1991 940T B230FT my sister has been having a little idle problem lately. Engine is vibrating the car a bit but doesn't drop down or idle erratic and is noticeably ticking or hissing constantly. "tss tss tss tss" as it idles. Sounds slightly louder I thought maybe an exhaust gasket as it smells slightly like exhaust fumes in the engine bay. Doesn't seem to come from the valves I popped open the oil cap while running and didn't hear anything unusual in there. Definitely coming from the turbo side of the motor.

When revving the motor it is still present and slightly louder. I'll try to get a better video of it in the morning but the video quality doesn't really depict the sound well. >> http://www.youtube.com/watch?v=4QG3tvkpnrA

Where to start? Fuel pressure regulator? Fuel pump(s) seem to prime up normally at startup..

 

exhaust leak is most likely by all you say... or a big vacuum leak

 

So I was able to mess around a little today and ran the car at idle for some time. I unplugged the maf to see if that was it at all but the car stalled so obviously its working. I got a trouble code 2-3-2 which is fuel supply to weak or too rich at idling... and 1-2-1 which was the maf sensor code because I unplugged the maf to test it. So does this mean the fuel pressure regulator is faulty? Any way to test that? Both external and intank pumps are brand new less than 3-4 months old. New fuel lines where I could replace them and new fuel filter. I definitely hear the external pump prime up every time I start. Also removed the cat test port and got a clearer sound >>

cat test port bolt removed under car >> http://www.youtube.com/watch?v=hi7DYi5do9c

under hood >> http://www.youtube.com/watch?v=BkrPKDapXok

EDIT: I unplugged the fuel injectors while the car was running one by one. The middle 2 cylinders unplugged didn't stall the car out at all and the idle did not change. The first and last cylinders stalled the car out. Used a test light on the fuel injector wiring harness and they were live so it looks like the 2 fuel injectors.

 

I don't understand what's making you think that this is a fuel related problem? By the sound of the engine on the video you have MAJOR internal issues, at least a valve is bad causing the missfire and noise. No FPR, injectors, or fuel pumps are at fault here... Guaranteed!

 

I'm going to take off the valve cover and see what I can do later in the week. Appreciate the help. I originally thought it was fuel related because of the fumes in the engine bay and the 2-3-2 code.

 

Caution reading codes! Many times one condition will set off a chain reaction of symptoms and confuse you... In this case more serious fault may be causing the fuel code. And ultimately, just code reading is not gonna get it... especially in the OBD1 which is what your Volvo has... Keep posting.

 

I rotated the engine around by hand with the valve cover off.. nothing out of the ordinary. I don't have a feeler gauge at the moment but I'll be picking one up soon to check clearances. I put some rags around and ran the car with the valve cover off to check them running.

Sorry about the quality it was getting dark out and the lighting sucked. I didn't have my work lights
>> http://www.youtube.com/watch?v=Xk_hdHk-GKE

 

Take a compression test-good place to start!

 

I seem to have a similar issue with my 1994 945T, found low compression on #3 cylinder @ 100psi, the remaining cylinders were all at 165-175 PSI, Not sure what I'm going to do with it yet. Before the tech diagnosed it, he replaced Distributor cap/rotor/wires/plugs on the car (was needed) but now car runs worse than it did before having those ignition parts replaced... totally frustrated and at a loss at the moment. Good luck with yours!

 

Rented a compression tester from Autozone and got all the spark plugs out, removed the coil ignition wire, removed the fuel injector harnesses and plugged the compression tester in.

1st cylinder (I'm not sure if this is #1 but I'm referring to the one closest to the radiator) 90psi
2nd cylinder 0psi
3rd cylinder 0psi
4th cylinder (against firewall/distributor) was stripped somewhat and was hard to get the threading in and I didn't want to damage it further

Rotated the engine by hand and got a 0.33mm feeler gauge in to check the valves and according to the manual that's just fine. (Cold valve clearance between 0.30 to 0.40mm)

My best guess is the head gasket is blown causing loss in the middle 2 cylinders? How would I test this other than removing the head? Has anyone ever tried something like this >> http://www.youtube.com/watch?v=QA7KVQq9vKA

 

There you go! That's more like it. Now, the head has to come off to see what you got... My guess you have a valve or two in need of replacement.

 

Well I found the problem.. the cyl head was sitting way over there >> http://img831.imageshack.us/img831/2716/imag0229v.jpg

It was as expected and not too serious of a problem. No fluids got mixed up too much as it was only a break in the gasket between the 2 cylinders but I will be pouring a quart or two of fresh oil when I get it all back together to lightly flush the crankcase.
http://img96.imageshack.us/img96/246/imag0230k.jpg

Otherwise, everything seems to be in remarkable condition for 101,xxx + miles and for sitting for a year or two with the previous owner. I'm reeeeeally starting to love these cars.
http://img217.imageshack.us/img217/1178/imag0231x.jpg

 

Well now I've got everything together, head-gasket, exhaust gasket, intake, new water pump o-ring. Everything is timed up right, cleaned off the distributor and it fired right up but had a little hesitation and seemed to bog down. After a while running and burning off all the coolant that was spilled on the engine it ran pretty well then just stalled on me. I double and triple checked the timing and its spot on. It runs very well when it does start but just bogs down and dies out of nowhere. Tested spark and got good spark on all 4.. getting fuel.. fuel pumps prime. When cranking it just goes and goes and when I release the key it just sputters. Hitting the gas doesn't help either. After I checked the timing belt for the 3rd time it started up but the same thing, ran great perfect idle then bogged out and stalled and wont start up again.

I did lean on this sensor with 2 connectors on top of the radiator (pass side top most sensor) it popped out as I was leaning on it to get the fan bolts back onto the water pump. I put some sealant/gasket maker around it and plugged it back into the radiator for now. Could that sensor be part of the problem? Any help is appreciated

edit - after looking at parts i believe it is the cooling fan switch that i broke in half. i'll have to pick a new one up and see if that helps

 

Check the timing. The harmonic balancer often separates and screws up the timing while giving strange symptoms like what you describe. It is two metal pieces isolated with rubber in the middle, and it may feel solid but under pressure it may slip.

 

I checked the timing and it's on track. Rotated 720 degrees and started the car and rotated again and it's right on.

So I found a leak below the cyl head near the exhaust manifold. Coolant is dripping out very very slowly and a little on the intake manifold side as well. I rechecked the head bolts and 2 of them 2nd closest to the firewall were loosening up. I'm not sure if that was my error or if they backed out. Either way I tightened them up and that seemed to solve the problem for a while but it came back.

I was on a budget on this and decided to skip machining the heads so what are the odds a bottle of 'steel seal' would work?

 

Hard to tell. There is some new stuff by Blue Devil that is supposed to be the best for sealing heads...