T4 - rough acceleration - what's normal?

I have a 98 S40 T4SE which has had inconsistent/rough acceleration for several months despite 9 trips to dealers. If possible I'd like some advice from other owners, on what's normal for this car.

I bought it as an 'Approved Used', full Volvo service history etc.. back in Nov 91, and have had several problems with it since, though most have now been fixed.

Since a couple of weeks after buying it, the car has had a problem with what seems to be some kind of intermittent misfire, ranging from a slight roughness under full throttle, to a car that would barely accelerate at any speed, in any gear, due to severe misfiring.
It also sometimes has strange idle behaviour if the A/C is on, and seems to go through periods where it can take up to 7 attempts to start (engine catches, but dies immediately).

The car is under warranty, and has been in to Volvo dealers 9 times now. This has produced a few "There's no fault code, the car is ok", and fault codes for: DSA, Lambda sensor, ambient temperature sensor, & a pressure sensor (I didn't catch the full name). It has had all the above 'faulty' items replaced or cleaned, an ECU software update and replacement of an unspecified valve, new plugs, leads & coils, and from a 5 day dealer visit last week, a new fuel pump!

The only thing that has made any noticeable difference was in July after it had become virtually undrivable for a few days (then recovered for a couple). The dealer fitted new plugs & wow! for 2 days I seemed to have a new car, & was driving round with a permanent grin, masses of smooth power every time I asked, seemed to be fixed!

How wrong you can be - 2 days later it started missing again, though nowhere near as severe as before the plug change.

Most of the time it feels as if the car is running at 85-90%, with the occassional burst of better acceleration standing out because it is unusual, and highlighting what's missing the rest of the time.

The missing/roughness is most obvious if I plant my right foot from say around 3000rpm, the car does accelerate, but seems to hesitate & stutter slightly, through until around 5000rpm when it seems to smooth out, and actually feels to pull more strongly, yet isn't this where torque should start to fall away?
In 5th, my wifes company V70D5 seems to pull much more strongly. I know it has more torque, but also more weight & taller gearing, surely it shouldn't feel quicker than a T4? The D5 feels effortless, my T4 like you're really working it hard.

This has been going on for so long, through several attempts by the dealer that have made no difference, that I'm now starting to wonder if the car was as good as I remember from the 2 days after the new plugs, or if all T4s are a bit rough and inconsistent, what I have now is normal, and I am chasing the impossible.

So the question is: Is this normal for a T4 and I am being too fussy? Are T4s smooth, like I would expect (and like every other car I can remember driving, though I've never had more than 155bhp before), or are they all a bit rough & inconsistent? I've never met another owner to ask, but was told by one Volvo technician that all T4s & T5s were like that, "feeling to hold back one day, then flying the next". He also told me that my car was ok, 4 days before it started to misfire so violently it was barely driveable!

I was hoping you guys could advise me from your experience.

Sorry to have gone on a bit, but this is only part of the story and I'm really, really hacked off with this car, & the inability of the dealers to fix it.

Thanks for reading

Andy S

Andy

Sorry to hear about the problems. I'll try and describe my acceleration traits to give you an idea. Mine is a V40 T4 SE AUTO so may be a bit different if you have a manual.

Driving normally it is as smooth as anything else I have driven. Prior to this I had a 2.0 S40 Auto. Normal acceleration it pulls smoothly and the auto box changes as needed. Push it a little harder and it will drop a cog, a bit like changing from 5th to 3rd to overtake but the response is smooth and steady.

Boot it hard and will drop to 2nd, throw you back in the seat and you need to keep your thumbs in the steering wheel notches to keep the wheels in a straight line - but the power acceleration always remain smooth.

If you are driving at low revs, say below 2500, which is very easy in the auto and boot it you get the above but sometimes notice a bit of lag from the turbo - then it's like all hell has broken loose under the bonnet - but still a smooth and very rapid movement.

The problems you describe are definitely wrong and particularly the car should start first turn.

Unfortunately, my knowledge under the bonnet extends to topping up the washer bottle so cannot really offer any advice as to the problem.

Not sure where you are but if you are near Bucks you are welcome to have a comparison run.

Good Luck

Mike
V40 T4 SE Auto

[Dan F]

Hi Andy S.

Your T4 sounds like one I test drove a while back...
Where did you get it from? Where do you reside?

Sounds like the wastegate solenoid is not working properly or the wastegate itself is constantly open due to incorrect adjustment.

If it is too loose it will open almost straight away and limit boost, however that would mean that it would never give you the proper acceleration you have experienced during your 'good' periods.
So the solenoid looks likely, also is your air filter blocked?

What fuel are you using? Optimax is a MUST in these cars.
My T4 goes like an absolute dream. The only problem I get, is that when I accelerate hard from standstill and snatch second, it really comes in with a bang as the huge torque being generated is hard to control for a smooth gear change, however 3rd and upwards are fine.
My car always gives smooth acceleration no matter what I do.
Your dealer needs to go and drive the car and also a chat with Volvo HQ would help. Maybe the recirc valve in your turbo is always open and occasionally closes letting higher boost enter the inlet?

All things to consider....Sorry I cannot be of more help but I will think about it and get back to here if I think of anything.
Make the dealer work for their money in the mean time... ;-)

Cheers,
Dan.

Hi guys,

Thanks for the replies, it's reassuring to know that these cars can drive as I expected, and it's worth pursuing. When you keep getting told "We've done X and it drives ok", for long enough, you start to wonder if you're losing it.

Mine is a manual, but other than the shifting, I assume everything else to be the same.

Thanks for the comparison offer Mike, but I'm in north Leicestershire so I'll pass on that. I did try to get a comparison drive with a few of the local dealers, but the only one agreeable, didn't have a suitable car.

Dan, I got the car from Wakefield, though it seemed to drive ok on the test drive, or it would still be there. It hasn't been back to the supplying dealer because its a lot closer to take it into Leicester.

Thanks for the suggestions - air-filter I don't know, but it was supposedly serviced before I collected it, and hopefully the dealer has enough sense to check things like that, especially given the number of times it's been back. However I didn't include all the car's symptoms, as I was simply trying to describe the most obvious behaviour for comparison with others, and didn't want to make it too long. Sorry if I mislead you, but if you're interested, here's some more info:

The acceleration I described is the most obvious problem, but I am convinced there is a general underlying roughness even under very light load when trundling round at town speeds, or cruising at steady higher speed, the idle does seem smooth however. It is often difficult to differentiate this roughness from the firm ride, and I doubt anyone not familiar with the car would spot it 90% of the time, but I'm sure its there, and that it shouldn't be.

- Could your solenoid still fit the problems (or maybe I have more than one fault, I could believe it with this car).

I've also had more than one occurence of both the following :

Stop at lights with A/C on - idle sits @ 1400 & doesn't budge. Switch off A/C and idle drops to normal 800 in 2 distinct steps. Switch A/C back on and idle stays put @ 800. Flick revs up to 2000 and idle sticks @ 1400 as above till A/C off. Repeat the above several times. Later in the journey (and most times when A/C is in use) idle just settles straight to 800?

Fill tank and drive for total 80 / 90 miles - fuel level shows 3 bars from top as expected. Park car for several hours on level ground. Start car again, and some kind person has filled the tank up while you were away! Fuel gauge shows full, and the estimated range agrees. Drive the car for several miles and the full tank persists, then starts to drop. By the time you have covered 10 miles or so, the gauge is back to 3 or 4 bars down?!

The dealers are handicaped I think by being in a city center - they have no real opportunity to open it up and experience the most obvious symptoms. They have been talking to Volvo for the last few attempts, but I don't know what's been said.

I don't know much about turbos or fuel injection, but do know a bit about embedded control systems (though not specifically ECUs). A few things have struck me in this direction, and I have suggested to the dealer that maybe there is some kind of problem with the A to D conversion for the ECU, but have no idea whether it was considered or dismissed out of hand. My reasoning is briefly this:
-How likely is it for 3 sensors to fail in a matter of months(lambda, temperature, pressure)?
-If the sensors had really failed - shouldn't there be a difference when you replace them? (there never was so did they fail?)
-If the sensors were ok (and all of these must be analogue devices) then a dodgy AtoD reading could look like an out of limit value & hence a sensor fault.
-I assume that the digital fuel gauge is driven by the ECU from what must again be an analogue signal (see fuel gauge behaviour above - something is intermittently wrong there for sure)
-The common thread - all are analogue signals, probably all converted by the same chip.
-If this conversion floats a bit (or a lot) for whatever reason, then
the ECU may see multiple inputs varying when they should be steady, or plain inaccurate values (though not necessarily out of range). If the inputs are wrong, the outputs, ie engine control is going to be less than accurate methinks!
Makes sense to me, Any thoughts, things I've missed, incorrect assumptions, plain stupidity?

I must confess to supermarket fuel, I tried Optimax earlier in the proceedings, even though it meant going a long way out of my way to get some. It made not a bit of difference, so I went back to the cheap stuff. However my work is moving, and the new location should make it much easier to get Optimax.

Interesting comment about torque coming in with a bang in 2nd. Usually if I push it hard through the gears, there is a flat spot as each new gear comes in before it picks up again, almost like a little turbo lag on each change - obviously not normal either.

If this seemed to go on, be grateful its not the e-mail I'm preparing to send to Volvo Uk, I've had other problems than trying to get it running ok, & I've more than had enough. That one currently runs to 5 pages, and is far from complete!

Any suggestions gratefully received, I don't know if the dealer is open to non-Volvo suggestion, but I'll sure try.

Thanks again, and if I ever get to the bottom of this, I'll let you know

Andy S

Andy

A couple of points.

The "digital" fuel guage you describe were never very accurate - they seem to be a lot more sensitive to heat expansion in the tank. On my previous car, S40 2.0 you could sit still with engine running and the bars would hop up and down !!! I suspect that's why they went back to traditional style.

Starting the car mine runs at 1000rpm then quickly drops back to a steady 800rpm. If I put a/c on at tickover it rises again to 1000rpm but never as high as the 1400 you describe.

Petrol. Never use supermarket petrol. The car is designed for 98 ron. Optimax is the one to go for or failing that a quality superplus 97 ron. If nothing else on optimax you should notice a few mpg improvement but it may take a few tankfuls to fully adjust to it so you notice a difference.

Good luck with Volvo - I still have a couple of "up yours" letters when I took matters up with them.

Mike

[don kalmar union]

I have had many customers with T4's who experience such problems.

There have allways been some problems with the ECU's in some of these cars causing lack of power, sometimes in quite dangerous circumstances!

During the Warranty period some people have bothered their dealers so much that they have got replacement ECU's free which do sort the matter... one got a complete new car he caused such a stink.

There does seem to be a linked problem that the nature of these Siemans ECU's struggles with. Some of their sensing is so acute that small build-ups of carbon on the valve seats can cause misfiring.... this may very well tie in with fitting clean new plugs.

Best to really bother your dealer as there are usually Master Techs who know the score , but generally are kept from the owner by the receptionists doing their job!

Hi don kalmar union,

Thanks for the info, could carbon build up on the valve seats be linked to the supermarket fuel I've been feeding it, & would the problem be likely to return so quickly after the new plugs, if this had been causing it?

As for bothering the dealer, I intend to, along with Volvo Uk who are about to get chapter & verse on my first (and at this rate last) experience of Volvos. The dealer has been fairly helpful, & they do keep trying, but we don't seem to be getting anywhere, they seem to be trying everything around the ECU, but avoiding the unit itself - I'll see what they have to say when I book it back in for attempt no 10!

Thanks

Andy S

How much did the bars hop up down on your 2.0? A bar wouldn't worry me as that could just be a reading right on the threshold between two bars, I often see that in mine. But what I have had twice, was a reading, not hoping up & down, but 3 bars out & steady for several minutes - definitely abnormal for mine.

Fuel - I will definitely give Optimax another try but for now I am tempted to leave things as they are, so any improvements from the fuel don't confuse the issue on whether any dealer 'repairs' have made a difference. That way I know when the car is fixed, and I can better see the effect of the Optimax.
The dealer I bought from had assured me that they were fine on normal 95ron, the handbook says that they will run on minimum 91 with 98 recommended, & my last car ran like clockwork for 113k on the stuff, so I had assumed that I would simply be losing a few bhp.

Cheers

Andy S

Andy

On the old 2.0 if the guage was on say, line 3, it would move up to 4 then down to 2 and so on.

The T4 will run fine on normal 95 ron of course. However, you'll only be getting about 170 bhp out of it - quite a drop.

Get it used to optimax or even super plus and you will notice the difference.

Mike

30 bhp down, ouch!! I'd no idea it would make that much difference.

Talked to the dealer today, and they have agreed to try swapping the ECU, so fingers crossed....

Andy