Volvo 480 B18FT rough idling.

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kaups
480 Newbie
Posts: 2
Joined: Fri Jul 22, 2022 3:07 pm

Volvo 480 B18FT rough idling.

Post by kaups » Fri Jul 22, 2022 3:31 pm

Hello Everyone,

I've recently become an owner of Volvo 480 and trying to revive it :D . I've tried looking in forum for someone with similar problems without luck.
I'm having trouble with rough idling. Engine is B18FT (1989). Previously the car was not starting at all, but after fixing the fuel issues it starts but idles very rough, sometimes even stalls. I was trying to follow troubleshooting from the heynes manual and got to ECU testing Followed the option for EZ210K as I understood from the manual that FT version should have it.

Most of the values are wrong. For example Voltage at ECU pin, 5 instead of 12.6V is 0.126V. Step 10 instead of 220ohm it's 46ohm, pedal position readings are also random. I gave up after this.
For ground, I'm using a screw on chassis. Maybe I should use one of ECU wires?
In the 2nd photo you can see some strange wire configurations which I don't believe is from the factory. Black wire splits into 2 and one side is connected to pin 5 other to pin 20 (if I remember correctly).

I've also replaced the idling valve.
Anyone got any idea if I'm doing it wrong or if pretty much all sensors are messed up?

PS: I've also replaced the idling valve, and spark plug wiring harness.

https://imgur.com/a/HPMpA3i

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jamescarruthers
480 Is my middle name
Posts: 2376
Joined: Mon Jul 07, 2003 3:19 pm
Location: Cambridge

Re: Volvo 480 B18FT rough idling.

Post by jamescarruthers » Fri Jul 22, 2022 6:25 pm

Hey,

I’ve sent you a few books privately via PM to assist better than Haynes. It’s not a great book TBH.

Pin 4: battery
Pin 5: ignition
Pins 14 and 20: ground

For pin 5, to check that the ECU is getting power, ignition surely needs to be on. Was it it in that state? Surely there’s no way is it running at all with 0.126V!

Step 10 in Haynes, measuring the resistance of the flywheel crank position sensor. Well maybe you’ve found your problem? It definitely should be 220 Ohms, or there abouts.

Ground is your reference point for readings. Check the resistance between where you are measuring on the chassis and pins 20 and 14. If it is not basically zero, all of your previous reading relative to earth should be repeated after that early connection is properly reestablished.

Throttle pedal position sensor should not be random, it should be one of either:
-zero Ohms with the pedal released— this then tells the idle air control valve to do its job. If it’s not zero at this value, then the car will never idle. Can you hear the switch physically as as you pull the throttle cable away from the idle stops (don’t be attempted to adjust them BTW unless you are sure they have been messed with in the past)? You may need to just loosen the nuts and rotate the throttle position switch to achieve this.
-1300 Ohms with the accelerator depressed, but this is less important for now.

The big fat wire stuffed in to the plug doesn’t look great but there were some mods along the way in these cars. Maybe this is an attempt to get a better earth by someone. Really hope not connected to 5 and 20 as that is surely a short?
Last edited by jamescarruthers on Fri Jul 22, 2022 8:18 pm, edited 1 time in total.
1987 Volvo 480 ES, 507274, 217 - Red (Ness)
2006 Citroen C6 Exclusive 3.0 petrol/LPG
2008 Mini Cooper convertible (Mau)

Previous 480's:
J123 CFU -- ES
J449 MNL -- ES auto
D864 CPV -- ES
L691 JFC -- Turbo
F70 MNR -- ES
H858 FGV -- Turbo auto
E981 KHM -- ES (509849)

User avatar
jamescarruthers
480 Is my middle name
Posts: 2376
Joined: Mon Jul 07, 2003 3:19 pm
Location: Cambridge

Re: Volvo 480 B18FT rough idling.

Post by jamescarruthers » Fri Jul 22, 2022 6:35 pm

Does your car have a diagnostics port on the front suspension turret? I can’t remember if the 1989 turbos have them or not. That can help you a lot!

Looks like this terrible picture: Image
1987 Volvo 480 ES, 507274, 217 - Red (Ness)
2006 Citroen C6 Exclusive 3.0 petrol/LPG
2008 Mini Cooper convertible (Mau)

Previous 480's:
J123 CFU -- ES
J449 MNL -- ES auto
D864 CPV -- ES
L691 JFC -- Turbo
F70 MNR -- ES
H858 FGV -- Turbo auto
E981 KHM -- ES (509849)

kaups
480 Newbie
Posts: 2
Joined: Fri Jul 22, 2022 3:07 pm

Re: Volvo 480 B18FT rough idling.

Post by kaups » Fri Jul 22, 2022 7:53 pm

Thank you very much for all the info. From what I've read the ports started to be installed in 1991 and I couldn't find one on my car.
I will let you know how it goes after further diagnostics :)

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