A5 1.8TFSI erratic idling issue - nightmare !

[pumi63]

Hello all,

I have a nightmare A5 petrol coupe 1.8TFSI that's been plagued with an erratic idling issue for 3 months now. It has stumped so called qualified Audi trained mechanics and master-technicians !

I have had the throttle body, MAP sensor, PCV valve rubber gasket replaced with no improvement upon advice from these expert idiots.

I have had a smoke test that has pinpointed no leaks at all. 

Have been told that now it is a case for Audi £££ charging ppl .

The car ran fine for 4 months and out of the blue the engine light came on followed by the rough idle. There has been no loss of power and no strange whistles or sounds from the engine.

When car is started from cold it seems ok but once warmed up or the throttle blipped then the rough idle begins!

codes state higher than expected engine rpm and codes cite possible air intake leak, MAP/MAF sensor correlation. 

It has already cost me serious money in parts replaced not to mention the hours wasted diagnosing what the hell is wrong!

Please help?

Thank you

 

[pumi63]

Penutimate post now preceding the car going to the main dealer now.

The last expert has stated that lengthy diagnostic would reveal the issue but would be time consuming . Something that they don't have time for since there are so many other cars to fix.

If Audi can't solve it, then nobody can and the result stands at car 4 and car experts 0!!!

 

[jdragon]

Reading your post, you haven't replaced or at least cleaned the MAF sensor, is that correct?

My B8 diesel had rough idle issue at one point, and a quick clean solved it.

Behaving when cold makes me think it's worth trying here 🤔 

[pumi63]

Hi Dragon,

This car (1.8TFSI engine) doesnt have the MAF, only the MAP sensor which has been replaced.

The mechanic said start with what is the cheapest parts first . The only thing that we haven't changed is the entire PCV assembly. But we did change the PCV rubber gasket which can deteriorate with time.

thank you

[Teddynewson]

7 hours ago, pumi63 said:

Hi Dragon,

This car (1.8TFSI engine) doesnt have the MAF, only the MAP sensor which has been replaced.

The mechanic said start with what is the cheapest parts first . The only thing that we haven't changed is the entire PCV assembly. But we did change the PCV rubber gasket which can deteriorate with time.

thank you

If your going too check the pcv just take the oil filler cap off see if that make a difference she may be on its way out normally you get a whistling sound after a while, if no difference I'll be more looking at coil plugs and the wireing spark plugs as the car starts fine but once warm it goes lumpy

[jdragon]

On 10/27/2022 at 2:18 PM, pumi63 said:

Hi Dragon,

This car (1.8TFSI engine) doesnt have the MAF, only the MAP sensor which has been replaced.

The mechanic said start with what is the cheapest parts first . The only thing that we haven't changed is the entire PCV assembly. But we did change the PCV rubber gasket which can deteriorate with time.

thank you

Yes indeed - apologies I completely misread that 🙂

[pumi63]

Hello ,

One of the first things that we checked was the oil filler cap, and it came off easy. Also, there is no whistling sound that indicates a faulty PCV valve.

As there are no signs of leaks following the smoke test, the only other causes could be electrical but surely would show up on the diagnostic tests.

Unless the problem involves mechanical/non-electric components?

Thank you

[pumi63]

Thank you, Jon

I really appreciate your input. You are the first person that has replied to this, and other forums elsewhere, although quite a few people have read this.

it is strange that there is so little information about this on the internet/ YouTube. So, this particular issue is rare hence no information and the mechanics are lost on this.

The culprit could be something really small but such a pain to find hence the expected wallet battering to the point where my son dreads collecting the car from the mechanic(s).

Thank you

[Teddynewson]

Try giving all the ground leads a good clean, especially if your not getting any codes up 

[pumi63]

Hi Jon 

Will try that as weekend looms and dreaded visit to Audi stealers, thank you.

Have a nice weekend.

[jdragon]

@Teddynewson suggestion is definitely a good idea.

Please do post how this progresses.

[pumi63]

Good evening Teddy,

Thank you for that suggestion. I asked my son to try it, but he has now given up and simply wants to get rid of it asap.

When you refer to ground leads, are these easily accessible and are they only in the engine bay?

No guarantees but i may try it myself.

Thank you.

[Teddynewson]

40 minutes ago, pumi63 said:

Good evening Teddy,

Thank you for that suggestion. I asked my son to try it, but he has now given up and simply wants to get rid of it asap.

When you refer to ground leads, are these easily accessible and are they only in the engine bay?

No guarantees but i may try it myself.

Thank you.

Hi bud I'm not sure on your car but my s5 got 3 big leads down by the alternator on the main frame 2 of witch is together and one on its own by the engine mount 

[Teddynewson]

2 hours ago, Teddynewson said:

Hi bud I'm not sure on your car but my s5 got 3 big leads down by the alternator on the main frame 2 of witch is together and one on its own by the engine mount 

You could also try wait until the car starts idleling pull the plugs one by one conect the coil plug and check the spark see if it's strong if it is move on to the next one and so on if thay are all good the you ruled out coils, coils wiring,and plugs 

[pumi63]

Thank you, Teddy.

Will have a look once it stops raining.

 

[pumi63]

Hello ,

My son to the car to Audi West London, and he had fully explained the issue and steps taken to fix it. As usual, the follow set procedure and plugged it in, fair enough at £130 per hour.

Got a message from them saying computer says it's a faulty throttle. Just because it is not the original part even though my son explained that this was a compatible replacement for the original part. The guys just go by the computer blindly without question and said they will start with original throttle body £ 570 not inc. VAT but quoted over £1000 including fit.

They said the part was faulty because it was a non-genuine part but these guys just didnt want to listen!!! My son said that he could bring the original part removed but they turned around and said that could also be faulty!

They then said this was no guarantee that this would fix the problem to which they said they want to help but this is the way to go. My son said that there was no difference in the Audi dealer approach and the independent mechanic, and they had no answer to that when my son said that they are guessing and car could cost £10,000 to spend hours diagnosing and changing different parts until they kill our wallet.

So, a very bad result indeed and no better than the independent Audi specailists!

[pumi63]

An update regarding Audi West London , the reviews are horrendous with some ppl quoted 14 hours, £1000s for diagnostic work unverfified . Car then taken to another Audi and diagnosed in 15 minutes by the master mechanic !

A lot of very angry and dissatisfied customers that have been ripped off!

[jdragon]

4 hours ago, pumi63 said:

Hello ,

My son to the car to Audi West London, and he had fully explained the issue and steps taken to fix it. As usual, the follow set procedure and plugged it in, fair enough at £130 per hour.

Got a message from them saying computer says it's a faulty throttle. Just because it is not the original part even though my son explained that this was a compatible replacement for the original part. The guys just go by the computer blindly without question and said they will start with original throttle body £ 570 not inc. VAT but quoted over £1000 including fit.

They said the part was faulty because it was a non-genuine part but these guys just didnt want to listen!!! My son said that he could bring the original part removed but they turned around and said that could also be faulty!

They then said this was no guarantee that this would fix the problem to which they said they want to help but this is the way to go. My son said that there was no difference in the Audi dealer approach and the independent mechanic, and they had no answer to that when my son said that they are guessing and car could cost £10,000 to spend hours diagnosing and changing different parts until they kill our wallet.

So, a very bad result indeed and no better than the independent Audi specailists!

If the part isn't VAG approved or OEM the car may not recognise it, which seems to be the case here because the error still suggests it's the throttle body.

Unfortunately you won't know unless your purchase a genuine/approved part.

[Teddynewson]

3 hours ago, pumi63 said:

An update regarding Audi West London , the reviews are horrendous with some ppl quoted 14 hours, £1000s for diagnostic work unverfified . Car then taken to another Audi and diagnosed in 15 minutes by the master mechanic !

A lot of very angry and dissatisfied customers that have been ripped off!

So was it the throttle body in the end

[pumi63]

Good evening,

Sorry for delayed response, i just got home. My son picked up the car from Audi and just in time . After claiming that it would take 4 days for the throttle to arrive, they were about to fit a new one in an hours time!

There was a new code however shown by the advisor ; J338. This apparently means non genuine part or faulty throttle! How can a part made by Pierburg to Audi parameters and spec be faulty ?

How did they arrive at a code that three other mechanics did not 'see' on their diagnostic machines?

They are looking for easy fixes we reckon and the chance to drain wallets.

My son had read that an owner had issues with coolant system that affected idling so car was taken to Halfords for a flush and refill , and car appears to be behaving a bit better but problem is still there.

My son is trying to find out if someone else can do a more reliable and sympathetic diagnosis on this patient

[Teddynewson]

5 hours ago, pumi63 said:

Good evening,

Sorry for delayed response, i just got home. My son picked up the car from Audi and just in time . After claiming that it would take 4 days for the throttle to arrive, they were about to fit a new one in an hours time!

There was a new code however shown by the advisor ; J338. This apparently means non genuine part or faulty throttle! How can a part made by Pierburg to Audi parameters and spec be faulty ?

How did they arrive at a code that three other mechanics did not 'see' on their diagnostic machines?

They are looking for easy fixes we reckon and the chance to drain wallets.

My son had read that an owner had issues with coolant system that affected idling so car was taken to Halfords for a flush and refill , and car appears to be behaving a bit better but problem is still there.

My son is trying to find out if someone else can do a more reliable and sympathetic diagnosis on this patient

Take to someone with vcds tell them what's happening with her and you want a adaption and realignment done on the throttle body that should sort it out takes about 10 minutes with a vcds that sort out the right air and fuel mixture sure there was a guy on YouTube that had the same problem but with a vw

[pumi63]

my son spoke to an Audi parts department today and asked about an idle sensor but was told that the car did not have one.

The parts guy enquired about the issue and went out of his way to ask the master mechanic . After a brief discussion, the parts guy said that this was a very rare issue hence there was no info on the internet.

The reason why the start with throttle body is that it appears the car does not recognise the throttle opening as it's a non-genuine part. Apparently some cars do not like non-original parts even after 'tricking' the ECU. He also said that given the cars low mileage it's unlikely that the throttle body is at fault but until there is a genuine one fitted, they cannot go further.

What they have said is really unusual is that the car is fine at start up and the problem begins when the car has warmed up , which is why they don't think it's the throttle body. A known good throttle body would eliminate that particular fault and may point them to the next area to investigate ?

So intrigued was the master mechanic about the issue and codes that they spent hours discussing this outside work before my son got the call with starting point to replace the throttle body and then moving forward. 

Years ago, life was a lot simpler and they could pinpoint faults much quicker but thanks to overdose of electronics much harder to fault-find.

It may even be the wiring !

Thank you

[jdragon]

Good luck getting this resolved.

Do report back on the outcome. It'll be helpful for anyone else who finds themselves in the same predicament.

[pumi63]

Thank you everybody for your suggestions. My son took the car today, to an 'old school' mechanic. He is the first chap that actually drove the car as part of the checks.

He also remarked that it is not likely to be the throttle. He also mentioned that going over humps or breaking could cause an issue as there may be a small break in an electrical lead. Smoke tests are not always conclusive, he said. So, it could also be the leak issue although he did check the integrity of the hoses and sprayed around the engine for any changes to idle but found none.

He did not charge for the tests, and has requested that the car be left with him on Monday probably for electrical issue checks?

Hopefully, these dialogs will prove helpful to any poor soul that may experience such awful issues in the future.

thank you

[Dassen]

Hello!

Did the electrical tests help?