Chasing a slightly lumpy idle...still

[AllHailKingVolvo]

Over axle pipe ordered! I’ll check the middle silencer when I get a min to see what kind of shape it’s in. It looked good when i was under the car yesterday but will investigate further, likewise with the cat section to see what length of pipe I need to remove it. If I have the Lambda bungs upstream of the cat i’ll use those and just cut the cat out and replace with a blank section of pipe. Looking forward to seeing how the car goes without the cat!

[Laird Scooby]

If you're doing it that way Phil, check you can remove the Lambda bungs and also that they are indeed Lambda bungs, it's possible they are simply captive nuts for a bracket on later cars to support the weight of the cat.

If i've interpreted the diagram correctly and the cat pipework is 54mm O/D, you'll either need a length of 2" O/D to go inside or 2 1/4" O/D (2 1/8" I/D) 57mm to go outside.

This is because the pipe wall thickness is 1.6mm or 1/16" which, when doubled up as the pipe goes all the way round is 3.2mm or 1/8".

Should certainly be livelier without the cat on it!

[LPTJoe]

I'm going to play devils advocate here slightly, my advice would be to manage your expectations

I bought my 940 15 weeks ago and within a week it was running like crap, stalling, revs hunting up and down from 500rpm to 3000rpm. Since then I've...

Extensively checked for vacuum leaks using all available methods.
Replaced distributer cap/rotor with Volvo parts.
Replaced plugs and leads (Bosch and NGK).
Replaced coolant temp sensor (Bosch)
Thoroughly flushed coolant and replaced.
Replaced thermostat (Volvo part)
Stripped down and cleaned breather box and associated pipework (Twice!)
Stripped down and cleaned the throttle body and all associated connections (Now spotless)
Replaced silicone vacuum lines from breather box/BCV and FPR.
Thoroughly cleaned ICV and then actually replaced it with an Ebay special.
Tried a good used fuel pressure regulator swap with mine.
Replaced the crankshaft sensor (Volvo part).
Checked wiring/cleaned connections.
Changed air filter and oil/oil filter.
Ran injector cleaner through.
Reset ECU a couple of times.

That's ignoring the none engine based stuff that I've done like stripping the whole interior to bare shell mode to track down a water leak, completely undersealing and cavity waxing the car and also having some bodywork done and repairs carried out the upholstery, also replacing the doorcards for good used ones. (Wow, when I read all that back I realize just how busy I've actually been over the last few months!)

The upshot of all that is that? Does the car run 110% perfectly/like a modern car...?

Not quite.

The idle sits at a steady 750rpm with very little fluctuation, sometimes very slightly (By about 50rpm or so, very minimal) and not particularly frequently. Also I can see/feel an occasional miniscule stumble for a split second every now and then at idle/low revs. The more I've read about redblock engines the more I've found threads written by people who go to the ends of the earth searching for perfection at idle and ignition and never seem to find it...

I've come to the conclusion that for an old girl she now runs really nicely and is worlds ahead of the way she was when I got her. I certainly don't perform as well as I did 22 years ago and as such I'll forgive my 940 the odd eccentricity on that basis too

They're old engines and I get the feeling that the silky smooth idle and running that we're spoiled with in contemporary coil pack ignition 16V engines is a pipe dream. With mine drivability is good and I have the confidence now in the car having got to know it so well that I'd confidently jump in it and drive it anywhere. I've pretty much made up my mind to leave things as they are and just enjoy the car from here on in

[graham3591]

Hello all, I'm new to the site and have an XC70 2.0 manual with 69k miles on a 2010 plate, I service it regularly with the last service done at 66k. the car is very jumpy/jolty when going up the gears to about 30mph (whilst reading this thread I just wondered if my fault is similar - apologies, if it is not,) I have had the car into a local Volvo garage (not a main dealer) who ran a diagnostic on the car without any faults showing. he went as far as suggesting that the ECG may need to be replaced(is this the correct abbreviation for the onboard computer) but as this would be an expensive option and the last resort, I was wondering if anyone has had this experience or may know what is causing the car to be jolting, this happens mainly when town driving and using the gears a lot.

[Laird Scooby]

Originally Posted by graham3591

Hello all, I'm new to the site and have an XC70 2.0 manual with 69k miles on a 2010 plate, I service it regularly with the last service done at 66k. the car is very jumpy/jolty when going up the gears to about 30mph (whilst reading this thread I just wondered if my fault is similar - apologies, if it is not,) I have had the car into a local Volvo garage (not a main dealer) who ran a diagnostic on the car without any faults showing. he went as far as suggesting that the ECG may need to be replaced(is this the correct abbreviation for the onboard computer) but as this would be an expensive option and the last resort, I was wondering if anyone has had this experience or may know what is causing the car to be jolting, this happens mainly when town driving and using the gears a lot.

Welcome aboard!

I think you mean ECU but you'll probably need an ECG when you find out the price of it!

To be honest, you'd probably be better off posting this in the correct section for the XC70 as they use different engines and are likely to have a different root cause of a similar problem :

https://www.volvoforums.org.uk/forumdisplay.php?f=19

Is yours AWD and if so, you haven't had just two tyres renewed recently have you? That can cause the Haldex unit to wind up and cause jumping and ultimately, damage to the Haldex and other transmission components.

[graham3591]

Thanks for the response, the car isn't all-wheel drive and funny enough I replaced the rear two tyres mid-July. The car has been jolty for a good few months previous to the new tyres going on. I will head over to the link you supplied and hopefully find an answer to the issue there.

[AllHailKingVolvo]

Originally Posted by LPTJoe

I'm going to play devils advocate here slightly, my advice would be to manage your expectations

I bought my 940 15 weeks ago and within a week it was running like crap, stalling, revs hunting up and down from 500rpm to 3000rpm. Since then I've...

Extensively checked for vacuum leaks using all available methods.
Replaced distributer cap/rotor with Volvo parts.
Replaced plugs and leads (Bosch and NGK).
Replaced coolant temp sensor (Bosch)
Thoroughly flushed coolant and replaced.
Replaced thermostat (Volvo part)
Stripped down and cleaned breather box and associated pipework (Twice!)
Stripped down and cleaned the throttle body and all associated connections (Now spotless)
Replaced silicone vacuum lines from breather box/BCV and FPR.
Thoroughly cleaned ICV and then actually replaced it with an Ebay special.
Tried a good used fuel pressure regulator swap with mine.
Replaced the crankshaft sensor (Volvo part).
Checked wiring/cleaned connections.
Changed air filter and oil/oil filter.
Ran injector cleaner through.
Reset ECU a couple of times.

That's ignoring the none engine based stuff that I've done like stripping the whole interior to bare shell mode to track down a water leak, completely undersealing and cavity waxing the car and also having some bodywork done and repairs carried out the upholstery, also replacing the doorcards for good used ones. (Wow, when I read all that back I realize just how busy I've actually been over the last few months!)

The upshot of all that is that? Does the car run 110% perfectly/like a modern car...?

Not quite.

The idle sits at a steady 750rpm with very little fluctuation, sometimes very slightly (By about 50rpm or so, very minimal) and not particularly frequently. Also I can see/feel an occasional miniscule stumble for a split second every now and then at idle/low revs. The more I've read about redblock engines the more I've found threads written by people who go to the ends of the earth searching for perfection at idle and ignition and never seem to find it...

I've come to the conclusion that for an old girl she now runs really nicely and is worlds ahead of the way she was when I got her. I certainly don't perform as well as I did 22 years ago and as such I'll forgive my 940 the odd eccentricity on that basis too

They're old engines and I get the feeling that the silky smooth idle and running that we're spoiled with in contemporary coil pack ignition 16V engines is a pipe dream. With mine drivability is good and I have the confidence now in the car having got to know it so well that I'd confidently jump in it and drive it anywhere. I've pretty much made up my mind to leave things as they are and just enjoy the car from here on in

I absolutely agree with your approach, Joe-I think accepting them for the cars they are (older tech, engines rooted in ‘70s development etc) and enjoying them is the right way to look at it. I think perhaps the idle issue has become more important in my head than it is in reality!! I’m enjoying working my way through the car and getting to know it inside out though, as you have. Once I’ve changed the distributor cap on Monday, I’ll have either cleaned, refurbished or replaced every component in the ignition system south of the ECU, and the car will be just about ready to go anywhere. I will clean the PCV this week and replace a couple of the small vacuum hoses that have gone hard, but after that the engine side of things is about done.

I’ve changed the air filter, cleaned the MAF and removed, cleaned, repasted and refitted the ignition amplifier today, and if anything the idle has smoothed out a little more. It’s certainly not bad, and has improved a great deal with the work that’s been done so far. I think once the new cap arrives and I’ve done the PCV, it’s a done deal.

Driving the car this evening I was struck by how much better it is to drive now as opposed to a month ago when I picked it up. It’s not been an inexpensive process, but the car is a keeper and it’s absolutely worth it to me. New discs and pads all round was the biggest improvement, no more binding brakes or judder...silky smooth now and freewheels like a peach. I’d love to be able to try a brand new example to see how it compares to the car 28yrs on.

[LPTJoe]

Originally Posted by AllHailKingVolvo

I absolutely agree with your approach, Joe-I think accepting them for the cars they are (older tech, engines rooted in ‘70s development etc) and enjoying them is the right way to look at it. I think perhaps the idle issue has become more important in my head than it is in reality!! I’m enjoying working my way through the car and getting to know it inside out though, as you have. Once I’ve changed the distributor cap on Monday, I’ll have either cleaned, refurbished or replaced every component in the ignition system south of the ECU, and the car will be just about ready to go anywhere. I will clean the PCV this week and replace a couple of the small vacuum hoses that have gone hard, but after that the engine side of things is about done.

I’ve changed the air filter, cleaned the MAF and removed, cleaned, repasted and refitted the ignition amplifier today, and if anything the idle has smoothed out a little more. It’s certainly not bad, and has improved a great deal with the work that’s been done so far. I think once the new cap arrives and I’ve done the PCV, it’s a done deal.

Driving the car this evening I was struck by how much better it is to drive now as opposed to a month ago when I picked it up. It’s not been an inexpensive process, but the car is a keeper and it’s absolutely worth it to me. New discs and pads all round was the biggest improvement, no more binding brakes or judder...silky smooth now and freewheels like a peach. I’d love to be able to try a brand new example to see how it compares to the car 28yrs on.

I too would have liked to try one new, alas the time has gone.

You've reminded me of another thing missed from my list. I fitted another used low mileage/thoroughly cleaned MAF! TBF during the whole exercise of me firing parts at the car expenditure wasn't too drastic, perhaps £100 give or take...

For me, out of the list of things done the most profound changes were after changing the CTS, close second would be cleaning the throttle body and ICV.

My thoughts are now turning to MBC and all of the fun to be had there

[Rversteeg]

After over 450K miles my 2.3 LPT is still idling quite nicely, with maybe a very faint shiver every now and then. I have the feeling that the ECU is sometimes setting the ignition timing differently depending on engine temperature, resulting in a more or less smooth idling. The engine also idles smoother on LPG than petrol, so besides slower burning of LPG it could be that the petrol injectors might benefit from cleaning as well.
Last week I was again surprised how quickly the engine came back to life after four weeks standstill and how perfectly it was ticking over from the first moment on!
Btw, slight idling speed variations can also be caused by electrical load variations and switching on/off of the A/C compressor.

[Laird Scooby]

Originally Posted by Rversteeg

After over 450K miles my 2.3 LPT is still idling quite nicely, with maybe a very faint shiver every now and then. I have the feeling that the ECU is sometimes setting the ignition timing differently depending on engine temperature, resulting in a more or less smooth idling. The engine also idles smoother on LPG than petrol, so besides slower burning of LPG it could be that the petrol injectors might benefit from cleaning as well.
Last week I was again surprised how quickly the engine came back to life after four weeks standstill and how perfectly it was ticking over from the first moment on!
Btw, slight idling speed variations can also be caused by electrical load variations and switching on/off of the A/C compressor.

You have a "secret weapon" in the fight against engine wear though Rob! As you run it on LPG, the oil stays much cleaner for much longer which reduces engine wear and clogging of the PCV system.

Also i suspect you are more attentive to any minor problems than the previous owners of Phils car have been, hence he has found so many "silly" things wrong that have all improved matters a little and combined have improved it a lot.