Ticking and fast idle on C200

[disclee]

Recently two problems appeared almost simultaneously. Engine ticks when going up a gradient and cold idle is terrible. Hesitates and sometimes dies - fast idle not stable. Someone suggested the very expensive sensor on the air intake just after the airfilter. Any ideas?

It's a 1997 December C200 Estate. Tried petrol additives.

 

[c320]

Hydraulic tappets?

Try an engine flush and fully synth oil.

Chances are the top ends are getting a little lazy or stuck.

 

[television]

Having a code read out often shows its the MAF, people change it and it's just the same. It would appear to be wiring harness fault that these cars have problems with.

Malcolm

 

[tom7035]

Hesitates and sometimes dies - fast idle not stable. Someone suggested the very expensive sensor on the air intake just after the airfilter. Any ideas?

It's a 1997 December C200 Estate. Tried petrol additives.

Thoroughly clean out any carbon residue in the throttle body. Butterfly valve may not be closing properly. No-cost job very likely to help.

 

[disclee]

Thank you guys. Responding to both replies -

Whats MAF? Is it that expensive thing? I really didn't want to spend £280 with no results. I did suspect wiring harness and intermittent connections but couldn't find any - yet. Also happened after a service. Went back and he poured some additive in th epetrol tank. Paid £15 with no results. Don't suspect he did anything to the harness cos servicing does very little anyway.

Cleaning the insides of the carb does eliminate hesitancy in warm idling. Been doing that for some time - so thanks, it was the first thing I tried.

Thing is the fast idle. Doesn't seem to want to go to fast idle. So when starting first thing in the morning it seems to go straight to warm idle speed and of course stuggles and soemtimes dies.

What's that thing attached to the other side of the carb. It's a wired black box and could be the fast idle controller??

Many thanks again

 

[tom7035]

A couple of other no-cost things you can try (My car is as below of course but yours should be similar);

(1) Clean the 'hot wire' of the Air Mass Sensor (often referred to as MAF) with carb cleaner to remove any oiliness or deposits which it may have collected over time and which will affect the running. Mine is a plug-in thing in the air intake pipe between the air filter and throttle body (Not carburettor - you don't have one). Be careful not to damage it, they're expensive.

(2) There's a black plastic-like cover about 5" x 3" on the side of the throttle body which uses 4 'security' torx screws to prevent 'unauthorised' access. (These screws have a pin in the centre so you will need the torx bits with the hole in the nose to undo them). Inside is a very lightly sprung (or weighted) electronically controlled lever 'gizmo' which on mine was sticking and affecting the tickover in all sorts of ways. A squirt in the innards with magic WD40 did the trick! This was around a year ago and no problem since.

Good luck, and let us know the results please.

 

[disclee]

Thanks Tom. Always wondered what's inside the black plastic cover which on mine is not screwed on but clipped on using those awful metal lugs into slots in the plastic which scares me to death in case the plastic breaks. Some of these anchors are also on the underside and I can only feel them. Do you think I should venture into removing the whole card, sorry throttle body?

Will also squart iso propyl alcohol onto the insides of the MAF. Hope it doesn't melt.

Many Thanks. Will try that out this Sat in 5 days time!

 

[tom7035]

Probably be easier I think, it's not a big job, but be careful not to damage the 'O' ring where it sits in the manifold (always assuming it's the same layout as the W124 of course).
I-P-A is exactly what I used to clean mine - it hasn't melted my vinyl record collection so far! (not shellac 78's - it DOES melt them!)
Cheers, Tom.

 

[disclee]

Might be a good idea to get a new O ring first then - I'll check if there's one. IPA's sucha wonderful thing. I buy 2litres at a time instead of the 10ml you get for £2.50 for cleaning CDs which can be cleaned with fairy liquid!

 

[disclee]

Just taken out the MAF and sprayed it and very gently cleaned the shiny pad which is just accesible. Car wasn't cold enough and it started OK. Tomorrow morning will be the big test.

Otherwise it shall be the carb if I can figure how the elecrical plug comes off.

 

[disclee]

No luck with the MAF. This morning it started straight away and died almost immediately. Need to rev it gently until it warms up a little. Shall try to remove the throttle body on Saturday but still can't see how the elctrical connection clip is removed.

Any experiences?

 

[disclee]

Removed the throttle body and had a look. It is controlled by a motor and geared wheels which moves along a resistor track to tell the ECU where the throttle is. Nothing can be done except to see it move into fast idle position when the ignition key is turned.

Idle is still bad. Changed the spark plugs so the only thing left seems to be the MAF and the ECU although every thing else seems to works so unlikely to be the ECU.

Oh well, £280 ...

 

[disclee]

Success! - cleaned MAF

Finally cleaned the MAF by totally immersing it in IPA in an ultrasonic cleaner and the car's behaving impecably now. Acceleration is better, no pinking and starts first time. Even the connectors were immersed. A short time drying it out - IPA evaporates and leaves NOTHING behind - screwed it back on and the idle settled at around 1100 in the morning for about 2 minutes and went down to 700.

Thanks to all who so kindly helped out.