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Long Term Fuel Trim at 10% What is typical for a 1999 S70-GLT

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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98RedV70GLT
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Joined: Fri Sep 21, 2018 9:03 am
Year and Model: 1998 V70 GLT
Location: KS
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98RedV70GLT

Re: Long Term Fuel Trim at 10% What is typical for a 1999 S70-GLT

Post by 98RedV70GLT » Thu Sep 26, 2019 9:10 am

For what its worth, my 98 v70 glt is pretty much always on -0.8 to 1.2+ is range after 1 year. I drive 24/7 with torque dash install. Only codes i see are evap gross leak and 02 sensor ones.

All vac lines replaced prior, minus one on intake tube, i guess mines doing great after reading the averages.

I can see up to 34mpg if on good section highway, although living in kansas i may see more flat areas than most. Long term average highway is generally around 28 to 29 with rush hour type included.

My car is no where near maintained well from prior owner and is at 215k, but with random speedo issues, and no prior owner knowledge, it could be much much higher actual. Wish there was a true way to tell.


98 V70 GLT
90 Q45

800artfreed
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Joined: Tue Apr 03, 2018 3:49 pm
Year and Model: 98 S70T5; 99 S70GLt
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800artfreed

Re: Long Term Fuel Trim at 10% What is typical for a 1999 S70-GLT

Post by 800artfreed » Wed Oct 02, 2019 4:52 pm

I thought I had made progress in getting the LTFT down. It was operating at 8.6%, down from 10.2% after some other vacuum line replacements but it has returned to 10% during local stop and go driving.
I have tested the performance of my fuel injectors by using an injector pulse tool and fuel pressure guage. Priming the rail to 53 psi. I then triggered each injector one at a time. All of the pressure measurements dropped to 35 psi. This indicates that all the injectors released the same amount of fuel in the same amount of time (as determined by the tester). I will do a fuel volume test to rule out fuel supply problems.

Exhaust leak or slow O2 sensor is another possibility. I do not have an O2 sensor DTC. As a matter of fact the car has no DTCs. The OEM O2 sensor is a bit expensive to swap out just for a test so I am putting that off for last.

I am going on a long drive this weekend and will see if running at 2500 RPM (65-70 mph) will change the LTFT. If it goes down there is probably still a leak on a vacuum line.



800artfreed
Posts: 47
Joined: Tue Apr 03, 2018 3:49 pm
Year and Model: 98 S70T5; 99 S70GLt
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800artfreed

Re: Long Term Fuel Trim at 10% What is typical for a 1999 S70-GLT

Post by 800artfreed » Sat Oct 05, 2019 8:01 pm

So I just drove 500 miles today. The LTFT diminished to 8.5% when driving at 2500 RPM (about 70 MPH). BTW I used a Bluetooth OBD2 dongle with an Android phone application. This let me keep the console lid in the mostly closed position without stressing the connector cable from my OBD2 reader.
In stop and go local traffic LTFT was still at 10.5%. Since it did diminish at a more open throttle position I will search for more vacuum leaks. After my trip am going to order and use a fuel injector cleaner. I will also run a fuel volume test. Does anyone have the specifications for our fuel pump's output? Thanks.



800artfreed
Posts: 47
Joined: Tue Apr 03, 2018 3:49 pm
Year and Model: 98 S70T5; 99 S70GLt
Location: Washington DC
Has thanked: 0
Been thanked: 9 times
United States of America
800artfreed

Re: Long Term Fuel Trim at 10% What is typical for a 1999 S70-GLT

Post by 800artfreed » Thu Oct 10, 2019 2:05 pm

Some success. I have replaced all the vacuum lines for the EVAP/Purge valve system and another Purge Valve with OEM parts from a PnP. This is the line that originates at the (1999/2000 year) intake manifold's center nipple (approx: 1/4 " or 6mm diameter). I also reused the original 3-way adapter (sealed with "liquid electrical tape" ) that comes from the cylinder #5 exit port (approx: 1/2" or 12mm diameter) of the intake manifold. I most recently replaced the vacuum line from the T fitting that goes to the nipple on the intake tube near the PTC valve. ALL of the adapters used on the vacuum lines are ONE WAY CHECK VALVES!

If you check out the photo of the spit hose and check valve you will notice the adapter/check valve on the line that caused a P0455 code. I have no idea how long this split existed. What I realized is that this created an unfiltered source of air being sucked into the check valve by manifold vacuum. I suspect that dirt OR disintegrating rubber from the hose was introduced into the valve and contaminated the check valve and prevented it from functioning properly.

In the picture you will notice there is an arrow. This indicates the flow direction of the vacuum. A quick test of sucking and blowing into the valve will show whether it is closing and actually functioning as a one way valve. Mine did not seal.

The 3-way adapter on the larger line is also a one way valve and there is an additional small grey one way check valve that goes toward the brake booster.

In one sense these valves allow for vacuum to be applied where and when it is needed. As an example if your engine stalls you still have vacuum in the brake booster for at least one application of the brakes. If you pump the brakes you eventually lose the "boost" on you brakes. This is one reason that the check valves are important. Another is when we are running under BOOST pressure. Others can contribute about how that effects the vacuum circuits but I am guessing the check valves play a role in keeping the engine performing under all conditions.

I thought I had made progress in getting the LTFT down. It was operating at 8.6%, down from 10.2%. I am going on a long drive this weekend and will see if running at 2500 RPM will change the LTFT. If it goes down there is probably still a leak on a vacuum line. After driving 500 miles the LTFT is at 8.6%. I will build a better smoke machine and do a better test. I will push smoke in the correct direction relative to the one way check valves i.e. from the brake booster end of the line into the engine.

As for the EVAP readiness monitor it as finally reset into a READY STATUS! What is puzzling is that prior to going after my high LTFT issue ALL OBD2 monitors appeared to reset easily. After sealing and correcting the vacuum issues the EVAP monitor didn't reset quickly (more like my 1998 S/V-70s). All of my cars are TURBO engines. That means the vacuum system is slightly different than that of N/A vehicles. After a couple of short distance drives (10 miles of stop and go driving) the EVAP monitor is READY! I still have a higher than average LTFT.



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