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1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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greg850r
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1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Post by greg850r » Sun Dec 04, 2016 12:24 pm

So my wife comes home the other day and reports the 96T wagon started to run badly. She said it was "stumbling". The code was for open circuit in injector 2. After changing injector, opening up wire loom and chasing wire, ohming everything out, I could not get it to smooth out and quit throwing that code. Finally, as a last resort, I yanked the brains and swapped in another set. Instant fix. I guess they do occasionally go bad after all.

:idea: I keep extra everything around by buying an 850 and hauling it home everytime one pops up on Craigslist for scrap price. Once it's picked clean enough, off to scrap it goes. I would guess I kill 3 or 4 850s a year this way and it keeps me in parts.
05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

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Re: That rare occasion when it IS the computer

Post by abscate » Sun Dec 04, 2016 1:36 pm

Thanks for the report and good sleuthing ....we will start to get ECU failures more and more as these cars age, so gathering symptoms is good
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1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
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Re: 1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Post by theWIFES_S70 » Sun Dec 04, 2016 7:10 pm

greg850r wrote:So my wife comes home the other day and reports the 96T wagon started to run badly. She said it was "stumbling". The code was for open circuit in injector 2. After changing injector, opening up wire loom and chasing wire, ohming everything out, I could not get it to smooth out and quit throwing that code. Finally, as a last resort, I yanked the brains and swapped in another set. Instant fix. I guess they do occasionally go bad after all.

:idea: I keep extra everything around by buying an 850 and hauling it home everytime one pops up on Craigslist for scrap price. Once it's picked clean enough, off to scrap it goes. I would guess I kill 3 or 4 850s a year this way and it keeps me in parts.
greg850r, how do you know when an owner is ready to scrap? Do you really see cars drop to $100? I've been checking out local P80s and they never drop below $500...
1998 Volvo S70, N/A, 5-speed, 183K
2007 Volvo S40, 2.4i, 5-speed, 97K

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Re: 1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Post by greg850r » Mon Dec 05, 2016 7:28 am

Keep in mind 850s are older and therefore cheaper, but any no-start in that price range is scrap. If it's advertised at $500, I'm buying it for 2 or 3 hundred. When you show up to a no-start with a truck and a car hauler and they want it gone, well it's a buyer's market at that point. Scrap they only get 100 unless they can take it there (they can't) because they guy hauling it to the yard needs his hundred. I get two because I haul it there. I also get to get rid of all the spent axles, brake parts etc that I can throw in it. The last one was a 95 wagon 5spd no start. When I saw the ad I was going to buy it for a 5spd donor car, but a cam position sensor fixed it and I'm going to license and drive this one for awhile. The one before that was a 96 N/A auto sedan that turned out to have new axles in it along with new brakes all around I can put in stock. Gave $120 for it because the head was warped or cracked and he needed it out of his driveway. Grabbed a fuel pump I was going to have to buy along with a perfect power antenna I put in one of mine that was weak the first day I had it.
05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

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Re: 1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Post by cn90 » Mon Dec 05, 2016 8:44 am

Haha, you qualify as the vulture lol.

OK, seriously, I find an easier way, go to local junk yard (or ebay) and buy otherwise-expensive parts such as ECUs etc. for cheap.
This way you don't have the haul the craigslist cars home.
Although your way is probably cheaper as you can get more parts out of a let's say $300 car.

I never buy kaput car from craigslist. I simply go to junkyard.
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

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Re: 1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Post by greg850r » Tue Dec 06, 2016 6:55 am

Vulture is a good analogy. I like having one on the property so when I need something It's a short trip. That same part from the junkyard for me burns at least half a day and maybe a whole one. Even a part I can buy at the AP costs me 2 hours vs 5 minutes if it's here. One day spent getting a parts car saves me a trip out every time I pull something off it. It does tend to save me money but it's really more about convenience and my time.
05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

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greg850r
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UPDATE- bad ECU....That rare occasion when it IS the computer

Post by greg850r » Sun Dec 18, 2016 12:01 pm

It looks like I mis-diagnosed and abscate is right again. This article may explain why I think I was actually chasing a bad o2 sensor. http://www.obd-codes.com/faq/fuel-trims.php
Going to a different ECU simply gave me a zeroed out long term fuel trim setting which made the car stop running rough. It took a few miles for the short term fuel trim to make it start acting funny again, but it slowly went back to its old tricks and I thought the next thing likely to help would be to replace the front 02 sensor. It did not run quite right (maybe got a 50% improvement) but all I did was back it out on the driveway because the roads were too icy. I revved it up past 3000 a couple times and all the sudden it idled right. It was 3 degrees out there this morning so I won't do the reset described here http://www.matthewsvolvosite.com/forums ... =5&t=21123 today. I'll come back to give the results after I do it a and drive it a bit.
05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

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Re: 1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Post by erikv11 » Sun Dec 18, 2016 12:33 pm

Especially if you are doing upkeep on several P80 cars, having a parts car saves you tons of time and money as compared to going the junkyard. Once you actually try it, you will understand. Easier, faster, cheaper. The drawback for me is deciding how long I want to have a shell of a car hanging around out in the back driveway. If I had some kind of large garage or outbuilding, I would probably have a parts car at all times.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 285k
'06 S60 R, 160k
gone: '96 NA 850 210k, '98 NA V70 182k

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abscate

Re: UPDATE- bad ECU....That rare occasion when it IS the computer

Post by abscate » Sun Dec 18, 2016 1:29 pm

greg850r wrote:It looks like I mis-diagnosed and abscate is right again. This article may explain why I think I was actually chasing a bad o2 sensor. http://www.obd-codes.com/faq/fuel-trims.php
Going to a different ECU simply gave me a zeroed out long term fuel trim setting which made the car stop running rough. It took a few miles for the short term fuel trim to make it start acting funny again, but it slowly went back to its old tricks and I thought the next thing likely to help would be to replace the front 02 sensor. It did not run quite right (maybe got a 50% improvement) but all I did was back it out on the driveway because the roads were too icy. I revved it up past 3000 a couple times and all the sudden it idled right. It was 3 degrees out there this morning so I won't do the reset described here http://www.matthewsvolvosite.com/forums ... =5&t=21123 today. I'll come back to give the results after I do it a and drive it a bit.

Thats twice since I joined this Forum. It's practically a trend ...
Empty Nester
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1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW
Link to Maintenance record thread
Link To Volvo Glossary

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greg850r
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Re: 1996 850 rough running, bad FI 2, bad ECU....That rare occasion when it IS the computer

Post by greg850r » Mon Dec 19, 2016 5:13 pm

I did the reset but must have not waited long enough. Disconnected battery, engaged starter, depressed brake pedal for good measure and hoked it back up. Long term fuel trim still read 21.5% so it didn't clear the memory. Drove car and short term fuel trim fluctuated between -17 under load to +27 under deceleration. I guess this meant it wasn't the 02 sensor and I better figure it out before I flood out the new one a ruin it. Will pull a MAF off something else tomorrow and drive it with that. If it still has big numbers on short term fuel trim where should I look next?
05 Cross Country wagon
99 C70 Convertible
96 850R wagon
96 850T wagon
96 850 GLT 5spd N/A sedan
97 850R 5spd sedan
66 GTO 421SD 4spd
67 GTO 455 T400
02 Powerstroke 4x4
85 Yota 4x4
24' 454 Challenger
07 Softail Custom
02 Sportster Custom
Parts cars not included

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