional Observations:

Idle RPM: The rough idle issue has been worsening over time. It drops significantly when stationary.

Reverse Lights: They don’t work, but there’s no arrow warning light on the dashboard or any engine light errors.

Oil & Fluids:

Engine oil level is good.

Coolant level is fine.

Transmission fluid color looks healthy.

Possible Causes I’m Considering:

1. PCV System: Likely contributing to pressure and idle problems.

2. Vacuum Leak: Could be causing rough idling and stalling.

3. MAF Sensor or IAC Valve: Potential contributors to the idle issue.

4. PNP Switch (Neutral Safety Switch): Could this be related to the stalling in Drive?

I’m a bit confused as to what’s causing these transmission issues and would appreciate any advice or guidance. I’ll update once I replace the PCV system, but any additional tranmission roubleshooting steps in the meantime would be greatly appreciated!

I am in a bit of a predicament with my car. It is currently parked in a public parking lot, and I am hesitant to touch it further. However, I am capable of performing a transmission fluid drain if necessary. I would greatly appreciate any recommendations you may have to get my car in a drivable condition so that I can replace the PCV valve. The transmission is damaged, as it was functioning perfectly just a few hours ago.

Thank you for your time and support!

[yanga001]

A quick search shows the 1996 actually has the same transmissions as the 98's. Assuming its the same setup as the 98 then this is what the buttons do.

In position D*, the gearbox starts in 3rd gear and changes up to 4th gear.
In position 3*, 2nd gear is locked and there is no change up to 3rd gear.
In position L, 1st gear is locked.
Crosspost from swede speed

Does your car drive in 3 or L? As a test try to activate winter mode and switch to L. If it idles in these gears then perhaps the transmission computer is working correctly and the PNP wiring is fine. If it moves with this setup then your gears are probably fine. This does not eliminate the shifting mechanics but it should help verify the gears themselves.

If these modes work then i would start to look elsewhere for issues.

Without knowledge of fuel pressure, long term fuel trims, and maintenance history of the fuel filter and pump it is hard to determine if these areas are an issue. My gut says its less likely given you can shift into reverse fine.

Did you attach the idle video? The first video almost looks like it is after the car has stalled?

[BeerDeer]

A quick search shows the 1996 actually has the same transmissions as the 98's. Assuming its the same setup as the 98 then this is what the buttons do.

In position D*, the gearbox starts in 3rd gear and changes up to 4th gear.
In position 3*, 2nd gear is locked and there is no change up to 3rd gear.
In position L, 1st gear is locked.
Crosspost from swede speed

Does your car drive in 3 or L? As a test try to activate winter mode and switch to L. If it idles in these gears then perhaps the transmission computer is working correctly and the PNP wiring is fine. If it moves with this setup then your gears are probably fine. This does not eliminate the shifting mechanics but it should help verify the gears themselves.

If these modes work then i would start to look elsewhere for issues.

Without knowledge of fuel pressure, long term fuel trims, and maintenance history of the fuel filter and pump it is hard to determine if these areas are an issue. My gut says its less likely given you can shift into reverse fine.

Did you attach the idle video? The first video almost looks like it is after the car has stalled?

Hello,

I hope you are doing well.

I have attached two videos for your reference. The first video was taken after my car stalled, and I was unable to start it. The second video was taken this morning when I tried to start the car again.

Did you hear the sound when car starts? That also happened when the car stalled. Like some kind of belt? (Attached). However, the belt was changed, and I still have 40,000 kilometers left before it needs to be replaced.

The car stalls when I am in Drive (D), but it does not stall when I am in Winter mode pressed. (Arrow shows in Dashboard). I have not tried starting the car in 3 or L.

I have never had any problems with the transmission before..

The shift lever for your reference. It shows the following positions:

- P (Park)
- R
- N
- D
- 3
- L

There is also a Winter button, which I have pressed. I was able to drive the car in Winter mode, but I could not drive it in Drive (D).

This problem happened suddenly and without any warning. I do not believe that it is a transmission problem, as the transmission has been working fine up until now.

I would be grateful if you could provide me with some advice on what the problem might be and how I can fix it.

Neutral doesn't stall. Parking is neither. Reverse is also. Winter is also. (D) stalls. It did not stall a couple of hours ago or never before.

Thank you for your time and consideration.

Best regards

[BeerDeer]

P - Park. Use to park. Locks up transmission to not allow car to move.
R - Reverse. 1 Gear only, used for reverse
N - Neutral. No power to wheels at all. Allows car to be turned off and on in this position
D - Puts it in drive, allows the TCU (Transmission Control Unit) to control which gear it is in, and when to shift the transmission
3 - Puts the car in 3rd gear. Allows downshift to lower, but will not allow upshifting to 4th. This is also the only way to have the torque converter to lock up above 35-MPH. This also keeps the gear in 3rd gear when it the throttle is off to help with engine braking.
L - Low Gear. This puts the transmission in the lowest gear possible. Please note the speed selections above. Mainly this will shift into 1st and 2nd gear, and keep it in that gear until upshifted manually. Torque Converter is not available in these gears, as I have noticed. This can also help with engine braking, but to a more extreme level. The car will rev higher and slow the car down a bit more extremely in comparison to "3".

From https://volvoforums.com/forum/volvo-850 ... 0-a-38958/

[BeerDeer]

My transmission has started working again. However, I noticed that it is overfilled. I will address this issue when I change the PCV system. I was experiencing rough idling and stalling. While the stalling issue seems to have resolved (Transmission), the rough idling persists near 1000 RPM.

I disconnected the MAF sensor, and the car's RPM dropped, causing it to stall due to low RPM. If I remove it while the engine is running, it immediately stalls. This might suggest that the MAF sensor is not the root cause of the problem I guess?

Subsequently, the lambda sensor displayed a light on the dashboard. There is noticeable shaking and rough movement of the vehicle. I am uncertain whether the IACV, O2 sensor, injectors, or spark plugs are the root cause of these issues. Unfortunately, my inexpensive diagnostic reader does not provide any error codes. I have attached videos for your reference.

[BeerDeer]

Would bad spark plugs cause this?

[erikv11]

Yes, this could be caused by bad spark plugs or by a worn cap and rotor, I would check them.

[BeerDeer]

Yes, this could be caused by bad spark plugs or by a worn cap and rotor, I would check them.

Hi, I will check them. What do I need to check out for?

What about my MAF sensor? Car dies when I starting without it and stalls if I unplug during idling.

What about IAC Valve? I will check the Spark Plugs, Cap and Rotor.