Long story short. I was having the same problem with my 94 850 turbo (starts, runs for about 5 miles, dies, won't start. mysteriously starts about an hour or 2 later.)
Logged onto this site, noted the possible causes and went to check into them on the car. First on the list was wires/grounds, opened the hood and IMMEDIATELY saw a loose
nut that holds a small wire to the positive battery cable. Started her up and took her for a test ride. It was like a new car! No stalling, no rough idle!!!

I have been trying to solve this problem for about a month! I checked out this forum for suggestions and solved the problem with one pop of the hood
and a 10mm open end wrench!!!!!!

YES VIRGINIA, THERE IS A SANTA CLAUS!

 

Oh yeah, Thanks a lot everyone!!!

 

Good job!


JPN

 

Another happy customer.

 

I will have to double check the small wires. I know for sure the large connections to the battery are fine as we just replaced the battery. I will certainly check the grounds and other wires. The ol' 850 does need a tune up as well, so that's still on the list. Unfortunately, on top of working full time, I'm currently in the middle of a project that takes up all my time after work as well, so the Volvo has to sit until I can spare even just a few minutes... but the good news is, the extra job will help pay for tune up parts.

Thanks as always... updates to follow. [8D]

 

Okay... another update:

The Volvo still isn't right... My wife and I are starting to call it the 4 mile wonder. Today I cleaned all battery connections with a baking soda/water solution and cleaned the contact surfaces with steel wool. I checked all the wires and grounds that I could easily see (without removing stuff, of course) and made sure all the connections were tight. The car has the new MAF and a new battery. The alternator was checked and deemed fine.

The carstarts right up, idles pretty smooth, and drives fine. For 4 miles. Any acceleration after 4 miles causes the car to stumble and set a code. I'm not sure if the Volvo will make it far enough to a parts store where I can have the code checked. Do parts stores do "loner scan tools?" I would think if it was a fueling issue, ie. filter or pump, it wouldn't run fine for a while then startt stumbling. I would think it would be rough all the time. On our list of things to replace when we have the money are the fuel filter and fuel pump relay.

I'm worried though, with it setting a code, that there's a more serious issue going on here and wondering if we should just nurse it to a repair shop and have it completely gone over and fixed proper...

Thoughts comments or suggestions? Thanks guys!

 

^You can fix the relay for 2-3 bucks if you open it up, and solder in a new part...Total cost 15 bucks maybe if you dont have a solder.

And fuel filter is only 20 bucks. Not that expensive..

As to scan tools, you can use a generic one from Autozone or whatever, but you're only going to get the generic codes. Anything more, and you need a VST (Volvo Scan Tool).

Also, check VolvoSpeed too and see if any of them can figure it out..

Edit: I honestly have no clue what your problem is, but if you're getting 4 miles consistantly, sounds more like a software (ECU) problem rather than a mechanical problem..

 

I would try to see if Auto Zone loans out scanners.
Once we know what the code is we can help you better from there.

The sad part is now it is just a guess and it could still be about 100 Different things.

Keep us updated. Please. I know you do already but you are almost up against a wall now till we know the codes.

 

Thanks for the advice. My wife says that she is thankful that its only 100 possibilities instead of thousands.

I'll definitely keep you updated as we chase this down. [8D]

 

Like I sadi if you can get the codes and we can narrow it down faster.

We are here to help. We love to help.

 

Hy Tjay,

It really does seem electrical/electronic problem, most likely the engine ECU.

Does the engine idle smooth, if you put the shifter in "N"? And is the engine warm when the 4-mile problem occurs?

Until you can get the codes retrieved, I can only assume the coolant temp sensor. I doubt it's the fuel filter but if you don't know when it was replaced the last time, I would replace it anyway (Bosch). Fuel pump has been giving problems to quite a few people lately, though the problem is usually no-start.

Other than that, the ECU itself may be shot, or, you could disconnect the negative battery cable, wait 20 minutes and pull out the ECU and spray electrical contact cleaner and put it backin to see if it cures, though I doubt it. And Volvos seem to have strange idle-re-learn policy. Whenever I disconnect the battery, I make the ECU re-learn idle by letting the engine idle for 10 minutes with ALL electrical systems turned off (I even disengage the parking brake to turn off the tiny warning on the dash to keep current draw minimum).And even after that, you may have to drive a specified distance in order to complete idle re-learn procedure.

If you're curious about testing the coolant temp sensor, you can do so by taking it out (may have to drain some coolant to make sure you don't make a mess when removing the sensor, and I would have a tube of thread sealant (not a thread lock; the one used for water pump bolts, etc) when putting the sensor back to ensure leak-free installation). After taking it out, you can immerse the sensing portion (bulb) of the sensor in water and heat it on a stove/hot pot. The following is the spec:

32F: 7300 Ohms
68F: 2800 Ohms
176F: 300 Ohms
212F: 150 Ohms

As you can see, the resistance should drop according to given temps. If the sensor responds to similar numbers, it is fine. If the number doesn't change or moves around like crazy, it is shot.

Wait doing this until you get the code.

I wish I could help you better, rather than keep giving you wild guesses.


JPN

 

>We are here to help. We love to help.

Tech, help me.


JPN


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JPN, what makes you think the ECT sensor?

On a hot day, the engine warms up in no time...

Oh, and as to removal, you probably want to head to the dealer and get some of those steel torx screws for the t-stat housing so you dont' strip them. Removing the ECT has the same instructions as the t-stat since it sits below the t-stat.

I'm still stuck on as to why it's dependant on mileage and not time...Especially since it's consistently 4 miles...

 

Hi Jimmy,

>JPN, what makes you think the ECT sensor?
I saw a ray of divine light from the heaven that told me, in an owe-striking manner that "Thou shall check the ECT sensor".....

.....[8D](the summer heat in Japan turned my own CEL on).

>On a hot day, the engine warms up in no time...
OK, here is a tutorial on thermostat. Basically, there are 2 differenttypes of thermostat placement; in-line control type and bottom bypass flow type. The first type, I believe, is the one used by Volvo. This type of thermostat has a tendency to cause what is known as "hunting" (no,the thermostatdoes not go out of its own to chase a deer[8D]). When the engine warms up, the thermostat opens, allowing cold coolant to rush into the engine block. This causes the thermostat to close again, until the "rushed" coolant warms up. Then, it opens again and keeps the cycle until the overall coolant temp stabilises. This is the reason why I thought of the ECT sensor as a possible candidate. If the ECT sensor is faulty, it would keep feeding the ECU without-of-spec signals (or not sending signals at all) and the ECU may misinterpret the actual operating condition of the engine.

The advantage of in-line control type is that you do not need a separate bleed port when refilling. On the other hand, bottom bypass flow type requires a separate air bleed port but provides much more precise control of coolant recirculation. Many German cars seem to use this type, so I could be wrong and Volvo may use BBF type as well.

The ECU is nothing more than a device that receives signals from sensors, do calculations according to the fuel scheduling map, which is pre-programmed and sends signal to the fuel injectors to control engine output; RPM. Some more sophisticated EECs (Electronic Engine Control) also control throttle valve opening, via DBW (Drive-By-Wire; the valve is controlled by electric motor rather than a mechanical cable) as a part of the traction control. Anyway, if one of the primary sensor parameters is faulty, it will send incorrect signal to the ECU or will not send signals at all. But this usually triggers CEL, but I am a bit skeptical about Volvo's self-diagnostic so it may or may not be responding, that is, if one of the sensors is faulty.

And after reading the car's misbehaving after about 4-mile drive, I thought of a parameter that changes within that duration and thought that the coolant temp could change within that duration. But it could be a different sensor, or a mechanical fault may be sensed by a sensor, which I cannot tell without testing the car myself. If you can think of other parameters that can change within 4-mile drive, please help us with your input. Another thing I can think of is the ABS module or whatever senses vehicle/engine speed, transmission fluid conditions (probably not), or vibration that causes a loose ground wire to make & break contact.....

At this point, we can only wait till Tjay replies with what code he can find, if at all.


JPN

 

^Hm.......But with a faulty ECT sensor, he should see some type of problem w/ his temp gauge..

The ECT allows for optimum performance/drivability as the car is heating up (think how your car seems kind of weak when your t-stat is stuck open). If you're faulty, the ECU thinks the engine is hotter, and fuel mix is richer, and timing is advanced. This means your car would drive like crap in cold weather...

And the coolant reaches optimum temp within 1 min typically, and a 4 mile drive is at least 4 miles, which means he's probably hit a cycle...

You're definetely on to something though, and quite frankly, I cannot think of anything that cycles within a 4 mile/4 minute time frame which would change... If it were a bad sensor, his car would run like crap all the time, but he's running good and then running bad which is way out of my knowledge.

I cannot for the life of me think of some type of device which would change after time..Or read something every couple minutes. Most sensors are running constantly so if there is something wrong, you'd get it right away....That's why I'm inclined to say something is wrong with the ECU......And the ECU does store some type of memory though doesn't it? I don't know about these ECUs, but some cars "learn" your driving habits, and perhaps there is some type of fault which makes the car run bad after time..

That being said, ECT sensors are cheap, and it can't hurt to change it.

 

No problem a little bit of Bondo and a few pulls with a chain and a truck and most should be good to go.

Espically the last one thats looks like a Black 850R. But how the hell did it get on the telephone wires?????

 

You took the words out of my mouth! I really does look like an 850R!

 

Could this be a vapor lock issue? I did not read all 77 however, it seems like if the car is stalling after 4 miles that is just enough time for the exhaust systemto get hot enough to vaporize some of the fuel before it's ignited. This may be caused by a missing heat shield, hole in exhaust line or something causing the exhaust system to putan abnormal temp near the fuel. It could bea bad fuel pump/fuel lines also.

In any case don't take my advice without some validation from the other members that have been helping you this whole time. They certainly have more knowledge on this stuff than myself. I just like to replace the mechanical things that I know will soon go bad, that way if it's not the root cause; at least I've done some preventive / scheduled maintenance. Electrical troubleshooting is money well spent at the dealer in my opinion. Good luck.

 

Okay, I finally found a OBDII scanner to borrow. I scanned the codes and it only had one code set twice: P0301. First Cylinder Misfire. With the replaced MAF the car seemed to be fine until that four mile mark. Am I looking at something more serious than a simple tune up? We have the money to go buy some new spark plugs, so that would be a start.

 

That would be a good place to start.
But look at the ignition cables and see if they are OEM wires.
If so Look and see what year the wires are There will be white or yellow writing on them. There will be 4 numbers the month and year they were made.
If they are original then I would think about replacing them soon.

Also you might want to pull the fuel rail and make sure #1 injector isn't dumping to much fuel into the cylinder.