1994 850 GLT -fuel injection code 5-1-2

[falcor75]

So while my car isnt really a Volvo its still got a Volvo heart. It recently ran very rich, enough that a quick rev left a sooty mark on the ground. (and my garage floor)
I checked the codes and there was only one, 5-1-2 from the A2 port. "Short term fuel trim too rich"

I checked the fuel pressure, was ok at 2.9-3 bar
Injectors has recently been out and off to service and passed with flying colours, they were beyond suspicion (for now)
O2 sensor could be the culprit but no other signs of it being bad. Engine runs great.
Air mass sensor could be suspect also but same as above, engine runs great.
The last remaining thing is intake side air leaks between the air mass sensor and engine or exhaust leak between the engine and O2 sensor.

Since my car is a self build and everything has been apart and I had no real history on the engine i thought the last point was my main suspect. I changed the soft metal donut between the exhaust manifold and start of the exhaust tube since I had a new one laying around.

The next check was for intake air leaks. I tried putting low pressure compressed air into one of the vacuum ports and found a whistle from the flame trap connector on the throttle body elbow, turns out that was missing the o-ring seal. I fixed that but still had some noises that was hard to identify where they where coming from. Youtube to the rescue, I found a DIY build of a smoke generator that worked really well letting me find two other leaks. One was the main throttle body elbow that had a very small crack and once that was sealed I found the leak shown in this video. This tube was quite snug on the port but seems it leaked slightly when given a little puff of air.



If you are struggling with vaccum leaks I really recommend building a smoke machine.

[falcor75]

Test drove it this afternoon and the soot issue seems to be solved !

[scot850]

Excellent! And thanks for sharing the video of the smoke machine.

Neil.