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Engine "dragging" at closed throttle

Help, Advice, Owners' Discussion and DIY Tutorials on S40 and V40. In this forum you'll find S40/V40-specific owners asking and answering questions on maintenance, ownership, repairs, tutorials and almost every do-it-yourself thing you can do to save money owning these Volvos.

1996 - 2004 S40
1996 - 2004 V40

Broodoobob
Posts: 14
Joined: Tue Aug 20, 2013 6:18 pm
Year and Model: 2000 S40 Sedan
Location: Washington
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Broodoobob

Re: Engine "dragging" at closed throttle

Post by Broodoobob » Sun Oct 14, 2018 12:09 pm

Thank you for your notes everyone. I have some updates.
  • I rechecked compression and cranked 8 times per cylinder and I got 190+ on all cylinders dry and 200+ with some WD-40. I'm convinced I made some mistake when taking my previous readings. Or maybe my gauge is unreliable... or maybe I didn't crank it enough. I don't recall if I did it warm or cold.
  • The misfire was cured by swapping out my spark plug wires going to cylinders 1 and 2.
  • The VVT code was cured by swapping the solenoid assembly ($12 from Pick n Pull, yay)
  • After the above, performance feels better but still not great. Dragging issue seems about the same, slightly less I think.
  • I ran an oil sample with Blackstone and it came back clean, so bearing issues are not the problem thankfully.
  • Today I pulled the vacuum hose from the fuel pressure regulator and fuel came out. So that's where my high negative fuel trims are coming from! I have a new (used) one on the way. The actual rail pressure is spot on though.
I hope that the FPR fix will restore my fuel economy. I don't know if it could be the cause of the dragging issue but a high amount of unmetered fuel can't be any good for efficient coasting. I also have 12 quarts of transmission fluid and will be doing a fluid change as preventative maintenance and also as a shot in the dark at the issue. Timing belt still waiting for a free sunny day to be done...



Broodoobob
Posts: 14
Joined: Tue Aug 20, 2013 6:18 pm
Year and Model: 2000 S40 Sedan
Location: Washington
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Broodoobob

Re: Engine "dragging" at closed throttle

Post by Broodoobob » Thu Oct 18, 2018 5:51 am

Well, I installed my FPR and it no longer leaks fuel into the vacuum line. But now my fuel economy has worsened greatly. I will check the rail pressure tomorrow. I did try resetting the ECU by pulling the battery for a minute. I checked the fuel trims on the road. At idle they are pretty centered on 0, which is good, but it seems to be misfiring a lot again. While in motion, the fuel trims go very negative (centering around -10%) which I suppose could indicate fuel rail over-pressure. I guess I'll find out tomorrow. It's from eBay so if it's bad I'll send it back and buy a well-rated aftermarket used one, unless someone here warns me otherwise. I try to use genuine parts, but $250 is just too much. I'd rather take my chances with another eBay unit.

Also, it made no change in the dragging issue. My previous theory was that high unmetered fuel use while coasting was causing the cat to work overtime and create exhaust back pressure. But now that unmetered fuel is gone assuming I don't have a leaky injector, I think that theory was incorrect.



Broodoobob
Posts: 14
Joined: Tue Aug 20, 2013 6:18 pm
Year and Model: 2000 S40 Sedan
Location: Washington
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Broodoobob

Re: Engine "dragging" at closed throttle

Post by Broodoobob » Mon Oct 29, 2018 4:42 pm

Well, mystery solved! It was the fuel pressure regulator. I put in another one and just like that, it coasts just like it used to. I traveled 500 miles round trip to Portland and I got a combined 29 MPG for the trip, which is fantastic. I'm very happy with the car's performance now.

The one remaining issue is that the VVT codes (Camshaft timing over-advanced & Camshaft timing over-retarded) have returned. Now I suspect a wiring issue, or a stretched or slipped timing belt. I'll find out if it's the latter soon. Maybe it could also be a bad camshaft position sensor? If you're reading this and have any ideas, please leave a note. Thanks.



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alschnertz
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Year and Model: 1995 854T
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alschnertz

Re: Engine "dragging" at closed throttle

Post by alschnertz » Fri Nov 02, 2018 6:15 pm

Good info.
29 mpg combined is about what I get.

It's a little tough to see, but it sounds like checking the timing marks is the next step.


'60 PV544, '68 220, '70 145S, '86 745T, '95 854T, '01 S40
'84 Prelude
'06 MPV
'13 Ford Focus SE

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