2000 S70 rough idle, no CEL, reduced mpg and power

[itsmekirby]

My S70 (130k miles) suddenly started running poorly today. The first thing I noticed was a rough idle with lots of vibration that hunts a bit but doesn't stall. At highway speed it mostly feels fine but is getting 25 mpg instead of the usual 29-30, and I can feel that it's lacking some power. Also it does transmit some unusual vibration at speed when I give it some juice up a hill but feels normal at lower power levels.

No check engine light but I did get code P1132 yesterday, which seems to happen occasionally to this car but with no symptoms I just clear it and move on. I cleared it yesterday and it did not return.

Any thoughts on what it could be or how to diagnose? I tried disconnecting the MAF which made it run way worse, which rules that out right? I was thinking ignition issue but surely that should throw a code. The ETM issue should progress more slowly than this right? This came on very suddenly. And front O2 sensor is the obvious culprit given the code but my understanding is that that sensor is not active until 1 minute into operation, and my rough idle is the same from cold start until warmed up. Vacuum leak maybe? I don't see anything obviously wrong and when I spray water on the hoses while running there is no change in idle, which I read can be an effective cheap test.

[scot850]

This thread may help. The OP made a type in the final note typing P1332, but the whole thread is P1132

viewtopic.php?t=31038

Neil.

[scot850]

The solution, for the linked car owner was not the front sensor, but the rear one.

However, following a PM from the OP on this thread, The difference here is that the issue is from cold when the O2 sensors are still not up to speed, and it continues with the issue.

The issues I would be looking at as suggestions as we are kind of flying blind are:

1) Checking for air leaks, especially as this is a turbo motor. Looking at intercooler pipes being loose or cracked, the intercooler itself being cracked and then checking the intake manifold for leaks (try spraying WD-40 around the area wen the engine is running and see if there is a change in how the engine runs. Check all vacuum and air pressure line for leaks,
2) Check the hoses and the TCV. Just changed one on a P1 that was down on power and running lumpy and now it is smooth again.
3) I would suggest checking the spark plugs and coil packs, but normally they will throw a code, but not knowing the history it is worth removing a plug and check the condition and they are gapped to 0.028"

It could be O2 sensors but don't think so now with more info. One other thing to check is the ECT wiring and connector near the power steering pump for corrosion. I am not sure this is the issue but it causes poor fuel consumption and hard starting.

Neil.

[itsmekirby]

It was the coil! Turns out it just takes a long time to throw a code for it but it finally just did and I confirmed by hand. Thanks for the help all. That o2 code will just remain a mystery

[scot850]

If the coil has been failing you may not have been getting full combustion. Maybe that tripped the O2 sensor being out of spec? I guess it is time to run and see if it returns. Glad all is good for now!

Neil.