99 XC70-P1171-New ETM-MAF-O2

[arda]

Hi,

Long time reader but first time posting. (sorry for the cliche) In advance please excuse the lengthy introduction to my problem; I wanted to be clear.

I own a 99 XC70 at 167000 miles. Last month the dreaded ETS light came on along with obvious signs of ETM failure. I had the yellow sticker ETM installed about 60K miles ago. (by previous owner) So I did the logical thing and made sure it was the ETM that was causing all the trouble, (idle problems, no cruise control, etc.)

I went ahead and ordered the Xemodex replacement ETM. While at it I cleaned the PCV system and replaced the hoses and the oil seperator. Installed the ETM put everything back in all cleaned and shiny. Started her up and VOILA! It was idling perfecly smooth. I took it for a ride in the neighborhood and was honestly impressed by the change. Smooth acceleration, improved throttle response, along with working cruise control. After about 10 mins of driving right before pulling into the driveway it started to idle rough along with black smoke.

PS.Last year when I was having the rough idle/black smoke problem along with all O2 sensor codes I went ahead and replaced both O2 sensors along with the MAF. All was well for about 10K miles.

I checked the spark plugs and they are pretty much covered in black. Exhaust is dark and smells liek unburnt gas. While it was idling poorly I disconnected the MAF to see if it would idle normal, but after a few seconds of increased RPM it goes back to idling poorly. At this point there is no CEL on or a code. I made sure all the vacuum connections were good, and they were.

Sooooo... Long story short after starting the car a few times and revving it, I check with the code reader and the P1171 code is "pending". Rich micture...
What may be the cause of this????

[FCPEURO]

I am thinking this is fuel related to be honest. Mainly because it took so mush to get the code. I would take a look at your Fuel Pressure Regulator and the Fuel Pump. One of them could have gone bad.

[arda]

Well I did a fuel pressure test and with ignition on at 2nd position pressure is @ 42-44 but when the engine is running it shoots up to 57-59psi consistantly. Regulator going bad?

UPDATE: Went back to the car to check all the relays, and they all check out OK. cleared the code p1171 and it idled and drove fine for about 5 mins. MPG was good as well. Then the same roug idle came back with black smoke. I guess I need to get one of these OBD live data readers or the PC-OBD cable and softwares to manitor the O2 sensors and the MAF. Any suggestions for the product to choose?

[arda]

Seems like Im just responding myself. No problems, maybe someone will have the issues I am having in the future and can read through this post. It is what I have been doing for a while with this problems anyways.

Update to the situation: I got a OBDLink obd-to-pc cable from Scantool with their software. I can see that while car is idling from cold start, the fuel trims are normal. Once the system starts to run in closed loop mode utilizing the O2 sensor it starts to increase the Short Term Fuel Trim all the way up to 25% and eventually long term fuel trim goes up to the same value as well and idle starts to crap out on me. STFT never goes back down it is constatly high and LFTF stays at its max at around 33%. All this time CEL does not come on for anything. Even if I unplug the MAF CEL doesnt come on.

Sounds like the front sensor is bad but why doesnt it trigger the CEL for LFTT too high? This is where I sit at the moment.

[MilwaukeeV70owner]

I too have an almost identical situation(p1133 & p1171):
-Newer ETM
-Newer MAF
-no vacuum leaks
But recently I've been smelling gas near my tank and it turns out my fuel sending unit is leaking. I really don't know yet if they are related.
Did you fix your issue (3-4 years ago)?