Hello, I am new to this forum that I found after doing some research regarding issues with my Volvo 850 1997 Non Turbo.

My car was running just fine a few weeks ago but then issues started all of a sudden. I noticed that when I start my engine (cold engine first of the day start-up) the engine RPM does not go to roughly 1000 RPM like it used to, it hesitates, engine runs rough for a few seconds and then finally runs smootly.... while the engine hesitates, I hear a weird knocking sound but I am not sure it's internal / metal to metal. Once the engine runs ok it's just fine, good power... I drive 5 minutes, shut the engine down to run and errand and the engine starts normally and it's all fine. The morning after, same story again. Anyway that was 2 weeks ago.

Then, it got worse, it continued to do this at cold start but then while driving and with the engine running just fine, suddenly it would missfire a few second and return to normal. Then I would drive and suddenly again, usually when decelerating to a stop, the engine would completely die all of a sudden like if the ignition was out. The engine would restart on first try and so on till it would happen again minutes later....

Anyway, I suspected bad gas or bad injector cleaner and after filling up my tank I noticed the engine stopped quitting on me like it used to. BUT, the noise and engine hesitations still occured at cold starts....

Yesterday, that hesitation and noisy rough running did not go away like it used to... now the car runs very rough like it's on 4 cylinders, I see blue smoke coming out the exhaust and because the engine is hard to start, it floods easily and I am even having a hard time to get it started.

My 850 has about 120k miles on it, never had any issues with the engine, any idea what is happening? As of now I can't even start it... The engine seems to get gas and all spark plugs ignite....

PLEASE HELP !!! Thanks !

 

I would have the codes pulled.

 

I disconnected the battery, waited 30 minutes and checked if the ECU had shifted from its rack so I doubt many codes will remain.... ????

 

Sometimes they still might be there.
If it was misfiring before it would not start it might be a tune up issue.

 

Pull the vacuum line of the fuel pressure regulator and see if it has fuel in it. If the regulator ruptured then raw fuel is drawn into the engine and will cause rough running, the blue smoke and a loss of power as it's flooding the cylinder(s) closest to the point where that vacuum hose connects to the intake.
Also check the cap and rotor to see if you have any carbon tracking and the spark is shorting out inside the cap and not getting out to all the plugs.

 

Thank you Kiss4aFrog, I will try this. I did check all the plugs and they all fire fine so it don't think it's an ignition issue. I think the issue is definitely a flooding of the cylinders like you describe... will keep you posted! Thanks again.

 

Ok so I removed the cover for the fuel rail and should be able to see the fuel pressure regulator, correct? It is located under the fuel rail, right?
Well I looked and there is no regulator there and I am confused. All I see is the 4 injectors, the hose going from the top of the head (breather line) and that's it. No other vacuum line at all. The only thing is some sort of a "capsule" that is under the fuel rail on the left hand side and it is not connected to anything and does not seem to have a fitting on it. Is my engine different, the tech manual pictures show that fuel regulator with 2 lines but it's not like this on my engine. ????

 

That is the fuel pressure regulator. On (some? mine was like this) NA models, you only have one fuel line (returnless). The regulator is attached to the fuel rail, and you have one line off of it that goes to your vacuum tree.

 

There is no line coming off of it. Do you think it's broken / missing ?

 

Ok I checked again, that "capsule" attached to the fuel rail has no fitting on the other end, it's factory sealed. It's not broken, so there was no vacuum line connected to it. Weird.

 

My guess is that you are missing an injector. Since the car is a I5 and you only have 4 injectors.

You may want to post a pic or find one that someone else has posted. Did you check for codes yet?

 

Well I did let the car sit all night without plugs so it could vent. I got new plugs and the engine ran few minutes very well on all 5. (no I am not missing an injector). Then I let the engine idle and it did idle well. By the way I no longer saw any blue smoke so it looks better. BUT, after idling a few minutes it died on me and then when I tried to restart it did not! Sounded flooded again. I pulled the plugs and they are clearly carbon coated so it's running rich.
No I did not check the codes yet as I need to drive it to a repair shop for that.

 

Sorry I did mean to say "5 injectors"

 

OK, you must have the "damper" on the fuel rail setup (like the V70 and S70 models that came after). I understand that if you follow the fuel line back, you you find the regulator sorta down low behind the engine. Probably need to access it from up under the car.

Have you noticed your coolant temp gauge doing anything strange, maybe going up and down a bit after the car should be warm?

 

Hi again, I will look for that regulator down below. Since it's one of the last 850's I am not surprised it could be like a V70 and S70.

Yes I did notice the past 6 months the temp gauge doing strange things but nothing worrying.... more like tiny quick fluctuations like you describe. Since I replaced the radiator 2 years ago, I assumed it had something to do with it...

 

The fuel pressure regulator should be down by the subframe. Is the car a 96 or 97 GLT low pressure turbo car? If so then it is also most likely a Motronic 4.4 fuel system.

It could be a bad O2 sensor or Mass flow sensor causing it to run way to rich.

 

It's a 97 850 Non Turbo 2.4L, does not say GLT like on some just 850.
I will replace the O2 sensor. Actually is there a front one and rear one?
Thanks!!!

 

Yes there is 2 but the front one is the most important one.
You can also try unplugging the MAF and see if it runs better.

 

MAF? Sorry I am not a PRO. ;-)

UPDATE: ok found it, disconnected it, will try!

 

Ok TECH, If I disconnect the MAF the engine does start way better and runs ok. While running, if I reconnect the MAF it kills the engine right away!