How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask 350matt Your Own Question
350matt, Engineer
Category: Mitsubishi
Satisfied Customers: 20357
Experience:  Mechanical Engineer BEng Hons 22 years experience in car engine industry, 10 years in formula 1
Type Your Mitsubishi Question Here...
350matt is online now
A new question is answered every 9 seconds

Are you a real person? I drive an evolution lancer 5. I

Customer Question

Are you a real person ?
JA: I'm an assistant to the Mitsubishi Mechanic. I work with them to help customers like you.
Customer: I drive an evolution lancer 5. I changed the alternator out. Now I have a rough idle and the car dies when under 1K rpm
JA: Is the rough idle intermittent or consistent?
Customer: Consistent . It starts fine and run smooths but soon as I let off the throttle it rpm blimp then the car stalls. I was told I have to let the car re learn itself
JA: What year is your Lancer?
Customer: 1998
JA: Are you fixing your Lancer yourself? What have you tried so far?
Customer: It just started yesterday.
JA: Anything else you want the mechanic to know before I connect you?
Customer: My car drove normal before brining it in for an alternator swap. Now it idles out and dies under 1K rpm
Submitted: 20 days ago.
Category: Mitsubishi
Expert:  350matt replied 20 days ago.


I'd suggest to remove the auxiliary belt again and turn the new alternator over by hand feeling for any rough or tight spots as you can sometimes get a faulty part from new

if thats OK then I'd suggest to check for an air / vacuum leak

after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allow the engine to rev up when not desired causing rough running.

As its a mechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane around each joint in turn. If the engine rev's up you've found your leak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Expert:  350matt replied 15 days ago.


do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. I am only paid for my work on this question if you rate my answer, using the star system at the top of the screen. Please do not forget! Thank you

Related Mitsubishi Questions