94 850 - Random Stalls and Hard to Start Topic is solved

jjs70pdx · Post by **jjs70pdx** » 23 Aug 2016, 18:10

This has been an ongoing issue for at least a year+ and can happen very randomly - every few months or 6 months. My car's engine will randomly stall/completely cut out, usually at a stop light or low speeds. When it happens the stalls occurs in pairs, meaning it will cut out, then restart and cut out again a short time later. Most recently, I've noticed a bit of hesitation upon starting and this past weekend it didn't want to start right away - took two or three cranks. Shortly after restarting the engine cut out twice within about a mile of driving. It restarted, set the CEL and I ran the codes - got a 121 from A2. I know that points to faulty mass airflow sensor but I doubt that is it since it was replaced with a brand new stock Bosch MAF about 13k miles ago, and I also cleaned it with CRC a few months ago.

Any other ideas of what it could be? I suspect possibly fuel pump relay or the other topic I read about on these forums is airbox thermostat failure, could that be a possibility? Trying to eliminate the issue from continuing to occur, any troubleshooting suggestions would be appreciated. Thanks in advance!

Post by **erikv11** » 23 Aug 2016, 19:52

The MAF connector is a known weak spot. If you haven't already, also clean well the contacts on the MAF connector. See this page for a thorough description: http://volvospeed.com/volvo_repairs_how ... ensor.html

Cleaning the MAF will generally not do anything at all, unless it is very dirty like visibly oily and/or dusty. More than anything else it's a good way to sell MAF cleaner, that's about it.

As a next-level test, if adjusting the connector doesn't get you anywhere, can you get your hands on a MAF that is known to be good, or try yours in another 850?

You can also run yours for a couple weeks without the MAF and see if the problem still crops up. However given the intermittent failures that may not be informative.

jjs70pdx · Post by **jjs70pdx** » 24 Aug 2016, 00:28

I haven't tried cleaning the MAF connector contacts yet so I will see if that helps the issue, then try swapping with a known working MAF if necessary. What is the longest that I could drive the car with the MAF disconnected without causing further issues? Thanks!

Post by **abscate** » 24 Aug 2016, 04:38

It will slightly rich for as long as you want, or until you have to inspect your ca r if you live in an emissions state.

The drivability will be a bit different, too.

Nothing to worry about , damage wise

Post by **erikv11** » 24 Aug 2016, 08:36

What he said. Your fuel economy will nosedive (what is it now?) but that's all. If you drive it like that for two years then maybe you have to worry about ash deposits and burning a valve.

jjs70pdx · Post by **jjs70pdx** » 26 Aug 2016, 15:45

Update to the symptoms my car is having: I haven't driven the car besides moving it to the shade in my parking lot a few days ago. Started without issue in the morning, but when I went to move it later in the day the engine would turn but not start after 4 cranks or so. I opened the hood at that point, and noticed the cooling fan was running - with key in ignition but ignition off. Had to disconnect the battery cable to get the cooling fan to stop. After reconnecting battery cable, car started up no problem, no CEL on. Thoughts? It started today with no cooling fan symptoms, haven't driven it beyond that though.

Post by **erikv11** » 26 Aug 2016, 16:03

The fan behavior may be a good indicator for your other problem, too. The fan running by itself suggests the ECT (Engine Coolant Temp) sensor is failing or has bad wiring/contacts. A bad ECT also leads to hard starts because the ECU thinks the engine is at a different temp than it really is, and so the air:fuel is way off.

You can test the resistance on the ECT, first step is to get a good look at it and at the wiring. If the wiring looks good, check the resistance in place or much more informative is to pull it out and then check it with a ohmmeter across several temps. You can get resistance values here in the repair database, or just do a search. If the wiring looks bad then you need to fix it. Be careful with the wiring at the connector, it is fragile at this age.

If you need to get a new one, be sure to not get a cheapie it will not work. I don't remember who makes the OEM one, again hit the search button you will find a lot of posts here about it.

jjs70pdx · Post by **jjs70pdx** » 31 Aug 2016, 13:00

Drove the car about 5 miles a few days ago to run errands. Then it wouldn't start in the parking lot, troubleshooted for an hour - swapped in another fuel pump relay and FP fuse, no luck. Engine was cranking but refused to start. During two hours of waiting for a tow, while attempting to start it on and off I stopped hearing the fuel pump priming during that entire time, so I thought the fuel pump went out. Got home and heard it priming again when turning key but didn't want to deal with it after waiting for a tow for two hours.

Fast forward to today, car started up fine, fuel pump is priming. Battery, alternator and starter tested fine. No codes to read (1-1-1 from A2/A6), no CEL on. I know the car is overdue for a general tune up since I bought it three years ago. I haven't checked nor replaced the distributor/rotor, spark plug wires (Bougicord, marked 93-43 so guessing originals - car is '94). Have kept up on oil changes and spark plugs replaced not too long ago. Fuel filter replaced 3 years ago when I bought the car, probably needs new air filter - replaced 13k miles ago. I don't feel confident that I want to drive the car until I narrow down what the issue is since whatever it is seems to be acting up more often recently. I did check the wiring on ECT and looks fine, didn't have a chance to test resistance yet. If this has been a random, ongoing issue for the past two years and seems to be getting worse, what would the next things be to troubleshoot/narrow it down? Could it still be fuel pump/fuel filter, or a sensor/electrical connection?

Post by **abscate** » 31 Aug 2016, 19:24

Measure fuel pressure at the rail to test fuel delivery.

Using original ignition parts, 22 years old probably contributory

jjs70pdx · Post by **jjs70pdx** » 18 Sep 2016, 18:34

I think I've figured out my issue(s). I didn't drive the car for a few weeks, but it would start right up in the morning when cold without issue on the times that I tested it without driving. I decided to drive it again a few days ago, and after running some errands/having warmed up the car I experienced the same no start issue (engine cranking, fuel pump not priming) Decided to leave it in the parking lot and take the bus home, see if letting it cool down for a few hours would allow it to start again. While home researching this issue I came across the following video:

When I returned to the car about 4 hours later, it still was cranking but not starting. Tried the test in the above video with key in On position, and low and behold once I tapped the fuel ignition relay I heard it click on and the car started right up! On the way home the car stalled/cut out once at low speed (about 25mph) - pulled over and the cooling fan was running with engine off, but again I tapped the fuel injection relay and it started right up and I was able to get home, with CEL on. Ran codes and now I am getting 1-4-4 (load signal from fuel injection system ECU absent) and 1-2-3 (coolant temp sensor signal absent or faulty).

Erikv11 already gave input on the cooling fan/ECT issue in the thread above (thank you!). Have yet to replace both parts but I will soon, and I will update if symptoms resolve. Would it be safe to say that one or both of these parts being faulty could explain the random stalls, and more recent hard starts when engine is warm?