2000 Volvo S80 2.9 Long Term Fuel Trim

jaru · Post by **jaru** » 25 Jun 2015, 12:48

I have a problem with what seems to be the LT FTRM1 & LT FTRIM2 since both of these values do not change and both remain at -0.8 See attached scanner readings. The car starts up and idles, but when reaching approx. 2000 rpm it will stall.(The car is not drivable) I changed both O2 downstream sensors, since they both stay at 0.565V, but it made no difference. I hope someone can shine some light on the this problem and help me resolving it.

draser · Post by **draser** » 27 Jun 2015, 10:47

Jaru,
I would use your short trim for troubleshooting, which indicates a very lean mixture and massive air leak. Between previous and current readings I see you get 0.1xx volts for pre-cat sensors which is lean indicator, previously you were getting zero or very low values. Since car is not drivable I believe long trim does not have time to follow short trim, normally it should mimic short trim. I would look for an air leak into intake past the MAF, try spraying around the air intake tubes, manifold, injectors and listen for idle change. Check plastic intake tubes for cracks (try squeezing tubes and feel underneath area).

jaru · Post by **jaru** » 28 Jun 2015, 19:38

Thanks Dreaser,

Is there an actual vacuum pump or what creates the vacuum?

jaru · Post by **jaru** » 01 Jul 2015, 18:37

Was unable to find any vacuum leaks, but found a empty hose connector. However, it made no difference when I put a cap on it.
Does anyone knows if there should be a vacuum line connected to (see pic) and where the other end would connect to?

draser · Post by **draser** » 02 Jul 2015, 06:44

See if you can find a loose hose burried down in the engine in that area. Do you see a vacuum diagram sticker on the inside of the hood?

Post by **regent** » 02 Jul 2015, 07:03

The open brass connector on the picture should accept one of the two small vacuum lines going to the air box (one is shown attached).
At this age of the car it would not hurt to check the integrity of both lines, especially the rubber sleeves and elbows (at the brass connectors), the rubber deteriorates and becomes brittle.

Post by **regent** » 02 Jul 2015, 07:14

Hmmm...

I checked this diagram http://volvopartslisle.com/assembly/789 ... t-Manifold
for the 6-cyl n/a it shows this to be a plug (pos. 13), and I feel confused now...
Can you verify that it is a plug?

jaru · Post by **jaru** » 02 Jul 2015, 11:05

It is not a plug. It is a connector just like the one where there is a vacuum line is connected to it.
There is no connector unoccupied on the air filter box. So I don't know where it would connect to and there is no loose vacuum line anywhere that might connect to it.
I closed that connector to see if the engine would act differently, but it did not. The one line connected to the manifold goes to the air filter box. There is another line of the same size running from the top of air filter box to a flap/valve on the bottom of the air filter box. I inspected these lines and the line coming from the brake booster to the manifold and the large line form the filter box to the ETC. They are all good. Thanks for any help!

Post by **regent** » 03 Jul 2015, 07:32

Your STFTs are really indicative of a bad air leak. On your picture, I can see a new clamp on the vacuum hose to the brake servo; is that a new hose, did you check your brake booster?

If yes, then I would try to locate the vacuum leak with some propane while idling the engine (move a propane torch around - of course DO NOT IGNITE IT - and you should notice a surge in RPM when you are close to the suspect point). Do that all around the intake manifold, along vacuum lines, around the throttle body gasket to the intake mfld, brake booster and line, etc. Check the lines from the charcoal canister all the way to the intake; there is an L-shaped or U-shaped hose which is a known offender, but as a rule all rubber lines are well aged and hardened at 15 years.
The leak is quite significant and should show somewhere or even be audible.

Vacuum in the intake is created anytime the engine is running because of the restrictions (or losses) along the line from the airbox to the intake; vacuum at idle is very deep (because the throttle is nearly closed) and that is why you are running extremely lean at idle. The STFT shows that the computer is trying to make up by adding a lot of fuel.
Your car appears to be equipped with a vacuum pump:
http://volvopartslisle.com/assembly/802 ... acuum-Pump Its job however is to create vacuum for the brake booster when the engine is OFF. (I am trying to explain that the vacuum pump is not causing the vacuum leak)

jaru · Post by **jaru** » 03 Jul 2015, 22:33

Thanks a lot for your help. I'm quite certain that the hoses I check do not leak. However, I will take you advice and use propane to find the leak. Does anyone know what the extra hose connector at the manifold is for? See picture above.

Thanks