Mitsubishi

Mitsubishi repair problems? Ask a mechanic for answers ASAP

Ask an Expert,
Get an Answer ASAP!

1990 2.4 rough ideling in gear. Constinat. Mighty max. Plugs…

Customer Question
1990 2.4 rough ideling...

1990 2.4 rough ideling in gear

Mechanic's Assistant: Is the rough idle intermittent or consistent?

Constinat

Mechanic's Assistant: What is the model of your '90 Mitsubishi?

Mighty max

Mechanic's Assistant: Are you fixing your Mighty Max yourself? What have you tried so far?

Plugs wires rotor cap

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Checked timing belt nd timing thats all good

Submitted: 10 months ago.Category: Mitsubishi
Show More
Show Less
Ask Your Own Mitsubishi Question
Answered in 4 hours by:
9/27/2017
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago
350matt
350matt, Engineer
Category: Mitsubishi
Satisfied Customers: 23,446
Experience: Mechanical Engineer BEng Hons22 years experience in car engine industry, 10 years in formula 1
Verified

Hello
This could be an airleak 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 or brake cleaner 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.

Air leaks are very temperature dependent as gaps can open up as things expand with temperature so depending on how the leak occurs ( on a hose joint with a clamp expansion will help seal and on a vacuum hose expansion ill make a leak worse) so leaks can be better or worse as the engine heats up.

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

Might also be worth cleaning out the idle speed control motor / valve as these get clogged up with carbon and some brake cleaner washed through helps free things off.

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.
if the engine condition is the same then chances are the meter or the connection to it is faulty

It’s also worth cleaning the MAF sensor wires, as they can get coated with dirt over time which then offsets the reading
Use some contact cleaner or brake cleaner to spray onto the wires to remove the dirt – on no account touch the wires with anything as they are very fragile

Ask Your Own Mitsubishi Question
Customer reply replied 10 months ago
Have already checked most of that vehicle only idles rough when in gear park and neutral is fine
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

Hello

when its in gear the engine will be under greater load so if you haven't checked fuel pressure then that would be wise to do so.

if that's OK then I'd say try clamping off the brake booster hose to see if this helps at all

if it does then possibly the brake booster is leaking and so allowing air into the engine as a vacuum leak

Ask Your Own Mitsubishi Question
Customer reply replied 10 months ago
Will check tonight and advise
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

understood

Ask Your Own Mitsubishi Question
Customer reply replied 10 months ago
No vacuum leaks found booster isn’t leaking and fuel pressure is good cleaned map and idle valve still idles very rough in gear and fine in park
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

Ok

if there's a lack of power as well as the rough idle then it would also be worthwhile doing a compression test across all 4 cylinders

but if there's no power loss then check the condition of the air filter and it would also be worthwhile cleaning out the throttle body with a lint free rag and some brake cleaner

I'd also check that the main engine ground connection is tight and clean, do the same for the main battery connections and also there should be a smaller ground wire that runs out of the engine bay wiring loom and is secured to the engine with a ring terminal

Ask Your Own Mitsubishi Question
Customer reply replied 10 months ago
No loss of power at all I’m lost
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

hello

can you check the ground connections and the air filter as suggested?

Ask Your Own Mitsubishi Question
Customer reply replied 10 months ago
Runs rough with air filter removed and ground wire running for cab to block is disconnected I will reconnect and try
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

Ok

just get back to me on this post

Ask Your Own Mitsubishi Question
Customer reply replied 10 months ago
Connected ground wire didn’t help the situation
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

Ok

does the truck drive ok? plenty of power and pulls as it should?

if it does then the fuel pressure is OK , if not then the fuel pressure needs to be checked

if this is OK then

This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;
Airflow meter
Crank position sensor
Cam position sensor
O2 sensor
Throttle position sensor

unplug each in turn and use some switch / contact cleaner spray on the pins to ensure its all grease / dirt free

Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.

Ask Your Own Mitsubishi Question
Customer reply replied 10 months ago
Truck runs great doesn’t even miss when idling in park just shakes so bad when you put it in gear
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

Hello

OK this could be worn mountings - check the tightness of the engine and gearbox mounts and their condition - this is best done by using a jack to take the weight of the engine off the mounts and seeing if any cracks or splits open up in the rubber.Also check the tightness of the mounts bolts

Ask Your Own Mitsubishi Question
Mitsubishi Mechanic: 350matt, Engineer replied 10 months ago

Hi
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

Ask Your Own Mitsubishi Question
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a mitsubishi mechanicLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask 350matt Your Own Question
350matt
350matt
350matt, Engineer
Category: Mitsubishi
Satisfied Customers: 23,446
23,446 Satisfied Customers
Experience: Mechanical Engineer BEng Hons22 years experience in car engine industry, 10 years in formula 1

350matt is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

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 PElm City, NC

used your service this weekend with "Trecers" help. thank you ,thank you, thank you. replaced an A/C fan motor. Local Auto Zone had part. $15.00 "tracer" fee and $40.00 for parts, I saved several hundreds of dollers at a shop. i will recommend you and use you in the future.

David L.Richmond, TX

9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much.

PhilMarysville, CA

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.

CharlesWalnut Creek, CA

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!

SueCharleston, WV

Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff.

JimCastleberry, FL

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

< Previous | Next >

Meet the Experts:

Doug

Doug

ASE Certified Technician

7,002 satisfied customers

Mitsubishi employed and Factory trained ASE certified technician

George H.

George H.

ASE Certified Technician

317 satisfied customers

ASE Master tech 15+ years

Jake

Jake

Automotive Technician

213 satisfied customers

Experienced collision repair technician, Pulaski Tech graduate and DSM hobbyist.

Tim Mohr

Tim Mohr

ase master

209 satisfied customers

30 yrs foriegn and domestic, gas and diesel

Chris (aka- Moose)

Chris (aka- Moose)

Technician

206 satisfied customers

16 years of experience

Mike Kelly

Mike Kelly

Mitsubishi Mechanic

104 satisfied customers

17 years experience as an auto mechanic, foreign and domestic. 5 years running my own repair business.

AMD

AMD

Master Technician

48 satisfied customers

L1 Advanced Level Diagnostics Specialist

< Previous | Next >

Related Mitsubishi Questions
It has gradually lost power over the last 2-3 weeks, had a
It has gradually lost power over the last 2-3 weeks, had a cracked exhaust manifold but replaced it last week, still have the power loss problem. 92 mighty max 2.4 … read more
supermechanic
supermechanic
Service consultant
Vocational, Technical or Trade Scho
10 satisfied customers
I just bought a 1990 mitsubishi mighty max pick up 2.4
I just bought a 1990 mitsubishi mighty max pick up 2.4 liter. It starts right up but after driving it a few blocks it acts like it's out of gas and stalls. After a few minutes it starts up and runs gr… read more
sprinkles08
sprinkles08
Technician
High School or GED
11 satisfied customers
91 Mitsubishi mighty max, 44wd v6. Cranks no start. Replaced
Hello, 91 Mitsubishi mighty max, 44wd v6. Cranks no start. Replaced ecu,coil, transistor, distributer, timing belt, fuel pump, plug wires, plugs. Still no start. Verified timing belt and distributor i… read more
Randall
Randall
Auto Technician / Consultant
Vocational, Technical or Trade Scho
69 satisfied customers
I have a 2001 eclipse with the 3.0 v6 I have the P0335 and
I have a 2001 eclipse with the 3.0 v6 I have the P0335 and P0340 codes. I have checked the plugs and wires going to the distributor. Crank sensor wires had gotten worn against a pulley so I had to rep… read more
roy
roy
Associate Degree
3 satisfied customers
Can't seem to find a replacement flywheel 1998 Montero Sport
can't seem to find a replacement flywheel for my 1998 Montero Sport ES 2.4 liter 5 speed manual. was seeing if there was another flywheel from another car that might be interchangable … read more
Doug
Doug
ASE Certified Technician
Vocational, Technical or Trade Scho
7,002 satisfied customers
Mitsubishi mighty max: 1994 Mighty max hesitates when cold,
1994 Mighty max hesitates when cold, almost dies, backfires till warm. Once warm, runs great. What I have done. Changed out all timing belts, hoses, water pump, thermostat, , cleaned air sensor. Timed… read more
George H.
George H.
ASE Certified Technician
Associate Degree
317 satisfied customers
1990 galant LS, 2.0 engine, 175,000 miles. Erratic idle 1000
1990 galant LS, 2.0 engine, 175,000 miles. Erratic idle 1000 to 3000 rpm, throttle potion has no influence, burning rich. When first started rough idle. New O2 sensor, all new filters, plugs, cap and … read more
Doug
Doug
ASE Certified Technician
Vocational, Technical or Trade Scho
7,002 satisfied customers
Mitsubishi Mighty Max: I have a 1994 Mitsubishi Mighty Max
I have a 1994 Mitsubishi Mighty Max (manual). The truck starts and runs, when I push in the clutch and put it into gear I hear a clicking sound under the passenger side dash, when it clicks it makes t… read more
Randall
Randall
Auto Technician / Consultant
Vocational, Technical or Trade Scho
69 satisfied customers
Mitsubishi Mighty Max: Have a 1990 mitsubishi mighty max 4cyl
Have a 1990 mitsubishi mighty max 4cyl 2.4 ltr. was seemingly running alright. Coming home the other night,started making a knocking sort of noise and lost power,through all gears. Truck still running… read more
kwiggins29059
kwiggins29059
Associate Degree
219 satisfied customers
Mitsubishi Mighty Max: I have 1990 Mitsubishi mighty max.
I have 1990 Mitsubishi mighty max. It ran just fine to get to the gas station, we filled the tank and then it would not turn over. The ignition coil was putting out spark so we moved on to the fuel pu… read more
Steve Porter
Steve Porter
1991 Mitsubishi Mighty Max: $500 and drove it home with no problems
Hi everyone, Last night I just bought a 1991 Mitsubishi Mighty Max 190,000 mi, 2wd 2.4. I picked it up for $500 and drove it home with no problems. Today I did a basic tune up: plugs, wires, filter, c… read more
HondaPlatinum
HondaPlatinum
High School or GED
148 satisfied customers
1990 mitsubishi mighty max: fuel pressure regulator..spark plugs
I have a 1990 mitsubishi mighty max and it has a starting problem. It will either atempt to start or start up and die within 5 seconds. I have replaced the computer, fuel pump, fuel pressure regulator… read more
Doug
Doug
ASE Certified Technician
Vocational, Technical or Trade Scho
7,002 satisfied customers
1992 mitsubishi mighty max: 4cyl..the coil and the distributor
i have a 1992 mitsubishi mighty max 2.4 4cyl notgetting any fire to the plugs so i changed the coil and the distributor and still not getting any fire… read more
Randall
Randall
Auto Technician / Consultant
Vocational, Technical or Trade Scho
69 satisfied customers
1990 mitsubishi mighty Max: 20 miles..park..restart..fuel Filter
Mitsubishi Mighty Max: My 1990 Mitsubushi Mighty Max Stalls My 1990 Mitsubushi Mighty Max Stalls every time I stop when I have been going over 20 miles an hour...If I put her hin park and shut her off… read more
HondaPlatinum
HondaPlatinum
High School or GED
148 satisfied customers
94 mighty max: my timing..manual says..terminal..grounded
I need to check my timing on 94 mighty max 2.4 the chilton manual says there is a terminal that needs to be grounded. where is this located and what does it look like… read more
indy-tech
indy-tech
Shop owner, technician
Vocational, Technical or Trade Scho
11 satisfied customers
3000 GT: bolt..wheel drive..electrical controlsand wiring harness
Can the engine from my 91 3000 GT (3.0 liter V6 24 valve) bolt up (belhousing,motor mounts etc.) to the 5 speed manaul transmission of my 1990 Mitshibushi Mighty Max XXXXXpickup ? The 3000 GT is avail… read more
indy-tech
indy-tech
Shop owner, technician
Vocational, Technical or Trade Scho
11 satisfied customers
91 2.4: seen the other head but I do think they are the same part.
Hello, I am looking to replace the cylindar head on my 95 2.4 mighty max pickup with a head off of a 91 2.4 mighty max engine. Is it the same head? I have not seen the other head but I do think they a… read more
Doug
Doug
ASE Certified Technician
Vocational, Technical or Trade Scho
7,002 satisfied customers
1991 mighty max: it started running rough until it now wont start
my 1991 mighty mac will not start. This started at first only when cold. Then it started running rough until it now won't start at all. I have replaced the fuel pump.… read more
Jettadan1
Jettadan1
Lead mech
Some college
1,421 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x