Running heater causing vehicle to want to excellarate on its on.

[Richard Flickinger]

99 explorer 4.0 sohc. 230,000 miles. My daughter said she had heater running about 30 mins. She said it seemed like it was hard to stop braking, like the vehicle want to excellarate on its on. Was curious if that's possible or what might cause something like that. Could that be cause from vaccuum leak.

Any suggestions or advice on what to check for is appreciated.

 

[Lee's Automotive]

99 explorer 4.0 sohc. 230,000 miles. My daughter said she had heater running about 30 mins. She said it seemed like it was hard to stop braking, like the vehicle want to excellarate on its on. Was curious if that's possible or what might cause something like that. Could that be cause from vaccuum leak.

Any suggestions or advice on what to check for is appreciated.

It sounds like a vacuum leak causing a higher rpm

 

[Richard Flickinger]

It sounds like a vacuum leak causing a higher rpm

If you are thinking a vaccuum leak. Where's a good place to start looking for it. Is the a good diagram for the heating system showing vaccuum lines.

 

[Lee's Automotive]

If you are thinking a vaccuum leak. Where's a good place to start looking for it. Is the a good diagram for the heating system showing vaccuum lines.

Look at the heater control valve and the vacuum ball under the air box also the diagram is on the core support as soon as you open the hood you'll see it

 

[Richard Flickinger]

Look at the heater control valve and the vacuum ball under the air box also the diagram is on the core support as soon as you open the hood you'll see it

Ok. Thanks. I will take a look at it. Do you think that will activate the check engine light for emission

 

[Lee's Automotive]

Ok. Thanks. I will take a look at it. Do you think that will activate the check engine light for emission

If there is a big enough vacuum leak you'll get codes for bank 1 or 2 lean

 

[usapadyra]

Might be worth checking with her what climate control mode she was using. If using the windshield clear function it will run the compressor and that could at least exacerbate an issue relating to a vacuum leak or anything relating to an out-of-adjustment idle since the IAC will open more to keep the engine speed higher for the compressor.

The compressor will run in all modes except the ones circled in red in the pic below.

Did you recently change the battery or have the battery disconnected for any period of time? If so, it may be that the ECM needs to relearn it's idle calibration with the compressor running. There is a process for this. I believe it's as simple as starting the vehicle from cold and letting it idle with the compressor running for a few minutes.

I have had this exact issue (car pulling when coming to a stop) when doing lots of fiddling that involves disconnecting the battery. Sometimes takes a bit of day to day use for it to figure itself out.

Incidentally, this will likely cause hard downshifts when coming to a stop since the engine is spinning faster than it should be during the coast down to stop.