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loss of power…until restart

Volvo 850 Made from 1993 to 1997, this Volvo line was available in both a wagon and a sedan, both with were graced with several trim levels.

loss of power…until restart

  #1  
Old 11-10-2018, 11:21 PM
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Default loss of power…until restart

Hi All, I’ve been trying to work through difficulties with my 850 1996 10 valve non-turbo with 162K Km
This is my third 850 over the past ten years. The car has been trouble-free since purchase. The car continues to start well and idle. After driving for about 3 minutes it loses power, if I use the accelerator it still has no power and may have small pops of backfire. If I pull over and shut the car completely off and immediately restart, good idle, the car has power again… but only for another 2-3 minutes of driving, this process continues to repeat itself over and over🤬.
Over the past two weeks, I have patiently carried out the following:
Made smoker and tested vacuum system for leaks - ok
Can’t get OBD II readers to diagnose car(“won’t connect”)- made a LED circuit to probe OBD port, got codes 5-1-2 (short term fuel mixture too rich) and 2-2-3 non-functioning idle aircontrol valve (doubtful cause - but found good used valve)
Replaced cam position sensor (suggestion after taking car to dealer)
Replaced throttle position sensor
Cleaned throttle body
Installed new pre-cat oxygen sensor
Tested Map sensor (vacuum plus multimeter)
Tested IAT sensor (multimeter)
Checked spark plugs - ok
Installed new fuel filter
Tested fuel pressure at injector rail (45psi)
Replaced fuel pump relay

I’d be so appreciative of any suggestions, I’m running out of ideas.
 
  #2  
Old 11-11-2018, 03:46 PM
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Did you check the fuel pressure when its running poorly? sounds like the fuel pump could be on its way out. Other than that, did you test the MAF?
 
  #3  
Old 11-11-2018, 08:12 PM
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Thank you MT6127, I really appreciate your suggestions and ideas! Tomorrow, I’ll extend the tubing on the fuel pressure gauge so that I can monitor it throughout the test drive. I’ll let you know what I find out. The car engine is a B5205S 10 valve with a Fenix 5.2 management system, it has a MAP sensor and Intake air temp sensor instead of a MAF. I went under the car (again) today to check out the condition of the catalytic converter - it looks OK - I knocked it around with a heavy rubber hammer - couldn’t hear any thing loose inside. I’ll take the new oxygen sensor back out tomorrow as well and test drive it to evaluate the cat. Thanks again!!
 
  #4  
Old 11-12-2018, 04:23 PM
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I connected the pressure gauge to the end of the fuel rail with a tube that’s long enough so that I can see the gauge while driving. Took the car around the neighbourhood. I experienced the same symptoms (loss of power & quiet backfires). The gauge read 40 - 45 psi throughout the test drive even during the loss of power. I completed the test drive about an hour and a half ago and pressure on the gauge has only bled down a very small amount. Thank you for the suggestion - this is so darned frustrating! Even though it’s a holiday here, I’m heading out to see if I can find a new distributor cap and rotor. I’m at the point that I don’t know what else to do.
 
  #5  
Old 11-13-2018, 09:11 AM
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What brand pre cat sensor did you get?
 
  #6  
Old 11-13-2018, 11:34 AM
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The three minutes is very interesting. The purge system could have a delay in it like that. I was thinking something that is computer controlled and part of a drive cycle, when it changes state, is just killing you.

It could be that an EVAP testing cycle is killing it. In either case, those systems could be disabled sufficiently enough for the purpose of diagnostics.
 
  #7  
Old 11-13-2018, 12:25 PM
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Hi,
I used a Bosch oxygen sensor. I replaced the distributor cap and rotor yesterday afternoon. Obviously I’m still having difficulty determining if the loss of power is as a result of a fuel issue, an electrical issue, a vacuum issue or something else? I’m confused why the loss of power disappears after I shut the engine down and immediately restart (either than it reboots the computer to base level). The fact that the engine is a 10 valve B 5252S and isn’t usually listed by new parts suppliers, makes everything trickier😬
 
  #8  
Old 11-13-2018, 01:02 PM
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Thanks for the EVAP bypass idea. Would I do that at the charcoal canister by joining the two vacuum lines together or?? I’ll try it today as soon as I get some info🙂
 
  #9  
Old 11-14-2018, 12:27 PM
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I was thinking unplug electricity from the purge valve to stop it from opening. You could plug the vacuum line to it if you wanted to.

Generally, an EGR can do the same thing, open inappropriately. But I don't think you've even got one.
 
  #10  
Old 11-14-2018, 12:41 PM
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I’m pumped, following your suggestion I have to be getting closer. I’m heading out into the chill and the rain to pull the power on that purge valve! I’ve got to have at least 65 hrs. of doin’ and researching on this puppy. Every suggestion counts big time. Thank you so much, Firebirdparts!!
 
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