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Old 1 Week Ago   #1
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Poor performance

Hi

So my 1.6 16v stilo has following symptoms:

Poor acceleration
Misfire type of idle at times(revving dont work,keep pedal down then eventually engine will react to your foot on the gas,happens now and then)
Stalling at times due to misfire above
Car doesn't accelerate like it use to
Even when driving at a constant speed,it will have a sort of misfire,like one cylinder went and came back again
The speedometer jumps down to 0 and then back up to your current speed and is accompanied with above symptom(the misfire while driving)
The car ,when accelerating,does this type of issue: e.g. you revving the car in neutral but you rev till a certain rpm then pause,then go higher and pause etc. But happening quickly as you accelerate. Like the Car feels very lazy.

The speedometer issue happens on almost every journey and poor acceleration and overall performance is a constant.

Misfire doesn't happen always ,just a quik 'jolt' if you wanna call it that and then back to 'normal'

This is what I done to the car:
Replaced a bad ignition coil,all the others are still working fine
Replaced fuel pump
Cleaned map sensor
Cleaned throttle body
Replaced all 4 plugs
Replaced oil and oil filter
Air filter fell out as i pulled away from my driveway somehow and broke,I couldn't afford the whole box so I replaced with a cone filter and pushed it on the air pipe where the box filter was.
Replaced timing belt and tensioner and main pulley belt.
Check engine light burning
Reset ECU like they explain on the net(take off battery terminals etc. )

Sorry for my weird explanations but I miss how my stilo use to pull.

Please any help...
Thanks
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Old 1 Week Ago   #2
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Re: Poor performance

Did you do the things you done to the car before or after it started going wrong?

To me it sounds like you have a fueling problem. It's interesting that you changed the fuel pump (so when and why did you do that?).

Have a look at the fuel rail pressure (you'll need a garage with the correct tools to diagnose it). If it's too low (or not increasing when you have more revs) then that will give you the hesitancy and general lack of poke that you are experiencing.

Another option could be an ECU problem, since 1.6 has the ECU on top of the head, so it gets heat-damaged over time and the pins move/lose connections. This might be the cause of the speedometer "hiccup" and again, if there's an interruption to the fuel pump supply caused by the ECU, it would cause your symptoms.

Have you had any aggro' at all from the ECU ever? Have you moved it off the cylinder head (it can be strapped to the side of the battery by all accounts). Otherwise, have a look at the ECU stored codes (you'll need a code reader software/kit). If you have a lot of random and unconnected error messages, then that might point to the ECU.


Ralf S.
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Old 1 Week Ago   #3
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Re: Poor performance

Thanks Ralf

I changed fuel pump when car started giving that hesitation

The problems started before I changed all these things.
However the speedo jump is from recent. Like in middle ish of this year.
Hesitation has been from start of this year.

I read about the ecu problem yes. Thats going to be my next change.

Where I stay,the road is gravel where you come in so I drive really slow. I use clutch control,now when driving on this road and the cars rough idle forces me to press the clutch in suddenly,then the engine would jolt from the rough idle and then a error message would appear and then disappear. Normally check engine appears
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Old 1 Week Ago   #4
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Quote Originally Posted by Ralf S. View Post
Did you do the things you done to the car before or after it started going wrong?

To me it sounds like you have a fueling problem. It's interesting that you changed the fuel pump (so when and why did you do that?).

Have a look at the fuel rail pressure (you'll need a garage with the correct tools to diagnose it). If it's too low (or not increasing when you have more revs) then that will give you the hesitancy and general lack of poke that you are experiencing.

Another option could be an ECU problem, since 1.6 has the ECU on top of the head, so it gets heat-damaged over time and the pins move/lose connections. This might be the cause of the speedometer "hiccup" and again, if there's an interruption to the fuel pump supply caused by the ECU, it would cause your symptoms.

Have you had any aggro' at all from the ECU ever? Have you moved it off the cylinder head (it can be strapped to the side of the battery by all accounts). Otherwise, have a look at the ECU stored codes (you'll need a code reader software/kit). If you have a lot of random and unconnected error messages, then that might point to the ECU.


Ralf S.
I changed the fuel pump in july
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Old 1 Week Ago   #5
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Re: Poor performance

It sounds more ECU related than fuel pump/regulator. I think the gravel path is jostling the car, which could be causing the ECU to move about and losing some connection.

A duff/weedy pressure regulator would be more apparent if you're in a low gear at high-ish revs (e.g. 3500rpm) but on a trailing throttle. If you then give it a large amount of throttle the car should accelerate strongly. If the car is running along okay at 3500rpm but then when you give it a lot of gas it responds hesitantly, then it's not getting enough fuel.

If it's randomly hesitating while you're driving along the highway at light or small throttle, then the fuel pressure is probably not the issue. If the ignition system is okay (you seem to have checked it already) and there's no poor earth etc. then it would point to the ECU. While you're waiting to check out the ECU, stick an extra earth lead from the engine/head to something metal on the car's body. You can't have too many earths.

Ralf S.
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Old 1 Week Ago   #6
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Re: Poor performance

Thanks a span Ralf

I'm going to try that test later with regards to accelerating from 3500rpm

I have changed my plugs now as a precaution.

It still has a shaky idle at lower rpm as the car gets warm and idles lower. Higher rpm it's okay but rev the car and keep it at say about 2000rpm then the cars rpm would dip and come back up significantlt. higher revs it doesn't do that as bad,like very slight. Thats what I'm feeling as I drive along on the highway and as I accelerate from traffic light. The car is overall sluggish. 5th gear the car seems to pull better than rest of gears.
I have moved the ecu already

Thanks
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Old 1 Week Ago   #7
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My old plugs I changed
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Old 1 Week Ago   #8
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Re: Poor performance

Is there a way I can send you a video of the symptoms?
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Old 1 Week Ago   #9
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Re: Poor performance

If you accelerate really slowly (i.e. on a very light throttle) through 1000-2000 rpm does it do the hesitation around 1600rpm... but then once you've passed 2000rpm it behaves more or less normally?

If it hesitates on a very light throttle, when fuel demand is low, then that's not consistent with low fuel pressure... it would have be very low. Possible.. but less likely that other things.

Your old plugs look not too bad... maybe a hint of running too lean (fuel again) but I might be seeing what I want to see.

Have you stuck the beast on a code reader? A potential cause of generally bad/uneven running is a worn out MAF sensor (the one by the airbox) and/or a dodgy lambda.

The MAF is distinct from the MAP sensor. MAP usually sits on the inlet manifold to measure the manifold pressure. The MAF measures how much air is coming into the airbox, and its temperature.

I see you replaced a "MAP" sensor.. if you meant MAF then that's good (hopefully it was a Bosch one and not an unbranded one). If you really meant MAP, then the MAF might also be one to replace. It's a bit dear for a Bosch one, so maybe leave that till last. MAF failures sometimes (but not always) give an OBD error code, which can be read.

If your car does the hesitation most at ~1600rpm and idles a bit lumpy especially when cold, then that's classic lambda sensor. The lambda has a heater circuit to keep it hot at low rpm, and the heater turns off when the revs reach about 1500rpm.. so if it's failing, it notices when the heater circuit turns off and that throws out its readings. If you can see an OBD error anything remotely related to the lambda, then change it.

As above, buy a Bosch or NTK one, with the plug attached. Cheaper ones only have bare wires which you have to splice in to your existing plug. Unless you are the World Champion soldering King of South Africa, a poor join can cause some electrical resistance which the lambda interprets as a "situation" in the exhaust, so it starts reporting incorrect readings. A lambda with a built in plug gets round that problem.


Ralf S.
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Old 1 Week Ago   #10
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Re: Poor performance

Haven't stuck it on the code reader yet

Please send a pic of your MAF sensor.

I dont see mine under the hood.
My airbox fell out and there is no wires running there.

I stuck a cone on the pipe in mean time.

I listen to the car under the hood at idle. It sometimes dips (uneven idle) then the filter sucks air like a vacuum.

Please show me what this part looks like so then i know if I must buy a new box and MAF
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Old 1 Week Ago   #11
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Re: Poor performance

I read that my 1.6 model doesn't come out with one?

Should I change my airflow pipe and cone filter to standard box?
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Old 1 Week Ago   #12
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Re: Poor performance

Your car must have a MAF sensor. They were part and parcel of the emissions equipment when catalytic converters were introduced.

Mine is an inline one, separate from the throttle body. It sits between the airbox and the turbo (my car is a JTD) but your 1.6 will have one similar, either between the airbox and the throttle body (usually right next to the throttle body), or it will have one that slots into the throttle body itself.

I have attached a picture of what mine looks like (this type are all quite similar) and there's a picture of the 1.6 Brava (same engine family as yours?) type, that slots into the top of the throttle body.

If the airbox fell off then that doesn't bode well... but the cone filter itself shouldn't affect how the car idles and runs. As long as there are no induction leaks past the throttle body, the MAF will measure whatever air is getting in, however it's getting in (even if you had no filter at all) and it ought to compensate accordingly.


Ralf S.
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Old 1 Week Ago   #13
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Re: Poor performance

Here's a picture of a 1.6 Fiat Bravo "MAP sensor" (according to Google, so it might be a lot of cobblers).

It looks like the second photo ("MAF sensor") above, so it could be you already changed it.

Meanwhile I'll have a rummage around some more.

Ralf S.
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Old 1 Week Ago   #14
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Re: Poor performance

Hi Ralf,

I have the second photo yes. The one in the air intake. I took that out and cleaned it. Cleaned throttle body too (both sides)

I do not have the first one however,the one that looks like it fits on a pipe.

There are no loose connectors laying around too
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Old 1 Week Ago   #15
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Quote Originally Posted by NebulaStilo View Post
Hi Ralf,

I have the second photo yes. The one in the air intake. I took that out and cleaned it. Cleaned throttle body too (both sides)

I do not have the first one however,the one that looks like it fits on a pipe.

There are no loose connectors laying around too
See this where the pipe and the filter meet. Its not a snug fit and its bending the pipe.

When i took the pipe off,the car seem to run abit smoother.
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