hot start issues

[fritzgator]

99 c4 6 speed, when hot takes at least 30-40 seconds to fire up and then very low idle which takes another 10-15 secs. sometimes when it fires up it has no throttle response either. but shutting off and restarting again corrects that. To get it start quicker i have to fully press accelerator for 3-5 seconds and try to guess when its starting to avoid revving to much. I changed the crank sensor already to no avail . ONLY difference i noticed was the hot idle was a little better. it had been idleing around 600-650. now normal 850-900. I was thinking possibly throttle pos sensor but cant seem to locate it. unplugging MAF causes idle to drop so I believe its functioning properly. No codes and car runs great otherwise. a bit more complicated than my previous 83 SC.

[rfuerst911sc]

How many miles ? Original injectors ? Sounds like fuel pressure is dropping . The injectors may be " bleeding down " when hot . Original fuel pump ? It could be on the ragged edge of needing replacement .

I would start simple , add some good fuel conditioner and fresh gas to the tank . Techron total fuel system cleaner is a good one . Run her hard and burn half a tank . See if any improvement with the hot start . Diagnose further if needed .

[Anothray099]

Just YouTube change solinoid on starter. Tons of videos and all starters are basically the same.

[fritzgator]

injector cleaner is part of my regular maintainance schedule. wasn't looking like injectors as it would hot start or lack of after only a couple minutes, not much time for leakdown BUT acted like vapor lock, hence holding down acc. pedal to have to get her to start. So I looked into causes of that symptom. What came up was check valve in fuel pump assembly and faulty regen valve allowing vapors into intake. Did a f.pressure test and had good initial pressures, running and residuals all checked out.(Much easier to test than the SC) With the regen valve being reasonably priced for the A/M part @$47 i took that gamble. BINGO swapped it out over weekend and 3 long 45 min runs with 20 minute stops no issues, drove to work today made a lunch run and moved it to wash bay to clean her up, alls well. 90-95 deg F here in La.so we're gonna call this one Fixed... for now. next project is replacing chain tensioners and cam chains and ramps

[pilot4fn]

Is the issue same or worse after filling the tank? If yes, there is a good chance that the evaporative valve under the intake runner is bad - constatly open and it allows tank fumes to enter the intake manifold and basically floods the engine untill you crank long time with throttle open to 'flush' the engine clear from gas fumes.