From my Foxwell, STFT ranges from -10.9 to 8.6%
LTFT 1.6-3.9 occasionally 7.8%
MAP 26-29 occasionally 42 KPA
MAF 2.85 to as high as 5-16 gs
Idle rpm 641-892
O2 440-535 V
Recent smoke test, new O2 Bosch, compression test, 130 to 144, MAF cleaned, new plugs, suspect original MAP at 215K although it was cleaned! Injectors were open but not misting like my 245?
No real long trips but getting about 20 mpg
Fuel pressure at 55 psi, appears to be high.
No misfire codes but will show p2177 a lean code off idle.
Timing belt reported to 10K per PO!
Xemodex TB was cleaned along with new gasket.
Thanks for any advice.

OK, just a shot in the dark suggestion. Could there be a cracked vacuum hose somewhere? Maybe raising the engine opened the crack wider or pulled it off a connector. Just a thought since no others have come forward.

Thanks David, I just did a smoke test and now wondering if I should increase pressure? Prior to this test I did find a leak in the vacuumn chamber in the AF. Cooler weather and MM heat shield replacement should be helpful!

Previous owner had the same problem and replaced plugs, FF and two sets of used coils
Tom

Hi Tom,

Odd how it misses more after motor mount replacement. Check grounds.
Take apart the nest of wires at the battery positive terminal, shine up
and use conductive grease or Penetrox-A.
Maybe a loose ECU signal ground wire (2) at the intake manifold?

You might look at the plugs carefully to see if there's any clue for which
cylinder /s is missing. Check the plug gap.
You can do a compression test while the plugs are out.

Since you inherited this problem, I'd service all of the ignition connectors.
Clean with isopropyl 90% and a soft toothbrush, blow out with air and inspect the
female connector pins, maybe you have some damaged/spread pins?
Adjust or replace any bad pins. Get connector parts at www.davebarton.com
While you're at it, look at the AMM, and CPS connectors.
Use Penetrox-A on the pins. Corrosion and / or loose connector pins
for fussy shielded wire engine sensors invite trouble.

Good luck, Bill

V70 now at 217K with a new Trans pro MAF and Beck Arnley MAP and the five banger seems to be cured! MPG went from 20.9 to 27+!
Thanks to BB members for all your help!
Tom

Stumble, Buck, Misfire? Returns at 300 miles with cruise control cutting out! Previously I turned off the ignition temporally and cruise control would return but not today!

Plan to check "Matthews Volvo Site" for similar problem where poster replaced electronic throttle body as cure!

Milage now at 217

Hi Tom,

Look for DTC codes missing CPS or RPM signals.
See my post just now to Robert regarding the CPS. (in this thread)
The stumbling can be the PEM. Gets too hot and starts to quit.

You might want to look carefully at the sheath of your CPS
if it's broken then the shielding is probably gone.

Try disconnecting the battery for 10 seconds, see if that helps.
(make sure you have radio codes etc first.)
You can wrap some aluminum foil tightly around the CPS harness as a test to see
if it calms down the engine malfunction.

I'll post back later about what happens with the EMI shield for the CPS here.

Bill

Now at All most 219K and running fine! (28 MPG Highway)
I have an O2 sensor issue, currently at .500V rather than .1-.9 V so will I help my MPG by using an expensive OE sensor?
Many thanks for all your help!

Thank you Bill, I have done a compression test and new plugs , new fuel filter and two sets of coils. I really want to check the electrical connection for the throttle body, but I have problems with releasing Volvo's terminals! Mainly as the splash guard has been missing, exposing that connection.
FYI "stumble, buck misfire" condition has appeared to improve? I have seen others with similar ETB's and pedal connection?

Hi Tom,

>"ETB" ?
>Splash Guard missing ?
Find out about your connectors.
Go here and look for your style of connector, maybe EFI:
https://www.prancingmoose.com/blackvinyl.html

Connector shells generally have latches to separate male from female connectors.
The info to separate your connector may be at this site?
Check out the wealth of info there to repair connectors.

The crimp on pins generally have spring latches that hold them into the connector shells. You can fashion a release tool from a stainless steel bicycle spoke,
where you grind a thin tapered open slot screwdriver type tip.
You slide this tip under the latch from the harness end to free a pin from the shell, then you can remove that wire and pin. You can reset the latch to re-insert that pin by carefully bending it out again.

Get an 8 oz. tube of Penetrox-A for connector pins. ($16-19 @ Ebay)

I hope this helps, Bill

"
Get an 8 oz. tube of Penetrox-A for connector pins.
"

Q: Would Penetrox A be a superior product to dielectric grease for inhibiting corrosion and connector protection?

Hi "Robert S"

Are you the same Robert that does Volvo videos with a Steeler's hat?

Dielectric Silicone is best for a little on the top of the plugs so the boot
is sealed and you can remove it easily for service,
and plug wires to coil and distributor. It's better than nothing on connectors
because it makes a weather seal, but it doesn't prevent electrolysis.

Yes, Penetrox is the right stuff for connectors, lamp sockets...
It deters oxidation/electrolysis.
See this write up by Brickboarder Ron Kwas.

http://sw-em.com/anti_corrosive_paste.htm

Cheers, Bill

Not the same Robert who is well-known for his DIY videos. I view them often.

I'll try Penetrox A.

My 2000 V70's particular issue is a random misfire which will always occur in Cylinder #3. The car will run fine for hundreds of miles, then out of the blue will trigger the CEL and run rough with a #3 misfire. I will unplug the #3 coil receptacle housing, remove the coil, reinstall the same coil or swap with a spare, and #3 fires again normally. Problem will randomly repeat later.

The #3 coil connector has been repinned into a new receptacle housing, new #3 coil wires spliced in along the top of the cylinder head, and grounds checked. Have also removed and reseated the ECU.

I have no logical explanation why the #3 random misfire occurs. It's especially mystifying when simply unplugging, removing and reinstalling the #3 coil will solve the problem until a few hundred miles later when it will happen again.

Hi Robert,

Look at the harness connector for #3 coil and you're likely to have a damaged/ spread pin. Clean with a toothbrush and 90% isopropyl alcohol, blow out with air
and you should notice if a pin is damaged.
Adjust or replace then lube with Penetrox.

BTW don't use solvents around connectors, some connectors get damaged from solvents, bullet connectors for one. I can visualize some tech cleaning connectors with spray carb cleaner and maybe damaging the connector.

Please remember to report back with your results.

Cheers, Bill

Thanks Bill, I tend to agree with you.

Can't explain however why the problem persists with new pin terminals several times over, spliced-in new wires on top, swapping different coils, etc. And the problem is only with #3.

One possibility may be frayed wiring in the harness from ECU to Coils running below the engine, which causes intermittent problems. I don't like to think about trying to troubleshoot that possibility. Another possibility is a coil driver in ECU. Didn't want to go there, either.

That receptacle housing where Penetrox would be applied is a small area. Use sparingly?

Hi Robert,

Clean the male and female pins for the coils with a toothbrush
if you see corrosion remove gently so you don't take off plating.
Put enough Penetrox that they all the pins have a smear, and enough to surround the female pins. You don't want giant blobs to attract road grit or make it impossible to seat the connector. Penetrox is a thick paste, I apply it sparingly
with a toothpick. You could use a Q-tip for lamp sockets.

What interval does coil #3 act up? When will you feel confident it's fixed?
Don't forget to report your results.

Cheers, Bill

I've felt confident before that the #3 misfire is fixed after a trouble-free thousand miles or so, only then to reappear. Intervals can vary from every 300-500 miles to 2,000 miles. Sometimes shorter. Can happen at any speed, including at start-up and after sitting overnight.

I'll report back after I try Penetrox in a week or so.

Hi Robert,

The long interval intermittent problems are the hardest to resolve.
Service the Air Mass Meter and CPS connectors.
Also service your PEM, including new thermal compound and use of Penetrox on the connector.

Doing this helped calm down a frequent intermittent in my 940 to the point where I was getting hopeful of a solid fix. But no, I got a code for sporadic or missing RPM signal (CPS).

Previous to this I suspected EMI/RFI corruption of the CPS signal and was surprised to find that the shielded cable for the CPS is un-grounded at the Bell Housing. This might be OK with new ECU's with their new electrolytic filter caps, but not so good with geriatric caps. So I added a pair of snap ferrites (RF chokes) to the CPS harness, one at the bell housing, and another near the harness connector.

I ordered some 28MM ID tinned copper braid for EMI/RFI shielding.
I plan to cover the plastic CPS connectors (NOT RF connectors) and find out exactly what size braid is the smallest that will pull over the connectors. I found out yesterday that the CPS harness has really crappy aluminum shield instead of braided copper found in a 2-conductor Belden mike cable for instance.
The old CPS I received measured OK 179.2 ohms but the sheath was falling apart
and the flimsy aluminum left it open to RF corruption to the RPM counter.
While I'm waiting for the braid to show up from China, I wrapped the CPS connectors in aluminum foil and black tape to add some shielding there.
It's ugly to look at but better than the lack of any shielding at the connectors. I expect to have this EMI braid in less than two weeks to do a better job of shielding the CPS harness and see if it resolves this vexing long term intermittent problem that was also bugging the previous owner of this 940.

EMI is not a new issue for cars, One Volvo TSB for a 240 ABS issue was to re-position the ABS harness that was acting like a tuned in antenna!

Good luck, Bill

Hi Bill and Robert! All is well that ends well! Daylight and a good night's sleep helped me open that connector to the exmodex throttle body! Had some de-oxit and will search for penetrox-A!

SBM= stumble,buck,miss

With the absence of SBM it should stop dropping out of cruise?

Thanks so much!

Hi Tom,

Thanks for correcting my acronym directory here.

Here's an old link to Penetrox
https://www.ebay.com/itm/385735185784 $16.04 Apr 2024

You didn't put the model year of your car, and I wonder if you're being victimized by an overheated PEM? I went through this with a friend, also with a similar
issue with a new 850 fuel relay (solid state) overheating.
The hotter they get, the flakier before outright failure, followed by working again after cooling down. Volvo had some PEM's in the trunk and some under the
car. The idea is to cool it but not have it get full of water and salt from the road. So you'll want Penetrox for it's connector and thermal paste for the heat sink. If it's outside maybe use some silicone sealant to improve the weatherproofing of the box?

look here:
https://www.swedespeed.com/threads/pem-failures-solved-theory-and-solution-inside.657803/

HM, Bill

Happy motoring :-)

Hi Bill and Robert! All is well that ends well! Daylight and a good night's sleep helped me open that connector to the exmodex throttle body! Had some de-oxit and will search for penetrox-A!

SBM= stumble,buck,miss

With the absence of SBM it should stop dropping out of cruise?

Thanks so much!

Hi Bill, thanks so much for Dave Barton's site however it's mostly about RWD, althogh I have bookmarked his site! Incredible!!!!
Tonight on a short drive the V70 did not "stumble, buck or appear to misfire" and did not drop out of cruise?
Also the cruise button may occasionally honk the horn, when "SBM' happens?

Hi Tom,

I'm guessing: "SBM" = Sudden Bowel Movement?

You're likely to find AWD is using the same old connectors,
if no, e-mail Dave Barton and and see if he can source it.

He's the VWM .... .. (Volvo Wiring Maven)

Cheers, Bill

Motor mounts were replaced last week and now misfires are much worst, apparently raising and lowering engine affected some of the wiring? Still no codes!
Basic fuel trims, MAP, MAF seem to be OK!
Help require!!!!

Will likely increase voltage to 12V as 9V may not create a good pattern?