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Auto_Enlightenment
Auto_Enlightenment, ASE Certified Technician
Category: Car
Satisfied Customers: 237
Experience:  ASE Master Certified Technician
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Isuzu Hombre: 96 hombre when I start it ideal up real high.

Customer Question

96 hombre when I start it ideal up real high. If i unplug map sensor it ideals down but backfires and sputter. plug map sensor back in and it real high again
Submitted: 3 years ago.
Category: Car
Expert:  Auto_Enlightenment replied 3 years ago.

Auto_Enlightenment :

Hello, I am a master technician and I would like to try and assist. Please refrain from rating my service until you are satisfied, we can chat for as long as you like. I'd like to start with some q&a to get a better understanding of the situation. Do you have any check engine lights on?

Auto_Enlightenment :

I see you've replaced a few parts concerning idle control/adjustment. Did this same problem exist prior to replacing these parts and is that why you replaced them?

Auto_Enlightenment :

Do you have a digital voltage meter and do you feel comfortable using one for diagnosis with my help?

Auto_Enlightenment :

As I'm sure you are aware the MAP tells the engine computer how much vacuum exists in the manifold so it knows how much fuel and timing to adjust for. With that said, the MAP could be just fine and there may be another condition going on which is causing the MAP to report information to the computer which is causing the idle to surge(i.e. vacuum leak).

Auto_Enlightenment :

Have you checked for any vacuum leaks?

Auto_Enlightenment :

A vacuum leak would introduce false air into the mix which would throw everything off(i.e. air is sneaking in the back door unannounced)

Auto_Enlightenment :

This would change the manifold pressure and the MAP would see it and reflect that to the engine computer in the form of a higher input voltage. The computer sees this higher input voltage as a loss of vacuum/increase in air flow which could cause the idle to surge.

Auto_Enlightenment :

does the idle hunt/surge at all(i.e. go up and down)?

Auto_Enlightenment :

I see that you are offline right now so I am stepping away but will check back periodically. If I am not online when you return to respond then please be patient as I will return as soon as I am notified that you have responded. Thanks. I am here to help and chat for as long as you need.

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