Sign in to follow this  
Followers 0
Joylove

Cat Light lit

15 posts in this topic

Today the CAT light began blinking on my dash, and more worryingly there was serious juddering in the engine towards the end of my run.

Now, lights on a dashboard I can cope with, but is the juddering computer induced? What is the dashlight doing lit - detecting an excessive number of toxic gases after the CAT? I ask because if I have to replace the CAT, will I need to have the ECU reset too?

Can I disconnect the sensor to remove the juddering while I travel to the garage? I don't have VAG-COM.

Share this post


Link to post
Share on other sites

When you say reset do you mean erasing any fault codes? If so then you would need VAGcom or equivelent to clear but fixing the dud component should get the car working normal again; might also be worth checking your Lambda sensors too if its juddering wink.gif

Share this post


Link to post
Share on other sites

What I mean is, if I go and cut in two new Powerflow Cats, will the ECU decide everything is OK and stop the buffoonery?

On the VAGCOM side, I have a MY1995, and my USB ODBII device doesn't connect. I think I need a genuine RussTech device, can someone confirm?

I am using V702 VAGCOM on Vista, could that be the problem? Would an older version on XP get me going?

Share this post


Link to post
Share on other sites

I'm not sure about after market Cats, but I suppose ECU will do what ever the O2 sensors say after the new cats are on.

The latest release is Vagcom704 which I run on XP but problems with connectivity and third party interfaces have been known.

Share this post


Link to post
Share on other sites

I just hope someone can clear up if VAGCOM is hardware, or software, or both?

Share this post


Link to post
Share on other sites

VAGCOM is both hardware and software.

Standard advice for CAT warning is to fill up with optimax or other high octance / quality fuel and go for a blast. This may help if the problem has been caused by crap fuel etc.

Alan

Share this post


Link to post
Share on other sites

On the way home, the CAT light went out and the juddering stopped. Do we think it could be a sensor? Wouldn't a faulty sensor show up on the system check before setting off?

Share this post


Link to post
Share on other sites

mine came on the day for the first time, i'd been checking a few fuses beforehand gave it a wash took it for a spin and the light flashed up, pulled over turned the ignition off/on still there..... off/on again and its disapeered and hasn't come back since.

Share this post


Link to post
Share on other sites

Pretty sure that the juddering will be the engine firing on 7 or less cylinders. The Cat light comes on because the cylinders that aren't firing are passing unburnt fuel through the exhaust.

Most likely cause is a dodgy coilpack in one of the cylinders. You'll find if you Vagcom the engine, it will show the same cyclinder(s) consistently.

If the juddering goes on for a while, the ECU can start to shut down other cylinders to compensate, so you might start firing on 7, then it might drop 6,5 etc. It can feel really scarey and will feel to get worse.

Stop car, switch off engine and the ECU resets, so it will at least start firing on all the cylinders it can.

I had it happen on the M74 once. It went away for a few days, but came back. 1 new coil pack later and no reoccurance.

Share this post


Link to post
Share on other sites

Thanks to IT_S8 for correctly indicating the failed coil pack.

Can anyone help identify the Europart/Bosch part number to replace? My Local independant garage has got in a part and it's the wrong one.

I suspect they either have the wrong part number from VW (077905101?) or they got the description of the vehicle wrong with EuroPart.

The car is a 1995 N reg 4.2 V8.

Share this post


Link to post
Share on other sites

The part number I am geting from VAGCAT.com is:

077905101 thats for the ABZ,AEM,AGH, AEW,AHC,AKJ, AKG,AKH engines of which yours should be one. smile.gif

Mike

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0