Erratic idle + erratic acceleration on a 2001 S40

mrbrize · Post by **mrbrize** » 29 Mar 2010, 10:07

Hi all!

I am new to the forum, and new to Volvo in general. Just bought a third hand Volvo S40 from 2001 petrol manual 1.8i, which would be absolutely perfect but for the following problems :

- The acceleration is erratic. There are "holes" in the power when I accelerate, compensated by surges forward. It is not dramatic and doesn't seem to present any danger just yet, but I am worried about it. There is no engine lamp glowing on the dashboard.
- The idle is erratic as well. The revs increase and decrease continually, between about 600 and 900 rpm.
- Not sure that whether this is normal or not, and if it is related to any of the problems above, but I find the car to fume quite a lot (white fumes), even after driving for 10 minutes.

So, since I am an absolute dummy when it comes to cars and technical stuff, I went to the mechanic to get the car checked (a random mechanic, not a Volvo dealer). He thought he had solved the problems after cleaning some sort of valve in the "throttle housing", which was incredibly dirty according to him. Problem persisted, and he advised me the whole "throttle housing" would likely need to be replaced, and "no surprise since that's a typical Volvo problem". He also mentionned the Lambda sensor might need to be replaced, if the throttle housing wasn't enough.
Further, he checked the gas emission, and told me I wouldn't be able to pass the NCT (safety car test) as it stands.

So, I have a legion of questions :

1 - Are my three symptoms (erratic idle, acceleration and emission) linked to a single problem? Please tell methey are

...
2 - Is the mechanic likely to be right about the throttle housing or is there some further check he should do before replacing anything?
3 - By the way, what is the throttle housing? I have read several things about throttle body, but not throttle housing.
4 - What would be the price for that part (in pounds, euros, dollars, whatever I'll make the conversion

5 - I have read an awful lot of things around defective ETM on Volvo's from 1999 o 2002. Does my version have an ETM as well, and what do I have to fear?
6 - Depending on the diagnostic you come guys up with, could you let me know how long I may drive the car like this? What's to expect if I don't do anything, in terms of safety and condition of the car?

Many, many thanks in advance for your help!

mrbrize · Post by **mrbrize** » 29 Mar 2010, 10:59

Sorry, just noticed I had made a double post...

Post by **jblackburn** » 29 Mar 2010, 11:04

I took care of your double post, no worries.

Your problem definitely sounds like an ETM issue to me. Head over to Don's ETM room of the site here, and you might get more help with the issue, or at least have some good reading to track down your problem more.

You can try cleaning the ETM, but it might need to be re-conditioned at this point. XMODEX has a great price on those, I believe they do S40 ones as well.

This video is for cleaning an S80, but once you get the throttle body off your S40, the procedure's almost exactly the same.

mrbrize · Post by **mrbrize** » 30 Mar 2010, 08:55

Thanks a million! I will repost in the ETM section then.

So there is no doubt that an S40 from 2001 also has an ETM? I saw in Don's VEXED forum that only the v50, 70 and 80 from 1999 to 2002 had had this problem.

And couldn't other defective parts be responsible as well? I have read about similar symptoms with different causes, such as :
-lambda sensor
-MAF sensor
-MAP sensor
-Idle Air Comtrol valve
-cracked engine mount
-leak in the vacuum pipe

Would it be relevant to check any of those in my car?

Post by **jblackburn** » 30 Mar 2010, 09:14

I won't lie to you, I know nothing about the S40 model. I had a friend in high school that had one, and I rode in it a couple times. That was way before I actually got into cars, or my own Volvo. I was under the impression that all 1999+ models had an ETM, but I could be wrong. It's easy enough to check - does your car have a throttle cable coming up and over the engine and a big hunk of metal stuck in the middle of the air intake pipe to the engine?

Actually, yes, the MAF sensor could be a suspect. Before you jump to anything, that is worth a check. You can try unplugging the sensor (just after the airbox) and see if the car can idle/drive any smoother. This will set a check engine light code, but you can easily have that reset. If your car idles/drives better, then your MAF sensor is actually the problem.

Vacuum leaks could be worth checking as well. Look for any obvious cracked lines - I can't tell you the obvious suspects on an S40 as I can on the 850's, though.

An idle control valve would cause idling problems, but not stumbling on acceleration. MAP sensor does nothing except get angry and throw codes as far as I'm concerned.

An O2 sensor (lambda sensor) would likely throw codes or cause bad gas mileage if there was actually a problem.

Anyway, I hope that gives you a starting point. I wish we had more people that knew S40's over here, but let us know what you find out!

Post by **OEMVolvoParts** » 30 Mar 2010, 10:36

Hi All!

This car is not a USA spec Volvo so the info I have might not apply here. There is no ETM on 00-04 S/V40's, they have a mechanical throttle body. The idle issue is mostly likely caused by, you guessed it, the idle air control valve which is very common. There is a fuel pressure regulator that is also very common, and could cause the poor acceleration problems. These cars are in my opinion pretty solid. They have their issues just like any car, but overall they are very predictable and solid. These parts also might not set a check engine light, which makes it a little more difficult to diagnose. Hope this helps and have a good one.

mrbrize · Post by **mrbrize** » 30 Mar 2010, 11:13

Guys, I really appreciate your help!!

I have posted in the ETM section to confirm whether my car has one or not.

As for the other pieces you have mentionned, (IACV, MAF sensor, vacuum pipe and fuel pressur regulator), are those parts I can get replaced by any mechanic, not necessarily by a Volvo dealer? (sorry for the dumb questions...)

Post by **jblackburn** » 30 Mar 2010, 13:17

Whoops, sorry for leading you in the wrong direction there!

I would start at the mass airflow sensor...I have had exactly that problem with one before. Simple, easy test. If it doesn't run any better when you unplug it, it's not your problem, and you can start digging into other things, the fuel pressure regulator is the next easy thing to test. There's a vacuum line (shield your eyes...don't ask how I know) that you can pull off, and if there is gas in that line, you'll need to replace it. It's under the fuel rail cover on my S70. The idle air control valve can be easily taken out and sprayed out with carb cleaner, brake cleaner...anything that cuts grease.

Not sure that whether this is normal or not, and if it is related to any of the problems above, but I find the car to fume quite a lot (white fumes), even after driving for 10 minutes.

Hmmm...is it cold or rainy outside when it does this? Does your car use any significant amount of coolant?

mrbrize · Post by **mrbrize** » 31 Mar 2010, 01:44

It's in Ireland so... yes, it is cold and rainy

However, it really seems to me that my car fumes all the time. I compared it this morning with the other cars around, none of them was fuming that much.
I guess that must be related to the bad gas emissions that were detected by the mechanic.

mrbrize · Post by **mrbrize** » 31 Mar 2010, 08:30

Ok, someone from the ETM section confirmed there is no ETM on my S40 :

"Your S40 has an old fashioned cable connecting gas pedal to the throttle, there is no ETM in it.
Have the vehicle scanned and see what the codes are, my guess bad O2 or high fuel pressure."

Could someone confirm I will have codes, even though I don't have any lamp on on the dashboard?

And to come back to one of my previous question, what did the mechanic mean I saw mean by Throttle Housing? Is that the same than the throttle body?
The mechaninc said that even after cleaning it, a valve within doesn't seem to work properly. Could that be the cause of all the problems I described?

Sorry for all the questions - thing is, I am out of warranty, parts and labour are extremely expensive here in Ireland, and on top of that, I am not quite sure a regular mechanic would proactively investigate some parts unless specifically asked.

Cheers!