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Mennox Nov 13th, 2017 18:48

Slow Acceleration between 40-70mph (and other issues)
Hi all - new here!

I bought a 2006 Volvo S40 1.6 petrol (126k miles) 11 months ago with full service history and must say it has been one of the nicest cars I have owned. However, other the last couple of months, I have had the error 'Reduced Engine Performance' appear which it goes into limp mode (although turning engine off/on clears it). Around the doors it drives spot on but when accelerating between 40-70mph, the speed slowly increases (which never used to be the case) and the rev counter goes from 3000-4000 slowly too, although the revs actually sound they should be higher! Once I am around 70mph, it again drives spot on and i have no issues increasing to 80/90mph - have done several 200 mile round trips with it going into limp mode once and MPG seems okish.

I took the car to my regular mechanics who tested it (i believe they drove around 20 miles based on my odometer reading) but the mechanic said that after 20 years of working in the industry, he couldnt find any issues (bar apparently some unrelated diagnostic codes which he cleared).....its annoying me as it feels like the engine is working harder between those speeds (revs seem higher than what the counter shows) and doesnt have the umph it used to have. I have also noticed that the steering will intermittently go heavier (generally after a few miles, sometimes after 30 miles) but then its fine the following day.

I am a bit reluctant to take to the garage again having to spend needlessly to try and identify the issue....has anyone come across something similar? Would purchasing a code reader (looking at the Autel MD802) help me to identify the issue and thus saving time and money?

As mentioned earlier, the car has full service history (had a full service 8k miles ago in March and MOT passed with flying colours).

Possibly separate issue, when accelerating and changing gear from 1st to 2nd, there is sometimes a loud CLUNK sound underneath the car (normally when revving higher than usual) - if I sometimes slightly miss putting it into 1st when pulling away, I would get a similar one point the sound was that loud I thought something fell off the car, but this is pretty rare. I did mention the clunking sound to the mechanic (when checking the above) and he says its just the cable catching the exhaust?? Mind, the exhaust on my Peugeot 206 used to hit the axle bar to the point it snapped but this was due to it missing a rubber mount to keep it in place!

LizardOfBodom Nov 14th, 2017 11:35

sorry to hear about your issues. Cant even suspect what causes that engine behaviour, so getting a proper readout would be your best chance. That OBD reader looks pretty good, but your ultimate best solution would be hooking it up to Vida+DiCE (dedicated volvo diagnostic equipment). You can maybe find a member with this around your area who would be willing to help you, or for probably similar money to MD802 you can get your own DiCE reader. You just need laptop and some technical knowledge to use it (search forum about this). The main advantage is that Vida will read EVERY code from your car and interpret it correctly, rather than giving you generic codes to translate.

Cant really give you any advice on your problem as otherwise its just guessing, sorry.

Mennox Nov 14th, 2017 20:34

No worries LizardOfBodom - due to the type of issue(s) it is and that I have already been to a garage with no success, I may look at the DICE option if the cost is not too high.

I did read good reviews regarding MD802 but as you say, it will depend if it reads all the codes and deciphers them well enough.

scoobysn7x Nov 15th, 2017 14:06

There a very good Volvo specialist on the trading estate at the tyne tunnel (north sheilds end of the tunnel) they maybe able to help you (Auto fix 0191 2964173), Also have you tired spark plugs, coils etc??, I had a bit of slow accelaration on my old S40 T4 like it was bogging down, changed the coil packs and plugs and was like driving a new car

Mennox Nov 21st, 2017 10:58

Thanks scooby - will certainly keep them in mind (not far from me either).

Ok, so I decided to buy a VIDA DiCE device which came yesterday. I had initial worries if I would receive cheap china version but its not thank god. I managed to get the software installed with not too much issues and connected to the car this morning and hey presto!

Expecting a list of codes as long as my arm, there was only one which was related to the climate control not working on a particular I cleared the code before I set off to work (only 10 mile trip) - gonna connect it back up when I get home tonight.

I also have a work trip to Leeds planned for Thursday (200 mile round trip) and I have had the car go into limp mode twice in the last several months so this will be a good test if it brings up further codes.

now....not sure if only having this one unrelated code is a good or bad thing as there is still an issue when accelerating between 40-70.

If its not related to the engine, then likely a physical problem? Any other ideas?

Mennox Nov 21st, 2017 22:11

Been racking my brains quite a bit and thinking potential spark plug issue...

My mpg has been slightly poorer around same time of the slow acceleration issues, both linked to bad spark plug(s). I have done 8k miles since last service so who knows (half of those motorway miles)

Eurocarparts have a black friday deal so can get 4 spark plugs and HT leads for only 25....if it doesnt make a difference then its not costing much at all.

scoobysn7x Nov 21st, 2017 23:12

At that price it's no brainer, and if it doesn't fix the issue at least it has new spark plugs and coils

Mennox Nov 25th, 2017 16:41

Just thought I would provide an update.

Changed the HT leads (on Wednesday) and spark plugs today (as they were a bit stuck with tools I had) and althought the plugs werent spoiled that much, it has certainly made a difference when going from 40-70 now!

Feels more responsive now and and a happier me! :)

Mennox Feb 1st, 2018 16:28

Found the Issue!!
Hi all,

Thought I would provide an update as I started having the issue again last week and the car went into limp mode on the way home from work last night.

I hooked up my VIDA DICE and there is an internal fault with the Accelerator Pedal Position Sensor - which now makes perfect sense, especially around the symptons

So I have now requested a quote from Autofix in North Tyneside to find out how much this may cost me (potentially 200 as it will likely be the full pedal and sensor).

I will provide a further update when it gets fixed (end of the month as its an intermittent issue) to see if this makes a difference!

Adamjbutton Jun 28th, 2018 20:05

Hi there. I also had (have) the accelerator pedal position sensor fault. Very annoying and exactly the same laboured acceleration issue. I replaced the pedal this evening but no joy! Same fault code and laboured acceleration. Does anyone have any further ideas?

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