2001 V70XC rough idle/sometimes very rough at start/sometimes no throttle

[saq]

Trying to troubleshoot an occasional problem on the 01 V70XC/2.4.

Somewhat rough idle is more common, "rough" meaning comparable to a GM 4 cylinder or maybe Toyota, so not super rough but not as smooth as a Volvo usually is. Frequently worse when brakes applied so I strongly suspect vacuum leak is a part of it, that part isn't going to be too hard to troubleshoot, just clamp off the vacuum lines and see if if solves it (well, won't be able to clamp off the turbo control vacuum line, but should be able to do the other ones anyway - or maybe I can do them all and just not have the turbo for the test period).

Second problem more vexing. From time to time a very rough idle at start (misfire somewhere), frequently if I stomp the gas it will smooth out. Sometimes there's absolutely no throttle response though. Turning off and restarting engine has gotten it running every time so far. Currently we are talking probably once a month one or the other will happen, last year it was about once a week for one or the other before I fiddled with key weight.

Last summer I put the ignition key on a separate ring from my other keys (over a pound of keys) b/c I was thinking that it might be something like my 740 had where a failing ignition switch wouldn't always switch everything back to "run" after start. After taking keys off the problem seemed to go away for about a year but it has come back less often, happened ~2 times in the past couple months for no throttle response. and a couple times for misfire/rough on start that goes away. No hunting idle, "dropouts" or any of the other Marelli common issues - if it isn't going to work it doesn't work from start, and so far if there is any throttle response after start it stays working just fine.

It could be bad ignition switch, possibly a failing throttle module (it's the yellow sticker Marelli... my parents had it die once before, at that time it just wouldn't drive faster than 20, but I imagine it can fail in different ways), possibly interacting with a vacuum leak and/or weak coil. Last time it was giving me HVAC fan operation when it had no throttle, so at least some of the "run" circuits are connected.

I don't know how to troubleshoot this because it's rare and when it happens I am not sure how to get any test equipment on the ETM to read the signals (I guess maybe build an extender for the wires?) I do have one of those "mongoose" style connectors and I can set up a laptop with the VADIS or VIDA, but that would just show what the Motronic unit is doing and I'm still not sure how to "catch a failure" to differentiate between ETM, power supply or something else, but I definitely don't want to do random parts changes without any troubleshooting behind them.

Any thoughts?

[jonesg]

vida can monitor up to 10 modules at the same time.

[Vova585]

1. I would get a cheap smoke machine and do the smoke test in air supply. Likely it will be ton of issues at tjis age: turbo control lines(ipd sells nice silicone hoses color coded), injector seals...
2. It sounds like your Magnetti ETM is on a way out. Check codes, it might be helpful..but of i would be a betting man I would just put aside $500 and send it to xemodex

[volvolugnut]

If your ETM is original and has not been replaced, it is a prime suspect for this random behavior.
Xemodex website has a flow chart that may help to determine if the ETM is at fault. Xemodex is a good source for replacement ETM with improved technology.
volvolugnut

[Noie]

I had, perhaps, a similar issue to what your describing. Mine seems to be more weather-based as the idle fluctuation on cold starts has subsided with the summer warmth. Here is a link to my previous post. Maybe you can draw some similarities. (Videos attached in it)

[saq]

Are the Sacer conversion kits still good? They seem to be harder to find, wish there were more parts sales people... also having problems finding the Volvo valve seal kit.
Looks like Sacer might only be available on eBay, I usually steer clear of there and Amazon but have people had luck with this? Seems like it is obscure enough to where it might be less likely to have fraudulent sellers.

[DavidE7]

Are the Sacer conversion kits still good? They seem to be harder to find, wish there were more parts sales people... also having problems finding the Volvo valve seal kit.
Looks like Sacer might only be available on eBay, I usually steer clear of there and Amazon but have people had luck with this? Seems like it is obscure enough to where it might be less likely to have fraudulent sellers.

The Sacer kit takes a lot of time to install and it won't fix the electronics deep inside the ETM if they are bad.

The magnet adjustment to the correct voltage on the throttle shaft can take a bunch of tries before it is set correctly: viewtopic.php?t=58045

[saq]

I went with the Sacer because the Xemodex would have had the car out of service for over a week with the throttle going back and forth.
Yes, the magnet adjustment is VERY finicky, the range of too-low-voltage to too-high-voltage was less than one degree on mine.
Oh, and I wound up slashing my hand open removing the access panel with a putty knife so the car was unusable for about 2 weeks anyway while the stitches healed. So much for planning ahead, fortunately was able to borrow a car.
So far that seems to have been the problem, when I looked at the sensor it was not "see through" yet but there were bumps of material that had been displaced, so occasional no-throttle-response-at-all does seem to be a potential failure mode with the Magnetti Marelli throttle.

[scot850]

It is the same issue with the P80 cars from 99- with this throttle bodies. Well done in getting it fixed. Sorry to hear about the cut damage to your hand. Hopefully it mends fully quickly.

Neil.