Hi,

I have a strange issue that I can't seem to figure out. Every now and then after I've driven for a while, stopped and turned the car off and then tried to start the truck when it is hot, it will run rough idle will go quickly from 750 to 0 and it will stall, if it gun the gas and get going, idle goes up and it acts like normal again. It does this about once a week, most of the time it starts right up like normal. It never does this when the car is cold. Things I can rule out.... (1997 Discovery)

Fuel pump is new.
Fuel pressure regulator is new.
Tested the fuel injectors and they are not leaking, also the o-rings on the injectors are new.
Fuel Temp sensor is new.
Coolant Temp sensor is new.
Stepper motor is new.
TPS is new.

I'm thinking maybe I'm getting vapour lock, but why would it just start happening? Are there any other sensors that could be causing this at random times? This never leaves me stranded, but sometimes it's a pain when you start it up and it stalls right out. Any help would be great! Thanks!

T
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97 Discovery

 

Have your base idle adjusted if you havent already, I had a problem like this one time, But instead of it shooting from 750 to 0 it would slowly slip to 0 and stall. I replaced the battery and never had the problem again, Had the base idle adjusted also. The battery is what i think solved my problem... Maybe check your battery?

 

I put a new battery and alternator in in August so that shouldn't be the issue. Base Idol was done at dealership around then too. Would your problem only happen once and a while also?

 

With the new stepper motor, you need to have the stepper and ECU reset or you won't have crap for an idle.
Also, go replace your fuel filter.

 

The stepper motor was put in before I had the adaptive values reset so that should be fine, it idle was well over 1500 before that.

 

It would only happen once in a while, And then more and more i noticed it happening more often.

 

You cannot vapor lock a fuel injected engine, vapor lock is when the fuel inside the mechanical fuel pump gets hot enough that the fuel inside it turns to vapor and thus cannot be pumped to the engine.
Fuel pumps pump liquid not vapor, thus it "locks" up.

Now that that is out of the way...it sounds like your alarm spider is acting up.

 

http://forums.lr4x4.com/index.php?showtopic=86

 

Thanks for the link as I'm sure that the spider unit will break soon also, along with everything else on the truck. I don't think that this has anything to do with that though, it doesn't really cut out, it just starts and dies, only when the car is hot and usually after 15-30 minutes. If I go to start it right away, it usually starts. Also, if I give it gas I can keep it running and after 20 seconds or so it runs like normal with no problems. I'm going to try a new fuel relay, I was reading on another post that sometimes faulty fuel relays act this way.

 

Please let us know when you get it figured out.