Clk320 1999 Petrol 13MPG and other niggles

PianoPaul

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Firstly a hi to everyone and to to say that I love the forum and have read mountains of info already. Wasted the first 40yrs of my life not owning a Merc but have rectified that and have a 99 Clk320 W208. I love it and will be owning more no doubt/with any luck!

BUT

Here are the niggles, this is my 1st post and i'll keep it updated with anything I do to hopefully sort the problem, you more knowledgeable people than me will no doubt have thoughts on some of this, so if i'm lucky I'll get tips if not it's some info for the mixing pot! I do 13 miles eachway to work on quiet roads with lots of 50mph cruising (5am there 1pm back)

1) It's been dire on fuel since I bought it approx 2 months ago. Filled the tank friday after work and went back sunday with 72 miles on the clock and put 5.41 gallons in it!! Ferrariesque drinking problem

2) Just squeezed through the emissions for MOT, it had been stood for a few months and done lots of trafficy driving on supermarket fuel so I ran a couple of tanks of premium and some fuel cleaner though her which I saw recommended on here, car did quite a bit of missing and limped home the last few miles of motorway. Clear on restart, no warning light.

3) MAF sensor has been taken out and cleaned at MOT place and was badly oil fouled, not missing since but still crap MPG, has cut out just the once on me nipping into traffic, slightly lumpy idle gone post MAF clean.

4) Has been on the star machine with gen merc software and numerous codes cleared and reset, was low on gear box oil, that was topped up. Indy said MAF and O2 sensors were ok, it showed a very slight misfire on 2 cylinders, HT lead a bit powdery but like I say no missing since MAF clean. Indy did exhaust analysis and said Lambda side OK but HC very high, smells rich idling and at startup

5) Sounds crisp and whooshy when cold but noisy (worse under load or uphill) when warm, so I suspected exhaust, sounds like cow mooing, sounds ill. Indy and another exhaust shop say it's ok, no leaks, I'd read about cracked manifolds but fine. I can floor this car from standing and it goes like hell but mid range from say 50 in top gear it's not good.

6) Terrible lag on kickdown and everyday coming home from work it does the following. I'm straight out onto a fast bypass going home, mile and a half to first roundabout, the faster I go on that 1st section of road and the harder I brake into the roundabout the more it holds onto gears on the next bypass section, I can be doing 5000 revs and take my foot off the pedal in 3rd another 3/4 of a miles down the road, won't change, then suddendly it'll shift 30 seconds later?

7) 13MPG is unfeasible long term, I'm not a Rothschild.

8) Decision made today at the exhaust shop today after he rewelded a bracket back on and checked for leaks that it could be a collapsed/blocked muffler so it's coming off on saturday and going custom@£180. If anyone thinks this is a bad idea pls feel free to tell me. Was at a loss of where to go after MOT shop, Merc Indy twice and Specialist exhaust man? And £180 not a huge gamble against an F1 fuel issue :-(

9) Long post but wanted to give as much info as poss, thanks in advance for any ideas anyone may have, I will update or give more info if necessary.

Cheers, Paul
 

c15htn

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The fuel issue is scary - i can get 13mpg out of mine, but not legally!
I know you've had it cleaned and fiddled with but are you sure about the MAF? Just changing that on mine gave me another 5 mpg on average at 60 - pushing it to 32.
The misbehaviour of the gearbox is also reminiscent of my trouble, again completely gone and the box is so smooth i can't feel it changing now - unless it's hitting very high revs.
When i stuck a cheap MAF on it it was great when cold, then ran like a tank when warm - still went fast, but ran really rich and sounded ****** awful...... Gearchanges erratic / sluggish. Economy hitting 22/24 at 60.

If it's running too rich it will, oddly enough, sound terrible in the exhaust...... Think of an old car fully warmed up, then pull the choke out full and drive it?

If you're going to blow 180 quid, why not do 130quid on a new Bosch MAF. You can fit it yourself in minuts and the result can be spectacular and immediate. The exhaust is not drinking the fuel, the engine is, so investigate that first...... I've been told numerous times that if you clean an innacurate MAF all you will get is a clean, inaccurate MAF!
I hope you get to the bottom of it - as the 320 is a fantastic bit of kit when it's running like it should be
 

c15htn

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Unless you fancy a drive down to me and you can have a go with my new unit..... But at the moment that will cost more than a new one !!! :shock:
 
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PianoPaul

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Unless you fancy a drive down to me and you can have a go with my new unit..... But at the moment that will cost more than a new one !!! :shock:

Haha indeed it would, thanks though! think I'm gonna have to bite the bullet and replace the MAF aren't I, although according to the Indy and the star machine it was ok, although I couldn't work out how you could tell it was ok sat idling as opposed to having 60mph wind blowing through it on the road??

Don't think it's going to be a bad idea losing a 14yr old back box though either unless it has other implications, but what Ive read seems to favour losing it.

I've had extremely good luck over the years with cars, our lass put an end to that 12 months ago when unbeknown to me she bought a cheap FIAT MULTIPLA from a friend, problems ever since lol!
 
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PianoPaul

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And yes it sounds awful, sounds like you've driven into an echoey cave!
 

c15htn

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Believe me, when it's right they sound awesome.... Even though is 'only' a v6
Personally, I'd do the MAF, leave the exhaust for now, check the misfire (although mine used to drop one cylinder every time the MAF played up and it showed on the star readout as two cylinders independantly misfiring (stored codes not active ones)
If he's cleared the codes and the MAF is wrong but tolerable for the car i don't know if it would show a fault i don't think, unless it's busted enough to light the eml lamp on the dash.
If the car has been stood for a while then the battery has gone flat so the car has forgotten all it's'learned' and average readings, the MAF input and every other sensor will be crucial to making it run properly once the battery is back on - it's how mine showed as badly faulty.
Has it been serviced? Air filter, plugs? That would cost you the best part of £100, but more prone to give you some improvement.
A back box will do very little if it's not running right to start with - but for info, a real one from ECP is £170!
I've seen some stuff about the secondary cats collapsing - this could be the issue? Not the tail box. As a test you could just take the back box off and give it a good run - although you may go deaf lol!
If the intake was oily, what's the air box like! That oily gunk got in from somewhere..... That would probably like a good clean - I'd come and help but you need too move house first!

Final thought for the night..... To see if the car feels better without it's current MAF, unplug the connector on it then drive to work in it. It should feel better and the gearbox should be smoother...... A few on here have suggested that for testing MAF faults and it worked for me. Certainly got rid of the ****** miss fire! And avg mpg stayed around the mid 20's at 60.
It may light the eml, but that will reset itself.

enough now, i need to sleep..... Unplug it and drive to work and see how it goes? Best of luck :lol:
 
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PianoPaul

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Secondary cats oh yes forgot about those! The car only has two, both together half way down, Indy said fronts had been removed and custom pipes fitted, and that it would be an idea to source front cats and put it back to original, he rang dealers and they were £130 and £900 respectively. However the exhaust guy yesterday who has been around a long long time said the front sections WERE original and that it must only have ever had two cats? I'm confused! A W208 CLK same year exhaust I saw on eBay had two front cats and two front O2 sensors, I appear to only have 2 cats 2 O2's in total
 

robparker

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I have seen both on V6 engines, 2 cats total and 4 cats total
 
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PianoPaul

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I have seen both on V6 engines, 2 cats total and 4 cats total

Thanks Rob, I've got the 2 one then, lucky me I suppose then really :)
 
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PianoPaul

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Wow, eventful afternoon!! Is it possible to be very happy and ****ed off at the same time? Feel a bit daft really but this car has just had it's MOT with touch and go emissions and a running fault reported and has been to a Merc Indy with running issues and has been on the machine so I can be forgiven for not delving myself early doors although I wish I had!!!

Pulled her over on the way home this aft and popped the bonnet, driven nuts by the awful sounding engine, first saw that the front top air intake was half off at the top and the concertina bit at the bottom barely on (I watched the Indy plug that back in after knocking it out doing gearbox oil). Anyway got home and looked properly, said front connection bent inwards both sides so lugs not connecting, air box not secure at LHS and wobbling all over, bottom clip of for MAF sensor non existant so loose as hell infact just not even fastened together lol, and top of MAF jubilee clip barely tight! Virtually everything I've said to two garages has been that symptons seem 'MAFlike' according to all the forums, enough said!

Anyway a bit of plastic warming and bending, ptfe tape and a few tie wraps and it all now is airtight and secure and she sounds ace!

Couple of questions though if anyone has any idea, the very first air intake section before the filter box is a T to top and bottom, I have the top plugged in with the lugs now fixed, the bottom is just open to the engine compartment, am I missing another connection to the bottom grille or is that how it is? How long will my ECU take to teach my engine how to burn a mix of gas and air instead of just gas?

Incidentally the MAF, filter housing and entire air intake was bone dry and oil free so I'm inclined not to believe the oil fouled sensor story from the MOT man. Trust is EVERYTHING I say and a couple of folk have done a poor job of gaining mine lol, anyway good news overall! :)

Perhaps the most un rocket science thing ever to add to forum knowledge!!!
 

c15htn

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Excellent news Paul..... Hopefully your fueling issue will resolve itself now too!

Here's a, picture of how it should go together! Hope it's helpful :lol:
 

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PianoPaul

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Bottom airbox snorkel?

Excellent news Paul..... Hopefully your fueling issue will resolve itself now too!

Here's a, picture of how it should go together! Hope it's helpful :lol:

Thanks for the diagram, can't see a bottom air intake piece though and can't find on the forum whether I should have one, sure I must though, and I'm pretty sure I've not got the slip collar bit, last one before the engine, seen mention of a sprung clip at the engine connection somewhere but mine just seems to slip rubbishly over the engine port, looks like some idiot has had a mess with this whole air intake!
 
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PianoPaul

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No downshifting, noisy, thirsty, not a joy!

Ok, sadly the air intake fix hasn't sorted it after all, still crap and noisy on the way home today :( D Don't want to blow my brains on stuff and find out it's dying.

Never had anything as quick or powerful as this before, or an auto, so I've not been noticing something, it's only downshifting at fully down past the click on the pedal, then it takes 5 seconds to make up its mind and invariably shifts down 2 gears and revs out, this would explain some of the noise no doubt if it's in wrong gears, I can vaguely remember driving a friends 320 diesel back from blackpool years ago which responded instantly with a quick downshift and acceleration to boot, 1400 corsa would match my CLK320 from 40-80 at the moment, unless I completely bury my right foot!

Bought new plugs leads and fuel filter today so will do them over the weekend, but I'm getting nervous about this car now! How reliable is a star machines diagnosis of a MAF being ok while it's stood ticking over? Because that is what I was told, MAF is sound.

Need to find a new Indy in Leeds/Bradford who knows and cares what they are doing, or a forum member who likes a few extra jobs and beer tokens lol
 
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PianoPaul

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Oh yes and I forgot to mention that today when it did its customary stuck in gear for a mile thing on the bypass (approx 60mph approx 4000 revs) I stuck the cruise control on and it instantly and beautifully blipped down through 2 gears down to approx 1500-2000

Something tells me this MUST be a dead giveaway for at least one fault!
 

jibcl500

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For some reason and everyone have a go if you feel like it but!! check the pilot bush for oil, its the connector on the drivers side front corner of the gearbox, you have to gain access from underneath the car and oil can spill a little.

Worth checking!!

jib
 
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PianoPaul

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Thanks Jib

For some reason and everyone have a go if you feel like it but!! check the pilot bush for oil, its the connector on the drivers side front corner of the gearbox, you have to gain access from underneath the car and oil can spill a little.

Worth checking!!

jib

What would I be looking for and what would be good/bad or right/wrong?
 

c15htn

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Is the fuel still dire on it?

When mine (with dodgy MAF) was starred, it only showed stored (historic) codes, as there were no active codes I assume!

Just to rule it out Paul, just UN plug the damned thing and try the car out - it won't do any harm - and it might get me off your back:lol::lol:
 
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OK you have the 112 engine. it should average out at 26 to 28 mpg

Have you tried unplugging the MAF to see.

Now if it is running too rich, the plugs will start to foul up making acceleration poor, kick down will be non existent as the engine cannot respond.

You have the engine temp sensor right at the front of the engine pull the wire off and insert a 500 ohm resistor into the lead and ground the other end, this will tell the engine that it is very hot and the fueling should get weakened.

This is the only thing telling the fueling that it is hot, sure the MAF measures the air temp and they seldom affect idle.

Your car had 4 CATs from new, two little upper CATs and two below, these cost £1600 to replace so most just empty them and they still pass the MOT
 

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