C180 misfire is driving me crazy.....

[bibamus]

I`ve had the car, 1997 C180 Elegance auto, about 8 months, for the last 3, it has had an intermittant misfire, associated with an engine speed related tapping noise at low revs and idle. The tapping noise is heard only inside the car, and loudest under the rear nearside seat ! ( opposite side to the fuel pump)
After changing plugs, leads, coild, maf, fuel filter and fuel pump, its still there.
When it runs without the misfire, it is fine. It always starts and runs well first thing, the misfire will come on later, but not all the time, and not for long.
When it misfires, I can feel pulsing, in time to the tapping, along the fuel lines in the engine bay and running into the fuel tank. When it runs fine, I can feel no pulsing at all.
HELP

The car also hesitates when pulling away when the tapping is heard.

I am starting to think this may be an injector, last night, I could also hear a slight tapping right at the back of the engine on the intake side, but I had to listen carefully.

How do I prove if its an injector, without resorting to buying a new set ( just yet) ? Or what else could it be?

Allan

 

[eric242340]

C180

There is one thing you can try before going crazy and buying new injectors. On the injector fuel rail their is a fuel regulator which operates with vacuum. If you disconnect the vacuum pipe does any fuel leak out, check it with your finger. If it does show signs of fuel change it. The regulator keeps the fuel pressure up and it just might be that no 6 is not getting the right quantity of fuel.

 

[jimsinessex]

Could the tapping be the result of the misfire and not the cause, i.e. the uneven firing causes the handbrake cable to touch somewhere or the exhaust catches on something?

Jim

 

[Parrot of Doom]

What is the condition of the cam? Worn lobes could cause that.

 

[Glenn Smith]

Faulty pump or pressure regulator maybe?

 

[bibamus]

What is the condition of the cam? Worn lobes could cause that.

Wouldnt worn lobes cause the noise all the time and would that cause a misfire? I had a Fiat a while ago with a noisy can follower, it had no effect on the running of the engine apart from the noise. This is intermittant. When the car runs ok, it is as smooth as silk and very quiet with no misfire.
I started the car today and after a minute or two ticking over, I head the ticking again. It can just be heard on the inlet side of the engine at the back and causes a noticeable pulsing in the fuel lines. I took off the injector plugs one at a time, there was a similar drop in revs with each one. After revving the engine it stopped.
I`m just going out to have a look at the plug leads again

Allan

 

[wscheffer]

A stretched timing chain could be the culprit.

 

[bibamus]

A stretched timing chain could be the culprit.

I have a feeling a mechanical fault like that would cause a permanent problem, but the car has only just done 104000 miles, surely it wouldnt stretch at that mileage?
I changed the fuel pump last week.
I noticed that the loudest tapping seems to be heard under the rear seat on the left side of the car ( looking forwards.) There are a number of pipes going towards the fuel tank at that point, the connections are under a plastic cover. Is there anything under the cover that could tick?
The fuel tank seems to be on both sides of the car at the back. When the level of fuel drops below the part that joins the two sides of the tank, how does the fuel get used from both lower portions? Is it just gravity feed from the bottom of both sides?

Allan

 

[eric242340]

c180

I believe I now know where your clicking is coming from, under the right rear wheel arch and behind the plasic mud guard there is cannister. This is the EVAP cannister which takes fumes from your fuel tank and passes them to the inlet manifold. If it is blocked the EVAP valve will make audible clicks as it tries to purge the cannister. However this would not cause a misfire

 

[bibamus]

Checked valve and it clicks sometimes, but this is not the noise I can hear.
I thought the injectors were faulty, or the pressure regulator in the fuel rail, so I changed the lot for a good used set ( rail, injectors and regulator.) Seemed to run fine for a while. Started instantly, no tapping and full power. Fuel consumption has improved too.
Anyway, now the tapping has come back but not so loud and the hesitation when pulling away has come back. If i blip the throttle when stationary, the revs drop first before going up. Then, shortly after, it performs perfectly again. This relates to no power when I try to pull away, then as soon as it gets going, it seems fine again.

So far, I have changed the plugs, coils, leads, MAF, o2 sensor, injectors, fuel rail, fuel regulator, fuel pump, fuel filter, air filter.

What else could cause this hesitation?

Allan

 

[television]

Your engine 111.920 or 921

 

[bibamus]

111.921
Allan

 

[television]

Knocking noise in fuel return line on cars with PMS injection.

Replace diaphragm pressure reguator.

It sits just below the oil filler cap and it is round, held in with a large circlip and has a vacuum pipe sticking out out of the side.

Problem is, I do not know if this effects the running or if a fuel problem.

 

[television]

Have you changed the MAF or just cleaned it

 

[lackofgrip]

ive just had the same problem and the previous owner had put a cat that was too small on the exhaust so that blew into the backbox and the smaller cat was put in. so by doing this the backbox slowly blocked up followed by the cat. at the moment its just had a new exhaust and plugs and genral service. it was still doing it but the backpressure and heat could have fubarred my lambda sensor and afm. as soon as i disconnected the afm plug it pulled like a train. im only posting this up as i see you havent looked at the exhaust.

 

[bibamus]

Knocking noise in fuel return line on cars with PMS injection.

Replace diaphragm pressure reguator.

It sits just below the oil filler cap and it is round, held in with a large circlip and has a vacuum pipe sticking out out of the side.

Problem is, I do not know if this effects the running or if a fuel problem.

I recently changed the fuel pressure regulator and the MAF was a new one, genuine Bosch. Still the problem persists.....

Allan

 

[Ultymate]

Is it possible that your intermittent misfire is causing an exhaust rattle at the N/S/R of your car ie the noise is not the cause of the misfire but a symptom thereof ?

 

[FIBAMAN]

possible fuel starvation, there is a filter I believe, which may need changing. Cant remeber exactly where and cant find my book ...sorry

 

[bibamus]

Is it possible that your intermittent misfire is causing an exhaust rattle at the N/S/R of your car ie the noise is not the cause of the misfire but a symptom thereof ?

No, its not the exhaust, which is all pretty new, even the cat.
The tapping, sounds like a tappet too wide, but isnt coming from the engine, it is most noticeable from inside the car, and if you put your ear to the floor under the rear seat on the left side of the car, looking from the rear, it sounds loudest. (There doesnt appear to be anything there that could cause the noise though!) It increases with engine speed. If I rev the engine, in N or P up to 3-4000 rpm, it generally goes away and the car runs fine. If you feel the fuel lines, you can feel them pulsing in time to the tapping. When the tapping goes, the pulsing stops.
I just fitted a new fuel filter and pump too, and together with the new fuel rail, pressure regulator and injectors, I dont think it is low pressure.
The misfire is obvious and results in a slow take off from rest till about 1200 rpm, then it runs fine, If I rev the engine in N or P, the revs drop before picking up, sometimes it feels like it is going to stall before it picks up.
The main problem is that it is intermittant. Everytime i change something, it runs perfectly for a day or so, then all returns to misfiring normal!

This really does ruin the car. I am looking to sell it soon, but cant do that with this misfire.

When I changed the fuel rail, I had to take off the throttle body, I did notice it was a bit mucky inside around the butterfly, so will be giving it a thorough clean. We have a VW Golf and VW LUPO. Both these cars suffer from intermittent stalling every few months, cleaning the throttle body cures it completely, a common problem with these cars. Maybe it is having a similar effect on mine?

Allan

 

[BarryG]

Could the fuel tank vent be blocked?