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 Matt Your Own Question

Matt, Mechanical Engineer
Category: Toyota
Satisfied Customers: 20380
Experience:  BEng hons Mech engineering, in auto industry 22 years
Type Your Toyota Question Here...
Matt is online now

I own a previa 1998 model 2.4 petrol. it has LPG gas fitted.

Customer Question

I own a previa 1998 model 2.4 petrol . it has LPG gas fitted . when starting from cold in mornings ( on petrol) engine is Hunting then revs up & down 500 to 600 refs till warm then auto onto LPG & runs sweet . Please any ideas
Submitted: 3 months ago.
Category: Toyota
Expert:  Shantal-Mod replied 3 months ago.
I'm Shantal and I'm a moderator for this topic.
I've been working hard to find a Professional to assist you with your question, but sometimes finding the right Professional can take a little longer than expected.
I was checking to see if you had already found your answer or if you still need assistance from one of the Professionals.
Please let me know if you wish to continue waiting or if you would like for us to close your question?
Thank you,
Expert:  Matt replied 3 months ago.


this could be a vacuum leak after the MAF (mass air flow) sensor thats mounted on the air intake pipe

any air pulled in here post meter isn't 'seen' by the ECU and so not compensated for and results in the engine running roughly and hunting as you describe

the best way to locate an air leak is to have the engine running and then spray lighter gas around each possible joint / rubber hose etc post MAF

if there's a leak then the engine will pull the gas in and rev up

now its not as dangerous as it might sound as you need a naked flame or spark to ignite the gas and I've used this method for many years without incident

usually this sort of thing is a cracked or perished rubber vacuum hose, so can be repaired very cheaply

Expert:  Matt replied 3 months ago.


do you still need help?

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

What Customers are Saying:

  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
< Previous | Next >
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
  • Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible. Charles
  • As a single woman, I really appreciate an excellent and affordable opinion.
    Thank you Geordie, I will not hesitate to contact justanswer in the future!
  • Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, do indeed know your stuff. Jim
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C.
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex

Meet The Experts:

  • Matt


    Mechanical Engineer

    Satisfied Customers:

    BEng hons Mech engineering, in auto industry 22 years
< Last | Next >
  • Matt's Avatar


    Mechanical Engineer

    Satisfied Customers:

    BEng hons Mech engineering, in auto industry 22 years
  • Mike Kelly's Avatar

    Mike Kelly

    Toyota Mechanic

    Satisfied Customers:

    17 years experience as an auto mechanic, foreign and domestic. 5 years running my own repair business.
  • indy-tech's Avatar


    Import tech

    Satisfied Customers:

    Import technician .
  • Ross's Avatar


    Diagnostic and repair technician

    Satisfied Customers:

    Licensed diagnostic and repair technician
  • Rob's Avatar


    ASE Certified Technician

    Satisfied Customers:

    30 years trade experience
  • uk_iaibal's Avatar


    UK Car Mechanic

    Satisfied Customers:

    Verified Car Mechanic.