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

[BeerDeer]

I have the VeePeak OBDCheck BLE+ Plus reader, it works with the "850 OBD-II" app and allows me to read and clear error codes.

I don't really know anything about automatic transmissions myself, I only ever buy manuals.

The lambda lamp is just a Check Engine Light, it lighting it up doesn't mean there's a problem with the O2 sensor.

I would still clean the IAC first, then check the ignition components.

I bought VeePeak OBDCheck BLE+ Plus now from Amazon. It will take 1 week to arrive... So I need to find out the problem now without reading the codes...

[erikv11]

I just removed the MAF while the car was operational, and the engine immediately stopped with a hard shutoff.

This procedure is not recommended, it can be bad for the ECU.

If I try to start it without the component, I have to rev the engine to keep it running; otherwise, it dies due to low RPM.

This is a good test to do.

I’ve also noticed condensation inside the oil cap and dipstick, which I believe is caused by the clogged PCV system. I’m currently waiting for the replacement kit to arrive so I can address this issue.

The PCV may be clogged or it may not - some condensation is completely normal in the winter, especially if the car is only operated for short time periods or short distances (e.g. 8 km or so) where the engine never gets very hot. A more relevant test for the PCV is the "glove test."

In the meantime, I’ve picked up MAF cleaner to clean the MAF sensor and carb cleaner to clean the Idle Air Control Valve (IACV).

Good ideas.

...
I’m not sure how to check the gap on the spark plugs. Could someone explain what the gap means and how to measure it? I’ll do my best to inspect the plugs and replace them if necessary.

Google is your friend you need a cheap spark plug feeler gauge.

[BeerDeer]

Here’s what I’ve done so far:

- Ignition Coil: Measured at 7.3k ohms, while it should ideally be 8–9k ohms. I replaced the coil with a new one since it had never been changed. The battery was also charged. Starting improved, but the main problem persisted.
- MAF Sensor: Cleaned with spray, and I also used EGR cleaner to spray into what I believe is the EGR valve.
- Idle Air Control Valve (IACV): I couldn’t clean the valve itself because it’s closed and I can’t see inside, but the tubes connected to it were clean.
- PCV System: Confirmed clogged. This will be replaced soon.
- Rotor Cap: Cleaned the inside of the rotor cap, which was moist and oily (pictures attached).
- Camshaft Seal: Seems to be the source of the oil leak. This will be replaced after the PCV system is fixed.
- Spark Plugs: The spark plugs were slightly discolored and haven’t been changed in about five years, according to the records.

Current Status:
After cleaning the rotor cap, spraying the MAF, and doing general maintenance, the car started better—stable and without any obvious issues. I’m not sure if it’s a coincidence or if the cleaning helped resolve something temporarily, but it’s a small sign of progress.

I drove the car around the block, and everything ran smoothly—no issues at all. We plan to do a more extensive test drive tomorrow to see if the problem reoccurs under different conditions.

Next Steps:
Tomorrow, I plan to purchase new spark plugs and a new rotor cap. Hopefully, these replacements will further improve the car’s performance.

I’ve attached pictures of today’s work for reference. Thank you for all the advice so far—your support is invaluable!

[erikv11]

That wet distributor cap tells the whole story - dislodged cam seal due to clogged PCV.

Did you re-install the cam seal under the rotor plate? I'd do that now, and until you can fix the PCV you can dislodge the dipstick to relieve crankcase pressure. Make sure you put the plate back on correctly, it is possible to put it on 180 degrees out of phase.

For cleaning the IAC see my earlier post. You can't see inside it, but you can shake it to feel the valve rotating inside. When it is clean, the inside piece will rotate more smoothly and easily.

Make sure you don't buy a cheap distributor cap and rotor. I try to only use the Bosch cap and rotor.

[BeerDeer]

That wet distributor cap tells the whole story - dislodged cam seal due to clogged PCV.

Did you re-install the cam seal under the rotor plate? I'd do that now, and until you can fix the PCV you can dislodge the dipstick to relieve crankcase pressure. Make sure you put the plate back on correctly, it is possible to put it on 180 degrees out of phase.

For cleaning the IAC see my earlier post. You can't see inside it, but you can shake it to feel the valve rotating inside. When it is clean, the inside piece will rotate more smoothly and easily.

Make sure you don't buy a cheap distributor cap and rotor. I try to only use the Bosch cap and rotor.

I replaced the spark plugs with Bosch ones and installed a new distributor cap, identical to the model the previous owner used. It was the most affordable option, but the shop assured me it was fine. After these replacements, the severe rough idle, weak power, and misfire issues were 99% resolved.

Today, however, the car failed to start on the first attempt. It eventually started without any misfiring or rough idling. After driving, everything felt perfect, but later, upon restarting, it experienced a brief rough idle (a 200 RPM drop) for about 1–2 seconds. This is sooo much better than before, where the idle was persistently rough, making the car undriveable.

The previous distributor cap had condensation inside when we cleaned it, but there was no oil present. It seems the seal is damaged, and I haven’t replaced it yet. Could this condensation inside be causing the brief rough idle?

The rotor appears clean and in good condition, with no visible issues.

Additionally, I’ve temporarily disconnected the main PCV tube at the top of the engine, and the dipstick is raised about 2 cm. Is that okay? A new PCV system is arriving this week, and I plan to replace the cam seal and reconnect everything. I hope the temporary disconnection of the PCV tube won’t cause any damage...

Could the condensation in the distributor cap, the disconnected PCV tube, or other factors be contributing to the rough idle? Your guidance would be greatly appreciated.

[erikv11]

Some good news! Nice work.

... Today, however, the car failed to start on the first attempt. It eventually started without any misfiring or rough idling. After driving, everything felt perfect, but later, upon restarting, it experienced a brief rough idle (a 200 RPM drop) for about 1–2 seconds. This is sooo much better than before, where the idle was persistently rough, making the car undriveable.

The previous distributor cap had condensation inside when we cleaned it, but there was no oil present. It seems the seal is damaged, and I haven’t replaced it yet. Could this condensation inside be causing the brief rough idle?

Yes. I advise you to remove the cap, remove the rotor and the metal plate under the rotor and look at the cam seal. If the seal is dislodged it will leak moisture into the cap. And more moisture accumulates, the rough idling will get worse. If the seal is dislodged you can push it back in until the PCV work is done.

Additionally, I’ve temporarily disconnected the main PCV tube at the top of the engine, and the dipstick is raised about 2 cm. Is that okay? A new PCV system is arriving this week, and I plan to replace the cam seal and reconnect everything. I hope the temporary disconnection of the PCV tube won’t cause any damage...

Could the condensation in the distributor cap, the disconnected PCV tube, or other factors be contributing to the rough idle? Your guidance would be greatly appreciated.

Disconnected PCV tube and lifted dipstick should not contribute to rough idle. They may leak oil and make a small mess and cause bad odors, but the car should udle smoothly.

[BeerDeer]

Some good news! Nice work.

... Today, however, the car failed to start on the first attempt. It eventually started without any misfiring or rough idling. After driving, everything felt perfect, but later, upon restarting, it experienced a brief rough idle (a 200 RPM drop) for about 1–2 seconds. This is sooo much better than before, where the idle was persistently rough, making the car undriveable.

The previous distributor cap had condensation inside when we cleaned it, but there was no oil present. It seems the seal is damaged, and I haven’t replaced it yet. Could this condensation inside be causing the brief rough idle?

Yes. I advise you to remove the cap, remove the rotor and the metal plate under the rotor and look at the cam seal. If the seal is dislodged it will leak moisture into the cap. And more moisture accumulates, the rough idling will get worse. If the seal is dislodged you can push it back in until the PCV work is done.

Additionally, I’ve temporarily disconnected the main PCV tube at the top of the engine, and the dipstick is raised about 2 cm. Is that okay? A new PCV system is arriving this week, and I plan to replace the cam seal and reconnect everything. I hope the temporary disconnection of the PCV tube won’t cause any damage...

Could the condensation in the distributor cap, the disconnected PCV tube, or other factors be contributing to the rough idle? Your guidance would be greatly appreciated.

Disconnected PCV tube and lifted dipstick should not contribute to rough idle. They may leak oil and make a small mess and cause bad odors, but the car should udle smoothly.

I’ve partially disconnected the PCV tube and left the dipstick slightly out. It's currently negative temperatures here, and I’m wondering if this setup might cause any issues. I’ve noticed a lot of white, foamy sludge in the oil on the dipstick, which I assume is due to condensation since I’m not losing any coolant. I hope this isn’t harmful.

I’ve already replaced the spark plugs and installed a new distributor cap. I plan to inspect further this week. Is it as simple as removing the distributor cap and rotor to check the seal? Should I also examine the camshaft sensor to see if there’s any oil buildup there?

Overall, I’d say 99.9% of the original issues are resolved. There’s no stalling, the persistent rough idle is gone, and I can drive normally. The only issue today was one failed start attempt and a brief rough idle for about a second.

Do you think I should be concerned about these minor symptoms, or is it just residual issues that will clear up with the PCV system and cam seal replacements?

[erikv11]

I do think you should not be concerned and these symptoms will clear up with the rest of your work.

The white sludge on the dipstick is completely normal in the winter if the car doesn't get up to running temps for long periods of time. My cars get it, too. You'll probably have some white goop even after you fix the PCV.

For the cam seal on the intake cam:
(1) remove cap (two captive screws)
(2 remove rotor (three Allen screws)
(3) remove rotor mounting plate (one 10 mm head bolt)
then you can see the cam seal.

When you replace the rotor mounting plate make sure it is in the correct orientation, it is possible to install it wrong then the car won't start.

I would probably not examine the camshaft sensor (exhaust cam) to see if there’s any oil buildup there, unless you have symptoms like no-start. That one is a hassle to get to, that's really the only reason!

[DennisCA]

Best way to resolve it is to go for a longer drive outside the city and let the engine get up to temp for a while.

[BeerDeer]

I do think you should not be concerned and these symptoms will clear up with the rest of your work.

The white sludge on the dipstick is completely normal in the winter if the car doesn't get up to running temps for long periods of time. My cars get it, too. You'll probably have some white goop even after you fix the PCV.

For the cam seal on the intake cam:
(1) remove cap (two captive screws)
(2 remove rotor (three Allen screws)
(3) remove rotor mounting plate (one 10 mm head bolt)
then you can see the cam seal.

When you replace the rotor mounting plate make sure it is in the correct orientation, it is possible to install it wrong then the car won't start.

I would probably not examine the camshaft sensor (exhaust cam) to see if there’s any oil buildup there, unless you have symptoms like no-start. That one is a hassle to get to, that's really the only reason!

Thank you. Also running with the main pcv tube disconnected at the top is not bad right? (Temporarily) so I don't get any other blown seals.