OK guys need your help!! Car stalling / bucking on highway

Post by **wheelsup** » 02 Jan 2009, 18:12

OK been having some issues with my 850. Haven''t experienced this before. I thought it was my tranny as I first had it happen while on a road trip, but I''m thinking it is engine related.

Recap:

Driving on 180 mile trip, 50 miles in the car "bucks" once going up a hill. By "bucking" I mean it feels as if the car is being turned off for a split second, then back on again. Did it again 10 miles later. Pulled over saw some foam on the tranny dipstick and thought it was the tranny. Added fluid. Still did it.

Car sat overnight. Drove back home, did the bucking again about 50 miles in and did it again every 10 minutes or so. Again thought the tranny was giving up the ghost. At the end of the trip, about .5 miles from my house the CEL flashed as well as the ABS light, a bunch of codes were pulled, the most notable was the MAF sensor absent (1-2-1). In addition I believe the ECT was thrown as well. But also a bunch of ABS codes and instrument codes (#7). But I recently replaced the ECT with an OEM one so I''m not sure why that is there.

I cleared the codes and none have since come back.

However, the bucking is getting more frequent. Over the past few days the car will start than immediately stall, although it doesn''t always happen. Now sitting in my garage it will try to die on me as it idles. If I give it gas and hold it at say 2000 RPM it will slowly bounce down and hover at 1500 RPM and then bounce around, it''s not steady. It''s not related to highway speed any more (as it was doing it on my original road trip) it will do it at any speed. Coming home today sitting on a side street the car just died while sitting in traffic.

I''ve cleaned the MAF and IACV contacts. Neither helped. I pulled the MAF sensor connector out, it idles kinda crappy and once given gas from idle it shakes a bit but once up at RPM speed it runs good. It doesn''t die with the MAF unplugged. Not sure where to go from here. Any ideas?

-matt

Post by **MadeInJapan** » 02 Jan 2009, 19:24

Sounds like it could be the MAF. Have you tried cleaning it?
Also, it could be electrical. Have you checked all of your lines from the battery, esp. the one that goes into the fuse box under the hood?

Japedo · Post by **Japedo** » 02 Jan 2009, 19:55

My car did some serious bucking before when I had a cracked intercooler. But it would only buck , exactly as u describerd it under load/ boost. The only time I had stalling issues it was due to a bad temp sensor. Good luck finding your problem.

japedo
94 850 turbo
01 V70 XC

Post by **wheelsup** » 02 Jan 2009, 20:03

No haven't cleaned it yet, that is first step tomorrow!

I will report back. I'm wondering if a MAF could even cause my symptoms though? I hear typical MAF failures show with lagging acceleration and such. Although maybe mine might be "shorting" out or something, causing the blip?

Post by **MadeInJapan** » 02 Jan 2009, 20:48

When my MAF went, the entire car bucked like a wild bronco. I also had a rotten egg smell- obviously was affecting the CAT.

StarmanDXE · Post by **StarmanDXE** » 02 Jan 2009, 23:27

Very similar problems on my 850 just a few months ago. Started with bucking (misfiring) on the highway and was interspersed with stalling while driving over bumps (e.g. train tracks or shortened curbs between a street and a parking lot) and, one morning, a bout of stalling immediately after starting and shifting into drive. (I "fixed" the immediate stalling by pulling all the wires from the distributor cap and putting them back on. Must've gotten lucky and moved something right by accident...

)

I had just done a tune-up (minus wires as they weren't that old) and checked everything and it looked ok. Replaced my ignition coil with a low-mileage one, but that didn't do the trick.

Thought it might be fuel related, so I replaced my fuel filter. (It was way over-due anyway...) Didn't fix it.

I found that I was missing a lot of compression in a few cylinders. Fixed this with Seafoam, but it didn't fix the problem...

Got some MAF cleaner and cleaned it. Still no-go.

My girlfriend's neighbor is a mechanic and he looked at it and found that the engine could be killed from an idle by pulling on the MAF's electrical connector. Those connections were quite corroded so I cleaned them off good. That still didn't fix the bucking... (I was kind of ashamed at myself for this one as, when I cleaned the MAF itself, I looked at the connectors and saw they were green, but, for some reason, thought nothing of it!

)

Finally, my dad took the 850 to our normal mechanic (as I borrowed his car to go back to school after Thanksgiving break) and they found that the CPS (cam position sensor) had gone bad. They replaced that, and the car has been fine ever since! (Seemed like a strange diagnosis as everyone seemed to think that a bad CPS would only cause it not to start [and not cause misfiring...] So, I suggest you replace your CPS

)

(On the up-side, that 850 has so much more power now than I was used to and gets much better gas mileage

If only I had done the PCV, too! I could only imagine...

)

Post by **wheelsup** » 03 Jan 2009, 07:02

Did you get misfire codes? None have flagged on my car as of yet. Wouldn't a bad CPS cause misfires which would register with the CEL?

StarmanDXE · Post by **StarmanDXE** » 03 Jan 2009, 08:22

wheelsup wrote:Did you get misfire codes? None have flagged on my car as of yet. Wouldn't a bad CPS cause misfires which would register with the CEL?

I forgot to mention: lots of flashing CEL, no logged codes.

Post by **confused_al** » 03 Jan 2009, 08:41

...Wouldn't a bad CPS cause misfires which would register with the CEL?

Nope, when my CPS went bad (from misfiring at start to finally wouldn't start at all), CEL never came on. However, I didn't have your kind of "serious bucking".

Post by **wheelsup** » 03 Jan 2009, 10:16

OK update. I cleaned the MAF today with MAF cleaner. Cleaned the CPS with electrical contact cleaner (just to make sure). Car runs better with MAF unplugged, it will now die completely if I plug it in. It runs OK with it unplugged but still drops in idle every few minutes like it is going to die, but doesn't. I'm trying to find an 850 around here that I can swap out my MAF to see if that fixes it. I don't want to buy another one right now because I have a feeling it won't fix it - because the car still bounces around every few minutes even with the MAF unplugged. If it didn't do this I would say I was out of the woods but it just doesn't seem right. It idles fine most of the time then BAM bucks/quits depending on speed.

Also I got another CEL today, just before the car died, another 1-2-1 from A2 which is the MAF sensor.

This might be a case for my mechanic next week, we'll see if I can scrounge up a MAF somewhere to swap. I'll know for sure that way, and can at least point him in the right direction.