Intermittant Problem, Loss Of Power, Stalling P0121

dahubb · Post by **dahubb** » 21 Oct 2011, 12:00

Hello to all.
I have been using the posts on this site for the last 6 weeks concerning loss of engine power,stalling and engine reveing,
I have learned alot.I guess not enough I now have brain freeze concerning this problem.
History. 93 850 174000 on car.
Started with engine missing while at idle in gear.Things I did to car. changed fuel filter, New plugs, cap, rotor and plug wires.
This helped a great deal.
Then right before a long trip I noticed a little hesitation when I tried to accelerate.Only happened one time.I then proceeded
to drive 320 miles at one time with no problems,avg 29 mpg.
Then I experienced Loss of power when trying to accelerate, not like out of gas, I then pulled over and idle was very rough
and going up and down until engine died.Checked under the hood for anything, nothing found. Started up and ran great rest of day going about 60 miles all kinds of driving.Next day same issue, no power rough Idle. So I cleaned Maf, throttle body.
Drove another 22o miles till fail again going 60 mph. Stopped for 10 min. and then took off with no issues driving another 120 miles.
I will now get to the point. Thanks for bearing with.I then checked air hose from air box to throttle body, cracked ,replaced. Checked for vacumm leaks.Installed new T P S because of 411 code. Installed new fuel relay. Also tested fuel pump.
The car ran great for 3 days,It seemed like since changing fuel relay engine ran a little stronger,Could be my imagination.
Then same problem again. Seems if I stop turn off engine and restart in a few minutes it will run fine for a while.
Last thing I did was hold open fresh air valve in air box.Ran for a day and failed again last night. This morning I tried starting the car with maf unplugged woukd start but then die. If reveing engine it ran good till I let off gas then die.
I'm thinking it might be MAF. Gonna go check plugs again. Also plug wires were not factory but seemed like quality wires.
Sorry for being so detailed. Also no codes last 2 failures. Had a maf code, 121, 2 weeks back. thanks for your time. Dahubb

Post by **jblackburn** » 21 Oct 2011, 12:41

I'm thinking the car told you what the problem was already - that 1-2-1 code at the very end of your post and the random acting up points to a flukey mass airflow sensor. Hopefully that (should) take care of it.

dahubb · Post by **dahubb** » 21 Oct 2011, 15:37

thanks jblackburn for reply,
I thought that I might have got that 121 code when I was testing maf by unplugging plugging back in maf.
I think I might have caused the error because car was running.
Same old story wanna be sure it is maf before I spend the money.
Question, will faulty maf's cause intermittant issues?
dahubb

curtismc56 · Post by **curtismc56** » 21 Oct 2011, 15:42

My 99 S70 MAF failed. I replaced it twice under parts warranty. Last time advice said disconnect battery before plug in. I allowed 15 min to pass. Has worked well ever since (fingers crossed) make sure you have radio code, anti-theft will disable it.

dahubb · Post by **dahubb** » 04 Nov 2011, 15:56

93 850,SAC. CA. Well I ordered and installed new MAF sensor,[ from dealer ]. Drove car around town for 6 days. Some freeway driving.Drove 100 miles to 6000 elevation and back.Car ran great. 28.5 mpg
Thought problem solve till I drove early in morning onto freeway and incountered same problem of loss of power .At stop sign idle ruff and up and down till engine quit.So where do I go from here?
I am thinking coolant temperature sensor.
Went to Dealer and priced one at $ 53.00.His picture showed sensor at manifold. I do not have one there. I believe mine is at the Radiator. Am I heading in right direction ? Also thought I might get a smoke test on vacumm system,
Thanks everyone for the help.
Dahubb

Post by **JimBee** » 04 Nov 2011, 18:51

A couple of days ago I surfed around the "All About the Volvo 850" pdf document that was mentioned here. There's some pretty good information on the electrical system and how several sensors work IN SERIES with the ignition. Confirm this in the document, but I recall that the heat sensor, ambient air sensor, maybe the idle air control valve, throttle position sensor and are all networked with the MAF to regulate airflow given a amount of throttle (oh, yeah, of course the O2 sensor).

I didn't study the electrical schematic but I had the sense they are all in series, so if one faults out or just begins to flicker, everything else that talks to ECC and ignition will, too. Maybe I'm way off on this, but it makes sense.

So today when I replaced the alternator in a project car I cleaned up all the connectors I could find. Took a mini wire cup brush to the male ends, flushed the female ends with electronic parts cleaner and dabbed on a little dielectric grease to the terminals.

Many of those connectors were oxidized and corroded—the worst of them being the engine temp sensor plug. That engine has been extremely erratic. I still have a couple of things to put back together, but I am eager to run it tomorrow to see if it behaves any better.

If so, I'll post about it back here. If not it needed to be done anyhow

dahubb · Post by **dahubb** » 10 Nov 2011, 23:29

93 850 Well,Installed new coolant sensor. Drove about 90 miles before car failed with same problem. Also got the check engine code 411.The throttle body sensor has already been changed.Running out of ideas.
I would think if I had a vacum leak it would be constant. Could I have a problem with the computer module it self?
Thanks again.
Dahubb

dahubb · Post by **dahubb** » 18 Nov 2011, 09:00

dahubb, 93 850, Sac. Ca.
Well, I think this will hopefully be my final update on this problem of mine.
My issue with loss of power never did seem like a fuel issue.
After changing many things that had never been changed in 174,000 miles finally changed the ignition coil. I had a feeling it might be the coil so I purchased a used one just to see if symptom would change or go away.Well so far have not had the problem.
Thanks for everyone's help.
If I do not post to this again problem fixed. Very happy.Car has never ran so well.
Dahubb