Boxster hot start issues

[IanT]

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.

[JFP in PA]

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

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.

[IanT]

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