Volvo 760 2.3 turbo - power issue

[lessertegasi]

Hi everyone,
Very new to this forum and in the Volvo world in general and I need some help.
I recently acquired a Volvo 760 2.3 turbo estate (1990) and although I serviced it properly and changed a few essential things I am dealing with a very strange issue.

Without any detectable pattern or specific circumstances the car when reaching below 2000 RPM starts rattling, the acceleration pedal feels clogged, there is banging noise from the exhaust and eventually switches off.
Sometimes I can do 300 miles and this issue does not appear and sometimes it happens 10 times in 50 miles.

See below things that have been changed in the past month

- rear exhaust system
- spark plugs
- drive belts
- v belts
- fuel filter
- air filter

also the following have been checked and appear to be performing in good order

- throttle (cleaned and sprayed)
- fuel pressure
- engine oil (no burning)
- turbo pressure

the mechanic performed some testing in the air flow pressure and found out that the air that the engine is getting is too little in certain occasions which makes the car perform as "weak" potentially (correct me if I'm wrong).

An additional thing to note is that there is significant fuel smell when starting the car for the first 50 miles and sometimes when you accelerate rapidly to overtake someone.

According to the mechanic there isn't any obvious fuel leak and also I recorded a 22MPG combined (40% city - 60% highway) which I think is quite ok for a car with 270.000 miles.

please see a video here https://www.youtube.com/watch?v=sQRD...ature=youtu.be with what's happening while driving and seconds before it switches off

Sorry for the long message but I am really desperate to resolve this as the car is in super nice condition and such a smooth runner when this is not occurring.

Thank you in advance for your help.

All the best

[Laird Scooby]

Are you sure you fitted the fuel filter the right way round?

Have you cleaned the PCV system? Have you checked for air leaks between the MAF and the throttle body?

[B10B]

Check the throttle position switch and wiring, I've had a rich running backfire out the exhaust on overrun years ago on my 740 Turbo that traced back to this.
The switch should click just as it moves off the stop, i hope you didn't move it when you cleaned up.
I cannot find the resistance check figures for the switch but have got the AFM ones as it may be worth checking.
This assumes you have Motronic.

-10C 8260 to 10560 ohms
+20C 2280 to 2720
+50C 760 to 910

terminal 6 and 9 500 to 1100
6 and 7 8 to 200.

[Laird Scooby]

Originally Posted by B10B

I cannot find the resistance check figures for the switch

It's a switch, it's either open (infinite resistance) or closed (zero resistance). but it's worth checking.

Do you happen to know if it has a cat on it or not?

*** EDIT *** Forgot to ask, what gap did you set the plugs to and what type have you used? Also have you refitted the HT leads correctly - it's easy to not get them quite home which can cause problems too.

[aardvarkash10]

Primary advice - read the diagnostic codes.

Observations: With the throttle closed, fuel is provided from base map calculations that assume no air leaks. Air leaks will cause surging. Split hoses cause air leaks. 30-year-old cars have split hoses like 70-year-old men have weak bladders.

Some guesses based on not a lot.

[Laird Scooby]

Originally Posted by aardvarkash10

Primary advice - read the diagnostic codes.

Observations: With the throttle closed, fuel is provided from base map calculations that assume no air leaks. Air leaks will cause surging. Split hoses cause air leaks. 30-year-old cars have split hoses like 70-year-old men have weak bladders.

Some guesses based on not a lot.

If it's LH2.2 unless there's something i've been missing for 30+ years, there won't be that facility Ash. Hence my question about the cat being fitted.
No cat = no Lambda sensor = no feedback therefore no fault codes.

[360beast]

Being a 760 turbo it should be motronic 1.0

[classicswede]

Originally Posted by 360beast

Being a 760 turbo it should be motronic 1.0

First person to speak any sense.

Really the very first thing needed to be know before anyone can give you any real usefull advice is if the the system is Motronic or LH 2.4. A quick photo of the air flow meter will confirm all

[Laird Scooby]

Originally Posted by 360beast

Being a 760 turbo it should be motronic 1.0

If memory serves correctly Luke, Motronic 1.0 was the L-Jetronic system with the air-flap type air flow meter - the motronic simply means the fuel ECU and ignition ECU are combined into one unit, they still operate the same way except for minor software differences and the fact it's one "black box" instead of two.

Given that it's a 1990 car, i'm fairly sure it will have the LH-Jet based Motronic which i think was 1.3 but not 100% certain, Bosch changed the revision levels on Motronics more than they changed their socks! Or perhaps 1.8 - see below!

With all that in mind, for the purposes of fault finding, it's pretty much the same as the LH-Jetronic. Being 1990, it might have the diagnostic box on the passenger side inner wig, if so it will only do the diagnostics for the fuel/igniton systems as the ABS will still be on the ABS system instead of the later ABS-2E with on board diagnostics.

https://www.volvoclub.org.uk/faq/Eng...InjectionFault

Should link to Motronic 1.8 DTCs.

[360beast]

There is an ecu labelled motronic 1.0 and a motronic powerstage in the engine bay too Dave at least there was on the 1987 and 1988 ones I broke.

I've got two lots of Motronic stuff and a flywheel for it to convert my 360 to a B230ET but I haven't looked at the stuff for years now as the project won't be going anywhere soon.

You're right it is an old style flap Air flow meter not an air mass meter like LH2.4.