940 poor running and jerking

[Willthevolvoaddict]

Hi guys,

I need some help, for the first time my Volvo is doing my dead in.

My 1992 940 2.3 GLE Auto non-turbo that is running like a dog. When I start it in the morning it runs perfect, idles fine, pulls well and smooth gear changes. After about 2 miles its starts jerking, the idle at stand still jumps up and down and the gear changes come too soon and are also jerky. Power just about disappears, my old 940 S auto would have ran circles around it.

I have given it a full service, all filters, new plugs and HT leads, changed the MAF and engine temp sensor. That was just about all I could find on the forums. Also checked the flashing light diagnostic and comes up no faults.

Has anyone had an issue like this?

Any help would be much appreciated!

Cheers,
Will

[stegreg]

check the crank sensor...pull it out and check the tip is clean, sometimes they pick up a bit too much metal swarfe and can glitch a bit.

You said, engine serviced, did you change rotor arm/dissy cap too?

[ThePurplePanther]

As above, i'd check the ignition system (Dizzy + coil)

Also worth checking, if your car has one (not sure when volvo introduced them) the Lambda/oxygen sensor. Cars start in open loop (not using the sensor) until they are warm then start using it which may explain the good start, poor later performance.

Other one to check is the temp sensor in the head - the ecu uses it to tell when the engine is warm, so changes the mixture from starting rich to normal burn. Stick a multimeter on it and check the resistance hot vs cold, or pull the plug when it is running and see if the engine note changes.

Hope those are of some help - good luck

PP

(BTW: just spotted you are in Langstone - assuming it is Langstone, Hampshire you're not far from me if you needed to borow a multimeter. I also have a spare lambda and temp sensor if you wanted to try swapping them in to see if it makes a difference)

[Willthevolvoaddict]

Thanks all,

In response, changed everything but the dizzy cap and rotor, but had a good look at both and both seemed fine. The Lambda sensor was replaced at last MOT. Oh, and its Langstone in South Wales, but thank you very much for the offer!

After checking the crank angle sensor wire, I saw the plug had some dirt on it and cleaned it off. I did a diagnostic test again and came up with 3-2-2 and 1-2-1 which pointed to MAF and MAF wiring. The new MAF Came from Euro Car Part (a HAAS unit), so I put the old original Volvo MAF back in, cleared the fault codes and took it for a drive.

The jerking seems to be much better and the idling has settled, even after stopping, turning it off for a minute and starting. Power still seems very low, I know they were never rockets, but my 2.0 S Auto felt much more responsive.

I bought the car recently sight unseen knowing that it failed MOT on emissions, so was a gamble to start with but its such a nice car, leather interior, working non leaking sunroof, even the headlight washers still work and actually spray water (none of my others sprayed water, just wiped).

Just want to get it in full working order so I can start using it as a daily driver. Much prefer it over my S40, although fuel consumption is a “tad” higher. Even replaced the dash bulbs so that I can see what button Im pressing! Would still like to find the bulb that lights up the gear shift patern. Has anyone done that before?

Thanks again for all your replies!

Cheers,
Will

[stegreg]

Now knowing it was an "mot fail" on emissions, how about doing a compression check?
better still, what readings were on the fail sheet for the emissions, this could give you and us even more clues.

[Willthevolvoaddict]

It passed after replacing the lambda probe, I will go look for the before and after reading and get back to you.

This forum is awesome! Thanks so much for all the help!

Cheers,
Will

[Laird Scooby]

Just found this thread - somehow missed it the other day.

My first ports of call would have been vacuum leaks, MAF and Lambda with the symptoms you've given in the first post, assuming things like plugs, leads etc were all ok.

Had a Lambda sensor fail on the emissions test once, didn't show any warnings on the fault codes until about 3/4 hour later but was fun watching the CO climb from 0.1% to 9++% CO at which point the tester hurriedly removed the probe from the tailpipes!

Lambda sensors are often overlooked, they do have a limited life (usually about 100k miles) and in some states of America, there is an emissions timer hidden in the car - it starts counting down to zero when it's first fitted and when it gets to zero (after 10 years or 100k miles, whichever comes first) it puts a fault on the engine management system that can only be cleared by the dealer after fitting new Lambda sensor(s) and resetting the emissions timer!

As such any car approaching (or indeed over) 100k miles that starts running rough is going to have a suspect Lambda sensor or two.

Glad you got it sorted anyway, bet it's much livelier with the new Lambda!

[Willthevolvoaddict]

Thanks so much for your reply Laird Sccoby!

Ive been swamped at work this week so Ive booked the car in for a compression test and to have a look at the dizzy cap and rotor. Im sure we can get it going nicely soon. My other 940 failed MOT on some welding near the battery tray and has a nasty oil leak at the rear crank seal! So 2018 hasnt started well on the Volvo front lol.

I wanted to ask, I found a post of yours where you gave a step by step guide to replacing your dash lights with LED bulbs, but the photos have expired. Do you still have them somewhere? Also, where dis you buy the correct bulbs? Ive ordered some additional regular switch bulbs from Volvo Abergavenny but at £5.20 a bulb they arent cheap and not sure how long they will last, LED are much brighter too!

Thanks again!

[Laird Scooby]

Originally Posted by Willthevolvoaddict

Thanks so much for your reply Laird Sccoby!

Ive been swamped at work this week so Ive booked the car in for a compression test and to have a look at the dizzy cap and rotor. Im sure we can get it going nicely soon. My other 940 failed MOT on some welding near the battery tray and has a nasty oil leak at the rear crank seal! So 2018 hasnt started well on the Volvo front lol.

I wanted to ask, I found a post of yours where you gave a step by step guide to replacing your dash lights with LED bulbs, but the photos have expired. Do you still have them somewhere? Also, where dis you buy the correct bulbs? Ive ordered some additional regular switch bulbs from Volvo Abergavenny but at £5.20 a bulb they arent cheap and not sure how long they will last, LED are much brighter too!

Thanks again!

Maybe i misunderstood - i thought you'd got it through the MoT now?
I've had a couple of Lambda sensors that only lived a short while because of poor (non-existent) packaging inside the box the postie threw them through the letterbox in. Worth double-checking the Lambda if you haven't though!

As for the LED conversion, i've still got the photos somewhere, Photobucket became notorious last year when they suddenly insisted all their previously free users had to pay $399 for the privilege of displaying the photos - third party hosting they called it. I now use :

postimages.org

but as yet, haven't been through all my old threads and photos. Some have expired in terms of being able to edit and add the new photo links so i've more or less given up but happy to have a hunt for them.

Here's a recent photo of my current 760 after doing the LED conversion :





Most of the LEDs are a straight swap, however some need a bit of intervention with a Dremel type tool because the OE wire-ended bulbs have their wires welded to the connector terminals. Those need cutting then the hole needs enlarging, dismantle the new LED from its holder, straighten the legs out and fit into the original holder. I think i took some photos when i did the auto shift light but can't find them just now. I'll have a look though.

I got the LEDs from ebay, i have tried the cheapest and ended up throwing them away fairly quickly. I'm trying some at the moment, not happy to recommend them as yet because although i've had no problems, they're still in the time period where the previous ones failed. Give it a couple more weeks and i should know with a bit more certainty.

Similar goes for LED headlamp bulbs, i've tried many and now the ones i can recommend are definitely not the cheapest! Well worth it though, not only do you get much better light output, beam definition and "instant on" but the lights stay clean because they're not hot! Long term i'd expect the reflectors to last longer because the heat isn't burning the chrome reflectors.

[rippedoffagain]

This something I figured out on mine.

On your air filter box, depending on the exact model (I had 2 940s, each had a slightly different air filter design), you might see that there are actually 2 fat hoses feeding air into it. One such hose opens out just behind the radiator. The other comes out near the exhaust manifold.

If yours is like that, if you look inside the air filter box, you will find a flappy valve thing that decides which of the two channels to accept air from. That valve is operated by a tiny thermostat piston thing. On mine, that thermostat piston thing failed. The result was it would start and run fine until it got warm, then would get worse and worse, misfire, and be utterly feeble even when not actually misfiring. Stalls became frequent. The built in diagnostics blamed it all on the MAF sensor.

Unable to find a replacement for the failed thermostat piston thing, I simply put a small bolt in its place, forcing the flappy valve thing to always draw air from the 'cold' pipe. I distinctly remember the fix cost me 10p for the bolt and a couple of washers. I figured it was a good design but probably meant for a climate where it gets much colder in winter than it does here. It worked absolutely fine.