2002 C70 Rich Idle Issues when Cold

ryanvolvo · Post by **ryanvolvo** » 21 Feb 2014, 11:53

Hi there,

It's my first post here - I've been reading for years but finally thought I'd make my first post and ask for some opinions, advice and tips.

I've read countless posts with similar issues but nothing that answers this specifically.

I have a 2002 Volvo C70. 180,000 miles and apart from the cold idle issue, still going strong.

Currently, I'm having some idle issues when in colder (5-10 degrees Celsius) weather. When starting from cold in the morning, the car cannot find a constant idle and it "hunts" and it's quite erratic with the revs dropping and falling. Once I run the engine up a little (even after just 5 seconds of increased revs), the engine stables at a perfect 800rpm idle with no problems.

I also notice the smell of fuel when I first start the car - which is what made me think it was running too rich.

I have changed the ECT sensor, replaced all coil packs with new iPD uprated design, installed a fresh set of Volvo spark plugs, replaced the MAF sensor (as I attempted to clean this foil type and rendered my original useless).

When changing the old plugs, I noticed they were a little black (also possibly indicating too rich).

I've also replaced the regulator pack/brushes on the alternator as I wasn't getting great voltage out of it - charging voltage has increased now after doing that.

I was thinking it could also be a leaking injector while the car was turned off - therefore explaining the reason it clears after 5 seconds of revving (clearing out the excess fuel from the cylinders).

What should I be checking guys?

Your thoughts, opinions, tips and suggestions are greatly appreciated.

Post by **misha** » 21 Feb 2014, 12:53

Did you reset fuel trims after Maf sensor replacement and the most important thing....did you bought OEM Maf sensor?
Is the oem for '02 Bosch or Denso?

At least...you can remove a negative battery cable for about 15-20 minutes and reconnect.This should reset engine ecu.

When you say that you can smell a fuel on cold start-up....do you mean a raw fuel or unburnt fuel?From exhaust or from engine bay?

Note that you're in the wrong section of forum.

ryanvolvo · Post by **ryanvolvo** » 21 Feb 2014, 13:57

Hi misha, thank you for your reply.

We haven't reset fuel trims - however we have done at least 200+ miles since MAF sensor replacement. We replaced with genuine OEM Bosch air flow sensor as the '02 is a Bosch film type sensor.

I will try the reset by killing the power to the ECU. Also, just to note that this ECU has been remapped to increase boost pressure along with a few other features. I didn't do it myself so I'm not 100% sure of the parameter changes made. Also, as far as I'm aware all Volvo firmware is up to date but I'll check this on the next remapping which is happening in a few weeks.

I'll post results once I've reset the ECU.

I mean unburnt fuel from exhaust of vehicle, sorry I didn't make that clear.

perkunas · Post by **perkunas** » 21 Feb 2014, 14:04

Rich idle in open loop would definitely be caused by a faulty MAF sensor, reading too much air in idle. This was the case with my C70.
However, with a new MAF, since you're running a custom map, this now might be the problem, causing overfueling in open loop (=cold engine)
Also, I hope the new MAF is an OEM Bosch one?

ryanvolvo · Post by **ryanvolvo** » 21 Feb 2014, 14:33

Thanks for the reply perkunas.

Yes that was my initial thought about the MAF sensor; which is why I tried cleaning the old and finally installing a new.

Thing is, I had it remapped over a year ago and it seemed fine and it idles fine in warm weather.

Yes as I said to misha, it's a new OEM Bosch part; no expense spared.

Do you also think it could be the fuel trims needing resetting on the ECU?

Thanks for your help guys.

Post by **misha** » 21 Feb 2014, 15:26

Try with fuel trim reset first...then we will see.

I have an ecu relearn procedure in the other computer and i can post it late tommorow.
This will help to speed-up initial settings after ecu reset.

Post by **abscate** » 22 Feb 2014, 07:10

You are in the right place, the C70 is covered through 2004 in this Forum!

Good luck getting this sorted out. Hunting is often caused by a small vacuum leak imhe

Post by **jimmy57** » 22 Feb 2014, 10:49

1. Cold start fuel computation is based on the long term fuel trim value (LTFT).
2. Important data for use of lookup table in ECM are MAF and engine coolant temp (ECT).
3. Lookup table has to be correct.

If the LTFT is high (more than 1.10) then that should be dealt with. MAF, oxygen sensor(s), fuel pressure, inlet tract air leaks are items to check.

MAF has been repalced but could still be an issue.
ECT value should be read before engine is started with a capable scan tool. Some better generic tools will display ECT, MAF, and LTFT.

Everything may be fine but the performance reprogramming may be affecting LTFT and that is what the ECT factor is multiplied by to get injector opening interval for fueling for cold running.

Post by **mikealder** » 22 Feb 2014, 11:26

Which ETM is fitted to your car, if it is an early 02 model it could have the same Italian crap fitted to it as the 99-01 models which do fail needing the potentiometers replacing - Mike

ryanvolvo · Post by **ryanvolvo** » 23 Feb 2014, 10:56

abscate wrote:You are in the right place, the C70 is covered through 2004 in this Forum!

Good luck getting this sorted out. Hunting is often caused by a small vacuum leak imhe

Thanks abscate - I read the description of the forum and could see this was the correct one

Wouldn't a vacuum leak also cause issues in warm/hot weather too though and constantly? My issue only occurs in cold weather and during the first 30 seconds of running the cold engine.