Poor running

[Simes 248 2 Cars]

Hi,

 

I've been suffering an intermittent 'miss' for a while now but now it is happening all the time.

 

Mi16 on throttle bodies and emerald ECU.

 

I've changed

 

the plugs

the HT leads

the coil 

 

and it still exhibits itself.

 

I've measured the fuel pressure and that is good and consistent when running; at 3bar.

The ECU is reading all of the values, Throttle, water and air accurately.

I've done a compression test and that is good at 190 190 210 190.

The only thing that's displaying oddness is the exhaust temps measured at the manifold. 

At the time I tested 3 were high with no.1 being much lower.

Early on in the testing (standstill) whilst the engine was cool and ear to the bodies you could hear it missing across all 4 in a certain rev range.

Later it appeared to be at one end but I was revving up to 5k by then.

I went for a short drive and there is basically a lack of power.

 

 

My next port of call is the inlet gasket.

 

Any other thoughts???

 

 

 

 

 

 

 

[jackherer 543]

If one manifold runner is colder and you've changed all the ignition parts maybe it's the injector. It might be worth getting them all cleaned and flow tested, if you do number them as you take them off to see if the one corresponding to the colder manifold runner turns out to be blocked.

[Thijs_Rallye 87 4 Cars]

You could swap over the suspected injector with another one to see if the problem moves with the injector move. Does the Emerald run closed loop with lambda?

[Simes 248 2 Cars]

Injectors next step.

No lambda.

 

thanks

[Simes 248 2 Cars]

Ok so stripped it down and knocked up an injector tester.

spray pattern seems fine on dodgy cylinder.

had another though re: fuel pressure.

 on the initial turn of the key it primes. When the pump clicks off the pressure drops down. Is that supposed to happen or is the pressure supposed to remain at 3 bar? The engine isn’t on at this point, just the intermediate click on the ignition.

[allanallen 528 2 Cars]

I wouldn’t expect to see an immediate drop when the pump goes off, the system can hold pressure for quite some time after you switch the car off. Saying that as long as there’s a consistent 3 bar (with the vac removed if you’re using it) whilst the engine is running I wouldn’t concern yourself too much about it. 

 

Have you had a listen to all the injectors? Might tell you if the suspect cylinder/injector is playing up.

[Simes 248 2 Cars]

Hi,

 

thanjs for for the reply.

Pressure drops off immediately. I’m not using the vacuum from the regulator.

when my ear is close up to the bodies I’ve heard it missing across all four.

Only one cylinder is running cooler.

maybe the pressure isn’t great enough so by the time it’s getting to the end of the rail there is less?

ill test all the injectors and probably buy a new pump.

[allanallen 528 2 Cars]

Weird than you can hear a miss across all 4. I’d still concentrate on the cool cylinder initially. 

I very much doubt there’ll be a pressure drop in the rail at the last injector. 

Have you tried swapping the injectors around to see if the cool cylinder moves? 

[jackherer 543]

I had the same problem with the fuel pressure dropping off immediately. It's probably the one way valve in the fuel pump, I replaced my entire fuel pump and it solved it.

 

Theoretically all it should do is make it take slightly longer cranking before it fires up while it builds fuel pressure though.

 

However it could be losing fuel pressure somewhere else, a slightly leaky injector for example.

 

The pressure in a hydraulic system like the fuel rail should be the same at any point.

[Simes 248 2 Cars]

thanks all.

[Simes 248 2 Cars]

I got a brand new Bosch fuel pump from Amazon prime. Fitted and all resolved!

 

[allanallen 528 2 Cars]

Fancy that! The cool cylinder perhaps a red herring! 

Glad you’re sorted, how much was the pump out of curiosity? 

[Simes 248 2 Cars]

£80.

[jackherer 543]

Nice one, is it holding fuel pressure with the pump not running now?

[Simes 248 2 Cars]

Yes. Doesn’t drop when switching off.

[Simes 248 2 Cars]

Ha, died again on the way home from a successful MOT.