2001 V40 1.8Gdi starting & idling issues, won't rev
 

Hi all, looking for some help with my V40 please :)

It seems to have been running ok until a few days ago, when the following happened:

- Started from cold (fine)
- Driven for maybe 3/4 mile and turned off (as part of a larger route before anyone wrongly pegs me as the "drive round the corner to the shop" type :tounge_smile:)
- Upon restarting I thought it had fired so released the key but it died
- It continued to turn over on the ignition key but wouldn't fire
- It did start a few times but the idle was very low, with the accelerator to the floor it wouldn't rev over 1500rpm or so
- I eventually managed to get it going and nursed it home - at constant light throttle vehicle speed would remain consistent for a while but would periodically bog down, then pick up again.
- The engine doesn't appear to be mis-firing or running rough, just running very sluggishly with very little power- it reached the heady heights of 15-20mph and refused to go any quicker..


A poke around when I got home revealed not a lot:
- Oil level OK, no signs of water
- Water level OK, no signs of oil
- Visible steam from exhaust but not an excessive amount IMO considering it was still cold
- Engine warning now light on
- Coolant temperature didn't go above about 1/4, with 1/2 being the norm when warm
- Reasonable smell of fuel at the exhaust


Additional info, FWIW:

One of / the ancillary belt slips sometimes for a short period when cold but there are no indicators that any important driven bits aren't working as they should (battery evidently has plenty of juice and it's never overheated so I guess the water pump is doing its job).

Upon turning the ignition key to position 2 prior to starting the throttle body(?) has always clicked repeatedly before starting, which I've read potentially implies an issue. Thinking about it I have experienced a slight but detectable loss of power of power / bogging down before, but nowhere near as bad as it is now; which renders the car un-driveable.


I'm wondering if it might be a fuelling issue caused by a failed throttle body (either the stepper motor that controls the butterfly, the throttle position sensor or perhaps accelerator position sensor) as I guess this would flag up a warning / fault code and I hear they're a bit squffy on these engines.

I'd like to have the plugs out for a look inside but a previous idiot I'd paid to service the car has evidently stripped out the thread in the cam cover for the plastic engine cover so I can't get access (yet another job to do - any pointers on removal much appreciated!) - as a result the plugs are probably overdue a change but tbh I doubt this is relevant unless maybe excessive gaps have knackered the coil pack..

I'm skint and miles away from the only garage I trust so ideally I'd like to sort this issue myself if I can. I'm guessing from the engine warning light that I should be able to get a fault code, although I'm struggling to get my head around this having trawled google..

Will my model display DTC codes on the dash if I use the correct procedure? I'm not sure if this applies to this particular age / type of car. Also, am I correct in thinking that I can use a generic OBDII fault code reader to interrogate the ECU, but that this will only give me basic codes and that I'll need a Volvo-specific reader to get more specific codes..?

Any help would me much appreciated - thanks :)

You will probably find the throttle butterfly spindle has seized , you can take it apart and free and lubricate it . you should be able to press it open by hand and it should spring back ...

You need to fit a new alternator belt and the other one whilst you are at it .. tightening it will probably cause it to snap as it will be worn excessively with the slipping ..

Gdi
 

Maybe other things but is highly likely to be related to fuel pressure, I have worked for mitsubishi on this GDI system but fuel system parts such as high pressure pumps are rarer than hen's teeth......

Thanks - I'll certainly check it and it would be wonderful if it's this simple, however I'm a but dubious given how it was fine one minute and not the next..

Ta for the thought on the belt too - tension seems good so I'm guessing it's slipping because it's worn and as you suggest needs to be replaced :)

Thanks - is there any way I can test this? I'm guessing it'd throw up a fault code if the fuel pressure is outside its acceptable working range.

Do you mean that the parts are rare on the used market or even if sourced new? A lack of aftermarket suppliers perhaps? I bet they're not cheap :(


In other news I've just remembered that the exhaust has been rattling for years and the last time I was under the car it all looked pretty ropy (original system after 78k miles) so I guess it could also be a blocked exhaust.

I think the next step (after checking the TB) is to try and pull some fault codes from the car - I'll have a look on the forum for the procedure / maybe start another thread on the subject :)

A small "progress" update, FWIW..

I tried starting the car from cold again earlier and it started fine but had a bit of a rough idle and again wouldn't rev to more than about 2k rpm. Keeping a light throttle and the revs below 2k resulted in varying engine speed / surging within a range of about 200rpm.

I've removed the MAF and ducting to get to the throttle body and sure enough as predicted by clan the butterfly is very stiff - it can be moved by hand but is too tight for the return spring to do its job and the butterfly just stays where it's put.

I've sprayed a load of brake cleaner in there (the closest I can get to carb cleaner); it's shifting the carbon on the surface of the body but not doing a lot to the free up the butterfly. Looks like I'm going to have to remove and strip it; however it looks like quite a lot needs to be removed and I'm currently stuck trying to remove the engine cover for better access, due to the one stripped bolt keeping it in place :angry_smile:

Not sure where to go from here as I lack any decent facilities - my first thought was to drill the head off the offending bolt but I've got no power supply to hand and don't have a battery drill :(

Most likely is the magnets came off the spindle in the throttle body. My son had a gdi Volvo and this happened to his. It needs a new one or you could strip it out and check it clean all the old glue/resin off both magnet and spindle and marry them together with a powerful adhesive/resin but it needs to be strong. Be very careful of the magnets they are very strong if you let go of them and they hit the spindle they could shatter. Hope this helps 👍

Thanks - looks like you've hit the nail on the head in every respect. Pulled the TB off, spent hours stripping and cleaning it; put it back together and it was still binding. Saw witness marks on the magnet and with some persuasion managed to move it with respect to the rest of the spindle assy. Took it off and did exactly what you warned against - shattering the magnet into a thousand pieces :angry_smile:

The really galling thing is that I'd possibly have got away with filing a bit off the magnet to get clearance with the housing and throwing it back together. Looks like I'm on the lookout for a new throttle body assembly :(

Thanks again for your help though!

Right, got this sorted and wanted to post the bare bones of how it was achieved in the hope it might help others in a similar situation in future!

After keeping an eye on ebay for a while (and getting let down by the absymal comms of one useless seller) I managed to score a used (but apparently previously refurbed) throttle body assy from Gata958 (Alex) who I believe is resident on here as gatos.

From the off Alex couldn't have been more helpful; making me aware of the need to allow the ECU to recalibrate itself to the new parts and taking the time to talk me through possible remedies to the issues I was having - thanks Alex - I'm foreven endebted to you for all you time and advice :regular_smile:


So, the new throttle body was fitted to the car with the old throttle position sensor as I'd struggled to remove its electrical connector when removing the old TB. Unbeknown to me at the time the TPS' mounting bolts holes are slotted to allow some rotation of the unit relative to the TB.. in the absence of any better info I fitted my old TPS to the new TB so that the plug was at approx 6 O'clock when view from the passenger side wing of the car.

Next I tried setting up the ECU using this method, however this achieved very little (other than wasting a load of time a fuel) as the car wouldn't idle at less than about 1400rev/min, which would randomly spike to around 2k :(

Alex suggested rotating the TPS with respect to the TB in an effort to offset this issue; and while I thought I'd won (as the adjustment was clearly making a difference to idle speed when carried out while the engine was running) as soon as I drove the car the idle was back up to where it was.

As a disclaimer, in retrospect I might not have carried out the ECU calibration procedure above to the letter (I didn't turn the ignition to "Lock" only position 2) so the failure of this to work might be on me..

Anyway, suspecting an issue with the TPS position I attempted to quantify the resistance across its terminals as per this diagram:

https://www.volvoforums.org.uk/attac...1&d=1400580378

Long story marginally less long I don't think that these values above are correct for the TPS on my car (perhaps they're for the earlier cable-operated throttle on the pre-facelift cars, which I believe has a different TPS..?).

Setting the TPS to give 2.5k Ohms across pins 1&4 when fully closed meant the TPS was noticeably offset clockwise by maybe 5 degrees, and also meant that at fully open the reading across pins 3&4 was something like 0.75k Ohms.

In addition to this I found that when fully closed the resistance across pins 1&4 was infinite (not the 2.5k Ohms stated), as it was when fully open across pins 3&4.

Evidently this needed a bit more investigation so I cobbled my own TB back together with the TPS from the replacement unit and set about poking it with the multimeter in the comfort of my own home in an effort to validate the results I'd had from the unit on the car.

After again setting the TPS to get a reading of around 0.5k Ohms across pins 1&4 with the TB closed gave a value of around 0.76k Ohms across pins 3&4 with it wide open. As with the unit on the car this setting saw the TPS displaced clockwise from the 6 O'clock position.

I split the difference between the two readings at around 0.625K Ohms in each case and fiddled with the TPS position to achieve this -ending up with a reading of 0.623k Ohms on pins 1&4 with the throttle closed and 0.622k Ohms across pins 3&4 with it wide open; positioning the TB exactly at the 6 O'clock position as I'd found it on each TB before disassembly.

Bear with me, we're getting to the end! I also found that across pins 1&4 from fully closed, as the throttle was opened the resistance value rose from 0.623k Ohms to a peak of 2k Ohms at around 50% throttle opening, before going to infinity beyond this point. In addition I found that across pins 3&4 from fully open, as the throttle was closed the resistance value rose from 0.622k Ohms to a peak of 2k Ohms at around 50% throttle opening, before again going to infinity.

So.. in summary it appears when "centralised" the resistance across pins 1&4 measures the throttle position from closed to half open (its value increasing as the throttle becomes more open), after which point the resistance across pins 3&4 takes over (its value decreasing as the throttle opens further).

I also found that, unlike as stated in the diagram above, the resistance across pins 2&3 isn't constant / irrespective of throttle position - it changed very much like that of pins 1&4 did over a similar range of values.


Armed with this knowledge / the confidence that both TPS units are working correctly I attacked the car this morning. I got the plug off the TPS by removing the unit from the TB and hooking a pick under the steel retaining wire then pulling it off completely (making sure it didn't fly!). You might also have luck in prizing the end of the wire away from the plug at its ends on each side to allow the plug to with withdrawn one side at a time.. I didn't have a flat-bladed screwdriver small enough to try this, though.

(Continued below as the forum seems to be imposing some weird word limit..)

...

I then slackened off the two TPS retaining screws so it could be rotated by hand with a little force, and set about checking the resistance values.

Basically checking pins 1&4 with the throttle pushed fully closed (screwdriver handle against the buttergly and wedged against the rubber inlet trunking), adjusting for a value of around 0.625k Ohms then wedging the TB fully open (again with the screwdriver handle) and checking the resistance value across pins 3&4. I kept doing this and adjusting the position of the TPS by tapping it with a screwdriver handle until I got similar resistance values under both conditions.

I ended up (more by luck than judgement) with a values of 0.659k Ohms both across pins 1&4 with the TB closed and across pins 3&4 with it wide open :cool:

The TPS retaining bolts were nipped up (which can sometimes change the resistance readings, although I'm not sure how close these have to be), the values re-checked and the plug refitted / inlet trunking re-attached.

Please note that if carrying out this process the pin numbers shown in the diagram above are for the female plug that attaches to the male plug on the TPS; so when looking at the pins on the TPS itself when fitted to the car they run in the reverse order - i.e. 4,3,2,1 from left to right ;)

After this was sorted I followed this guide for re-setting the ECU, which was much quicker and easier than the previous one tried. It also had the benefit of wiping the fault codes so no more check engine light on the dash :teeth_smile:

One word of warning though; disconnecting the battery will kill your OEM radio, although that didn't bother me personally as it's never worked since I've had the car and I refuse to pay the parasites at the local dealership for the code.

I did find it hard to maintain 1200rev/min for 2 minutes as the guide prescribes since it was running very close to this anyway, however this doesn't seem to have done it any harm as it's no idling at around 900rev/min after a 6 mile drive..

It might be my imagination but the car also feels a bit smoother / less hesitant at low revs; which tbh wouldn't be surprising given the state of the old TB!

Anyway, thanks again to those who've helped (especially Alex!) and I hope this might sort others with similar issues in the future as there doesn't seem to be a lot of info around on the net.