2000 S70 Base Getting 12mpg

[precopster]

Fuel lines should maintain reasonable pressure for weeks at a time. Symptoms are pointing more and more to a faulty fuel pump regulator which is integral with the pump.

[abscate]

A leaky injector seal will hiss..it's under heavy vacuum. Listen with hose (same color as car) in your ear to. Isolate the position of the hiss.

[oragex]

17mpg already is almost correct, although still a bit low.

Clean the MAF sensor, here's how https://www.matthewsvolvosite.com/forums ... =9&t=26833. It doesn't need to be replaced, just cleaned.

Check also the fuel pressure at a garage, it's a simple check with a manometer.

[thankswww]

NOVEMBER 19, 2013 UPDATE:

Hi fellow Volvo friends and enthusiasts. Are you like me? Do you like a good mystery? If you like good mysteries, then you are really going to like this one:

After several tanks of gas, the car is back to getting lower MPG. All in all, it's averaging 15.89mpg (14.8L/100km) under standard conditions with no load and easy driving. This is still better than the 12mpg I was getting before, but seems quite a bit lower than it should be. Today I located the charcoal canister (I've been busy, no time to work on it until now). On my 2000 Base model non-turbo, the canister is located under the battery, and is a large cylinder shape with two rubber hoses coming off the top. Instead of dropping the whole canister, or pulling off the bumper or fender liner, I simply snaked my hand up in there and pulled off the two rubber hoses one at a time, to inspect them.

I found that these two hoses were in extremely good shape, with no leaks. In fact, they are in TOO GOOD a shape, when compared to the rest of the original hoses on the car. Why? Somebody has obviously replaced them trying to tackle this problem before. I'm guessing it was the previous owner and/or mechanic or maybe even the dealer. I also found a new looking zip tie holding the two plastic hoses leading up to the canister together; more evidence that the previous owner had someone under there trying to find the cause of the poor mileage/error codes. Here is a photo of the top of the canister, for anyone else wondering what it looks like:



So I've got good (new) hoses from the intake manifold, to the evap canister purge valve, to the canister, and out the other side of the canister to what I'm assuming is the fuel tank. No cracked hoses.


Faulty Injector?

Next up, I took the advice of a board member and checked the plugs for any obvious differences due to a possible leaky injector. This was suspect, because the fuel system did not seem to have any pressure in it when I changed the fuel filter, hinting at a leak somewhere in the system. I pulled all five plugs tonight, and to the naked eye, they look pretty much the same. Here are a few photos:






It is not the error codes in particular that bother me; it is the fact that the error codes are accompanied by SYMPTOMS (bad fuel economy) that hint to me that the error codes are in some way accurate.

By the way, when I replaced the 02 sensors, I got a nasty surprise; the ones I pulled from the car were relatively new looking (definitely not the originals), hinting again that someone else had been under there, searching and searching for the cause of the check engine light. The fact that the CEL was later disabled hints to me that whoever made an attempt at fixing the car tried everything they could, and eventually just gave up.

So in summary, I've got no vacuum leak at the evap canister, or anywhere else that I can see. I can hear a distinct hissing sound that I feel is coming from the fuel rail area, but it's hard to pinpoint because the PS pump is also whining and making it difficult to locate the source of the hissing sound.

Other than poor fuel economy, the car runs well. It does sometimes feel like it is hesitating to change gears or that it is "heavy" (almost as if it were not accelerating as smoothly as it could, as if it were pulling a small trailer or something). Signs point to a vacuum leak, (or some other type of leak) but where?



I've never had a car that was so difficult to diagnose. If it were any other car, I'd send it to the scrapper. But I'm determined to keep this car.

My last resort is to take it to the dealer here. The dealer here is so incompetent that it borders on criminality. Small country, few dealers, and very very few pre-2008 volvos. My last trip to the dealer went something like this:

Me: "My car is getting 19.5l to 100km (12mpg)"
Dealer: "That's normal, it's an old car."
Me: "Errrrr....it's a 2000 non-turbo, I don't think it's normal for the fuel economy to decline by half."
Dealer: "Yeah, but it's an old car, we probably can't fix it. You should buy a new one."

[oragex]

Your plugs are fine.

How old and what brand is your air filter? I've just purchased a Mahle filter from this seller
http://www.ebay.com/itm/Mahle-Original- ... 25807f7657

Do you have a clean MAF sensor both sides?

[precopster]

I placed a Bosch O2 part number in my Denso 2000 V70 with almost 300, 000kms a year ago. So far no problems; O2 codes are gone and good fuel mileage. As long as it's the correct part number for the Denso system go for it.

I get 25+ mpg in light traffic conditions and around 32mpg on long high speed trips, however my engine has been reworked.

I think it's time to stop guessing and purchase some tools like fuel pressure testers and compression testers. While you're at it put a new set of injector seals on. You need to draw up a table of possibilities and slowly cross off what the problem ISN'T as you eliminate possible suspect components.

By the way I think those 1670 codes are ETM codes not immobiliser

[precopster]

Sorry the 1670 is immobiliser and 1671 CMP actuator.

I had a feeling a knock sensor code would be in there also. It's a very cheap and easy part to swap

[thankswww]

Ive got a new knock sensor ready to go. Ive never removed the intake manifold on this car, so I am reading up on it as much as possible before attempting the knock sensor replacement.

[precopster]

At least with 2000 non turbo models they finally dispensed with the vacuum elbow. However the PCV system isn't listed by FCP as it has many different pieces to '99 models.

I take back that I said it's easy. I tried to spot my knock sensor with a phone camera today and bombed out. It is well and truly tucked away in there.