2001 V70 Occasional starts with no accelerator response & AC

[hankbates]

This car, a T5A with 146K miles, has a yellow label etm installed about 50k miles ago, one day before warranty expiration. It is also on about its third or fourth MAF, the last two being non-bosch units.
It has been running rough recently at idle, with some surging when near idle, more noticeable with the AC compressor cycling.
A couple of weeks ago, it stumbled a lot when starting, after which it idled very smoothly, but absolutely no throttle response. I got it going after looking in the fuse box and pulling in and out both the fuses for the etm and the accelerator pedal/ac compressor. At the time I noticed that when the accelerator wasn't responding, the ac compressor also didn't work. Neither fuse was blown.
I cleaned the maf sensor after returning home, and the rough idling got better, but not completely so.
Now, after about 1000 miles, the idle is still ok, but the exact same throttle/ac issue repeated in my driveway. It stumbled and stuttered when first cranked, then started up and ran ok after 10 minutes of retrying.
No codes have been shown on my innova 3100e.
i have purchased a new Bosch maf and am waiting for it to arrive, and am considering (perhaps against my better judgement) getting a xemodex, even though following Xemodex' diagnostic flow chart indicates the problem isn't the etm.
Is there is a relay which is in line with both accelerator position sensor and the ac compressor? Or does the "limp mode" sometimes shut off the feed to the common fuse?

[abscate]

I seem to recall TPS and AC share a common fuse circuit. If thecAC clutch is pulling excessive current, it could be affecting the TPS voltage. The ETM does not like bad inputs and will go to limp mode if itdetects anything wrong quickly.

If you turn the car off, shut AC off, then restart and the problem clears I think that is a good diagnosis.

Fault trace the wires from the fuse to the AC too

If you can drive the car to Cuttyhunk I can take a look for you

[abscate]

Hank ...some discussion about AC and throttle control interplay by user Faust over in MA!

I presume you keep your soul if you read the thread

https://www.matthewsvolvosite.com/forums ... e&start=28

[hankbates]

Hi,
Thanks for your help!
After the first problem, I resolved not to start the car unless I also had the AC off, and it wasn't turned on when I had the second issue.
I have noted, that whenever I start the car it does blow cold air at first. Perhaps the ac is initially on whether I have the switch on or off... I think I can check to see if this is so by looking when someone else tries to start the car. Perhaps I can disconnect the clutch at a wiring junction....
How long will you be in Cuttyhunk?
More later today, we have guests for breakfast.
Hank

[hankbates]

I set the fan to off, and vents to medium (not auto) and when my wife started the car the ac compressor was engaged for 3-4 seconds, then shut off. Not sure what happens when everything is warm in there.

I recall that when we first got the car 6-7 years ago the compressor was very noisy, but this gradually went away. I thought of adding some r134 with oil, but this shouldn't matter as the power to the compressor only turns the clutch on and off. It seems to cycle normally, and works fine.

There is, even with the engine cold, some irregularity of engine speed (25 rpm or less) with compressor cycling, but it occurs before the clutch clicks in or out.

Your input has convinced me that running out to buy a xemodex this weekend (15% off sale) is probably not prudent, that it may not correct the problem.

I will do some wiring checks, I have already used some deoxit 5 in the fuse box....

[abscate]

You should have an AC button that can turn the AC off so that it doesn't come on at all. If not, maybe just lift the low pressure connector off, that should kill it.

We depart Chunk tomorrow morning, lifting anchor at 0500 to catch a flood tide or else we wait another 6 hours...

[hankbates]

Thanks!
I will let you know what comes of this.
Hope to meet up with you next time you are near.
H

[hankbates]

1000 miles later, after installation (as a last resort before getting into more expensive items) of a new Bosch MAF, I found that the Xemodex flow chart was really helpful and correct, the car runs as it should...

I never thought that a bad MAF could cause the accelerator to ETM link to stop working.

[abscate]

Thanks for the followup Hank. Aftermarket MAFs definitely cause problems on these cars.

Just in time for the "don't need AC" season in New England.