Technical Question

[philipb82]

Hello

Just a quick question, I hope not daft!

I suspect I have warped brake disc/s as when i'm braking the car is slightly jerky when coming to a stop, its like the wheels are square! Also I get a bit of a random flat spot when setting off in 1st gear and also is present in 2nd. I was just wondering if a disc could be warped enough to make contact with a brake pad when setting off. Thus causing what feels like a flat spot but also like the car is being held back, then when it loses contact, oomph the car is off. Is this possible?

The car is in for a service soon anyway and have instructed my mechanic to clean the EGR just on the off chance which hopefully will be the cause.

Thanks

Phil

 

[MarkThompson4]

Easy way to test your theory is to jack the car up and spin the wheels when they're in the air, the effect should increase when free wheeling if it is coming from the discs. From my experience warped discs only have an effect under braking but I'm probably wrong how old are the pads/ discs?

Mark

 

[gadge]

A good way to check if a disc is warped is when you are driving - say at 30mph - just press the brake pedal and see if it judders, you'll feel the pedal move up and down slightly as the calliper piston moves in and out as the warped disc goes round.

 

[Clivvy]

as both posts above, that's the best way to test for warped discs. In my experience, a badly warped disc CAN affect the drive, but not so much when you are accelerating like that in 2nd or 3rd gear, but you have to remember that a warped disc will keep contact with the brake pads on and off as the disc turns - [problem here is it can affect your caliper and make it stick. So yeah, a warped disc can affect it but I wouldn't be convinced just yet unless your disc is that badly warped - essentially itll be like driving with the brakes slightly on.

SO, get the car jacked up and spin that wheel! Also, you can take the wheel off, so turning the disc you will see it rub against the pad on and off if it is warped.

 

[philipb82]

Thanks for the replies.

I don't know how old the discs are but the pads are about two years old. I had them checked a couple of months ago and they have plenty of 'meat' on them as i was told

Phil

 

[Clivvy]

what do the discs "look" like? can you see a lip at the edge of the discs? if the disc looks dirty and scorched, then it could be warped. If the disc is definitely cool, you can run your finger down it and you will feel the unevenness if its warped.

I had a similar issue a few years ago with my old V6 MX3. Wasnt so quick, braking ok though just a little juddery. I swapped the discs-one side was almost gone completely, the other side that you can see was warped-the lip around the edge was huge. Swapped the discs and the car felt "free".

 

[philipb82]

what do the discs "look" like? can you see a lip at the edge of the discs?

My mechanic serviced my car yesterday and whilst underneath he commented about the disc. There is a lip on the driver side brake disc. So after my holiday I may have to consider replacing the disc and pads, although the pads are fine. As the pads have plenty left on them I wouldn't be in such a rush to change the discs. However we use the car quite a bit on motorways so it's probably best to change them. Do you change just the affected disc or both sides?

Thanks

Phil

 

[MarkThompson4]

They come in pairs so you don't a have a choice keeps the brake balance in check that way also

 

[philipb82]

They come in pairs so you don't a have a choice keeps the brake balance in check that way also

Ah right, i didn't know that, i thought they were sold as one! Thats good then

Phil

 

[gadge]

I must correct slighty The pads are sold in pairs (4 pads - 2 for each side) but the discs are actually sold singularly bizarrely but mark is right you should NEVER change jut one side. It's alfa way best to replace both at the same time

 

[Clivvy]

yup, as above, ALWAYS buy in pairs! its not a huge expense for Stilos either, and easy to do - personally id do the discs and pads and grease up the calipers with fresh copper grease and give them a good scrub.

 

[philipb82]

Hello

I've had new brake discs and pads fitted and that's cured the juddering and steering wheel shake I used to get when braking gently and from high speeds.

Also had the EGR valve blanked. The car seems more revvy at high end but not sure if its totally cured my low end flat spot/holding back problem. I'll need to test further! If its not the EGR then I'm wondering if the MAF (although new) or MAP could be the culprits as the pipes etc are all ok. I may need to get data from a diagnostics.

Phil

 

[philipb82]

Hello

I've had new brake discs and pads fitted and that's cured the juddering and steering wheel shake I used to get when braking gently and from high speeds.

Also had the EGR valve blanked. The car seems more revvy at high end but not sure if its totally cured my low end flat spot/holding back problem. I'll need to test further! If its not the EGR then I'm wondering if the MAF (although new) or MAP could be the culprits as the pipes etc are all ok. I may need to get data from a diagnostics.

Phil

It feels like the flat spot is still present at low revs and occasionally higher up the rev range. So that must mean the EGR is ok? I should be looking the MAF, right? As the flat spots are present when the engine is warm i'm guessing its the MAF but i hope not as its fairly new.

Phil

 

[Clivvy]

possibly, but I wouldn't rule out the injectors either. The MAP is worth checking (I thought you had cleaned it? if so, may need a new one) and also consider the boost valve under the battery/passenger headlight. If its when the engine is warm, there are other factors to consider, including CKP sensor although its probably not that (CKP affected by heat and failing can result in a whole manner of oddities but mainly stalling and poor starting or no starting at all but incorrect or out of range numbers from it result in the ECU using defaults and this can occur on and off as it cools/warms up)

Did you manage to check your I/C pipes, are they all ok? What about the fuel lines, all good? Also consider all your Air intake pipe work - lots of it, any cracks, splits etc?

I have diagnostics software, laptop and connector if that is any good to you. Haven't used it much on mine so not 100% sure what it will tell you and it may require a run out with it plugged in to log the results - that'll certainly point you in the right direction.

 

[philipb82]

possibly, but I wouldn't rule out the injectors either. The MAP is worth checking (I thought you had cleaned it? if so, may need a new one) and also consider the boost valve under the battery/passenger headlight. If its when the engine is warm, there are other factors to consider, including CKP sensor although its probably not that (CKP affected by heat and failing can result in a whole manner of oddities but mainly stalling and poor starting or no starting at all but incorrect or out of range numbers from it result in the ECU using defaults and this can occur on and off as it cools/warms up)

Did you manage to check your I/C pipes, are they all ok? What about the fuel lines, all good? Also consider all your Air intake pipe work - lots of it, any cracks, splits etc?

I have diagnostics software, laptop and connector if that is any good to you. Haven't used it much on mine so not 100% sure what it will tell you and it may require a run out with it plugged in to log the results - that'll certainly point you in the right direction.

Hello Clivvy

I did clean the MAP yes but maybe it could be faulty? The CKP is new, I brought one for my new engine last October! All the pipe work is apparently all ok but I've not had the fuel lines checked so that's something I will look at. Today I downloaded Multiecuscan I might get an interface cable to connect it all up or pop and see a mate who has all the diagnostic stuff I know that unplugging the MAF is a way of testing if that's faulty but I have been told that this could result in the engine over fueling This is the last thing I want to do with my new engine.

Phil

 

[Clivvy]

if you have the cable, and multiscan then that's all the diagnostics stuff you need. Just hook it up, and set it logging then go for a drive. This will flag up the flat spots and point you to the source (hopefully)

Unplugging the MAF will result in one of two things, either poorer running, or better running - I suspect yours is ok and it will run worse. I wouldn't worry about over fuelling it I seriously doubt that will happen unless you are being silly with the accelerator for a lot of miles (trying to make it go when it simply isn't going to!)

I think, best thing is to hook it up and go for a drive...

 

[philipb82]

if you have the cable, and multiscan then that's all the diagnostics stuff you need. Just hook it up, and set it logging then go for a drive. This will flag up the flat spots and point you to the source (hopefully)

Unplugging the MAF will result in one of two things, either poorer running, or better running - I suspect yours is ok and it will run worse. I wouldn't worry about over fuelling it I seriously doubt that will happen unless you are being silly with the accelerator for a lot of miles (trying to make it go when it simply isn't going to!)

I think, best thing is to hook it up and go for a drive...

I will do that . So when I go for a drive it will log the data but then does it tell me exactly where the problem is coming from? Do you use Multiecuscan Clivvy? What cable do you use?

Phil

 

[Clivvy]

well, form the use I have had of mine, it is quite clever in the descriptions when identifying the problem, but will it say "the problem is xyz" I don't know, but lets put it this way when I diagnosed my AirCOn not working, it quite literally told me the sensor was faulty and to replace it so I did, and that fixed my aircon!

When you run a diagnostic when driving, you will need to set it to log and it will monitor everything the ecu is doing and log it, then you should get a graph or set of results you an filter through to find peaks and troughs - I haven't done a scan this way before in the fiat but on other cars it has always pointed to a certain component when there is a peak or a trough in performance so I am assuming the same with Multiecuscan.

I use a USB ELM327 cable (I think) and it comes with the three different cables.

 

[philipb82]

Today i took the car on a 'vigorous test' . There is no flat spot at higher revs, it will happily rev away now!

Regarding this hesitation in 1st and 2nd gear, i'm not sure now. I think it might be.....ME! It might have been the way i was driving but i may do a diagnostics just to see if everything is working as it should. However its safe to say my EGR is knacked! I'm also hoping its the EGR that is causing my now very rare, juddering/kangarooing. It would make sense as it happened with my last engine and the same EGR i had on the old engine was transferred to my new one. Like i said before i said it must be a part that was used with my last engine. It would be good if it was, solve 2 problems with 1 part

Phil

 

[philipb82]

Today i took the car on a 'vigorous test' . There is no flat spot at higher revs, it will happily rev away now!

Regarding this hesitation in 1st and 2nd gear, i'm not sure now. I think it might be.....ME! It might have been the way i was driving but i may do a diagnostics just to see if everything is working as it should. However its safe to say my EGR is knacked! I'm also hoping its the EGR that is causing my now very rare, juddering/kangarooing. It would make sense as it happened with my last engine and the same EGR i had on the old engine was transferred to my new one. Like i said before i said it must be a part that was used with my last engine. It would be good if it was, solve 2 problems with 1 part

Phil

Ignore my last post. I've filled up and its there again

Phil