Finally! Hesitation and rough cold start fixed!
1st Gear
Joined: Sep 2017
Posts: 11
Likes: 1
Lots of good info here. I would agree with the turn key on and wait a while it seems to start and stay running when I do this. In cold weather this doesn't help and I think there is something to the fuel rail psi bleeding off comments that were made here. What would cause a fuel rail to lose psi. I did change the fuel filter over the summer and it looked original. No change in symptoms but I did feel good about doing it. I do not have any service engine soon lights and did not check codes. Im sure there are lots of misfire codes because it ran like a bad lawnmower. I did a major project in Nov changing the Supercharger oil and since the MAF sensor was off I cleaned it. The rough running at start is all driven by temp. Below 32 degrees this happens. It seem to be fuel related. Sounds like an engine starved of fuel. I am getting ready to do front and rear struts and will have to wait until after the New Year to dive into this problem. Good news is temps are suppose to stay above normal here in NJ for the next few days.
5th Gear
Joined: Oct 2004
Posts: 1,005
Likes: 156
From: Northern Jersey
I'd imagine it would be one of the seals in the one way valves of the fuel system (FPR, any one way valve in the fuel tank) allowing the fuel in the line to bleed back into the tank. I would instinctively say its the FPR, but I don't know what other valves are in the fuel pump section, or the fuel filter part.
5th Gear
Joined: Jul 2018
Posts: 766
Likes: 80
From: Texas
I have this issue that is resolved 95% of the time with turning the key on and waiting. I changed the fuel pump because my fuel pressure was not holding after turning key off. I didn’t check fuel pressure after changing pump so I’m not sure it isn’t still bleeding off. I changed the fuel filter also. There are valves on the passenger side unit. I believe the fuel pump pushes fuel over to the passenger side unit and then to the injectors after the fuel is filtered. In my case the issue is probably on the passenger side. I will check fuel rail pressure and report back.
Neutral
Joined: Apr 2020
Posts: 1
Likes: 0
My MCS has about 111K on it, and it has had two problems for awhile.
1. Rough idle on cold start. Only happens if the car was sitting overnight. After about 10 seconds it would smooth out perfectly.
2. I have always felt low RPM hesitation, especially with A/C on. I know it is supposed to be a bit hard to accelerate from idle with A/C on, but mine was unacceptable.
After replacing the BPV (did wonders for higher end power), fuel filter, injectors, fuel pressure regulator, PCV valve, and a bunch of other small stuff, I STILL had both of the above problems. I even did the seafoam treatment several times to no avail. My car did run better after all of this, but didn't repair those lingering problems.
I then heard about this carbon buildup cleaner called BG 44K. Found some on ebay for $12 and said what the hell I will try it. Everyone was talking about how great it was on all sorts of car forums, from mercedes, to bmws, to hondas, to mustangs.
After using it for 1 tank, I can confidently say that BOTH my problems have disappeared completely!!!! I have consistent smooth cold starts, and very little hesitation on the low rpm end, even with A/C on.
For anyone else experiencing these problems, go try some. I wish I would have tried this before replacing all those parts. Although the DT BPV is pretty sweet.
1. Rough idle on cold start. Only happens if the car was sitting overnight. After about 10 seconds it would smooth out perfectly.
2. I have always felt low RPM hesitation, especially with A/C on. I know it is supposed to be a bit hard to accelerate from idle with A/C on, but mine was unacceptable.
After replacing the BPV (did wonders for higher end power), fuel filter, injectors, fuel pressure regulator, PCV valve, and a bunch of other small stuff, I STILL had both of the above problems. I even did the seafoam treatment several times to no avail. My car did run better after all of this, but didn't repair those lingering problems.
I then heard about this carbon buildup cleaner called BG 44K. Found some on ebay for $12 and said what the hell I will try it. Everyone was talking about how great it was on all sorts of car forums, from mercedes, to bmws, to hondas, to mustangs.
After using it for 1 tank, I can confidently say that BOTH my problems have disappeared completely!!!! I have consistent smooth cold starts, and very little hesitation on the low rpm end, even with A/C on.
For anyone else experiencing these problems, go try some. I wish I would have tried this before replacing all those parts. Although the DT BPV is pretty sweet.
4th Gear
Joined: Jul 2007
Posts: 350
Likes: 4
From: Westminster, CO
Did anyone ever find a fix for this? My 2005 R53 on 1st start of the day, especially when cold outside, runs very rough for about 20 seconds. Once it gets past this rough phase it runs perfectly fine!
Going to try BG 44K to see if that helps? But have yet to see anyone with a definitive fix?
Thanks!
Going to try BG 44K to see if that helps? But have yet to see anyone with a definitive fix?
Thanks!
6th Gear
Joined: Jun 2009
Posts: 1,306
Likes: 474
From: Atlanta, GA
I don't have an answer to the original issue, but the R53 doesn't have a fuel pump on the motor.
6th Gear
Joined: Jan 2014
Posts: 1,140
Likes: 329
From: Panama City Beach Florida
You can also try cleaning you map an maf sensor with the appropriate cleaner.
A third thing you can look at is the throttle body. They are known for gunking up an causing the throttle body to stick.
6th Gear
Joined: Feb 2018
Posts: 1,680
Likes: 311
Did anyone ever find a fix for this? My 2005 R53 on 1st start of the day, especially when cold outside, runs very rough for about 20 seconds. Once it gets past this rough phase it runs perfectly fine!
Going to try BG 44K to see if that helps? But have yet to see anyone with a definitive fix?
Thanks!
Going to try BG 44K to see if that helps? But have yet to see anyone with a definitive fix?
Thanks!
this could be a number of things. Best to pull codes
1st Gear
Joined: Dec 2021
Posts: 11
Likes: 0
Old thread rehash, the one thing not many commented on but I saw with bad fuel years ago, is the injectors leaking down. If one or two injectors leak down,
it will either flood the cylinder or wash down the oil and you lose compression. The injectors would still work fine,
It is a very slow leak, few hours, maybe overnight
it will either flood the cylinder or wash down the oil and you lose compression. The injectors would still work fine,
It is a very slow leak, few hours, maybe overnight
Neutral
Joined: Apr 2023
Posts: 2
Likes: 0
My MCS has about 111K on it, and it has had two problems for awhile.
1. Rough idle on cold start. Only happens if the car was sitting overnight. After about 10 seconds it would smooth out perfectly.
2. I have always felt low RPM hesitation, especially with A/C on. I know it is supposed to be a bit hard to accelerate from idle with A/C on, but mine was unacceptable.
After replacing the BPV (did wonders for higher end power), fuel filter, injectors, fuel pressure regulator, PCV valve, and a bunch of other small stuff, I STILL had both of the above problems. I even did the seafoam treatment several times to no avail. My car did run better after all of this, but didn't repair those lingering problems.
I then heard about this carbon buildup cleaner called BG 44K. Found some on ebay for $12 and said what the hell I will try it. Everyone was talking about how great it was on all sorts of car forums, from mercedes, to bmws, to hondas, to mustangs.
After using it for 1 tank, I can confidently say that BOTH my problems have disappeared completely!!!! I have consistent smooth cold starts, and very little hesitation on the low rpm end, even with A/C on.
For anyone else experiencing these problems, go try some. I wish I would have tried this before replacing all those parts. Although the DT BPV is pretty sweet.
1. Rough idle on cold start. Only happens if the car was sitting overnight. After about 10 seconds it would smooth out perfectly.
2. I have always felt low RPM hesitation, especially with A/C on. I know it is supposed to be a bit hard to accelerate from idle with A/C on, but mine was unacceptable.
After replacing the BPV (did wonders for higher end power), fuel filter, injectors, fuel pressure regulator, PCV valve, and a bunch of other small stuff, I STILL had both of the above problems. I even did the seafoam treatment several times to no avail. My car did run better after all of this, but didn't repair those lingering problems.
I then heard about this carbon buildup cleaner called BG 44K. Found some on ebay for $12 and said what the hell I will try it. Everyone was talking about how great it was on all sorts of car forums, from mercedes, to bmws, to hondas, to mustangs.
After using it for 1 tank, I can confidently say that BOTH my problems have disappeared completely!!!! I have consistent smooth cold starts, and very little hesitation on the low rpm end, even with A/C on.
For anyone else experiencing these problems, go try some. I wish I would have tried this before replacing all those parts. Although the DT BPV is pretty sweet.
If these issues go untreated. Will it just stop firing altogether? I have these 2 issues. Ive changed coils spark plugs fuel filter but The car just turns over now. Doesnt run.
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