TDI Cold Start problem

pottaz
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TDI Cold Start problem

Post by pottaz »

Hi everyone,

I know this topic was discussed but that was back in 2012 and no one seemed to resolve this.

Some background:

I drive an Audi A3 2004 2.0tdi. The car would not start when warm. Sounded like the battery was flat. I replaced the starter and now it starts first turn when warm. Fix one thing, and the next thing pops up.

But now the car struggles to start when cold. We drove the car around as there was a noticeable sound when boost should be felt (low on power when this happend). If I can explain the sound it would be "hrrrrr" as if the engine sounded harder. This would only happen from 1950rmp -2800rpm when you plant your foot from low revs (1500rpm). After the 2800rpm range it would then disappear and the car will pull again. If you take the revs up gently (as in very slow) there is no sound.

After we drove around and test this (kinda hard driving, no red line). The next morning the car would swing for about 15-30 seconds before starting. This only happens when cold. It would then idle rough (surging sound not showing on rev needle) till warm. After which the car idles fine when warm. The sound (when hard accelerating) is still noticeable even when warm. I changed the glow plugs hoping it would be this. But no luck.

My thinking is clutch for the sound, and hard start when cold a fuel issue? Hopefully not injector as these seem to be expensive :eek:

If any one could assist in this. I would appreciate it. :hug:
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panic-mechanic
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Re: TDI Cold Start problem

Post by panic-mechanic »

Hard start could be something as simple as a failed water temp sender. But imposible to just say without seeing the car. The hesitation might be maf which coulmalso affect starting to a degree.
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pottaz
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Re: TDI Cold Start problem

Post by pottaz »

Wouldn't the car give an error?

How can I test this. What sensor could be the culprit?
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Re: TDI Cold Start problem

Post by THANAS »

Get it compression tested, the hard-starting when cold could be owing to a lack of compression. Also somewhat ties in with the other symptoms you're experiencing.
pottaz
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Re: TDI Cold Start problem

Post by pottaz »

I have uploaded a video of how the car starts when cold. Will this be likely a compression issue or the temp sensor?

https://www.youtube.com/watch?v=g8eHNDllf3c

Sorry for only posting the link. Don't know how the video or youtube links work on the thread.
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Re: TDI Cold Start problem

Post by THANAS »

Try unplugging the MAF on the next cold start and see if it makes any difference.
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Re: TDI Cold Start problem

Post by pottaz »

Okay will have a look at the MAF.

Apparently the garage has tried it but will have a look myself and report back.
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Re: TDI Cold Start problem

Post by panic-mechanic »

Water tmep sensor can fail that it give a wrong reading without a code presenting. Diagnosis is not about going to the fault code and voila there it all is. Sometimes you have to use your brain, look to see if the values in reading blocks are valid and so few mechanics can do that these days. The think and diagnose bit that it......
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Re: TDI Cold Start problem

Post by jaunrothner »

Good luck,

My brother in law had the same issue on his 2009, 320d E90 BMW,

Took it to a few people, changed all injectors, changed all glow plugs with glow plug relay and the car still did not want to start when cold (first start in the morning).

Took it to BMW and they quoted him R75000 to repair (replace diesel pump, replace injectors again, replace glow plugs again and some other bits and pieces which I cant remember now),

Needles to say he flogged the car 3 days after he received the quote from BMW.
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Re: TDI Cold Start problem

Post by pottaz »

So car was sitting outside at work. I pulled the MAF with no luck. Still the same when starting from cold but when it started it would die. Put back the MAF and after long swing time the car started and kept the revs.

While driving home if I stay at 2000rpm and push the clutch in. The revs will drop to below the expected idle (as if it wants to die) and then corrects itself. The idle has this surge sound even when hot.
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Re: TDI Cold Start problem

Post by pottaz »

panic-mechanic wrote: Mon Jul 29, 2019 12:46 pm Water tmep sensor can fail that it give a wrong reading without a code presenting. Diagnosis is not about going to the fault code and voila there it all is. Sometimes you have to use your brain, look to see if the values in reading blocks are valid and so few mechanics can do that these days. The think and diagnose bit that it......
I don't have a VAGcom to perform this. Any other way I can test it. I pulled the temp sensor (on fuel line) and also tried to start cold. No luck. Will the temp sensor default to static values? I have replaced this sensor about 6 months back.
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Re: TDI Cold Start problem

Post by Ashveer03 »

Does it struggle to start when cold or when parked for a long period of time?

If with regards to time, check injector seals. Same tests/checks apply as the 1.9.

Had a similar issue on a 1.9 with regards to the sound, was a faulty injector.
Vcds group 13 on idle, and group 23 on a log while driving will tell.



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Re: TDI Cold Start problem

Post by panic-mechanic »

He just said he does not have vcds...
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Re: TDI Cold Start problem

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Ashveer03 wrote: Mon Jul 29, 2019 10:13 pm Does it struggle to start when cold or when parked for a long period of time?

If with regards to time, check injector seals. Same tests/checks apply as the 1.9.

Had a similar issue on a 1.9 with regards to the sound, was a faulty injector.
Vcds group 13 on idle, and group 23 on a log while driving will tell.



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Think it is when parked for a long period of time (so engine will be cold).
I think it might be an injector as the car surges when idling. As mentioned I don't have a VCDS.

Anybody know of someone in Cape Town that knows their stuff and can help me diagnose this on a VCDS?

Also if it is an injector, is there a good shop in my area that won't charge an arm or a leg to fix this? Asked for a quote on injectors that almost gave me a heart attack (R6100 pull all four and test. R5500 per injector to recon). Is that what I am looking at? :eek:
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Re: TDI Cold Start problem

Post by Ashveer03 »

I know of somebody not sure exactly where about. Pm'd u his details

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Re: TDI Cold Start problem

Post by panic-mechanic »

or just PM thanas he could help with the vcds bit already
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Re: TDI Cold Start problem

Post by Tdi jetta 4 ever »

Could be a timing issue also.
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Re: TDI Cold Start problem

Post by pottaz »

Tdi jetta 4 ever wrote: Sat Aug 03, 2019 2:49 pm Could be a timing issue also.
I am actually starting to think it is. Running very lean. There is smoke but not black. That lean kind of smoke when pulling away.

To my knowledge an injector would give of black smoke?

Correct me if I am wrong.
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Re: TDI Cold Start problem

Post by Ashveer03 »

A faulty injector/seals will be white smoke.

Again, vcds can tell timing on the intake cam, the exhaust cam is the problem. If u alter the setting on the exhaust cam, the idle consumption will change. It should be about 0.5-0.6L/hr with all accessories off.

If u already do have a high idle consumption, it doesn't necessarily mean the timing is off, a number of things can cause them to rise with the most common being a faulty injector or seals. And u can get an idea as to what's happening with the Injectors by using vcds or any other scan tool that has vehicle specific Info.

I honestly think u have an injector/seal problem. As per the video, the car is clearly losing prime after been parked.

The problem u experiencing when at low rpm, could also be a turbo problem. If the Vanes close too much and cannot be controlled properly(either just being clogged up with soot or from a faulty actuator, etc) the engine chokes and u get sort of a diesel knock because the requested fuel is being delivered and the air is not.

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Re: TDI Cold Start problem

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Ashveer03 wrote: Fri Aug 16, 2019 5:53 pm A faulty injector/seals will be white smoke.

Again, vcds can tell timing on the intake cam, the exhaust cam is the problem. If u alter the setting on the exhaust cam, the idle consumption will change. It should be about 0.5-0.6L/hr with all accessories off.

If u already do have a high idle consumption, it doesn't necessarily mean the timing is off, a number of things can cause them to rise with the most common being a faulty injector or seals. And u can get an idea as to what's happening with the Injectors by using vcds or any other scan tool that has vehicle specific Info.

I honestly think u have an injector/seal problem. As per the video, the car is clearly losing prime after been parked.

The problem u experiencing when at low rpm, could also be a turbo problem. If the Vanes close too much and cannot be controlled properly(either just being clogged up with soot or from a faulty actuator, etc) the engine chokes and u get sort of a diesel knock because the requested fuel is being delivered and the air is not.

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Thanks for the reply.

Okay yes then it all makes sense. You explained it very well thank you.

Will driving the car with the injector/seal like this cause further damage?

Can the injector cause the low rpm problem aswell? If not and it is the turbo, will the diesel knock cause more damage?
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Re: TDI Cold Start problem

Post by Ashveer03 »

Anything that's faulty will cause some sort of damage.
With the Injector seals, I know people who have driven their cars for years with that problem, 2 of them ended up with a proper misfire at the end, new Injectors were needed on the bad cylinders.

The diesel knock on the other hand is not good at all, it's detonation pretty much the same as pinging in a petrol. Again it's not even confirmed that it is a diesel knock.

Get it checked out properly because without actually see what's going on we all just guessing and making assumptions.

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Re: TDI Cold Start problem

Post by pottaz »

I took my car in for diagnostics.

They said:
My MAF is giving wrong values and that there is n slight miss (this was there before all this happend) caused by a lose connection on the one injector.

Went home changed the MAF sensor, and nothing changed accept having slight better fuel consumption.

After the car sat for a long period, it would swing for very long and sometimes even make a fault code sound whilst swinging before then starting.

Yesterday the same happend, starting with fault code sound caming on but the steering wheel light stayed on all the way home.

I shutoff the car and tried to start it again. Normally the car would start instantly. This time the car hardly swung. Sounded like a dead battery. So I switched back off. Turned it again and the car started up. The cluster was all dead. Nothing moved no lightes but the car was running. Gave it a bump of the gas. Then everything came back to life.

So now I am thinking, crank position sensor?

I have noticed a bit of sweating below intake manifold gasket area. Could this be a suspect, leaking intake manifold gasket?
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Re: TDI Cold Start problem

Post by Ashveer03 »

Maybe check the earth cables

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Re: TDI Cold Start problem

Post by pottaz »

Sorry for not posting. I don't want this to stay open. I was in Johannesburg for 3 months so couldn't look at my car.

I talked to a mechanic I know and he said that it might be my fuel pump. Some mornings when I started my car I remember this grrrr..... sound when priming.

I bought a new pump and installed it. The car is still warm so didn't struggle to start. But on the road it does the same thing:

- boosting irregular
- when driving and pressing clutch the revs fall below the idle amount and then jump back up.

Will have a look tomorrow morning on first start what happens.

The car doesn't throw white smoke. Only black as a diesel normally would.
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Re: TDI Cold Start problem

Post by pottaz »

This morning the car still struggled to start after replacing fuel pump in tank.

https://youtu.be/g8eHNDllf3c

Here is a compilation I made this morning on how the car runs. Maybe it can help diagnose the problem.

https://youtu.be/3lKwR09CLFQ

I really want to get to the bottom of this and maybe help someone that also struggles with this.

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