Technical Stilo 1.6 - Delayed acc pedal response...is this a injector problem?

[ivand]

Hi guys
I don't know if this is normal reaction, but when I hit the accelerator pedal, it won't rev instantly.
Instead, i get „delayed“ revving, with sound like sucking false air.
And the car on light & long accelerations makes a bit strange silent noise (like it is an V-machine), but that could be just an subjective hearing.
On idle it seems to have some vibrations pulsating every 3-5 seconds (I can feel them on steering wheel).
From the first day I got a feeling that my car drinks more than is normal.
It seems there is a „hole“ at low rpm, the car is very sluggish till 2000 rpm (that is most irritating).
When cold starting, it takes some time to fire up, but with warm engine it starts instantly.
The fact is that with this car I had problem only once (with coil that was changed) so only once the famous „engine light“ switched on. At fiat service mechanic told me that he „saw“ an problem with injector. I thought that was due to ignition coil failure, so I didn't worry.

Just to mention the car has 67.000 km (thats about 42.000 miles), and it had cam-belt changed last year. Spark plugs were changed at 44.000 km (27.000 miles), so I guess they are still fine.

I did throttle body cleaning, resets, and the idle is now much smoother. But, delay on accelerator pedal stays present...
I have made some observations via ELM scanner, and there are no fault codes.
I have checked resistance of injectors - they are all about 16.5ohms. Also i did actuator test for injectors and all of them were "ticking" the sam way.
MAP sensor seems to be good (based on parameters, and your graphs).
Lambda reading seems good.
But, LTFT and STFT readings are not good...
What is weird I get negative readings for fuel trims on minimum (tickover), and as I rev the engine the readings of fuel trims change to positive:
At idle LTFT = -15% ; STFT = +4%
at 1500 rpm LTFT = + 33% ; STFT = -4%
at 2500 rpm LTFT = + 16% a STFT oko +9%
I took readings while driving too, and the results are the same...
Could this be because of dirty (clogged) injector(s) ?? What should I check more ?? Help please. :worship:

 

[richydraper]

i think anything greater than around 5-10% on either STFT or LTFT is considered 'excessive'

https://www.fiatforum.com/stilo-guides/183828-cleaning-injectors.html

this may Help

 

[Deckchair5]

Just to mention the car has 67.000 km (thats about 42.000 miles), and it had cam-belt changed last year.
Did you own the car before and after the cambelt change? If so did the uneven tickover stat immediately after the cambelt change? The pulsating vibrations at tickover sound like a mistimed belt installation. Also a poor pickup on acceleration is very often a mistimed belt as the crank and cams are out of synch. The negative and then positive fuel trims also points to cam timing errors

Spark plugs were changed at 44.000 km (27.000 miles), so I guess they are still fine.
The plugs are 23,000km old? Have you checked the gaps recently?

 

[ivand]

Thank you guys for fast response. And thank you Deckchair for making such good threads.

I bought the car after the cambelt change, and havent checked spark plugs yet.

 

[richydraper]

how long after you bought the car did you start experiencing problems? or have the issues been there since you bought it?

 

[Deckchair5]

I bought the car after the cambelt change, and havent checked spark plugs yet.
Ah well you must check those plugs, NGK plugs on 0.9mm gap are recommended

After that then you may well find the crank and cams haven't been synched/ timed properly with the correct tools. A very common mistake with the 1.6 engine is to install the cambelt badly and it's a critical setting for a smooth running tickover and acceleration

 

[ivand]

how long after you bought the car did you start experiencing problems? or have the issues been there since you bought it?

The problems were there from the start, and I thought that all of them are caused by dirty throttle body.
After cleaning throttle body I got much smoother idle rpm but it's not rock steady as it should be.

Maybe for real this is timing problem instead of injectors.

 

[ivand]

Ah well you must check those plugs, NGK plugs on 0.9mm gap are recommended

And, to be honest, I generally don't trust any mechanic here in Croatia, maybe just a few of them.
So, there is a big question if they did replace the spark plugs at all...

Maybe is best to buy new ones anyway?

 

[schumraid]

27,000 mile old plugs should have been changed a while ago

Good luck with the fix!

 

[ivand]

Tomorrow I'm going to check plugs.
Here is a picture with graphs that shows LTFT & STFT on idle, 1500rpm, nad 2500rpm.


This is a graph showing LTFT & STFT during normal ride (LTFT average +6,37% and STFT average is +8,5%):


Uploaded with ImageShack.us

Today I went to service FIAT and asked them about inspecting cam timing alignment...
They said that this is a large job to check, and thay need to remove everything including belt ??
One of the mechanics told me that it might be a fuel pump problem, or fuel regulator problem...

But, lets first see what the spark plugs looks like...

 

[richydraper]

...They said that this is a large job to check, and thay need to remove everything including belt ??...

COW POO!!!

for a fiat garage it should be a 5 minute job!
theres a cam locking tool for each cam and you have to turn the crank to Cyl. 1 TDC...
if they think they have to remove the belt then take it to a different garage.


Setting the timing on the otherhand... that would require belt removal.

 

[sambo6487]

Yer m8 iam suffering from this problem too with my 1.6 too took off my throttle body and cleaned it and done the reset. Car feels sluggish and can lose power when my foots on the floor sometimes nothing happens and juders when pedals on the floor ! She drinking alot of petrol too . And stuck on what to do next any ideas guys ? trying to avoid the garage route to get told nothing and wasting £££

Where do i start ? :worship:

 

[ivand]

This mornig I have changed old spark plugs with new ones. They are of the same mark and number (NGK BKR5EZ), and I regapped the new ones to 0.9mm.
The old plugs were with exactly of the same gap (0.9mm), they looked all the same (brownish) with no sign of any difference between them.
The car is acting like before. Nothing has changed.

Maybe it would be helpfull to mention that I measured about 23.54MPG (average).
Also the famous "gap" when giving instant hit to acc pedal is about 0.3-0.5seconds.
In other words the "waiting" lasts for about 0.3-0.5sec.
When pulling acc pedal slowly (gently) this gap is not so noticeable (or it looks normal).

Should the next step in detecting problem be injector cleaning ???

Thank you guys.

 

[Deckchair5]

They are of the same mark and number (NGK BKR5EZ), and I regapped the new ones to 0.9mm.
That's good

I measured about 23.54MPG (average)
Depends what you were doing and if the engine was hot. Try 50mph (80kmph) in 5th gear on flat ground- should be easily high 45- 50mpg

Should the next step in detecting problem be injector cleaning ???
Sure, it's cheap, easy and will do not harm


Richy
theres a cam locking tool for each cam and you have to turn the crank to Cyl. 1 TDC...if they think they have to remove the belt then take it to a different garage.
Absolutely

Richy Setting the timing on the otherhand... that would require belt removal. ..
No, it's easier than that, with the crankshaft locked up you just slacken the cam pulleys centre bolts, rotate the cams until they line up with the cam alignment tools and retighten

As you still have pulsing vibration at tickover and poor acceleration flat spot, it's had it ever since you bought it and you know the cambelt was changed before that time then I'd check the crank to camshaft timing

Another major player in poor acceleration is the MAP sensor, that will also give poor mpg but not so much a flat spot if it's overfuelling as it would feel like it always wants to go with the smallest amount of throttle. If you're happy with that then I'd go for the crank/cam timing

 

[ivand]

Another major player in poor acceleration is the MAP sensor, that will also give poor mpg but not so much a flat spot if it's overfuelling as it would feel like it always wants to go with the smallest amount of throttle. If you're happy with that then I'd go for the crank/cam timing
OK, before I go to garage for timing belt, I'll do one more check with map.
(But I did this before and the graph looks similair to one you posted before).
I don't know if it has any influence but somebody told me that when the motor oil is over maximum - that matters for MAP working? In my case I have a little more oil on dipstick over max. That is also done in the same service :-(.

...What I also did this morning is that I took a Stilo 1.6 (of the same year) from my company at work for a shorter ride. It has 120.000km, and has been fully serviced in local service shops here (certified service).
What is noticeable from the start is that this car has much more power in lower range of rpm, or should I say it has much better response to acceleration from 1000-3000.
This car is much smoother and "softer" to ride. It also has a "gap" when reacting to accelerator pedal, but it's much shorter. And it doesn't have that silent "V-motor" sound (grint) as mine Stilo has.

...Another thing is that i went to third service for fiat and explained to major service man what I think & feel about my car. He said that I should take car to their office so they can make a ride to see what's happening. Above all, he told me that it's not a problem for them to check for 100% if this is the belt timing problem. The cost would be arround 20GBP (just for checking). What to say, I am happy that I spoke to somebody that is willing to help and listen.

Could you please tell me once again the procedure for checking MAP sensor, to be 100% sure ?
Am I boring with all this thanks ?? (Thx)

 

[Deckchair5]

I wouldn't worry about your MAP sensor for if it was causing over fuelling and your high mpg then your car would feel as if it really wants to go all the time and the opposite, ie hesitant.

Feeling unbalance at tickover and a constant flat spot always at the same rpm range is very likely to be the timing out of synch and your Fuel Trims are all over the place

Best way to test a petrol engine MAP sensor is with a vacuum pump and gauge and watch the voltage change. What you can do is tell your ECU to recalibrate the MAP sensor
Disconnect the MAP sensor. Start the engine, turn engine off
Reconnect the MAP, Clear all fault codes
Turn ignition on and wait 10 secs
Turn off ignition so it stores the data in the ECU
Then start the engine and run on tickover until the engine is fully warm
Turn off ignition
Job done

Make sure they DO check the timing though rather than just "have a look at it" as it is quite critical on a 1.6

 

[ivand]

Could this calibration be done with ECu reset (taking off batery terminals for a hour) ?

 

[richydraper]

...Where do i start ? :worship:

first things first... check for 'vacuum leaks' on the inlet manifold, whip the black plastic ducting off the throttle body and with the engine running and put the palm of your hand over the hole on the throttle body (it will suck like my ex... i.e. HARD) the engine should stop immediately... if it still runs (albeit lumpy) then you have a vac leak look all round the manifold and trace any rubber hoses branching from it. check them THOROUGHLY for splits in the rubber hoses and make sure they are connected to something at the other end!!! sounds silly but is happens.

i recently did a timing chain on a 1.2 VW lump and accidentally knocked a vac pipe off, it happens to the most experienced guys and sometimes you convince yourself that your so cautious that it cant possibly be something this simple... for me it was, i reconnected the pipe and did the hand over the TB and hey presto she stopped.

if its not a vac hose then you go down the route of plug gaps, map sensors and timing. plug gaps are free, MAP relearn is free... timing will be the bugger!

HTH let us know how you get on!

 

[ivand]

...but the readings of MAP sensor at idle are within normal limits. In this case (false air suck) I guess it would "drop" the readings of the sensor. Am I right ?

 

[hanzs]

Normal readings on idle are about 330mBar, when there is a vacuum leak will raise to 500mBar and more.