Stutter rough idle when first starting car and clears up after 3-4 seconds.

[old guy]

One test, after driving (engine hot) take note of the hpfp pressure at idle, turn engine off, over the course of 5 minutes the pressure should build to 2-3xs idle pressure, if it doesn’t, or it drops, its either an injector (if fuel in oil) or the hpfp is on its way out.

Just got back from the liquor store;-). When I got there I noted the fuel pressure at idle was 570 psi. Turned off the ignition and observed for around one minute. Fuel pressure increased to 700 psi. By the time I got back to the car about 10 minutes later the residual pressure was 1375 psi.

LPFP did not prime when I opened the door.

[NitroViper]

I went out today first time since yesterday and heard the pump prime. The pressure was a 98psi and the car started normal. It stayed around 760psi and dropped to about 570 after a minute. Its hard to know if it peaked higher then 760 because the obdeleven app freezes. I should have torque app and dongle tomorrow. HPFP is here today and im not installing it until I see some proof mine is low.

I need to test it when the car stutters so bad that the check engine light comes on, but that doesnt happen alot.

[dalmation53]

I would change the HPFP. if problems persist send it back..

I went out today first time since yesterday and heard the pump prime. The pressure was a 98psi and the car started normal. It stayed around 760psi and dropped to about 570 after a minute. Its hard to know if it peaked higher then 760 because the obdeleven app freezes. I should have torque app and dongle tomorrow. HPFP is here today and im not installing it until I see some proof mine is low.

I need to test it when the car stutters so bad that the check engine light comes on, but that doesnt happen alot.

[Novarider]

The HPFP should be a maintenance item anyway IMO.

[Traptalk]

I have a brand new oem Bosch lpfp and screen from when I did my walbro 450 swap you could drop into your existing basket. Then pick up a new filter and be good as new

Edit : actually I forget you got to cut some plastic to remove the pump fully so would have to get creative with putting it back together

[NitroViper]

I have a brand new oem Bosch lpfp and screen from when I did my walbro 450 swap you could drop into your existing basket. Then pick up a new filter and be good as new

You giving that away for testing purposes? lol

[Traptalk]

You giving that away for testing purposes? lol

Note the edit lol

[Traptalk]

If you’re up for the challenge tho, just cover shipping since I have zero use for it now

[Traptalk]

The pump easily disassembles to this point



This bracket is what you’ll have to modify to remove and swap the pumps



A new pump is like $200

[NitroViper]

I don't know if this helps at all but here it is. This (crappy) video was taken on a cold start 2013 2.0 TFSI. The ambient temperature was 89° f.

What could be noteworthy:

- Prior to ignition the fuel pressure was 362 psi.

- Upon ignition the fuel pressure was 850 psi → 860 psi with fast idle ~1200 rpm

- Timing advance at -17° → -20° ATDC

-Charge voltage ~ 13.5v

-AFR remains around 14.7. O2 equiv. ratio remains at 1.

- At approximately 1 minute the rpm dropped to 750 and the fuel pressure dropped to 560 psi → 570 psi

-Timing advance increased to +3° → +5° BTDC

EDIT: Went back and performed a warm start. (No crappy video)

- Fuel pressure at 650 psi

- Upon ignition fuel pressure dropped to 560 psi → 570 psi and remained there.

-Timing advance +3° → +5° BTDC

- No stuttering with either cold or warm start.

Got my torque app, not sure what you added exactly but do these look right? I like how it stays live. OBDeleven wont stay live without freezing. What a watse of money. Only thing it was good for is enabling AUX permanently.

The car ran like crap for a few seconds, dunno if you can tell. I used an app called V Recorder to record my phone screen.

[NitroViper]

The pump easily disassembles to this point

This bracket is what you’ll have to modify to remove and swap the pumps

A new pump is like $200

Ive took apart and put pumps like that before to work on peoples cars, its a pain sometimes. Sometimes it works and sometimes it doesnt because of the heat shrunk tubes.I actually have a fuel filter already. The guy had one in the trunk, Ill bet money he had this problem and never told me.

[Traptalk]

Ive took apart and put pumps like that before to work on peoples cars, its a pain sometimes. Sometimes it works and sometimes it doesnt because of the heat shrunk tubes.I actually have a fuel filter already. The guy had one in the trunk, Ill bet money he had this problem and never told me.

No heat shrink tubes on this, won’t have to splice any wires either

[NitroViper]

No heat shrink tubes on this, won’t have to splice any wires either

I mean if the HPFP doesnt fix it it would be worth a try and maybe help other ppl figure out this issue. Seems like there is many here.

[dalmation53]

Bro if you putting your F23l your car at 100k the pump is tired same like mine. You should indeed change it and let us know since. you already bought the pump. once your issue is resolved we would all appreciate it and change it as well.

I mean if the HPFP doesnt fix it it would be worth a try and maybe help other ppl figure out this issue. Seems like there is many here.

[old guy]

Got my torque app, not sure what you added exactly but do these look right? I like how it stays live. OBDeleven wont stay live without freezing. What a watse of money. Only thing it was good for is enabling AUX permanently.

The car ran like crap for a few seconds, dunno if you can tell. I used an app called V Recorder to record my phone screen.

Was that on a warm start?

I will take a closer at a warm start on mine tomorrow. One thing that stands out to me is that your ignition timing is initially a little ATDC. I believe mine is stayed around 3° → 5 ° BTDC on a warm start but will confirm. I only saw ATDC timing with the fast idle and 860 psi fuel pressure.

Your fuel pressure looks fine as compared to mine on a warm start. Bounces around 560 → 570 psi.

[Traptalk]

Idk if obdeleven allows but you could watch your high pressure fuel request and actual and see if your coming up short or dropping pressure at wot.

These mechanical pumps really don’t outright fail but the metering valve can and the internal seals can breaks and leak into the oil and cause loss of pressure.

If it’s only in cold start after the cars been sitting could be the lpfp loosing pressure and gas leaking back into the tank. Can try cycling the power on a few times with the key to build prime pressure before starting the car and see if that eliminates it.

I had a stutter once, doesn’t sound as bad as yours. Was a single hiccup not 3-4 seconds of stutter. Seemed to be related to a tiny boost leak that was hard to find. Found it out of chance actually.

[NitroViper]

Was that on a warm start?

I will take a closer at a warm start on mine tomorrow. One thing that stands out to me is that your ignition timing is initially a little ATDC. I believe mine is stayed around 3° → 5 ° BTDC on a warm start but will confirm. I only saw ATDC timing with the fast idle and 860 psi fuel pressure.

Your fuel pressure looks fine as compared to mine on a warm start. Bounces around 560 → 570 psi.

That was a semi warm start, about an hour and a half after driving it.

[old guy]

Understood. Since we both now have TorquePro lets set the same info on one page so we can compare a cold and warm start.

I will set mine to the following:

RPM
Block temperature
Timing Advance
Fuel Pressure
Vacuum
AF Ratio

Then we can compare any differences on a hot and cold start. I won't be able to get on it until tomorrow afternoon. Heading out for a 56 mile bike ride on the local Rails to Trails in the morning

[NitroViper]

Understood. Since we both now have TorquePro lets set the same info on one page so we can compare a cold and warm start.

I will set mine to the following:

RPM
Block temperature
Timing Advance
Fuel Pressure
Vacuum
AF Ratio

Then we can compare any differences on a hot and cold start. I won't be able to get on it until tomorrow afternoon. Heading out for a 56 mile bike ride on the local Rails to Trails in the morning

Ill set mine like that, its just mine is so random who knows what it'll say lol. Tomorrow ill record it before i drive and then ill come home shut the car off and do a warm restart in a few minutes.

I dont see a block temp. I see a coolant temp tho.

[old guy]

Ill set mine like that, its just mine is so random who knows what it'll say lol. Tomorrow ill record it before i drive and then ill come home shut the car off and do a warm restart in a few minutes.

I dont see a block temp. I see a coolant temp tho.

Sounds good. Coolant temp is same as block temp.

I will probably have to take a nap when I get home before I can record mine (being an old guy;-)

[NitroViper]

Sounds good. Coolant temp is same as block temp.

I will probably have to take a nap when I get home before I can record mine (being an old guy;-)

below is how I have it set up right now.

[old guy]

Okay. I'll set mine the same.

[old guy]

Here's my cold start. I noticed that the pid for vacuum isn't reading accurately so I picked the vacuum/boost for the warm start. It appears to be accurate. A/C was turned off. Pump did prime when I opened the door. I also added the STFT so you can see when it goes from open loop to closed loop.



As noted I used a different pid for the vacuum/boost reading. Pump did not prime when opening the door. I also noted that the timing advance did bounce between ATDC and BTDC.

[NitroViper]

Here's my cold start.

I went out to do that today and the engine started normal. There really is no reason for me to post that reading becuase its not showing whats wrong if you know what I mean. Ill keep trying to get that crappy cold start every few hours. Your cold start psi was 295psi. Ive never seen mine that high.

Ill edit this thread as soon as I can getting a bad stuttering cold start.

[old guy]

I went out to do that today and the engine started normal. There really is no reason for me to post that reading becuase its not showing whats wrong if you know what I mean. Ill keep trying to get that crappy cold start every few hours. Your cold start psi was 295psi. Ive never seen mine that high.

Ill edit this thread as soon as I can getting a bad stuttering cold start.

Understood.

I will continue to note my cold start residual fuel pressure to see how much it varies.

[JLAllroad]

One test, after driving (engine hot) take note of the hpfp pressure at idle, turn engine off, over the course of 5 minutes the pressure should build to 2-3xs idle pressure, if it doesn’t, or it drops, its either an injector (if fuel in oil) or the hpfp is on its way out.


Sent from my iPhone using Audizine

@NitroViper and @Oldguy, have either of you done this and compared?


Sent from my iPhone using Audizine

[old guy]

@NitroViper and @Oldguy, have either of you done this and compared?


Sent from my iPhone using Audizine

Read post #81 ;-)

[NitroViper]

@NitroViper and @Oldguy, have either of you done this and compared?


Sent from my iPhone using Audizine

Yea mine was like 1600 once, I was suprised to see that after having my car off for a bit.

[old guy]

I went out to do that today and the engine started normal. There really is no reason for me to post that reading becuase its not showing whats wrong if you know what I mean. Ill keep trying to get that crappy cold start every few hours. Your cold start psi was 295psi. Ive never seen mine that high.

Ill edit this thread as soon as I can getting a bad stuttering cold start.

Cold start today was 110 psi.

[NitroViper]

My car wasnt stuttering enough to catch it on a cold start with our torque icon placement So I put the one that did stutter in this video. I been putting off changing the HPFP until this test is done but my car doesnt seem to want to stutter with testing going on lol.

If I slow it down or pause it the major difference I see is the timing between the cold start stutter and the cold start good. In Editing I lined all all engine starts at the same exact moment. The sound in the video is from the stuttering start.

[Smac770]

That’s only one of the fuel filters. How do you replace the inlet pick up screen?

You’d have to disassemble the entire to pump and clean the screen and reuse it to really do it proper

Eh, that's a bit of a stretch, but not something to be disregarded. It's like saying there's two air filters, when there's only one. The snow screen is just that, a screen. Which does need to be cleaned from time to time (it's actually in the Audi maintenance schedule).

Is there an inspection and/or cleaning process for the inlet screen? I have no idea. Never seen anyone refer to the screen before.

[old guy]

Your cold start stutter video doesn't show the coolant temperature. It is acting like a warm start. The fuel pressure and timing as well as the RPM's are similar to all of my warm starts. My cold starts all have the very retarded timing, higher fuel pressure and higher RPM's.

Can you capture a stuttering cold start that also shows the coolant temperature? I know that on my A4 B6 a defective coolant temperature sensor will cause starting problems. It could be that you have a cold engine but the CTS is indicating to the ECM that it is actually a warm start and consequently the ECM isn't providing the fuel necessary for a cold start.

[NitroViper]

Your cold start stutter video doesn't show the coolant temperature. It is acting like a warm start. The fuel pressure and timing as well as the RPM's are similar to all of my warm starts. My cold starts all have the very retarded timing, higher fuel pressure and higher RPM's.

Can you capture a stuttering cold start that also shows the coolant temperature? I know that on my A4 B6 a defective coolant temperature sensor will cause starting problems. It could be that you have a cold engine but the CTS is indicating to the ECM that it is actually a warm start and consequently the ECM isn't providing the fuel necessary for a cold start.

Ive been trying every since we decided on an icon setup in torque to get a cold start stutter. It just hasnt happened yet and ive tried many times. Im sure on that cold start stutter the coolant was cold like the regular cold start tho. But I couldnt see it, maybe it didnt.

[old guy]

Ive been trying every since we decided on an icon setup in torque to get a cold start stutter. It just hasnt happened yet and ive tried many times. Im sure on that cold start stutter the coolant was cold like the regular cold start tho. But I couldnt see it, maybe it didnt.

If that stutter start was indeed with cold coolant I suspect your CTS may be reading incorrectly. I will continue to watch mine closely to see at what temperature the start up protocol goes from a cold start settings to a warm start settings and we can compare.

[NitroViper]

If that stutter start was indeed with cold coolant I suspect your CTS may be reading incorrectly. I will continue to watch mine closely to see at what temperature the start up protocol goes from a cold start settings to a warm start settings and we can compare.

Ill keep trying over the next few days. I have a feeling it isnt my HPFP and ill send that back if its something else, but you can see the timing difference. That stuttering start was indeed cold coolant. With the timing being that different youre right the ECU might be thinking the car is already warm and fumbles on start because the coolant temp sensor is stuck. If it was the HPFP the timing would still match.

I cant seem to find one on fcpeuro for some reason.

https://www.fcpeuro.com/products/vw-...-vw-06a919501a

I think thats correct even tho the site says it doesnt fit my car... Just ordered one screw it. The timing is a huge difference and make me thing this is the issue.

I went out there a couple hours ago and the coolant temp read 106.6... I just went out a few minutes ago to test it and it said 107... thats about 4 hours of cooling... suspect?

[old guy]

I believe it is item #6. Clicky click

107° after 4 hours sounds about right to me.

I just checked mine after sitting overnight. Outside house thermometer reads 72°. Dash display reads 72°. Coolant temperature sensor reads 75°. Residual fuel pressure reads 112 psi.

[Theiceman]

older generations of Audis used a 4 pin sensor and the sensor was essentially split in half, one feed feeding the ECU and the other half feeding the gauge. so essentially to your point one side could fail and the other half would be fine. On our generation of car they have gone to a two pin connector with only one coolant temp feed. It feeds the ECU and that data us routed to the gauge. Also they don't really get " stuck" .
All that to say i think you are on the wrong path.
But if you do decided to change it its not too bad to get too and don't forget the Oring.

[old guy]

Yep. I'm very familiar with the 4-pin sensor. I've replaced it several times on my a4 B6.

What I find interesting is that Nitro's stuttering cold start had all the conditions (fuel pressure, timing advance, RPM's) of a warm start. I'm speculating here but typically you provide more fuel on a cold start. Thus the higher fuel pressure. So the question is, why did the ECM perform a warm start on a cold engine?

CTS reading is one thing that comes to mind. Then again it may have nothing to do with it at all. Fortunately it is pretty easy to change out.

[NitroViper]

170° is pretty hot after 4 hours. seeing the coolant temp normally gets to 192° about. Was fine today on cold start with starting coolant temp of 76.

Last night I went out again and the temp was 92° the fuel pressure was 72psi... that is the lowest ive ever seen it. It stuttered at the start.

[old guy]

170° is pretty hot after 4 hours. seeing the coolant temp normally gets to 192° about. Was fine today on cold start with starting coolant temp of 76.

Last night I went out again and the temp was 92° the fuel pressure was 72psi... that is the lowest ive ever seen it. It stuttered at the start.

I agree that 170° is too high after 4 hours. You inadvertently typed 107°.

Did you observe how quickly the fuel pressure increased at the start? Did it take several seconds to get up to your normal cold start pressure?