2000 S70 ETM/MAF diagnostics

Caberguy · Post by **Caberguy** » 23 Jun 2014, 16:30

Thanks.

The bucking seems to happen more when the engine is warmed up. That is, I get rough idle right away, but it doesn't buck right away. I've only had the proper "bucking" at take off on a few occasions, and each time it's been after a stretch on the highway.

However, as I mentioned, it has been rather cool and damp lately, and the idle has seemed rougher.

MAF is reading right around 4 grams/second at idle without much fluctuation, which Google tells me converts to 14.4 kilos/hour.

I'll test the coils in the morning.

Incidentally, I emailed Xemodex and gave them a rough outline of what I've said here, particularly as it pertains to their flow chart. I received the following response: "The double click you heard when you put the #2 fuse back in confirms that the ETM is failing. It is unable to find a reference point because the potentiometers have different values."

Post by **precopster** » 23 Jun 2014, 21:50

There are 2 distinct clicks when an ETM starts. It drives the plate backwards towards its closed end stop which can be heard easily then (in under 0.5 secs) the flap rests at partial throttle angle. Then 6 seconds later the unit powers down so that's in reality a 3rd click.

Caberguy · Post by **Caberguy** » 24 Jun 2014, 01:26

That makes sense based on what I actually heard. The two clicks when it powered on were distinct both in the sense that I could clearly hear both of them, and in the sense that they sounded different from each other. My inclination was to think that, as you suggest, I was hearing the throttle plate open fully and then close again, and then, yes, another distinct click when it powered down.

Caberguy · Post by **Caberguy** » 27 Jun 2014, 14:03

I finally had a day that wasn't rainy and foggy. I pulled all of my plugs/coils hoping that maybe one of them was fouled, and that would point to a potentially bad coil on one cylinder.

What I found was that they were all quite fouled. I was told that the plugs had been replaced right before I bought it. I've put about 400-500 miles on it, these things were pretty good and black around the ground electrodes. They were also a brand that i had never heard of, they're Beru Ultras, and they have three ground electrodes rather than one. I cleaned them and put them back, but I think I'll go buy some new plugs and make sure they're gapped right:

Yuck

Post by **precopster** » 27 Jun 2014, 14:25

That is the correct type for your vehicle being nomalljy aspirated. Volvo OEM plugs for 2000 NA are part number 8642660. Those electrodes look ok. Your car is running rich. I would look at the ECT first being a cheap item and secondly the first O2 sensor located on the downpipe before the catalytic converter.

Caberguy · Post by **Caberguy** » 30 Jun 2014, 17:32

Is there a reliable (and easy) way to test the ECT. My scanner reported a steady temp of 92C under normal operating conditions today (on rather hot day) and the needle on the gauge stayed pegged in the middle of the range.

As for the O2 sensors, as I pointed out in the data on the previous page of this thread, the downstream O2 sensor will occasionally spike to read quite a bit higher than the upstream sensor. Looking at the data today, the upstream sensor generally fluctuated between about .2 and .5 volts, the downstream occasionally spiked to about .7 or .8. This would seem to indicate either a failed O2 sensor, an exhaust leak, or a bad cat, right?

It also seemed, given the data that I recorded, there was some correlation between surging episodes, and the out of whack O2 sensor figures.

Post by **precopster** » 01 Jul 2014, 08:52

The point about the ECT is that the resistance it produces correlates to a 92 degree temperature yet the engine can be warmer resulting in rich fuel mixtures and poor performance. There are some ECT graphs here on Matthews which involve dropping the ECT into a independantly temperature measured water and testing for resistance at those given temperatures.

Or simply replace.

Caberguy · Post by **Caberguy** » 04 Jul 2014, 09:41

Ok, replaced ECT sensor and T-stat. Drove around for about half an hour periodically checking live scanner data. I noticed that the ECT reading varied significantly more than last time. Last time it was dead steady at 92C once it warmed up. Today it fluctuated from about 86-91C, averaging probably about 88. Today was about 20F (6.5C) cooler than the last test (sorry, I'm American and think in F, even though I'm measuring in C). I suppose I should clean the plugs again and check to see if it's still running rich after a couple of days, or should I be looking for something else?

I also noticed that the upstream O2 sensor only really fluctuated between about .4 and .55 volts.

And, unfortunately, that swapping out the ECT was not a magic cure for the surging, that would have been nice.

Caberguy · Post by **Caberguy** » 25 Jul 2014, 14:22

Okay. I've replaced the ECT sensor and the upstream O2 sensor (denso), and I'm still having the surging problem (not yet sure if it's still running rich). Still no codes. Any other ideas?

Post by **precopster** » 25 Jul 2014, 16:34

Basic test: undo the rubber ribbed hose leading to the ETM and turn on ignition. Have a second person operate the throttle by pressing the pedal. You have a 6 second window for this test. Make sure the throttle flap is indeed moving to and from rest to fully open position.

I know I mentioned everything seems normal with the clicks of the ETM however without a video or sound file it's difficult to say based on your description.

2000 S70 ETM/MAF diagnostics

Re: 2000 S70 ETM/MAF diagnostics