98 2.5 10v Fixed O2 sensor, no more codes but unstable idle

wega3k · Post by **wega3k** » 16 Apr 2014, 18:09

Hello. I inherited my 98 2.5 10v (Denso) V70 late last year, with ETM and CEL lights lit. My parents had ignored them for tens of thousands of miles!

Apart from the fault codes / lights, the car was great and drove well apart from sometimes being very easy to stall and the idle dropping to maybe 600 RPM if the vehicle was in motion, say when coasting up to a set of lights, but would always then stabilise at around 1000rpm as soon as the car was very nearly (like 1mph) stationary.

I'm not 100% sure what the code causing the CEL illumination was, but it pertained to the front O2 sensor.

The first thing I did was replace the clutch position sensor (£40) which cleared the ETM codes and the light went out. There was no appreciable difference to the way the car drove though. The idle would still drop alarmingly if the vehicle was moving at all.

I then gave it fresh oil and filters.

The CEL light was then fixed by replacing front O2 sensor (Denso). The CEL went out by itself after replacing the part.

Within about a mile of replacing the front O2, the CEL then came back on due to a P0136 (rear O2 sensor). This was the only code.
Interestingly, I noticed the idle was rock solid whilst driving with the P0136 code.

Tonight I disconnected the battery for an hour to see if it would clear the P0136 and reset the long term fuel trim.

After reconnecting the battery, no codes were present. I started the car and it wouldn't idle. Trying to start it again, it seemed like it was flooded. After a minute or so it fired again and after revving it for a few seconds it settled into a smooth idle.

Checking for codes again, I had a P1081 (immobiliser related). I cleared this and went for a 20 minute test drive including shutting the engine off and restarting a couple of times. CEL stayed off and no codes. However I noticed throughout the test drive the rolling idle was quite unstable - dipping down to 500rpm before stablising. Possibly the worst it's ever been. The exhaust smells like a bit like a coking plant / coal briquette fire if you know what I mean, not really sulphery and is visually clear. Aside from these observations, it's driving well and it's really novel to have no warning lights lit!

Any thoughts?

Post by **mecheng** » 17 Apr 2014, 04:29

Clean the IACV

wega3k · Post by **wega3k** » 17 Apr 2014, 04:57

Ah yes, that would seem like an excellent candidate. I will take look over the weekend. Thanks!

wega3k · Post by **wega3k** » 17 Apr 2014, 05:43

Thinking about it, I'm betting the IACV and the throttle body need cleaning. I wouldn't mind a bet that the car only uses the IACV when it is stationary or very near stationary, hence the behaviour I described at the beginning of my first post above. Looking forward to getting it sorted!

Post by **rmmagow** » 17 Apr 2014, 07:06

You may want to take it for a good, long fast drive after the IACV is cleaned. I'm thinking that with all the time not running right it is possible the CAT is sooted up a bit and needs to get very hot to burn itself clean. Make sure the ignition is all in decent shape too.

wega3k · Post by **wega3k** » 19 Apr 2014, 10:33

I've just cleaned the throttle body with some Wynns carb cleaner. I couldn't figure out how to get the cable past the starter motor so I took the hoses off, unbolted the ETM, put some plastic sheeting and a rag under it and thoroughly cleaned it on top of the engine bay - there's just enough length on the wiring to do it this way.

I also put some Wynns injector cleaner in the tank.

The idle seems much more stable, now smoothly dropping down to a shade over 1000rpm when in motion and then dropping to perfectly stable 900rpm when completely stationary.

Is it also worth cleaning the IACV and would the Wynns carb cleaner be safe for doing that?

Post by **precopster** » 19 Apr 2014, 16:19

You don't have an IACV if your car is an ETM vehicle. Idle is controlled only by the ETM.

To remove the ETM you need to remove the starter. Does it have a white label?

The year of your car and the fact it's a 10 valve has thrown other posters. Was it built in '98 and first registered in '98?

wega3k · Post by **wega3k** » 19 Apr 2014, 16:57

Well. I'm not sure about a white label off-hand, but I noted the manufacturing date of the ETM was in 1998.

Is this not the IACV?

wega3k · Post by **wega3k** » 19 Apr 2014, 17:06

OK, wow. I've just looked at the V5C. It was registered in December 98 and is a V70 XLT 20V!!!!

It doesn't say 20v on top of the engine and a Volvo specilalist told me it was a 10v!

Oh well. I guess that means I have 20 more horse power than I thought.

Apparently the 20v XLT was available for just 6 months from September 98.

Post by **precopster** » 19 Apr 2014, 17:08

You could be right but it's not the type that fails and can't be cleaned like the Bosch type on earlier cars.

I was referrinfg to the label on the ETM. If it's the original ETM it will have a white label.