2011 C70 nightmare reduced engine performance saga

[jengvalljr2]

I've got plenty of awful vehicle stories (from 1972 Chevrolet 6 cylinder pickups, Land Rover Discovery -- several-- Porsche -- old ones mostly) and have solved most of them myself, but this one has literally kicked my ass.

13 months of hell.

12/10/22 I floored it while entering the freeway and got a "Reduced Engine Performance" error and indeed it was reduced.

Originally, it spit out many codes, some of which were CEM related and ECM related; ECM codes were 922D, 921D, 850D, 290B (fuel pressure), and long ago -- December 2022 at early stage.

NOW, 13 months later, I have repeatedly only codes p2135 and p0638 -- which in English means a bad throttle body position sensor or accelerator position sensor.

I have replaced both -- the throttle body which comes with sensor and the accelerator pedal that also comes with its own position sensor/plug.

Twice (once with aftermarkets and once with Bosche/Volvo OEM), with no improvement.

Over the past 12 months.

I do NOT have VIDA but the mechanic I took it to in 2022 does have VIDA; replaced fuel filter and cleaned leads to CEM and/or ECM, because I told him try the cheapest thing first -- which is to say I am not blaming him.

After the car left me stranded literally the next day on Loop 610 in Houston -- with cars going by my at 80mph, I tried replacing the throttle body (which comes with the sensor as part of it) AND the throttle pedal (which also comes with the sensor; tried aftermarket and then OEM Volvo used pedal and throttle body from Erie Volvo -- one of best sources or used Volvo parts in the country.

Result?

Same 2 codes, same dangerous engine performance, surging, sputtering and not being able to drive more than 15 mph.

THIS DAMN car was my son's, so I let him drive my old but reliable X3 the last 11 months and drove my old Rover -- separate nightmares, but hey, at least those are on the brochure and expected from the historically most UNreliable vehicle on teh planet.

Bottom line, I let the C70 sit for the last 11 months and I really don't want to spend thousands getting it to run reliably.

Please offer suggestions and/or humor if you have any.

Also, I have read literally dozens of threads on dozens of sites, including this one, and here are questions I have:

1. Does anyone really know whether the throttle bodies on T5 engines newer than say 2001 or 2002 have to be "calibrated" or is that only on the older ones?

2. Is Xemodex the most affordable next step -- maybe spend the $500 or $600 bucks to make sure the ECM and/or CEM isn't fubarred?


3. Some non-volvo threads have suggested limp mode can be caused by plugs or coils going bad - but not seeing any Volvo chains on that.

Should I try that as a cheap dart at the board?

4. Have not replaced PCV system -- I bought this C70 (my second one) with 78k miles on it and it has 99k now -- and I DO NOT KNOW much at all about the maintenance history on the car b/c bought on internet from dealer in Florida.

Should I try PCV replacement as a cheap dart at the board?

Thanks in advance for any help or humor you can provide.

[Simmy]

as a starting point i would check the condition of the battery 13 months of inactivity could have had a detrimental effect on the battery Volvos don't like voltage problems it makes the electrical system throw all kinds of codes and glitches. check the alternator out put clear all codes run the car and re scan with vida or other quality diagnostic equipment an see what is found.

[jengvalljr2]

The battery was replaced right after these problems arise, last January.

I started the vehicle many times since -- several times each week; only let it "sit" in the sense that I did not drive it, because it would not go faster than 10mph on almost no notice -- was dangerous to drive.

[Simmy]

if you are experiencing limp mode. ie not being able to go more than 10 mph you should have some indicator fault code / light which when read with vida should point to the problem which is giving the reduced performance if you can try driving with vida connected with some one watching the live data . recheck battery voltage. should be no less than 12 .5v static. and over 14v running. just because a battery is fairly new is no guarantee its good. or you could take it to the dealer for a health check.

[T5R92011]

Sounds like a fueling issue.

Replace the fuel pressure sensor on the end of the fuel rail. These typically go at around 100,000 miles.

It's a Bosch part number 0261230110 and they are cheap on ebay.

When it malfunctions you can expect:

Symptoms:
- Sudden severe hesitation during acceleration
- Limp home mode
- Random Stalling.

Doesnt always register a ECU code either.

Watch THIS video for a guide on how to replace. It's literally held on by 1x torx bolt, though access is tight.
https://www.youtube.com/watch?v=zZkBeSE9kwE

Good luck.

[MDS40]

I replaced the fuel pressure sensor on mine a couple of months ago.
Didn't have the same symptoms as the op or the ones listed by the previous poster.

My faulty sensor was causing the fuel pump to work overtime trying to increase fuel pressure that was not needed ( groaning pump ). In other words it was understating the real pressure but i guess yours is overstating it.

Access is so tight that you will need to use one of those torque bits that normally fits a screwdriver type attachment and turn it with thin locking pliers.
Got my Bosch sensor for £50. I didn't have any error codes showing.