Hi all,
I havea problem I would love to get some input on.
My car isa '94Volvo 850 2,5 10v Engine: B 5252 S.
The problem is that when Imove the foot fromthe gaspedal and take it out of gear/or use clutch, the engine goes to approx. 500 rpm. It continues to be there when rolling, but when the car stops, it goes to approx850 rpm.
If I tap the gaspedal, it goes down to 500 as well, for a second or so, struggling to stay alive.
Besides, the exhaust emits to much CO at 3000 rpm, 0,4% should be 0,3%.
I have read out the error codes, and there are only 1-1-1, indicating no error.

My theory is:
The Idle air control valve if fine, since it regulates to 850 rpm, but something makes the engine go very low when the valve is not active. Probably something is clogged, or a vacuum pipe is defect. This may cause the engine to pollute, however the catalytic converter may need to be replaced. The car has 180.000 km / 110000 miles. Might be the MAP sensor?

WhatI have done so far:
newdistributer cap and roter
new sparkplugs
new airfilter
new lambda sensor
new battery
new oil+filter

Today I will clean the Idle air control valve and the throttle.

I hopeyou can help, thanks inadvance.

Magnus

 

Also make sure the Vent system is clean and working normally.

 

Also don't forget the plug wires, fuel filter + large bottle Techron into the tank.

https://volvoforums.com/m_48928/tm.htm


JPN

 

Hi again,
Thanks for the inputs, im not sure what the vent system is, but guess that its part of what I cleaned. Anyway here goes.
I took off the big plastic tube to the throttle. Attached to that was a small and large vacuum tube. The large one went between the manifold and downwards, and the small one went to the idle control valve.
On the connection to "tube to the throttle", there was a lot of white stuff from the larger vacuum tube, and the small one was completely clogged. After cleaning the small tube, the connection and the vacuum control valve connections, I reassembled, not cleaning the throttle. (sprayed it a bit with wd40)
I went for a spin, and now the idle works perfectly.
Today I measured the pollution level again, and it was unchanged, still over the limit.

So, a couple of questions.
Is there a filter or so on the large vacuum tube that could need replacement?
The same white stuff was on the oil level stick before I changed oil, not seen it after change. No white stuff on the filing cap, and no water used. (maybe a little ½dl/month), but suspect thats from hose connection.
Techron, ? is that carburetor cleaner?
I would like to try everything before replacing thecatalytic converter, (it's 800$ here) so any suggestions would be appreciated.
JPN, would it help to change the fuel filter and plug wires,or was that to cure the idling prob?

Magnus

 

see above

 

The vent system, is that the pcv?

 

Yes it is the PCV system.
Sometimes that big plastic hose that runs under the intake will break and cause the problem you have.
Or the Vent box itself might be clogged.

 

Techron Fuel System Cleaner. There are 2 sizes bottles available and I recommend using the larger one. You pour it into the fuel tank, fill up the tank to full with fuel then drive until the tank is close to empty. And for neglected cars I do this twice in a row. Some people use it with only a half-full tank to get thicker concentration.

http://www.chevron.com/products/ourf...tives/tcp.aspx

NEVER use WD-40 into the throttle, you can damage O2 sensors/cat converter.

Fuel filter & ignition wires are neglected way too often. While I cannot guarantee that they would solve poor idling, they need to be done anyway if not done IAW the specified intervals.

The following thread may be of some ref:
https://volvoforums.com/m_92002/mpage_2/tm.htm

PCV components:
http://www.fcpgroton.com/volvo850oiltrap.htm
http://www.eeuroparts.com/searchresu...0&cat=1021
(could not find '94 B5252S)


JPN

[IMG]local://upfiles/6892/2A4DA75D15C94AA6800E0F5AF92F1417.jpg[/IMG]

[IMG]local://upfiles/6892/C341226ED974459989B33101D526E07D.jpg[/IMG]

[IMG]local://upfiles/6892/CA862A469AFD4CA187CD43E6F6371508.jpg[/IMG]

 

Great finally found something wd40 is not good at.. (-:
I ordered 2 bottles of chevron, and plan to do the half tank trick, also recommended by the sales guy.
The fuel filter and ignition vires will be replaced, this weekend and I am still in doubt weather to replace the pcv system.
Now, the only problem is the high co level. The problem with the engine going to approx. 500 rpm, when clutching, was solved cleaning the small wacuum tube to the idle control valve.
The NOx level is fine.
Thanks for the checklist, made me wonder if the 2 central injectors are leaking. (still in doubt if it is a spill from changing oil I see.)
Do you think I should take off the manifold to inspect the PCV, and in case, what should I look for?

Ironically, I work withdeveloping the next generation system forreducing NOx in the exhaust by injecting ammonia. (www.amminex.com)

 

Thank you for the input.
I tried sucking in the plastic hose, and I could fill my lungs...didn't give me any pleasure though....
The fact that there are white stuff in the small filter in the connection, does that mean there is a problem there?
And more important, would a problem in that area cause the co level to be to high?
If you can think of anything else I could do to solve this please let me know...
What are your experience with the durability of the catalytic converter?

Magnus

 

I still say it might be something in the vent system.
Does the big hose from the induction hose throttle body hose move easy?

 

Follow Tech's advice.

Also, CO is produced as a result of the lack of oxygen during combustion. The following would affect the amount of oxygen supplied to the engine:

- Vent (PCV) system noted by Tech.
- Clogged/inferior-quality air filter.
- Blockage/leak in the induction/vacuum line(s).
- Incorrect/out-of-range O2 sensor signal feedback.
- Excessive fuel supply in a given moment.

After the spent gas leaves the engine, there is only the cat that takes care of cleansing out the exhaust gas. In general, cat can get damaged by excessive amount of fuel, most likely unburned raw fuel. The 2 most common signs of cat failure are the rotten egg odor and rattling noise from the cat.

The CO level can be reduced by higher combustion temp & pressure, which in turn produces more NOx, so the emission control system has to work very precisely to get the balance.

NEVER suck on any hose in a car; it'll make everyone sorry.


JPN

 

A collegue of mine was at the Volvo research facility, and they had a problem with the catalytic inverter.
Thay raised the temperture of the inverter by increasing the fuel inlet. Took 10min, and all they did was to send some commands to the ecu. The problem was that there was to much soot/carbon, and apparantly it was burnt out with the excessive amount of fuel.
Worked fine afterwards.
I tried everything but the vent, since I have to remove the manifold to get to that. I gues I have to try that next.
thanks.
Magnus