Problem starting when engine is warm

[bovine]

I have a 2006 Jeep Liberty that has recently begun to have problems starting when the engine is still warm from driving. Letting it cool off for 10-15 minutes is usually enough to allow it to start.

The starter will crank and the battery is new, so it isn't an electrical issue.

When cranking, the tachometer does move so I suppose that means that crankshaft position sensor is working.

I've recently changed the coolant, water pump, and thermostat but that hasn't helped. Coolant temperatures seem fine while driving.

Attempting to start in "clear flood mode" (by holding the accelerator) also does not help, so it's not an issue of being flooded.

I've cleaned the intake air temperature sensor with some electrical cleaner, without any improvement. The MAP sensor was replaced a couple years ago (before this problem started), so I would expect it to still be good.

There are no check engine codes, and the engine has never stalled once it has started.

Does anyone have any other suggestions on other things I should investigate?

Video --> https://photos.app.goo.gl/9YuGFs7VbjCWNV8k2

 

[LibertyTC]

Try cleaning the IAC- intake air control...See if that works for ya..
Make sure port is also clean, not all carboned up. .
Link: http://www.jeepkj.com/forum/f202/how-02-03-iac-removal-cleaning-59462/
Also post 10 here: http://www.jeepkj.com/forum/f196/idle-air-control-no-screws-44826/#post475141

 

[Billwill]

There have many posts like this when the engine does not start when hot.

Usually turns out to be a bad Cam or Crank Sensor failing when hot.

You can unplug the sensors and measure the resistance with a Multi meter when cold and the check the resistances when hot...resistance should not change!

Or else simply replace the sensors....I am sure some members here will chime in soon to say which of the sensors is the most likely culprit!

 

[bovine]

Sounds good. I'll try individually testing to see which of the IAC, camshaft sensor, or crankshaft sensor it ends up being. Thanks

 

[Billwill]

Yeah you can heat up the sensors with a hairdryer....make sure when using a Multi meter set on the Ohms scale that you do not touch the lead ends with bare hands as it picks up your body resistance.

 

[bovine]

Cleaning the IAC and replacing the camshaft position sensor did not help. However, replacing the crankshaft position sensor seems to have solved the problem.

There was a fair bit of corrosion building up around that sensor, to the extent that it was actually quite difficult to remove it from its receptacle and to insert the new one.

Thanks again for your help!

 

[LostChord]

Cleaning the IAC and replacing the camshaft position sensor did not help. However, replacing the crankshaft position sensor seems to have solved the problem.

There was a fair bit of corrosion building up around that sensor, to the extent that it was actually quite difficult to remove it from its receptacle and to insert the new one.

Thanks again for your help!

Awesome and congrats. And thanks for posting the follow up!

 

[flytonehundred]

I replaced the Cam and Crank sensors for the same thing a couple years back. Unfortunately, my crank sensor snapped off in the block because of the reason you mentioned. Not a fun night getting it out (ended up putting a screw in it, and slowly prying it out over a couple hours)