Cayenne 4.5 V8 emissions problems, failing MOT

[infrasilver]

I've been working on my mates Cayenne as he has taken it to Porsche for its MOT and they failed it on emissions and suggested a few things to looks at. I did suggest he took it to a normal MOT station but the few he tried didn't want to take it on, which I found strange?

OPC suggested a service so we changed plugs and coils packs, he also had a leaky spark plug tube that was letting oil past he spark plug, I sorted that out with a new gasket, I thought this may have been causing an issue too?

He has just taken it back to them and it is still having issues with emissions and now they are saying the cam may be out of time, we are wondering if the chain has slipped which I doubt, stretched possibly or maybe a tensioner isn't doing its job. They are saying numerous faults in DME for SAI and Camshaft position.

I am a bit sceptical as to their diagnosis as the first time he took it to them it had a list of things to do, this time he has a list of things to do but they are mostly different to the last list?

I don't have the car with me so I am advising him remotely until I can get to see the car and I wondered if anyone had any emission issues with one of these before with a similar diagnosis and what was the fix? I don't want to be fitting new timing chains if I can help it.

I am sending him a lead for his PC so he can read any codes or live data from the car and hopefully someone can decipher what it is reporting?

 

[YPVS]

4.2 V8 Petrol? Is there one?

There's a 4.5 and 4.8 V8 petrol or a V8 4.2 Diesel, but with plugs and coil packs, clearly this is a petrol.

As well as taking mine for a good thrash beforehand, just before an MOT, I always lob a bottle of Cataclean petrol into a quarter of a tank on my 4.5 V8 Petrol to bring emissions down. It's very effective.

When it had the service with coils and plugs, was the engine oil, oil and air filters done too? Fresh engine oil and a clean air filter will also help.

I've avoided main dealers for well over a decade due to their poor diagnosis of faults and charging the Earth not to fix anything. Luckily I have a PIWISII clone though.

 

[infrasilver]

It is 4.5 petrol then,

Changed title to reflect that. :thumb:

He has changed the oil and filters himself, I just did the plugs etc and gave it a look over and fixed some of the other issues listed, made a weekend of it in the garage with a few beers.

His MOT has now expired so he's sort of stuck at the moment so I said I would ask on here for any pointers. He has a local MOT station that has tested it before so I have told him to take it there and just pay for an emissions test but test both banks in case one passes and the other fails, just so we know if it's one bank or the other?

 

[YPVS]

Testing both banks may help a little, but not a lot.

The pipes are pretty close together when they enter the shared back box. I'm not sure if they're separated inside or not, so each bank may be mixed a fair bit by the time they exit each tailpipe. Obviously O2 sensor readings would be more useful.

I would definitely get him on Amazon and order a petrol Cataclean bottle for under £20. They really do make a massive difference to emissions tests and reading reviews, I suspect half their sales are just for that reason.

Pour it into around a quarter of a tank if you can, drive it hard for 10 miles, then take it for testing at an independent MOT test station, not the dealer.
It needs to be in the fuel at testing, not just through the system completely to clean, then topped back up with fresh fuel.

My 06 955 4.5 Turbo (WLS - So has the Turbo S performance parts and 50bhp more, but essentially the same engine), with 120K miles on the clock, having just had new plugs, coils, oil and filters in the last 1,000 miles, passed it's MOT less than 4 weeks ago with these readings.

Fast Idle - 2500-3000rpm
CO = 0.04 % vol. Limit 0.20%
HC = 12 ppm. Limit 200
Lambda = 1.003 . Limit in range of 0.970 to 1.030

Natural idle -
CO = 0.00 % vol. Limit 0.30

I often wonder if some testing stations properly poke the tester in to make them pass, but mine passed by country mile.

 

[infrasilver]

Thanks for the pointers, he has just messaged to say he has it booked in with a regular MOT station next Friday so I'll get him to dump some Cataclean with enough fuel in the tank to run it and have it in when the test takes place.

I never thought the silencer may be shared with both banks, if it is that test won't make any difference.

I'm sending a Durametric lead up to him today so hopefully I'll have some data to post up over the weekend.

 

[deMort]

i'll just post my thoughts ..

Fault codes would be useful .. you mentioned Cam position .. i would certainly check with a tester the Camshaft deviation from standard ..

I wont say these chains cant slip only that i've never seen or even heard of it with an engine that still runs !

The chain does stretch though and from memory a deviation of 11 degrees or higher and its out of limits .

You can adjust them though without a full strip down and replacement of the chain .. i would need to take advice from a colleague here if it is that as i've never reset one .. i've changed vario cam units but never the adjustment on its own so unsure how atm ... ie what bits to remove and what tools are needed .

Is that going to cause the emissions issue though .. hmm .. it might but it could easily be other things .. im dubious ..

An air leak .. many plastic and by now brittle pipes which can crack .. you would need to look at the fuel adaptations with a tester to see ..

The mafs .. what's the voltage reading from each one with ignition on but engine not running .

Post the emissions report if possible.

A misfire would cause issues but coils is the usual cause for that and they have been done.

Btw .. forget OPC for this sort of car .. if a car is not running right a service won't fix it .. it needs to be diagnosed .

You have looked at the plugs ? no issues with the Bank 2 ones i take it ? oil fouling on a plug indicates score on these .

What year is this cayenne ?

 

[infrasilver]

Thanks for your input deMort, all food for thought, I will post up what I can when I get it and get the emissions report posted up too. The plugs were changed with the coils and that's when we found the oil leak into one of the plug tubes with wet plug. We think it was misfiring from that as it drove better afterwards, we had hoped this had sorted the emissions but it seems not.

It is a 2004 car.

You are not wrong about brittle pipes we broke a couple just moving them last time, my 996 pipes are older and nowhere near as brittle.He also has a Cayman, 2006, and when working on that a couple of pipes turned to dust, horrible to work on when everything breaks. :evil: some arr currently taped up with self amalgamating tape as it was on a Sunday evening when they broke and he had to drive home afterwards. They are air tight though.

 

[deMort]

Early Cayennes suffer badly from brittle plastic pipes im afraid .. same with the coolant pipes under the inlet manifold which were modified to ally many years ago .

For air leaks then a smoke test or a look at the fuel adaptations is needed with a tester .. the car can compensate to a degree as all Porsches can but it might be on the limits hence no fault code ..need fault codes there .

the Turbo model and the turbos at about 100K can leak oil .. this in turn can contaminate the maf sensor depending on the bank .. either way as a Maf is very important to the fueling its worth seeing what it reads .. if nothing else with it running then compare bank to bank .. they should be almost the same .

Air filters .. i assume they have been changed but a possible if very old .

You are after ruling out any engine issues left with the cats .. a look at post cat lambda sensors for switching .. ie voltage 0.2-0.8 would indicate a cat is not working .

Have to admit though .. i've not seen a dead cat on these so far .. seen it on many .. many other models but not these .. never say never though as in this job i do see faults i know damn well i will never see again so i never discount anything these days .

 

[infrasilver]

I've not got any reading yet but I have the emissions fail sheet to be going on with.

He is running cataclean in the car this week and has ordered a couple of air filters as he didn't fit new ones when he changed the oil, I thought he said he had.

 

[deMort]

The first fast idle test .. that looks like a 100 cell cat .. hard to get through an mot test as its borderline to get it working enough to do its job .. hence a 200 cell cat is the min as far as i'm concerned .

So .. that looks like a cat and cat clean is the best idea .. a little high but possible cat issue .

The second fast idle and its way out .. not sure what happened there but it doesn't strike me as a cat fault ... that's a running issue depending on what the tester did on the second test .

You need a fault code read out and a look at some values to get an idea ..

It may get through with the cat clean .. fingers crossed but i'm dubious atm .

 

[YPVS]

"Temp gauge showed warm engine"......

That could just mean "we left it running for 5 minutes at tick over prior to the test"

I'd be giving it a good thrashing before taking it in on Friday.

 

[YPVS]

We're all waiting with baited breath.... Did it pass? :lol:

 

[infrasilver]

Short answer is no.
It went for another MOT on Friday and it is still failing on emissions, it was very close this time but still a fail. I have sent him the Dura' lead and he has set it up on his PC but he hasn't had the time to send me any data yet.

I'm just waiting for this info then I will post this up as soon as I can. I was going to go up to his place this weekend and take a look myself but he is busy so it will have to wait.
I wanted to do a smoke test just to see if any pipework is leaking, which I do suspect it is. As deMort mentions these pipes are brittle and there were a couple that were suspect.

It is a slow process doing this remotely.

 

[infrasilver]

Just to add, he sent me the fail sheet again.

the CO was a PASS
the HC was a PASS
But the lambda failed again. Should be between 0.97 - 1.03 both his fast idle tests read 1.07 so failed. It's not too far off and slightly better than last time on the second idle but still some work to do.