shaky idle, Transmission Fluid Temperature Sensor? S70 2000.

hud304 · Post by **hud304** » 28 Mar 2008, 13:36

Hi,

I'm having the following problem with my 2000 S70 (52,000 miles, located in the US). Basically there is a good deal of shaking when I am in sitting still in Drive. Here's how it goes:

- Start the car. Sitting in Park, the engine goes through a 10 second cycle. Every 10 seconds, a click sound comes from somewhere near the drive belts (sounds like an electrical switch to me). Immediately after this click, the idle goes into a deeper and shakier idle. About 3 seconds later the idle goes back to normal, which isn't that shaky.
- Ok, here's the main problem: when I shift into Drive, the idle becomes very shaky. The steering wheel is probably moving around at the mm level. As soon as I let off on the brake and let the car creep forward, the shaking goes away. When I shift to 4, 3, or L, the shaking remains *and* the transmission arrow light comes on. The transmission arrow light is not on when I am in D or R.
- The other lights that are on are CEL and ABS. They are on throughout this.
- Like I said, when the car is actually moving/driving, there isn't much shaking. The shift from 1 to 2 and from 2 to 1 are a little lurchy, but not that bad. The most amount of shaking comes when I roll into a stop at a red light.
- I only have one code present: P0711, "Transmission Fluid Temperature (TFT) sensor performance. TFT output did not change or changed in excess of expectation after 2 minutes from cold start. Possible Causes: 1) Failed TFT sensor. 2) Open or short circuit condition. 3) Corroded or moisture in connector."
- Every once in a while I have very weak response when trying to do medium acceleration (after a stop sign, for example).
- Finally, I should also mention that I really slammed into a big pothole about a month ago (Chicago winters...). Should I be worried about motor mounts?

There may be more than one problem at work here. I am most concerned about the shaking in Drive. Any help is appreciated.

Thanks,
Ryan

Post by **lewismug** » 28 Mar 2008, 14:31

Welcome to the board Ryan! It sounds to me like the "10 second cycle" you are talking about is your ac compressor cycling on and off. Your engine is shaking because it is under more of a load from the compressor. Sounds to me like something is causing your car to idle incorrectly. I know when my ac compressor kicks on, the idle elevates a tiny bit to compensate for the extra load. Maybe something to do with the system that controls that function.....I dunno? I'm sure someone else will chime in with the answer you have been craving. I just hope some of my advice will get you started in the right direction!

--Will

Post by **JRL** » 28 Mar 2008, 15:12

I agree, turn your AC off for now.
If it's cycling so fast, it's low on freon but that's another topic.
You need to get it to a VOLVO mechanic who can look it over and read your codes.
At only 50K miles, it sounds like a very UNDER serviced car so it needs to be looked at, you may have multiple problems/issues

Post by **VCA** » 28 Mar 2008, 15:18

Hi Ryan,

Does it cycle with the AC turned "off"?

This is an ETS (Electronic Throttle System) equipped car and as such, it doesn't have an Idle Air Control valve in the throttle, so that's out. How is the car's performance at all other times except idle? First things on my list would be checking for vacuum leaks (as these can easily cause a shaky idle) and checking the PCV system for proper operation. If those pan out, my suspicions would move toward the MAF sensor (if you can clear codes and don't have an emissions test up soon): disconnect it and see if the car idles any better. If it idles better with the MAF disconnected than without, consider the MAF failed.

Are any idiot lights on while you're driving? Do they work? (turn your key into the II position from 0 and take a look while bulb test runs -- the ones you should check right now for operation are "Check Engine" and "ETS")

Victor

Post by **MadeInJapan** » 28 Mar 2008, 15:24

I think it's a combination of the A/C compressor cycling on and off (so turn it off as JRL suggested) and bad motor mount(s). Check the top one over the engine. It's round and if you can see light through it, the rubber attachments within it are gone and the entire mount needs to be replaced. A combination of the A/C and a bad mount or two can cause excessive vibrations.

Post by **VCA** » 28 Mar 2008, 15:50

MadeInJapan wrote:I think it's a combination of the A/C compressor cycling on and off (so turn it off as JRL suggested) and bad motor mount(s). Check the top one over the engine. It's round and if you can see light through it, the rubber attachments within it are gone and the entire mount needs to be replaced. A combination of the A/C and a bad mount or two can cause excessive vibrations.

Oh yes, I should've mentioned that (just did the hydraulic motor mounts in my '99 S70 GLT -- what a pain...), that for the idle to be considered problematic it needs to fluctuate more than 500 rpm or so...watch your tach needle to see how much it varies. If it basically stays steady, except for when the A/C compressor clicks on, then it's more than likely a mount.

hud304 · Post by **hud304** » 28 Mar 2008, 20:14

Hi guys. Thanks for all the suggestions. Here's' where I stand now:

- The 10 second cycle was indeed just the AC compressor turning on and off. The clicking goes away when I turn the AC off. This was just a red herring and I'll add freon sometime.

- I did a rough check for vacuum leaks by spraying some carb spray around the big vac hoses, listening for the engine to rev different, but nothing happened.

- I did a rough check on the PCV system by checking that there was suction at the dip stick (there was suction).

- VCA, yes, both the "Check Engine" and "ETS" lights are on when I turn the key to position II.

- MadeInJapan, I'm not sure if I found the motor mount you were referring to. I've linked to a pdf where I show you my best guess for this motor mount (and it looks ok).

- VCA, the shaking does not significantly change the RPM (it is steady at 850 +/- 50 RPM, shaking or not shaking).

- And now for the elephant in the room...it looks like the damage caused by hitting the pothole is worse than I thought. Basically, the impact was enough to bend some (hopefully just protective) piece of metal at the front end of the car. The force was then transferred to a joint to the transmission and crankcase (I think that's what these parts are, but I'm not sure. Please correct me). Now those parts (which I'm calling transmission and crankcase) have oil all over them. Now my oil level is at the low end, almost need to replace.

So it appears that the impact of hitting this monster pothole has caused a pretty serious oil leak (if not more). I wish I would've looked into this more carefully after the pothole incident (again, a month ago), but I've been traveling like crazy in the past month...

Here is a link to a pdf (1.3 Mb) to show you pictures of what I'm talking about:
http://spt.uchicago.edu/blog/rkeisler/v ... damage.pdf

Any ideas on what to do next? I guess it might be time to take it to a dealer. I'd love to work on it myself (especially for $ reasons), but it seems like it's out of my league.

Thanks,
Ryan

Post by **MadeInJapan** » 28 Mar 2008, 20:32

The mount I spoke of indeed is the picture you show. But, the lower tranny to engine mount (your first picture) is also one that can vibrate your engine too, especially if it's a goner. Now for the surprise- I really don't think that bending the front piece of metal caused your oil leak but it might have damaged that lower mount to break. I suspect that the oil leak superseded the pot hole incident. I would spray the underside with cheap brake cleaner spray (use the dechlorinated spray you can buy at any auto parts store to avoid engine and transmission gasket damage) and clean the area all up to where you can see where the leak is. On that side of the car, I would suspect (if it's not transmission fluid- which I doubt because of the color and what you said about losing motor oil) the leak is either the rear camshaft seal (cheap and not difficult to repair), the turbo's oil return line (also not very expensive but a bit of a pain) or the rear, main seal (expensive, sorry). Let us know what you find. the lower mount there is not expensive and I actually have a used one still in decent shape sitting around if you need one badly.

bigfinn · Post by **bigfinn** » 30 Mar 2008, 08:48

I also had abnormal vibration when my S70 was at idle. Thought my main cause was worn out motor mounts, so I replaced the upper and lower motor mounts. Vibrations still were there. Just cleaned the body throttle and the flame trap (it was full of oil), as well as did the air box modification (I have a non-turbo), and now I can say that the idle is smooth, and my performance is great!

My cause for vibration and rough idle was caused by my engine not being able to breath. I plan on replacing the entire breather system (PVC) in the coming months, because this hasn't been done in at least 50,000 miles, and I want to do it before the oil seperator gets too full.

hud304 · Post by **hud304** » 30 Mar 2008, 15:23

Hi bigfinn,

Sounds like we were having pretty similar problems, and I'm encouraged you were able to fix it. I'm in the process of removing/cleaning my throttle body and flame trap. Two questions:

1) When removing the throttle body, how the heck is the hard plastic 90-degree boot at the bottom supposed to come off? I've taken out the 2 torx screws which connect it to the throttle body, but it still seems very stuck to the throttle body.

2) Can you give me some tips for finding the flame trap? I don't know what I should be looking for.

Thanks,
Ryan

P.S. MIJ, I have cleaned up the oil leak area and am trying to diagnose it. Thanks for all the advice. Also, I ran idle with the MAF unplugged, and no difference, so I think my MAF is fine.