Boost drop? Other issues
#1
05-16-2018 | 07:53 AM
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Boost drop? Other issues
i have a 2008 mcs, completely stock (sadly) and automatic. I’ve had some issues in the past with timing and misfires but had though I had figured it out (just a ignition coil issue that needed to be replaced). I recently replaced my thermostat, myself and my technician friend who is farmiliar with German cars. The next day I had complete loss of engin power due to what I think was vapor lock. Later that day we presumed we got the vapor lock figured out and it was running perfectly expect: my boost typically starts at 25rmp and lasts till 45/50rpm, I did some pulls and noticed my boost kept falling off at about 30rmp. Not really sure what’s going on there or if all of the previous issues I listed have something to do with it? My car keeps having some vapor lock I think when I first start it up in the morning. I’ve only had my car for a year and am still learning things so give me a break if it sounds like I don’t know what I’m talking about. I’m new at this! Any ideas would be appreciated
#4
05-16-2018 | 11:10 AM
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#6
05-16-2018 | 11:46 AM
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That is the next logical step. If it isn't the temp sensor then the next step would be the radiator itself and replacing that. Hopefully it is just the temp sensor. Low coolant temps likely means the ECU is cutting boost to protect the engine. You will know shortly!
PS-if it's not too late and they are still in there, you may want them to replace the oil pressure sensor as well. Same location and an inexpensive part that typically fails around the same time a temp sensor fails.
PS-if it's not too late and they are still in there, you may want them to replace the oil pressure sensor as well. Same location and an inexpensive part that typically fails around the same time a temp sensor fails.
Last edited by 08miniS08; 05-16-2018 at 11:54 AM.
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#7
05-16-2018 | 04:06 PM
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#10
05-18-2018 | 10:31 AM
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From: Harvard, MA
How are you monitoring boost pressure?
I doubt you had vapor lock in the usual sense. What were the symptoms (other than power loss)? The rotary cell pump used in these and many other fuel injected cars essentially aren't susceptible to vapor lock.
If your cold starts require several restarts, that is a pretty solid indicator that the HPFP (High Pressure Fuel Pump) is on its last legs. These can be rebuild - search NAM.
Get a Blue Tooth OBD II dongle and an app for your phone that will display live data and monitor fuel pressure during a cold start, post pressure data here. Then lots of people can offer completely uninformed opinions as to the cause
.
The loss of boost you describe has a number of causes, but since it is coupled with a thermostat change I would also cast a jaundiced eye on the vac hoses. You can replace these very cheaply by buying hose from parts store or (not so cheap - $50) a kit from Mini. Make sure you did not cross couple any sensor plugs near the T'stat.
Additional thoughts ( not related to the above): Treat the vacuum pump as a wear item and replace by 80K. The Pierberg after market one if fine.
I doubt you had vapor lock in the usual sense. What were the symptoms (other than power loss)? The rotary cell pump used in these and many other fuel injected cars essentially aren't susceptible to vapor lock.
If your cold starts require several restarts, that is a pretty solid indicator that the HPFP (High Pressure Fuel Pump) is on its last legs. These can be rebuild - search NAM.
Get a Blue Tooth OBD II dongle and an app for your phone that will display live data and monitor fuel pressure during a cold start, post pressure data here. Then lots of people can offer completely uninformed opinions as to the cause
.The loss of boost you describe has a number of causes, but since it is coupled with a thermostat change I would also cast a jaundiced eye on the vac hoses. You can replace these very cheaply by buying hose from parts store or (not so cheap - $50) a kit from Mini. Make sure you did not cross couple any sensor plugs near the T'stat.
Additional thoughts ( not related to the above): Treat the vacuum pump as a wear item and replace by 80K. The Pierberg after market one if fine.
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