2001 V70XC, occasional no throttle but starts fine

[saq]

Working on troubleshooting a occasional issue with a 2001 V70XC - sometimes it will start just fine but there will be no throttle response, it will just sit there idling. Turning off key and restarting will bring throttle response back (so far). When it happens the ventilation fan is not operating either, which leads me to suspect the ignition switch, but on the 740 when that happened backing off a bit on the key would start up the accessories (and of course there was no engine issue, as throttle was cable operated). It is the Marelli, but was replaced with the yellow label one years ago by my parents (prior owners). The lack of any other throttle problem except on start leads me to think it isn't the Marelli position sensor issue, but I don't want to throw parts randomly at it - especially as it seems odd that the throttle would be disabled in starting position, but with things nowadays you never know.
Then again it could be a connector issue with the engine control computer too, and a reset fixes it... or something. Any thoughts on the start switch hypothesis?

[volvolugnut]

Three thoughts:
1. Has throttle ever stopped functioning while driving?
2. If the ETM is many years old it may need to be replaced again. My Xemodex throttle failed after several years and a new one fixed problems of no start.
3. For low cost testing, try to beg or borrow a working ETM to try for a while.
4. Bonus thought - can you hear the ETM buzz for several seconds with key to position 2? Get your head under the hood to hear it. This should happen every time you turn to position 2..
volvolugnut

[jonesg]

maybe it fails the 'key on initial sweep test' but resets on restart.
try key on twice, then start.
have you ever cleaned the etm?
Does the intercooler need draining?

[MoVolvos]

Working on troubleshooting a occasional issue with a 2001 V70XC - sometimes it will start just fine but there will be no throttle response, it will just sit there idling. Turning off key and restarting will bring throttle response back (so far). When it happens the ventilation fan is not operating either, which leads me to suspect the ignition switch, but on the 740 when that happened backing off a bit on the key would start up the accessories (and of course there was no engine issue, as throttle was cable operated). It is the Marelli, but was replaced with the yellow label one years ago by my parents (prior owners). The lack of any other throttle problem except on start leads me to think it isn't the Marelli position sensor issue, but I don't want to throw parts randomly at it - especially as it seems odd that the throttle would be disabled in starting position, but with things nowadays you never know.
Then again it could be a connector issue with the engine control computer too, and a reset fixes it... or something. Any thoughts on the start switch hypothesis?

.
2002 V70 XC purchased from auction sight unseen. Unfortunately, sometimes you have to throw parts at it. I was able to diagnose the one bad injector from watching Youtube videos and another code indicated it could be the MAP sensor from researching the various forums but was not definitive. Installed Mar 2024 and has been fine with around 86K miles currently.
.
BOSCH 0261230029 Original Equipment Manifold Absolute Pressure (MAP) Sensor - $40.33
https://www.amazon.com/dp/B00BL764CY?ps ... ct_details
.
Have purchased many parts and recommended friends who purchased from A-Premium for the 3 Year Warranty
5-Pc Fuel Injector 2-Blade Terminal A-Premium APFI145 - $56.99
https://a-premium.com/product/volvo-c70 ... SNF2NKPCeO
.

[saq]

Did clean the inside the throttle body after some misfire/rough idle at start, but didn't clean the pots, so might try doing that. Never had any problems with throttle once driving - when it doesn't work it won't ever accelerate from idle. No limp home, no codes, no CEL. No DICE yet but have the Windows 7 laptop ready when I decide which type to get from Ali.
Sounds like the co-occuring "no ventilation fan when no throttle response" may be unrelated and something else to troubleshoot.
The part that makes it hard to troubleshoot is that it happens maybe twice a month, and I don't know in advance when it will. Will try key on twice - is this the "key on for 90 sec to reset" trick or just turn twice to run?

Edit - it did it once when I was at home and I grabbed a generic code reader. Nothing related to the throttle showed, but by the time I plugged it in it did have a CEL and codes for O2 sensor not switching. Restarted, verified throttle operation, reset the light and it didn't come back on, so something here is affecting throttle operation and creating a rich mixure.

[scot850]

Contact Dave at Boot & Go in Denver. He sells Dice units and also Win10 operating Vida 2014D.

https://diaglaptops.com/wp/vida2go/

Neil.

[saq]

Update (though still sort of "crossing fingers and hoping" rather than "this logically solves it")

Transmission was starting to give occasional hard shifts so changed the fluid and at the same time I took the car keys from of my (very large) keyring-o-everything and put them on their own ring to make it a bit more manageable. Since then I haven't had the issue - suspect that the force from the key weight on the ignition more likely to be the issue than old transmission fluid, but again... I guess we will see.

[scot850]

Yeh, the ignition keys don't like huge bunches of keys hanging from them. Could be worse, it could be a P1 plastic key and jello ignition switch.

Neil.

[jonesg]

Update (though still sort of "crossing fingers and hoping" rather than "this logically solves it")

Transmission was starting to give occasional hard shifts so changed the fluid and at the same time I took the car keys from of my (very large) keyring-o-everything and put them on their own ring to make it a bit more manageable. Since then I haven't had the issue - suspect that the force from the key weight on the ignition more likely to be the issue than old transmission fluid, but again... I guess we will see.

yeh, sounds very plausible.