So I am having a problem with my 1994 850 turbo. Ive owned a few in the past, currently two so i have come across a lot of the real common problems with these cars but this one i can't figure out. The other day i was driving and it was a scorcher so i decided that it was time to refill the refrigerant for the ac. After running the AC on full for about 45 minutes my car lost pretty much all acceleration. I was on the highway at the time going about 55 i would say. The engine didnt stall out but was surging between about 900 rpm down to almost cutting out. I was able to get it to idle to a side street where i could keep it overnight and look into it a little more to see if there was anything i could fix right away. In nuetral i could only get the rpms up by feathering the pedal. If pushed the pedal down in one motion it would drop the rpms. I was thinking MAF sensor so i tried disconnecting it but the engine shut right off. I then tried cleaning the sensor with some maf cleaner still same symptoms. Im not to familiar with these so could this be a bad maf sensor? could it be something with the ac? or was that just a coincidence? I dont know where to look next, i pulled the codes on it and got p0138 - Oxygen Sensor Censor High Voltage Bank 1 Sensor 2, p0331- knock sensor 2 circuit range/ performance (bank 2), p0102- Mass or Volume air flow A circuit Low Input, p0141- Oxygen Sensor Heater Circuit Bank 1 Sensor 2. The check engine light was on before the the car broke down not sure which codes where on there though. Thinking the p0102 could also be from me disconnecting the MAF. The car ran well before this, a little hesitation starting it but once started it ran great. Any help or input on what it could be or what to look at would be greatly appreciated. Thanks in advance!
-Johnny

 

Yes pulling the plug on the MAF could cause all of those codes.

I would say clear the codes, crank it up and see if you get any new codes.

It could be 100 different things, we have NO IDEA of what shape the car is in. How old are the plugs? Is the fuel pressure good? Is a turbo intake tube loose? Is compression good?

It's real important to check your codes before disconnecting anything in trouble shooting. I guess it's really not a good idea to drive around with the light on either.

 

thanks for the input, ill clear the codes today and see what pops back up.

 

Sounds like you may have had a hose between the MAF and the throttle body come off or split.

 

13.8 @ 103mph Manual with 18T
13.7 @ 99 mph Automatic with 18T


Yada, yada, yada - - - I want to know what it'll do with the 20G/Black ARD

 

so i went back to the car today and cleared the codes and after runing it and restarting it a few times i got no codes after that so im thinking maybe those were just from disconnecting the maf. Out of curiousity i turned on the ac and turned the fan up to high and the engine ran A LOT rougher and rpms dropped. i also noticed a little bit of a burning smell coming from the serpentine belt. im thinking now maybe the ac compressor may be dragging the belt down. would something like that cause these symptoms? if so what should i look at next?

 

Tried replacing the maf and it didnt help. Another thing i noticed its been doing is its hard to start but once it goes it revs up high for a second or two then drops down. Same thing happens after feathering the pedal a little to get it to rev up then it will rev on its own for a second or two. Could this be the tps? What else could i take a look iwant to avoid having to take it to a mechanic. Any help is appreciated.

 

The TPS works like a light dimmer. As you press on the throttle it sends a voltage signal to the ECM. It's like a rheostat and a winding can wear out or skip. If it goes bad partially it will have a dead spot where no electric signal is sent and the engine stumbles. It wouldn't be the cause of it revving up. At least I've never know a bad one to cause that kind of problem.

Looks something like this inside.

 

So, what about the 20 questions I asked above? Have you pulled the serpentine belt to see if the AC compressor is dragging down the idle? Has the car been tuned in the past 30,000 miles? Have you cleaned up the throttle body? Is the PCV in good shape?

 

Robert,



And Johnny, Have you pulled the serpentine belt to see if the AC compressor is dragging down the idle? Has the car been tuned in the past 30,000 miles? Have you cleaned up the throttle body? Is the PCV in good shape?

 

LOL, funny.

 

Why don't people get it ?? You think we just ask questions for the heck of it. Were trying to narrow down a problem on a car we can't see, hear or feel. We don't know if the reason it won't start is because you forgot to put the battery in, it's out of fuel or something else broke.

Johnny, same with your problem. We ask and sometimes we ask really dumb or basic questions but it's because we need to know to eliminate something or to see if it points us in a direction.

If you want help , , , help us by answering questions.

 

Sorry been really busy with work, but i checked the compressor its spinning freely. Was planning on gettinga tune in the near future. I just got the car from a friend who was going to junk it because of an oil leak, oil cooler hose an rear cam seal.saying that im assuming thepcv could use se work being that from what ive read a bad pcv can push that seal out. Ill clean up the throttle body as soon ad i get some free time . It did seem to move freely when i checke would hurt to give it a good cleaning though. Ill post agin after i do this stuff. Thanks for the help eveyone i appreciate it.

 

We are all Helen Keller Mechanics

 

What scares me at times is how good we can be with a brief description and or a short video clip

Then again there are those three and four page disasters looking for a no start


And you may know this but some people don't. The part the belt runs on sits on a bearing and is NOT connected physically to the compressor. It should always be able to spin freely and quietly when the AC or defrost are not turned on. If it's noisy or difficult to spin it's the bearing that's bad not the compressor. To see if the compressor is damaged you need to try to turn the outer most part of the compressor clutch as it is physically connected to the compressor. It should turn and turn smoothly.
This is with engine and belt off.

 

The outer part of the clutch feels like its a little hard to turn, would this affect the engine when the clutch is not engaged?

 

i also posted a video, it may be a little help.

 

when the AC is off, the Defrost is off the clutch is dieengaged so the belt is just spinning the pulley on the bearing. The compressor is not spinning or at least it should not be.

If it felt a little stiff it's because you are spinning the compressors guts. If it felt a little stiff that's no problem but if you hear or feel any grinding that is a big problem.

 

I don't understand the video. What was its purpose?

 

The video wa to try and show how when i step on the gas the rpms dont really react. I tried to get a good shot of both the pedal and tach it wa tough to really show what was going on. Just trying to give a better idea of what it is going on figured it couldnt hurt to try and show it whether or not its helpful.