My 94' 850 turbo has been running fairly rich recently. My exhaust smells of significant fuel, and my gas mileage is never better than about 16-18. My car is mostly stock, the biggest changes are a manual swap, exhaust, ARD Orange Tune, and a big bore throttle and intake. I have gone over stage one very thoroughly. Everything has been replaced with OEM parts. The car runs and drives great 90% of the time. Once in awhile however, typically under load at lower RPM's (in any gear), the car jerks very quickly, once or twice, and immediately catches up and drives normal again. It used to do this a year ago when I first got the car running. Then without warning the problem dissolved for 7 months or so, and now its back. No CEL's as of now. Any ideas on what might cause this? If you have questions for me, just let me know, I check this site regularly. Thanks in advance.

Here's a pick of my baby. (first car) I like 850's if you can't tell.

 

Does the miss (what it sounds like) go away when you back off the load (ease off the gas pedal)?

If so, sounds like ignition secondary breakdown. That should set a misfire code though.

Have you ckd fuel pressure?

 

Fuel pressure is next on my check list. What are any suggestions on how to solve if you have a leaking injector? Any way to test them for normal function?

 

Why do you suspect a leaky injector?

 

One . . . you have a tune. Ask lucky what you should expect for mileage. If you are mostly stock from what I've read you should actually be able to have better power and mileage so 20, 20+ if you aren't lead footin' it

You can have a coolant temp sensor starting to get out of calibration and that will cause loss of mileage and performance and all without setting a light until it really gets bad or fails.
Same can be said of the UPSTREAM O2. Not the downstream, doesn't do anything with fuel. Upstream does and it can get slow an lazy and kill your mileage and performance right up until it gets bad enough to set a code.

You'd need a reader to see live data and check your physical coolant temp against the value being reported by the sensor and for the O2s you need to see cross counts to see if they are responding quickly enough.

Pressurize the system a couple times or jump the relay (without starting the car) and then pop the injectors up. You should be able to see if any have dripped gas or have drops on the ends.

 

OK, so I have been getting some very interesting problems from my car. This isn't out of the blue, however, much of it is intermittent. My idle has more variability then I would like it too. Many times when I'm sitting at a light my idle will climb to 1000 RPMS and hold for a few seconds, then drop back down. The other day, I was cruising through town in 3rd gear and I let off the throttle. My car was not slowing down, the throttle was not stuck, and before this incident, I lubed the throttle cable and cleaned my throttle body. I won't do this in any other gear, but in 3rd it has happened at least 3 times now. Among the bad gas mileage and the hard random stuttering, my car actually will no longer start as of last night. I am beginning to suspect, very uncertainly, that my tune is possibly not calibrated right. I am receiving no CELS and I do have a scanning tool. I plugged it in to double check my CEL light wasn't burned out.

@gdog: I have measured the pressure in the fuel system and all seems ok. My car is running so rich that I'm calculating 13 MPG with city, and no more than 16 MPG highway. I have already replaced my FPR, and I can't think of anything else other than leaking injector(s)?

@ Kiss4aFrog: Your info is helpful thanks! I talked to lucky on multiple occasions, and he keeps telling me the same types of things. I replaced my upstream O2 sensor with a Bosch OEM replacement, and I gaped my plugs very carefully to his recommendation of .0025. With my windows down, driving a normal speed, my car smells so bad of rich running it gives me a headache. When friends drive behind me they tell me they get a headache. However, I ask them if they see any smoke, even when I get on it, and they tell me that they don't see anything except a little black puff when I really step on it. If my coolant sensor was bad, wouldn't it appear on my temp gauge when the car was running? In the past when I had a failing coolant temp sensor, my temp gauge would always remain slightly under half. I'd like to know more about testing my temp gauge, as I understand that can cause a car not to start.

All set aside, my main priority is to get my car to start again. I have plenty of fuel pressure, but I have yet to check for spark. I'm checking my crank and cam sensor tomorrow, but after that if it doesn't start, I'll need help!

 

You keep telling us that this is "good" and that is "good" but you're not telling us what "good" is. Give us the real data (i.e. fuel pressure).

Did your stage0 include a compression ck? Have you tried new spark plugs? If it was running that rich they could easily be fouled.

The car was running rich enough that it should have set codes. You said you have a scan tool; once you get it started why not look at vitals like coolant temperature, spark advance, LTFT, STFT, O2 sensor function, etc.

 

Only thing I mentioned was ok for sure was my fuel pressure. I had this checked back when the car was still running because i thought it could have been the cause for the intermittent stuttering. It held 43 PSI through idle, and also with a few REVS of the engine. From what I understand, this is what it should be at.
My motor has had a compression check back when I bought it from an engine dealer in NJ, they showed me the numbers and they were a near even 170 PSI in all cylinders. The motor only has 90K miles or so.
I pulled the plugs out to check them, they don't have any indication of being fouled. They only have about 2500 miles on them. When I had a few plugs out, I tried cranking the motor to confirm there was spark being made. There was not! It would appear that I had a bad cam sensor, however I just replaced that with a known working one, and no luck. I'm a little confused at what else could prohibit spark? The coil wires, rotor, and cap are all OEM new with 2500 miles also. I suspect possibly an Ignition Coil? Though I've not heard of too many of these ever failing. Let me know if you have any more advice. Thanks

 

"We" are trying to help you with the problem. It is helpful that you've had a compression test done but that was then and this is now. "Now" is when you are having a problem with it running rich so the suggestions we are making are in the now to help us help you.
It's like a guy who wanted to green flag his battery because it was new, only a year old. New is new and a year old isn't new, it's a year old. Being only a year old takes some likeliness of it being bad away but it's still a year and a battery can easily fail in a year as a primary problem or killed as a secondary problem from something else. We aren't trying to fight with you but we will make suggestions on what to test and it's up to you to determine if you think there are worth the effort of if the person suggestion the test or cure has any clue what they're talking about.
It's also important for you to answer what's asked. Someone went through the trouble of reading your post and doing some thinking and they came to a point where they need more information or clarification. How helpful would it be if you posted the problem only to have it be the first and only post in the thread ??

Testing the coolant temp sender would necessitate using something to physically measure the coolant temperature and then compare it to the reading you get from a scanner.

It's also helpful when you say you've replaced something if you say new or used. Like you did with the cam sensor, used but known good. I don't trust people or the test who pull used parts for testing nearly as much as you never know if the used part was good at the time the person scrapped the car. That's what (IMHO) Gdog was getting at. We like to know how you know or how you tested something.

43 is what it should be at but when you blip the throttle the pressure should jump and return. If you have it idling and you remove the vacuum hose from the regulator you should see 5-10psi jump in pressure. If not there is something wrong with the regulator. The main thing on yours is to make sure there is no raw gas dripping from the regulator. If the diaphragm inside the regulator ruptures it will allow raw gas in and the engine will run very rich and usually rough too but it sets off the check engine light for mixture rich.

Did you check for a leaky injector(s) ??

What exactly are you saying when you say "OEM" ?? Did they come from a Volvo dealer, do they say Volvo on them or ??

This last post you brought up no spark, is it dead now or was that just intermittent ??
You can have spark from the coil but still not have it at the plug. Have you tested for spark from the coil ??
Bad cam, crank sensors, poor connection at the connectors, nicked wiring, blown ECM fuse, bad ECM (very last thing to consider).
Have you checked to see if you have injector pulse ?? You can get a loaner kit at most auto parts stores. If the coil itself failed then you'd still have injector pulse but if you have no injector pulse too then it's likely the sensor or wiring that's causing it.

At 13 miles to a gallon city you should see fouled plugs so that's why we are kind of shooting in the dark. Either you have fuel dripping out of something before it gets to the engine or it's going through the engine and would necessarily need to be fouling on the plugs.

 

Thanks for the tips, I apologize if my information isn't clear. Not trying to be haughty or give bad vibes in my posts. I'm not as well educated on the more technical aspects of how many different parts work. I am good with a wrench and can easily identify/replace parts. I have more than one 850, so when I say something is working, it is because I swap different parts over from a car I know that they are working properly on. When I say OEM, I'm not talking about OEM quality, I'm actually referring to parts from the dealer that came in boxes marked Volvo with original manufacture part numbers on them.
Since the last time I posted about not having spark, I have had zero spark at the plugs. I'm not entirely sure on how to test spark at the coil, I can probably find a link though. I'll post back when I check the injectors for leaks and learn what injector pulse means I'll take a picture of my spark plugs and you guys tell me what you think about possible fouling. I'm not any kind of expert, they appeared fine, but you're right for how much fuel I'm burning, they've got to be pretty beat up. Thanks guys, I'll keep updating

Update: Coil has no spark when cranking car with coil wire on a ground. What is the process exactly for using a voltmeter to test the coil? If the coil was beginning to fail, would this not be able to explain the jerks and jitters my car was experiencing under load?

 

There is a really good no-start procedure in the manual. I will try to find that later and post it. I can tell you that if the main fuel injection relay drops out, you won't have any spark. the relay drops out because of physical plug deterioration. Really, any of the round "bullet" shaped original volvo plugs have a limited lifespan.

 

I agree w/ the above experts and feel I'm in good company when I throw my 2 cents worth in with them. I have a '95 940 and had a similar problem...I took the air sensor off that is attached to the breather and sprayed carb cleaner into it to clear the carbon and other gunk that would catch inside the little wires that sense the airflow. I also sprayed carb cleaner in the intake throat and allowed a few minutes for it to clear. I reattached the air sensor and my problem cleared. I now make that a every 6 month part of my maintenance..

 

NEVER ever use carburetor cleaner on the throttle body or MAF. It's way too aggressive a cleaner and can do more damage than good. Especially if it's used repeatedly. Google or ..... a search on MAF or TB cleaning and you'll see the warnings.

There is a coating on the throttle body plate to prevent corrosion so the plate doesn't jam in the body. If you use carb cleaner on it you will start to peel that protective film off and can produce more of a problem than you're trying to solve. Carb cleaner can also damage the shaft seals and it's hard on the materials used in the MAF.

If you can't see the sense in buying both MAF and TB cleaner I'd recommend the TB cleaner for both.

 

I have some new updates. I don't like when threads have abrupt stops with no real solution! Here's the latest. I ordered an ignition coil for my car, it took two weeks to get here, and the temperature outside has been about 5 to 15 degrees Fahrenheit. In the two weeks that I was waiting, my battery had completely died, even a jump from another car was not getting the cranking up to speed. Battery was only two years old, but I noticed the CCA were only 600. I've heard from several people that this is two low for our winter temps. I installed the new ignition coil, and a new battery with 750 CCA. The car cranked 5 or 6 times and fired to life! It ran very well, smooth idle, no more cutting out under load! I ran it for 10 minutes to get it up to temperature, then shut it off. 5 minutes later, went to start it again, no luck. It just kept cranking and cranking. Eventually it fired back to life after several cranking attempts. Here's the thing. Once it is started, it runs 100% normal. No check engine lights, boost is all there, idles fine, doesn't cut out under load anymore. (Ignition coil may have fixed this)? Well, I don't feel comfortable driving it anywhere and shutting it off, because it picks and chooses when it wants to start. I had my car at a shop in Lancaster PA called Car Crafters Inc. and they did an oil change for me. Well the sticker on my wind shield is saying that they put in 15W 40 oil... isn't this far to thick to use in any 850? They are so experienced there, I'm confused why they would do this? He did say the oil contained a heavy detergent because they felt that was necessary to clean out some sludge in my oil pan. Let me know what you guys are thinking about the hard starting. I THINK, the problem of no starting was really just a problem of VERY hard starting.

 

For your part of the country I'd say the 15w40 is a bit much. When it's cold and so far this has been a very cold winter you'd be better served with 5W or 10W something. I would think their computer would have recommended a 5W30 ?? Don't know
California or the southern states where you don't see below zero or rarely see freezing, I'd have no problem with the 15w40. Looks like you can see temps in the teens so it's kind of a toss up. Bottom line, IMHO before they tossed that weight oil in they should have asked you.

Not sure what oil they would have used with a heavy detergent or that it would have anything to do with their choice of that weight. All oils have detergents in them unless they are marked "non-detergeant" (lawnmower, small engine use) and from brand to brand the amount isn't much different. I've actually used a quart of trans fluid in with the new engine oil to drive on to clean out an engine. Did it a couple times on my 850 as it was a pit when I first got it. Trans fluid has way more detergents than engine oil. But a can of Seafoam or a commercial engine flush product will get the job done too. One guy recommended using all diesel fuel and I can see where it would work but it's not a lubricant and I would be terrified someone would damage an engine that way.
If you use a commercial "engine flush" read the label. Some are very aggressive and say to only use it just before a LOF and not to drive with it, others you can add a day, week, month or whatever before the next change and drive with it. I prefer the milder stuff as it's more likely to slowly dissolve sludge and suspend it in the oil or go to the filter rather than it all letting go and plugging the oil pumps pickup

The only way we are going to be able to help you is if you give us some information. WHEN it's not starting you have to have on hand whatever you need to check for spark at the plug and if not there, at the coil. You need to check what the fuel pressure is when it's not starting to see if the pumps working and giving you adequate pressure.

Since you are saying it's cranking then you are missing spark or fuel on those intermittent occasions and we need to know which or both is dropping out to figure out why.

 

After some time online and asking multiple volvo owners about my issue, I decided to try changing the engine coolant temperature sensor. This was a pain to do in 10 degree climate with a 0 degree wind chill. Of course I stripped out one of the thermostat housing bolts! After all of that I unplugged the battery for awhile to reset the computer. The car was hard to start once again for the first time. (It may have been flooded from all of my long cranking attempts)? I let it sit about 14-15 hours, and viola, it fired right up. I drove about 50 miles tonight, for no reason except I'm happy to have my baby back, and my trip computer is holding a steady 20-21 MPG, in contrast to the 12-15 MPG before the replacement of the ECT. The car smells less rich. I have an appointment at my Volvo mechanic on Monday, and he is going to look into the issue and see if I properly resolved it. I'll post back with a certain answer on what fixed my car, but in the meantime she runs again!