740 B230F power loss failure (stuck at low speed, car can't climb)

[paulgossart]

Hello everyone,

I drive a 740 2.3 GLE B230F 1990 (385K Km) I've got since January. I'm stuck for a week now with a failure that nobody explained since : everybody only says it's "strange".

Some weeks ago, I've taken off the injectors for cleaning. I cleaned them, and replace. At the time, I didn't notice, but two o rings were bad. They have been replaced since. During this operation, I've noticed that a hose (the "S" hose) was disconnected, from what I've learned, later, was the oiltrap. I don't know if it was me that have disconnected it, or if it was such since a long time.
The car ran with no problems for a few days, but on short drives. I did a longer drive and then, after 30mn of driving, the car suddenly start to lose power, especially in climbs. If the road wasn't horizontal, I was stuck at 30 km/h max in second or third gear. On horizontal driving, can't go further 80 km/h. There was no "hole" or anything when getting speed : just the feeling that the car was completely unable to get enough power, like a "limit". No particular noise, except when I press the throttle pedal, opened window, I could hear a very slight air noise.

Of course, considering I've had the injectors recently taken off, I thought I did something wrong. So I've repaired those. In the meantime, I've cleaned (again) the throttle, and cleaned PCV system, which was completely clogged, especially the flame trap housing (the "pin" that connects the little hose was completely full of hardened material). I've noticed that there was nothing in the housing : but parts catalog indicates that there should be a kind of filter here. I don't know why it is missing. Maybe it was a bad idea to run the car with clogged PCV system connected, because the cable could have popped itself out before. Maybe it damaged something.

I've also checked all the connectors visually, and cleaned them with contact cleaner. The crankshaft sensor was very dirty.

Now the same failure still happens. Yesterday, I've tested the car for the third time, letting it get hot. I only ran for 30 seconds, and it happened, on quite flat road. So it's not the injectors rings.

My idle gives slight oscillations (very light), but I have the feeling that it is quite low since I've first cleaned the injectors. It is around 600 rpm. To be honest, I don't remember how much it was before.

I've changed the main fuel pump and filter maybe a month ago, absolutely no problem with it. New air filter and spark plugs also.
The diagnosis box gives me normal codes, so it doesn't help.
I think it could be a bad sensor, but actually, I don't know where to start. When taking off the PCV oil trap, I've noticed that the connector of a sensor (just below the inlet, ECT I think) was looking bad. The cable can move a bit in and out of the connector.

Other symptoms :
My exhaust system is getting old. When it runs idle, if you get to the exhaust pipe back of the car, you can really hear that is gives irregular "pulses". Even when the engine is hot, there is water coming out from the pipe. But no smoke or something, and my oil cap looks very clean. The car runs with volvo coolant and synthetic oil. The exhaust makes rattling noise since a long time, mostly coming from the catalytic converter I think. I don't know if it could be linked the the failure.

Thanks for your answers, because I don't know where to look now.

 

[Wobsmangbaffler]

Did you bend the fuel rail when removing and replacing the injectors? They're somewhat easy to bend if you tug on them wrong, which makes it easy for an injector to but stuck out a bit, preventing the orings from sealing properly

Alternatively, could be a MAF? Might be worth checking a scrapyard or borrowing one from someone local for testing. Also worth checking TPS to make sure that it is clicking off idle properly. Also worth checking that the bendy hose from MAF to throttle bottle to make sure you dont have any splits that would be leaking air in

 

[paulgossart]

Did you bend the fuel rail when removing and replacing the injectors? They're somewhat easy to bend if you tug on them wrong, which makes it easy for an injector to but stuck out a bit, preventing the orings from sealing properly

I've tried to be careful, but it was quite hard to remove. I've tried to pull it the most "equally". It seems right, but I've noticed that the injectors were not specially "equal" in position. The yellow ring on some is more visible than on the others. Could be a wrong position indeed. Is it possible to "correct" the eventual bending of the fuel rail ?

Also worth checking that the bendy hose from MAF to throttle bottle to make sure you dont have any splits that would be leaking air in

I'll check it again for leaks, but it seemed fine to me. Cleaning it was one of the first things I did on the car, with the throttle body. The hose was full of burnt oil.

Alternatively, could be a MAF? Might be worth checking a scrapyard or borrowing one from someone local for testing. Also worth checking TPS to make sure that it is clicking off idle properly.

So I guess that the diagnosis box can't detect a misfunction for these sensors ? I think I'll check with a multimeter what can be tested this afternoon. The MAF seems difficult to diagnose however, for what I've read.

 

[paulgossart]

I've done some ECT tests on the ECU :
When the engine was hot (gauge needle on the middle), it was oscillating between 280 and 300 ohms.
I've noticed that if I press the throttle pedal, it goes immediatly 0. Is it normal ? If I turn off the engine, the value goes 192. If I put contact on, it goes 223.
Also water squirtings on the exhaust (I can hear them and see them) when pressing throttle slightly. When you speed up, it is more regular, but in the first steps of the throttle, the engine acts irregularily, audible in the exhaust sound too.
I will give a look to crankshaft sensor and O² sensor, and try to find a way to test MAF.

 

[Pietercc]

There is really no good way for you to test the maf, other than finding a known good one. Unplug the maf and see if the car is better or worse, that at least will give you a bit of an idea. Where is water falling on the exhaust? That could be a bad head gasket

 

[paulgossart]

Where is water falling on the exhaust? That could be a bad head gasket

Initially it was mostly between the catalytic converter and silencer (which had been replaced), as shown on the photo I took some time ago. But it comes also from the exhaust pipe itself. There is a continuous slight stream of water at the end, and it shows little squirts when the engine "pulses" at idle.

There is really no good way for you to test the maf, other than finding a known good one. Unplug the maf and see if the car is better or worse, that at least will give you a bit of an idea.

That what I thought too. I've seen something with nails, but it looks weird. I'll check with unplugging.

 

[Pietercc]

Are you loosing coolant? Water in the oil?

 

[bobxyz]

For the lack of power issue, check the big air intake hose between the MAF and the throttle body. You may need to remove it to inspect the bottom & back sides.

"I've noticed that the connector of a sensor (just below the inlet, ECT I think) was looking bad. The cable can move a bit in and out of the connector." If the ECT sensor isn't making a good connection, the ECU thinks the engine is very cold and will over fuel.

 

[paulgossart]

Are you loosing coolant? Water in the oil?

Not particularily. When I took the car in january, we had flushed it, it was not the volvo coolant. The level has gone a bit lower after I got back home (maybe 200km later), and it doesn't seem to lower since.
When I cleaned the pcv system, I cleaned this side of the engine, full of old oil leaks (the oil trap was covered of it, like pompeii). There was some coolant (I think, it looked like) just on my finger on the photo. The Inlet seal was then a bit wet. But it didn't came back since I did the cleaning. It was a clear liquid, with no particular smell. There is still darkened parts around (other photo), that indicates something is leaking here.
The oil cap doesn't have any traces of what I've heard to be sign of coolant/oil mixing (white color).
EDIT : Unplugging MAF makes the engine nearly stall. So the MAF works I guess.

 

[MasterBlaster]

the car suddenly start to lose power, especially in climbs. If the road wasn't horizontal, I was stuck at 30 km/h max in second or third gear.

Other symptoms :
My exhaust system is getting old. The exhaust makes rattling noise since a long time, mostly coming from the catalytic converter I think. I don't know if it could be linked the the failure.

A good catalytic converter looks like this inside:




One that has failed (rattles, then gets worse as the insides start to break apart) looks like:



If those broken chunks bounce around enough, they can turn sideways, or break into smaller pieces that can completely block the exhaust from getting through.

If exhaust can't get out, new air/fuel can't get in, and you have no power.

 

[paulgossart]

If those broken chunks bounce around enough, they can turn sideways, or break into smaller pieces that can completely block the exhaust from getting through.

If exhaust can't get out, new air/fuel can't get in, and you have no power.

When we had the exhaust disassembled to replace the silencer, there was indeed broken/rusted parts inside the cat. I've shaken it to empty it as much as I could and put it back in place (for economical reasons, I couldn't replace the cat then).

By the way, there is a hose which is missing, that goes from the air box (or somewhere around) to the exhaust, left of the engine (pre heat hose ?). But I've read that a lot of people run without it.
So I should disassemble the cat to see how it looks, in my diagnosis plan.

Edit : Just found out my ECU was different. It's a 2.4 0280000951. Curiously, according to VOC website it should not be this one. Guess it had been replaced by previous owner.

 

[paulgossart]

Final update : changed the cat, the rear silencer (middle one already changed), and the 0² sensor by the way. New thermostat in the same time, because I had (and still have unfortunately) a slight leak at this place. The car runs now great after a first test, longer than the previous ones, and I have the feeling that it gets speed way better than before. Cat was like having a ball rattling inside, and the rear silencer... When I took off the exhaust pipe, the inside of the silencer came out : completely rusted. The core seems to be full of particles. I guess the cat and the silencer were both dead, and the exhaust system not working anymore. So when the engine was looking for more power, he wasn't able anymore to get the gases correctly out.