interesting issues with a 940 turbo

[lixah]

vehicle information

Volvo 940 1997
B230FK
manual M90 gearbox

Mileage: ~113000

(i thought it was interesting to note, this is a low mileage and low owner car, and only recently had the timing belt done , a sticker showing 09/2020 (109195 miles)) - at least according to the sticker

symptoms;

lambda warning light illuminated on the dashboard.

very hard to explain; a rattle/grinding sound - SOMETIMES. this sounds like it's coming from the offside front, i actually originally thought it was suspension related, however after having driven this car for a couple of hours, i have changed my mind) so it almost sounds like something's loose and just rattling/grinding on metal, i've very much tried to match it to a certain speed or RPM, however there seems to be logical connection, and it will come and go randomly - however, it's quite apparent that the engine vibration can affect or even remove completely the noise , example; driving at 70 MPH on the motorway, no noise, foot down, noise starts slightly , let off and it's gone again. however /generally/ as a rule it seems to be when first moving off from stopped. it almost makes me think there's something loose inside the gearbox??

lastly, this is the first day i have owned the car, it was purchased from a scrap dealer who didnt want to scrap it- and it's understandable why, it's tidy inside and out, and also has low miles, i wanted to save it too!

i also dont believe he knew anything about the issue, likely. since i only heard the vibration/rattle before this, it was about an hour into my journey home that i started to have a real problem. drive started to cut out, it felt like fuel cutting out, like a fuel pump failure or something. i quickly took the next exit off, and managed to get into a quiet spot in an emergency lane.

for the next 30 min i couldnt get much power, however the engine never cut out, but would almost die when trying to accelerate (IN FIRST)
another weird thing, because of where i was stopped, trying to merge back onto the roundabout/get the lane that i needed, combined with not being able to accelerate, i had to reverse a good few times, what has me puzzled, is that it never seemed to have an issue in reverse, and then randomly i was also able to pull away again, in first. and while the rattle/vibration noise didnt go away (i was very very careful to try and keep to just gently rolling behind faster traffic) i didnt have any other issues on the way home.


other potential symptoms: when i first got to the car to collect, the coolant reservoir was empty, we put about 1L into it, and it doesnt seem to have gone done , i checked it again when home (around 120 miles) but thought it might be worth mentioning - ALSO, it appears to have had a new radiator very recently, i checked both top and lower radiator hoses got up to temp, and the car held a good temp all the way. i put this down to likely bad maintenance / not being cared by the last owner.

I am quite stumped at where to start looking at this, but i would really like to save this car, rather than part it out, as it's still low mileage, and the best combination, and half tidy.

Regards, Matthew

[Laird Scooby]

Firstly Matt, the rattle sounds (from your description) like a loose heatshield on the cat or some other exhaust part, crawl underneath and tap various parts of the exhaust system to see if you can recreate the sound - if it's speed related check the pads and discs on the front.

Second, you'll need a "not quite OBD" code reader from Loki_the_GLT and read the codes to find out whaat the ECU thinks is or isn't happening.

Third, pull fuse ~1 for at least 30 seconds then refit and take it for a drive (preferably from cold) and note how long it takes before the engine management light comes back on.

Fourth, have you any idea when the fuel filter was last changed?

Fifth, do you know how to check the cam timing?

Sixth, check the HT leads for condition and security, also remove the dizzy cap and check the crabon brush is whole and in place, not broken or missing, also check the rotor arm isn't dirty on the contacts (rub it on the tyre sidewall or across the grain of your jeans to clean it) and also check the contacts inside the dizzy cap.

There may be other things to check as well, those should give you a good start. Also worth checking the air filter for cleanliness (renew if dirty) and remove and check the plugs for cleanliness on the insulator and gap them to 0.65-0.7mm and refit.

[griston64]

Thinking along the exhaust lines as well. Could it be the cat that's rattling ? Loose stuff inside could be blocking it which could also be the Lambda light issue

[lixah]

thank you guys, i plan to take a more detailed look tomorrow. your suggestions are greatly appreciated

-Matt

[lixah]

ok, so i first got the car on ramps, and it's pretty obvious to see the issue.

https://youtu.be/8B2JwWWzIb0

so this raises a few questions, are any of these parts aftermarket? if so, shouldn't there be a lambda sensor somewhere on that downpipe? is that what the bolt is for?

the catalytic converter also looks suspiciously wrong, but i cant say for sure, since ive never had one of these cars













lastly just, what's this meant to be ? is it some past of the AC system that's not longer being used?

[griston64]

Originally Posted by lixah

ok, so i first got the car on ramps, and it's pretty obvious to see the issue.

https://youtu.be/8B2JwWWzIb0

so this raises a few questions, are any of these parts aftermarket? if so, shouldn't there be a lambda sensor somewhere on that downpipe? is that what the bolt is for?

the catalytic converter also looks suspiciously wrong, but i cant say for sure, since ive never had one of these cars













lastly just, what's this meant to be ? is it some past of the AC system that's not longer being used?

The bolt just above the cat is just a blanking hole. The sensor should be on the downpipe not far below the turbo. Looks like an aftermarket cat which isnt that unusual on a 25 year old car

[360beast]

Yep aftermarket cat, the bolt is being used as a blank as the aftermarket downpipes don't come with the blank installed. You can buy proper lambda bungs of you want to make it a bit tidier. As Mark says the lambda is further up, roughly on the underside of the downpipe in your first photo.

From the photos the exhaust system looks fine (you asked me on ebay for an exhaust system, I don't have one but it looks like you don't need one).

The last part is the heater control valve for the A/C cars, why has it been bypassed? Are you getting permanent hot or cold air? Potentially the heater matrix is leaking and so it has been bypassed.

[lixah]

looking further, seems like i was able to solve most issues.

the reason the downpipe was knocking against the subframe, was all the nuts between the downpipe/turbo were literally barely on, i undid most with my fingers.

Im not sure who installed it, but it was a terrible job, they'd cross threaded 2/3 of the mounting studs. VERY fortunately, i was able to cut off ~1cm of both, where they were damaged, and replace the nuts, and get it all put back together, as two mentioned before, yes, the lambda sensor is much further upstream, almost @ the turbo itself (i thought it was further down, dont know why)

so, i put it all back together, and when everything was nice and tight, there's no more knocking against anything. the downpipe is very tight and snug.

the only other concern is why did the car die on me on the way home, as someone suggested; i have today replaced the fuel filter, along with a full service compliment. however, i notice there's a buzzing noise coming from the rear nearside wheel of the car ( i will upload a video, not sure how well the audio will be)

is it worth considering replacing the (in tank? i assume) fuel pump?
I didnt get chance today, but i hope to also give the ignition system a good looking at, and cleaning if required.

regards, Matthew

[360beast]

If the downpipe was loose air could get in and give the lambda a false reading which could then overfuel it and cause running issues. The lambda probably needs changing as it has had a knock on surprised it hasn't brought the code on as they're a sensitive piece of equipment.

[lixah]

I also forgot to mention, i reset the engine management by removing fuse #1 as advised above. and the lambda light has gone out, for now. i havent driven much, i assume not enough to allow the light to come back on yet.

however the few times i went around the block the light hasn't come back on, and is driving well