Resurrection of my CQ20V

[Bowie69]

Weirdly, I had one incident of the oil pressure warning last night, so it seems my journey is not quite at the end, still suspect the single blue connector near the bulkhead, I think I may just replace it. It was a nasty add on for vehicles with gauges in its day, and still nasty now

[Greg_S]

Ive had similar problems with the oil pressure sender connection with corroded connections. I have cleaned them up and pressure is reading much better again now

[Bowie69]

OK, so since I have owned it, the oil pressure warning has come up on the autocheck when revving over 3000, more so in winter for some reason, and has been getting worse over the years.

So last week I decided to get to the bottom of it, I had already changes oil pressure sender and switches to no avail, so I concentrated on the wiring and the PCBs within the autocheck and the dash.

The other reason for this was that I was also getting a coolant level alarm after going over a bump which then persisted until I restarted the car, hardly ideal as it stops you from seeing the low fuel warning....

I went over the PCBs with a magnifier, and found a few faults, one that was stopping the taco from working, another that was intermittently turning the clock off and so resetting the time, and another for the transistor that was feeding the engine temperature gauge. I hit them all and fixed the first two -the coolant temp gauge was also intermittent in operation....

A lot of searching and wiring diagram reading, and it appears that the MFTS corroding internally can be the cause of the overheat warning coming up on autocheck (I had narrowed it down to this by disconnecting the level warning on the header tank). The advice was to hit it with a rocker, literally.... I used a half inch extension bar which has done the trick nicely, gauge working and the overheat warning is gone!

Bonus

At this point I tackle the leaking oil pressure switch, the 1.8 bar one, that fits separately to the oil pressure sender/0.3 bar switch unit. I found a NOS Lucas part, which is so much better built that the rest of them out there... Fitted this, and then started examining the wiring... I pulled the connectors off the oil pressure sender only for one of them to fall off in my hand(!). I fitted a new crimped on connector, and then pulled that part of the wiring loom out of the car to inspect. It was somewhat damaged, the protective sleeve had melted in a couple of places, but on the whole not too bad. I replaced another connector as it looked ropey, and then refitted with plenty of contact cleaner going in.

I followed the wiring for the 1.8 bar switch back to a single wire factory blue connector near the firewall, pulled it apart, cleaned contacts and reconnected during this as well, this, I think, is where the actual fault has laid for a long while, after doing this the oil pressure warning stopped coming up!

I also replaced the autocheck with one from Lithuania (£40 posted), as the LCD had lost 3 or so lines across it.

So... after all this, I now have a fully functioning autocheck system, with no false positives showing!

Final job was to swap the lambda probe as the old one was showing out of range on OBDEleven, could be the cause of my cold misfires, and should help the fuel economy....

Oh, and changed the oil again! 20l 15/40 semi synthetic for £26 from ECP, bargain! Also bought them out of filters....

[Bowie69]

OK, this is just a test for Sonic ....

[Bowie69]

Oh, steering rack is manifesting more of a leak than it used to as well now... sigh, something else to look into at some point... thankfully the pump is still bone dry thanks to Error404

[diesel des]

No problems

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[Bowie69]

Des, that video is a life saver! I've only watched around 30 minutes of it, but wow, really great detail, thank you very much!

[Bowie69]

Thanks awfully des, PMing you now

[diesel des]

Uploading now. I have it set as private but I can share if I know people's email address. So pm me..

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[Bowie69]

Thanks des!

[diesel des]

I will get a look at how to do that...

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[Nj]

Nj ha a point, that should work

and maybe you can PM the link too in case I need it?

[Bowie69]

Nj ha a point, that should work

[Nj]

There is a very helpful video that I could share with you if you have a big drop box setup...

just upload it to youtube but as private so you can share the link and only the person receiving the link can see it.

[Bowie69]

Ah, I have, or rather should have, an AXM, I know it has been changed (I did it!) and vaguely remember that the replacement box came from a later model, which had a slightly higher 5th gear.

I've looked before, but can't see/read the stamping, anyone any ideas where we can get the various ratios from for the quattro boxes?