Need help diagnosing issue with Torque app!

[Adey1981]

Hi guys, I'm having a couple of issues with my 1.6 TI-VCT at the moment and I want to try and get to the bottom of it hopefully using the Torque app.

The thing is I don't really know what readings I should be monitoring and what values they should be.

The issues I'm having are;

1) Rough Idle at cold start, basically the car always starts quickly and easily, but the rpm's waver around at 1000-1200 and are not steady, and i can feel the occasional very light judder.  Once  the engine is warmed up, the idle revs sit nicely around 750 with maybe the very occasional slightest of fluctuations (barley noticeable). 

2) When i feather the throttle with the lightest of pressure (in supermarket, or housing estates is most noticable) it jerks like its skipping a beat. This also sometimes happens when i completely lift of and i'm just 'coasting'. I also notice too, there is always a jerk when i apply the throttle, i cant feather it on. I tested while stationary, in neutral with the car warmed up, and if i gently apply the throttle as slowly as possible, the lowest rev i can apply is 1500, it jumps from 750rpm idle straight to 1500rpm. If I apply any amount of throttle over minimum it seems fine, the car accelerates very nicley. It's just when I'm coasting. This when cold or warm, though maybe a bit better when warmed up, it's hard to really say.

 

Some extra info: I had some work done recently on the variable valve system. I was getting P000A error code and they replaced some parts (including new cam belt). The error code is now gone and the twitchy acceleration and poor performance (which was throughout the most of the lower rev range) is also now gone.

Something I noticed a few weeks ago was that the air box 'lid' was not on properly, only 1 screw was in the right hole, and the whole lid was skewed off to the side leaving a gap down one side that at its widest, was maybe 5-10 mm wide. This has caused the screws to become very corroded, and most of them now have no purchase. I think the lid is now on reasonable securely, but It's probably not super tight all the way around, could this cause these issues?

 

I have looked inside the throttle body and there is a yellowish hue to the inside of it, but no build-up of debris or material that i could see. The air filter is also very clean.

I suspect the MAF sensor could be an issue, I know some people disconnect it and see if things improve, but seeing as i have an OBD2 reader I thought I might as well use that to see if i can find the reason for my issues, whether it's the maf or something else. The thing is I'm not sure what i should be looking at to diagnose this. I have looked at the misfire counter, but they always read zero misfires so I'm not sure this is actually accurate? I'm not getting any codes or EML either.

 

Gotta be something simple right?

 

Cheers guys!

 

[simcor]

Torque is going to tell you very little, at best it will read generic or maybe specific manufacturer engine codes for the power train ECU.

It also is unlikely to tell you everything, if reading error codes was that easy would proper dealer diagnostics kit or even semi pro garage multi diagnostics kit cost into the thousands?

You firstly need a proper diagnostics kit that will read all engine DTC's and give an explanation for them and possible causes. Then that gives you things to start looking at, clearing the codes and seeing if they return would be the next step.

The running any diagnostics tests on any systems that are showing error codes would check them for correct operation.

Then once the fault is narrowed down looking at live data if required and having figures to compare them too which no one has access to other than main dealers most likely.

Then it is a case of testing manually any defective part and replacing it and seeing if the fault has been resolved.

It is never as simple as reading a code and swapping a part that is flagged up by that error code, sometimes the diagnostics itself won't tell you what is causing the issue as there is no code stored for what is wrong but something mechanical is causing certain readings to show like it is a faulty part.

If any of that makes any sense, cheap diagnostics are pretty useless, it depends on how much work has been done in reverse engineering the actual official diagnostics equipment, how good the interface is that reads the data stream and separates it to the correct data for the relevant modules in a car.

I

[Adey1981]

I totally see what your saying. I was just hoping there might be some reading that might at least point me in the right direction. 

There are some checks that i believe I should be able to carry out with a bit of reading up first, so I'll just stick to that for now and see how it goes.

Thanks simcor!