general engine question 4cyl Mitsubishi

[DSRTRDR]

'92 Mitsubishi Expo clone 2.4 liter 4cyl fuel-injected 170,000 miles, computer module replaced once (around 100,000 miles or so)

it's running like a champ except for some sort of hesitation around 2000-2500rpm at steady speed or coast, goes away when under load or revving higher

present whether engine is cold or warm

the vehicle is typically driven at rpms below it's optimum (which I believe to be somewhere around 3500rpm), meaning high gears low revs

for the past 5,000 miles it has seen more city traffic and not a lot of highway driving

does somebody have an idea where to start ?

 

[ellington12]

if you have a service manual, i'd check for codes first.

how does the car idle?

something else you can try:

get the car to that point between 2000-2500rpm where it hesitates and then manually downshift the tranny but keep your foot steady on the throttle. (i'm assuming this is an automatic?) cruise for a bit at steady throttle at this higher rpm and see if the hesitation is still there. basically this will help narrow down whether it's a throttle angle issue or rpm issue. if the hesitation is still there at that same throttle angle even though the revs are higher, i'd probably take a look at the throttle position sensor.

i had a very similar problem on my 73 benz, ( felt like slight misfiring at steady cruise,) and after checking all of the basics plus just about every sensor, turned out to be a bad throttle switch (essentially the same thing as a throttle position sensor.)

be sure to check all of your basics but if at all possible, check for codes first.

 

[DSRTRDR]

if you have a service manual, i'd check for codes first.

how does the car idle?

something else you can try:

get the car to that point between 2000-2500rpm where it hesitates and then manually downshift the tranny but keep your foot steady on the throttle. (i'm assuming this is an automatic?) cruise for a bit at steady throttle at this higher rpm and see if the hesitation is still there. basically this will help narrow down whether it's a throttle angle issue or rpm issue. if the hesitation is still there at that same throttle angle even though the revs are higher, i'd probably take a look at the throttle position sensor.

i had a very similar problem on my 73 benz, ( felt like slight misfiring at steady cruise,) and after checking all of the basics plus just about every sensor, turned out to be a bad throttle switch (essentially the same thing as a throttle position sensor.)

be sure to check all of your basics but if at all possible, check for codes first.

thanks for the suggestions

some more info:

idle is smooth, no funny noises, no irregular sounds, no knocks or so

this is a manual transmission; downshifting will result in higher rpm, and the hesitation goes away

your symptoms sound like the same, though

and: I have no equipment to check for codes

I guess, I'll have to leave the actualy diagnosis to the dealer, then, but I first need to understand what mumbo jumbo they might be telling me would in all likellihood be bull**** ;p

 

[ellington12]

you can check codes with an analog volt meter but you'll still need the manual to interpret the codes.

local library perhaps? the main library where i live has a pretty extensive selection of auto repair manuals.

you could also try searching the internet for a site like this devoted to mitsus...

 

[DSRTRDR]

you could also try searching the internet for a site like this devoted to mitsus...

tried that already - slower than the Buick forum

seriously: no information out there on this problem

 

['74 UA FJ]

What does the hesitation feel like? A skip?

 

[DSRTRDR]

like if you suddenly took the foot off the gas

Ellington's bet sounds right-on