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Boxster hot start issues


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My 1998 Boxster suddenly had hot start issues where if left in the sun here in Texas for a few hours would then crank but not fire unless you kept cranking and pressed the throttle. No issues when starting cold. It had thrown some evap leak codes a few times and a secondary AI once but nothing consistent and would also suffer from idle issues if hot start was hard.

 

Having read many threads I decided that it was not fuel pressure related as in my experience fuel pumps either work or they do not and the same applies to the associated relay.

 

I read someone blocked off the valve under the lhs air intake plenum and when I did this the hot start problem disappeared but gave other idle issues.

 

I decided to replace this valve and in the process also decided to clean the throttle body and iacv when I discovered oil in the aos and j tube the aos was replaced 3 years ago.

 

Having replaced the valve and the aos the car appears to be running better than ever.

 

I had no white smoke issues or oil cap pressure test problems and the old valve was in the closed position when I removed it so that may not have been an issue.

 

This whole situation had gone on for many weeks and also gave air leak codes in both banks but using a smoke generator revealed no issues.

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48 minutes ago, IanT said:

My 1998 Boxster suddenly had hot start issues where if left in the sun here in Texas for a few hours would then crank but not fire unless you kept cranking and pressed the throttle. No issues when starting cold. It had thrown some evap leak codes a few times and a secondary AI once but nothing consistent and would also suffer from idle issues if hot start was hard.

 

Having read many threads I decided that it was not fuel pressure related as in my experience fuel pumps either work or they do not and the same applies to the associated relay.

 

I read someone blocked off the valve under the lhs air intake plenum and when I did this the hot start problem disappeared but gave other idle issues.

 

I decided to replace this valve and in the process also decided to clean the throttle body and iacv when I discovered oil in the aos and j tube the aos was replaced 3 years ago.

 

Having replaced the valve and the aos the car appears to be running better than ever.

 

I had no white smoke issues or oil cap pressure test problems and the old valve was in the closed position when I removed it so that may not have been an issue.

 

This whole situation had gone on for many weeks and also gave air leak codes in both banks but using a smoke generator revealed no issues.

 

Welcome to RennTech :welcomeani:

One of the most common hot start related issues is the crank position sensor or CPS.  Located on the side of the bell housing, it is a Hall type sensor that tends to become heat sensitive as it ages.

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I did replace the CPS but as an Electrical Engineer do not hold much faith in a part that works on cold start and even eventually on warm starts. As a matter of interest the tach moves only very slightly on my 1998 and the same is true of my wife’s 2002 S neither goes to 400 rpm as some suggest. I guess my view is the CPS is ok unless it will not start at all as in my case it must have been ok as it sends a signal to the CPU

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