'98 V70 T5: System too rich, Throttle Sensor & ODB data

[Clogs]

LTFT 3.9% all the time, STFT 0% on idle and then to -2.4% and back to 0% as revs increase... everything is OK!

[Distendo]

Originally Posted by Luxobarge

However, if there are any stray sparks around this could be a potential fire risk, with amusing consequences.

Yes, that 'no eyebrows' scenario was the first thing that occurred to me when the man said "propane", and I really should have declared that reservation when I promoted the idea!

So thank you for pointing out the 'obvious to some but not reliably to all'.

[Distendo]

OK, so I changed the Throttle Position Sensor for a new one (I was going to check the voltages in the plug, so thought I might as well change the sensor while I was at it).

On removal, the TPS itself seemed fine, changing resistance incrementally as the bush was rotated.

I checked the voltages connecting the -ve on the meter to battery -ve, and found found all three terminals were +ve live. Like a dummy I didn't note down the actual voltages, but as I recall they were more than 5v. I'd have expected one of the terminals to be connected to -ve ground (so no voltage differential).

Later, I took meter readings being between each of the contacts within the disconnected TPS plug, ignition on (see diagram, looking at contacts within plug), the voltages* (and polarity relative to one another) were as follows:

Voltage between terminals A/B: A- B+ 7.6 volts
Voltage between terminals A/C: A+ C- 3.06 volts
Voltage between terminals B/C: B+ C- 10.7 volts* (battery was duff @10.7 volts, see below)

Does any of this mean anything to anyone?


Replacing the TPS made little difference, as I understand is often the case, the actual issue tending to be elsewhere, possibly in the wiring, or even the ECU... I did check the throttle body to make sure the vane is closing properly.

It starts ok, but the cold idle is a bit rough. When it's warm, it idles ok-ish (some slight hunting), and the short and long term fuel trims hover around 0% @ about 1,500 rpm.

When I say it made no difference, one difference is that the orange arrow warning light and the 'W' transmission mode selector both started flashing... (I did the 'rapidly moving the selector through all positions' thing, in case it was the pnp switch.)

The only other thing I did at the same time was replace the battery (*10.7 volts after many hours charging) with a new one.

I'll understand this becoming rather tedious to anyone otherwise inclined to help, but any pointers welcomed.

I'm just wondering when my local Volvo indie service chaps will unlock themselves up, so I can pass the buck tho them...

[SteveSarre]

Hi Distendo,

I haven't been following the thread in detail, but can you tell us what the current problems are (are any codes set) and what you did for the cylinder head refurb? It may be relevant.

Did you check the one way valves that andrewc1267 mentioned?

Thanks
Steve

[Distendo]

Hello Steve,

I just checked in with a mind to write "Ignore that last post" (or delete it if no views), as I think my info-gathering was shabby*, but since you've (again) been kind enough to take an interest, here goes...

(*I am thinking of re-measuring those TPS voltages again, now I have a good battery in the wagon, so the readings are more sensible. I'm assuming the TPS itself is not the problem.)

No, I haven't checked those valves yet: I've looked at info on them, and found a similar-looking item on Skandix, and the ones I think andrewc1267 recommended for sale on Ebay, but which appear to be for fuel rather than gas (air).

The cylinder head job was to replace a burnt-out exhast valve. In fact I replaced all of them, with new seals (in & ex), and all gaskets, all with Volvo original parts throughout (the PCV was a quality alternative). The cyl head was skimmed (and treated with kid gloves). The cyl block was carefully cleaned (Scotchbrite & acetone), etc.

On first start it fired up perfectly, then conked out after a few minutes. Turned out the ignition coil hadn't coped with the car standing still outdoors over winter. When replaced, it ran beautifully (better than before) for around 40 miles out-of-town test jaunt, until I hit a small bump in the road, when the lambda light came on.

I rather suspect some dodgy connector, perhaps at the ECU, which was/got damp during the winter and so developed some corrosion, so was thinking of (disconnecting the battery and leaving it a while before) removing the ECU and cleaning the connections there: since the MAP & MAF sensors appear congruent, and the fuel trims (I believe) are ok, but that weird transmission error code suddenly appeared (after the new battery was fitted [the transmission, btw, was refurbished to near new condition 3 years ago]), I'm thinking all these could be explained by duff signals to/from the ecu, and that cleaning its contacts might not be such a bad idea before suspecting/replacing anything else.

Having said that, I will order a couple replacement one-way valves (not least because doing so has been recommended, they're cheap, and not so difficult to fit [probably...]). I was thinking of going for the Skandix ones, but would welcome any observations as to which (i.e. or the Ebay aluminium jobs) are the most convincing.

Once again, Steve, thanks for taking an interest. Having painstakingly gotten this faithful wagon so near back to working order (having heeded invaluable advice from this forum), these glitches are dispiriting.

[sdg1970]

Originally Posted by andrewc1267

I had the Same issue on my v70r it turned out to be the two one way valves on the intake system I replaced with aluminium check valves from Ebay for a 5 quid each as Volvo said that they had discontinued them

Wot he said. Mine was also pre-cat 02 sensor AND temperature sensor. It took a long time to rid mine of the dreaded 0172 code, but a combination of all three did it.

[Distendo]

Originally Posted by sdg1970

Wot he said. Mine was also pre-cat 02 sensor AND temperature sensor. It took a long time to rid mine of the dreaded 0172 code, but a combination of all three did it.

Thanks sdg1970, noted.

Would you go for the Ebay valves (or is there a more appropriate component?), or the Skandix?

[PNuT]

You need an evap system delete.. two bolts will do!

[sdg1970]

Originally Posted by Distendo

Thanks sdg1970, noted.

Would you go for the Ebay valves (or is there a more appropriate component?), or the Skandix?

Yap I bought mine off Ebay, they were around two quid each. That was 18 months ago and they've not given any problems since. I also replaced all the vac hoses that goes in/out of the valves with a combination of 8 & 10mm silicone hose.

[Distendo]

Huh?

One bolt for either side of my neck, perhaps?

Ok, so I've had a quick look for 'evap system', which appears to possibly be something under the rear end near the fuel tank for keeping fumes at bay. The only thing I found on 'deleting' it seemed to involve removing a small gadget from the engine and blocking the hole(s) it came from.

I have 0 idea how we got to the evap system from the lambda and flashing arrow lights...