Hello all,
I acquired a 1994 Estima S/C 4WD last year, and its a blast to have two drastically different vans to compare and of course drive/work on. This is a rhd van, but for all other intents and purposes it is pretty close to identical to an Alltrac S/C sold in America.
Oddly enough, this van has given me way more problems than my 2wd with 3 times the mileage. However, there are a few larger issues that are plaguing me and being difficult.
The current problem on the chopping block is something I find very odd. I noticed a few days ago that when I tip into the throttle on the highway to avoid losing speed going uphill, that the van seems to fall flat on its face. I can feel it slow down or lose power, and feel subsequent jolts through the seat and floor; almost like it is misfiring or something similar. The van only has 52k kms on it (roughly 31k miles), but due to what I know about the van's history I elected to change the spark plugs, wires, etc. The van is pretty much all original, besides a few obvious things. From what I was told by the previous owner, it was primarily used for short trips back in Japan; followed by use as a mail delivery truck by the previous owner himself. Lots of low speed, short trips, and tons of idle time; nothing like the balanced or primarily highway mileage I'm used to in used cars.
I found that at one point, someone had replaced the plugs with Denso Iridium (likely when the van was imported to the US), which were visually worn out a bit. The rest of the ignition was 100% original.
I swapped the plugs out for NGK Platinum, and replaced the distributor cap/rotor and wires with NGK as well. Same stuff I put in my 2wd Previa that has 230k miles.
This does not seem to have fixed the problem, which I was kind of expecting; but I am glad I know the ignition is sorted anyhow as it seems to run a bit stronger and idle smoother. I did not see any signs of the valve cover or distributor o-ring leak, so its good there.
I did verify that this issue seems to occur only in 4th gear. It is not limited to hills, nor is it limited to speed; the two key factors are adding throttle and being in overdrive.
My two leading theories are that the van is 4WD, perhaps the engine doesn't particularly like being loaded up in overdrive with this drivetrain. My 2WD van has absolutely no qualms with cruising on the highway in 4th, especially when using cruise control; this is my first all-wheel drive vehicle, especially being full-time, so I could just have unrealistic expectations of what is reasonable for the drivetrain. My other theory is that there could be some kind of issue with the supercharger system; perhaps when I place this load on the engine, it tries to engage the s/c clutch but the intake stepper motor does not open?
It is not a primary suspect of mine currently, but I would not be surprised if this fuel related.
I will be digging into my US FSM for some supercharger related things to test, but figured I'd post here for other suggestions and thoughts.