I have a 3.5 l '02 Montero Sport 137,xxx miles that has, what I would describe as, an engine hesitation problem within the first 5 minutes of starting my vehicle.

I notice this problem only on warmer to hot days and NEVER in the winter. It almost feels like a cylinder is mis-firing but never throws any error codes. It happens when slowly accelerating anywhere from 0 to 45 mph and usually happens in a series of 1-10 times before going away once the car is warmed up. I notice it occuring slightly more frequently when going up an incline. I do not notice the problem when at cruising speed.

If I am in the middle of experiencing this issue and I give it a lot of gas (which typically downshifts the vehicle) it goes away. I have not replaced the plugs and wires (I know I probably should but they are not fun to replace!) but dont think that is the issue since I assume I would be noticing this problem year around if I had bad plugs or wires. Am I probably safe to assume this?

Also when iddling at a stop light I sometimes (very rarely) notice a shake/hesitation as well. But definitely much more when accelerating.

Any thoughts/ideas that might be causing this problem?

 

11 year old plug wires

 

you only have 3 and a half cylinders, find the rest of your engine might help!!

but yeah, there are a whole host of things to be checked without knowing the history. plugs and wires, as suggested, also the ignition coil + units, clutch, sensors, bearings..... so many things.

 

Haha! you've never seen a 3.5 cylinder before?! Nice catch... Shouldn't I be able to rule out plugs/wires since it only happens on hot days? I just think if it were plugs/wires, I would experience this year around... or would you say that's not necessarily true?

Should #1 replacement I start with be the plugs/wires?

 

as temperature of a conductor increases, so does resistance.

If the insulation along the way is degraded it will arc to ground which will mean no spark in the cylinder.
It might not be your problem, but a good (relatively cheap) thing to rule out...

 

Replaced plugs and wires and problem still persists... any other ideas?

 

oooh. Bugger.
Some electrical wizardry with the auto.
Or, clutch. Sounds more electric though...

 

Hey DaveZman, I am experiencing the same problems on my 98 montero with the 3.5 engine. I too changed the plugs and wires but it did not help. Please post a reply if you get your car fixed. Thank you

 

Any other ideas?? Anyone?

 

what is the ignition? electric, CDI or coil? you can test coils resistance, electric - as i said, it's wizardry...

compression test, timing check...