2000 S70 Still runs poorly after Xemodex upgrade

[draser]

All good points. Looking at front o2 sensor reading of .5 lambda that indicates a very rich condition, which is in line with red cat, but long term fuel trim should be highly negative as ecu tries to compensate. I did not see that in reply. At any rate, just as mentioned, even if cat is replaced if this condition is not corrected will make new cat red.

[Chapelgirl]

Update: took the car to a Volvo mechanic with 25 years of experience who is now independent and has access to VIDA. He checked timing belt, fuel pressure, throttle pedal, ETM. Everything is perfect. Still no codes. Operation is getting worse and fuel mileage is down to 10.6. His thought was that everything was pointing back to the cat being stopped up but he didn't want to take the exhaust loose at the flange due to a bolt or stud that he knew would break if he touched it. Took the car back to the muffler shop and had them cut the pipe before the cat. They cut the pipe and operated the car. No change. This is unreal. They are welding the pipe back up for me but not sure what to do next.

[blutopless]

I went through almost everything you are experiencing and finally just replaced the Mass Air meter and it cured the problem. I did need the Xemodex upgrade, as my car would barely move on its own, the cruise wouldn't work. The first throttle body they sent didn't fix anything and they replaced it for free. I replaced both O2 sensors, nothing. It threw no codes, but as soon as I replaced the Mass Air, it ran perfect. I don't think there was anything wrong with O2 sensors, just wasted $200.

[Beck]

Sounds like a MAF failure

[draser]

You can verify if engine is in closed loop by creating a lean/rich condition and looking at fuel trims to change using a scanner. During same test look at oxygen sensors to change as well. Need to make sure the coolant sensor works and puts engine in closed loop. Check coolant sensor ohms to change from 1000 ohms or so to a few tens when engine hot. Pretty annoying but more investigating required. If all checks out test MAF by looking at fuel trim to be around zero at idle then rev up to 2500 steady and see if fuel trim settles around zero. If not MAF may be bad.

[Chapelgirl]

I'm interested in the "coolant sensor putting the engine in closed loop" comment in an earlier response. Replaced the MAF sensor today with a known good used part. Little or no change. Had muffler shop cut pipe before the cat. No change. Will go after the rubber air tube behind the power steering pump this weekend. Didn't know it was there until removing a ps pump in a scrap yard the other day. This is quite the mystery.

[abscate]

What do the plugs look like chapel? Are you running really rich?

[Chapelgirl]

Perhaps I should recap all that has been done so far because this story is long and drawn out.

Problem: poor throttle response, low power under load, especially going up hills, poor fuel mileage at anywhere from 8 to 11 mpg. No codes. No check engine light. Engine will rev normally while in park or neutral but idles poorly until warmed up. Cooling fan runs longer than normal when the car is shut off even on a cold day and especially after struggling up the hill on the way to my house.

Repairs to date:
Seafoam treatment
Replaced spark plugs with OEM Volvo
Replaced vaccuum lines from airbox to the manifold and one from the intake to a switch of some kind located over the radiator.
Took car to Volvo dealer to have sweep test performed-they verified ETM failure. They updated the ETM software in order to run the test.
Removed ETM and sent to Xemodex for rebuild. Reinstalled and did the re-learn process-no change.
Changed fuel filter. No change.
Took car to muffler shop to troubleshoot cat - they drilled holes fore and aft of cat and verified it was ok. Also verified fuel pressure was good.
Found a new local Volvo shop run by a previous 25 year Volvo mechanic. He verified the ETM is working properly, the throttle pedal is working properly. Also checked fuel pressure and found it was good. Suggested problem was in the cat.
Took car back to muffler shop and and had them cut the pipe before the cat to verify. They cut the pipe and the car still ran poorly. Welded pipe back up.
Went to salvage yard to find a used MAF and could not find the same part. Ordered a used MAF from Erie Vo-Vo and swapped it out. Throttle response improved maybe 10% at most.
Now the coolant level light is on in the dash but the coolant level is good in the tank.
The car would not make it up my steep driveway yesterday so had to back the V70 down and pull it up with a cable.

I have to swap out the power steering pump this weekend so will replace the air hose behind it and look over any vacuum lines that I have not replaced but beyond that I would not know what else to check.

[E Showell]

Change thermostat and ECT

[Chapelgirl]

That is interesting. This is the second mention of the coolant temp sensor. I'll have to look into that. The thermostat is new because on top of everything else I've done I replaced the radiator, thermostat, and coolant hoses a couple of months back. I'll look into the sensor issue and report back. Thanks.