Weak Start
Thread Starter
TECH Apprentice
Joined: Jan 2015
Posts: 303
Likes: 53
From: UAE
Weak Start Hey guys, hope you’re all doing well.
My car is a 2002 WS6 and last year (July 2025) we’ve had an unfortunate death in our family and I got sick at the same time so I had to leave my car parked for 3 weeks, after that I started it and I felt that the start up was weak which is understandable but over the next few weeks I noticed that cold startups were a bit weak and not as they were before, now when the car is hot after running an errand and I go to start it again it would start even a lot weaker and it would start on the 2nd try. Last Sep 2025 I was driving the car and when I stopped at a red light it started to shake and vibrate like it had an aftermarket cam, luckily I was near my home,so I parked the car, a friend told me to disconnect the negative battery cable and wait a few days then re connect the battery and drive the car, the startup was a bit weird and didn’t start till the 3rd time, the vibration and shaking were gone but I had to drive the car for sometime so that it would relearn again (don’t quote me on this).
Now the car is at the shop for some work to be done and he suggested to change the Crankshaft position sensor, a friend suggested to drive the car everyday for a week and this issue will go on its on as it seems it’s a tuning problem but my car is untuned, after researching on the website it seems that this might be a lot of things and not just one part in particular ( fuel filter - battery - crankshaft position sensor- fuel pump …etc) one thing to note is that my fuel gauge has been acting up for over a year now and it gives me inaccurate fuel reading , so it might be the fuel pump but I’m not sure. My car has bolt ons (exhaust - SLP lid and k&n filter, stock tune)
I appreciate your help on this guys. Many thanks
My car is a 2002 WS6 and last year (July 2025) we’ve had an unfortunate death in our family and I got sick at the same time so I had to leave my car parked for 3 weeks, after that I started it and I felt that the start up was weak which is understandable but over the next few weeks I noticed that cold startups were a bit weak and not as they were before, now when the car is hot after running an errand and I go to start it again it would start even a lot weaker and it would start on the 2nd try. Last Sep 2025 I was driving the car and when I stopped at a red light it started to shake and vibrate like it had an aftermarket cam, luckily I was near my home,so I parked the car, a friend told me to disconnect the negative battery cable and wait a few days then re connect the battery and drive the car, the startup was a bit weird and didn’t start till the 3rd time, the vibration and shaking were gone but I had to drive the car for sometime so that it would relearn again (don’t quote me on this).
Now the car is at the shop for some work to be done and he suggested to change the Crankshaft position sensor, a friend suggested to drive the car everyday for a week and this issue will go on its on as it seems it’s a tuning problem but my car is untuned, after researching on the website it seems that this might be a lot of things and not just one part in particular ( fuel filter - battery - crankshaft position sensor- fuel pump …etc) one thing to note is that my fuel gauge has been acting up for over a year now and it gives me inaccurate fuel reading , so it might be the fuel pump but I’m not sure. My car has bolt ons (exhaust - SLP lid and k&n filter, stock tune)
I appreciate your help on this guys. Many thanks
Joined: Nov 2001
Posts: 34,564
Likes: 2,472
From: Schiller Park, IL Member: #317
I think you may have a couple of different things going on here.
First off, it sounds like the battery is probably getting to the end of its service life. When it sat for those three weeks it may have discharged enough that it never fully recovered. That can certainly happen to an older battery and would be a sign that it's time to replace it or at least have it load tested.
Secondly, and this really shouldn't be related to the "weak" starts which sound like a battery issue, you have mentioned having to try 2 or 3 times to get the engine to start (in addition to some rough idling). Since you didn't mention any codes (SES light) being present, I wouldn't suspect the CPS (Crankshaft Position Sensor) as the culprit here. My first check would be to look at Long Term Fuel Trims (LTFT) with a scanner, and to also check fuel pressure for overall delivery PSI as well as retained PSI during a key cycle (but no engine start). Fuel pressure should be at 58-60psi at all times when the engine is running (under load or not), and it should retain pressure for quite some time after turning the key to "run" even if you don't start the engine. The fact that it's needing multiple start attempts to get running could certainly be a sign that pressure is low and bleeding off quickly after a key cycle.
The issue could also be spark related, but my first diagnostic checks would involve the fuel system (after making sure that the charging system is in proper order - meaning a fresh battery with a good base charge and a healthy alternator putting out good voltage).
First off, it sounds like the battery is probably getting to the end of its service life. When it sat for those three weeks it may have discharged enough that it never fully recovered. That can certainly happen to an older battery and would be a sign that it's time to replace it or at least have it load tested.
Secondly, and this really shouldn't be related to the "weak" starts which sound like a battery issue, you have mentioned having to try 2 or 3 times to get the engine to start (in addition to some rough idling). Since you didn't mention any codes (SES light) being present, I wouldn't suspect the CPS (Crankshaft Position Sensor) as the culprit here. My first check would be to look at Long Term Fuel Trims (LTFT) with a scanner, and to also check fuel pressure for overall delivery PSI as well as retained PSI during a key cycle (but no engine start). Fuel pressure should be at 58-60psi at all times when the engine is running (under load or not), and it should retain pressure for quite some time after turning the key to "run" even if you don't start the engine. The fact that it's needing multiple start attempts to get running could certainly be a sign that pressure is low and bleeding off quickly after a key cycle.
The issue could also be spark related, but my first diagnostic checks would involve the fuel system (after making sure that the charging system is in proper order - meaning a fresh battery with a good base charge and a healthy alternator putting out good voltage).
Thread Starter
TECH Apprentice
Joined: Jan 2015
Posts: 303
Likes: 53
From: UAE
I think you may have a couple of different things going on here.
First off, it sounds like the battery is probably getting to the end of its service life. When it sat for those three weeks it may have discharged enough that it never fully recovered. That can certainly happen to an older battery and would be a sign that it's time to replace it or at least have it load tested.
Secondly, and this really shouldn't be related to the "weak" starts which sound like a battery issue, you have mentioned having to try 2 or 3 times to get the engine to start (in addition to some rough idling). Since you didn't mention any codes (SES light) being present, I wouldn't suspect the CPS (Crankshaft Position Sensor) as the culprit here. My first check would be to look at Long Term Fuel Trims (LTFT) with a scanner, and to also check fuel pressure for overall delivery PSI as well as retained PSI during a key cycle (but no engine start). Fuel pressure should be at 58-60psi at all times when the engine is running (under load or not), and it should retain pressure for quite some time after turning the key to "run" even if you don't start the engine. The fact that it's needing multiple start attempts to get running could certainly be a sign that pressure is low and bleeding off quickly after a key cycle.
The issue could also be spark related, but my first diagnostic checks would involve the fuel system (after making sure that the charging system is in proper order - meaning a fresh battery with a good base charge and a healthy alternator putting out good voltage).
First off, it sounds like the battery is probably getting to the end of its service life. When it sat for those three weeks it may have discharged enough that it never fully recovered. That can certainly happen to an older battery and would be a sign that it's time to replace it or at least have it load tested.
Secondly, and this really shouldn't be related to the "weak" starts which sound like a battery issue, you have mentioned having to try 2 or 3 times to get the engine to start (in addition to some rough idling). Since you didn't mention any codes (SES light) being present, I wouldn't suspect the CPS (Crankshaft Position Sensor) as the culprit here. My first check would be to look at Long Term Fuel Trims (LTFT) with a scanner, and to also check fuel pressure for overall delivery PSI as well as retained PSI during a key cycle (but no engine start). Fuel pressure should be at 58-60psi at all times when the engine is running (under load or not), and it should retain pressure for quite some time after turning the key to "run" even if you don't start the engine. The fact that it's needing multiple start attempts to get running could certainly be a sign that pressure is low and bleeding off quickly after a key cycle.
The issue could also be spark related, but my first diagnostic checks would involve the fuel system (after making sure that the charging system is in proper order - meaning a fresh battery with a good base charge and a healthy alternator putting out good voltage).
