Taking a punt here...
Vehicle: 1993 Hilux Surf V6 petrol 3VZ-E
It has a misfire / hesitation under load, at lower revs. I have researched this for hours on lots of different forums - particularly US / Canada - and the problem is described lots of times, but solutions are not forthcoming. Lots of guys have done the usual - new dizzy cap, rotor, HT leads, but the problems persist. Some have done this, then replaced all their vaccuum lines. Problem persists. I am very reluctant to throw money at it and repeat the same mistakes.
Vehicle had the head gaskets replaced under the recall. No coolant loss, no oil in water, or vice versa. No steam out the pipe other than when warming up.
Symptoms: when the vehicle is cold, it starts first time and drives away fine. As it reaches normal operating temp, a hesitation / miss starts under load, i.e. start of a hill. Sometimes the hesitation starts sooner rather than later. Once the revs have picked up the engine runs normally.
At idle, stationary, blipping the throttle induces a hesitation / miss right away. It's very obvious. Some days its much worse than others, and it stumbles a lot. Other days its a minor miss and not too bad, but noticeable.
Today I cleaned the rotor and dizzy contacts, and replaced the spring that controls the movement of the graphite electrode under the HT line into the cap, that sits on the rotor. I really thought that was it - problem solved - drove off coldish and was fine, but after 10 mins or so the miss came back with a vengeance.
A highly experienced mechanic told me that they can leak around the throttle butterly shaft and cause a flat spot. Again, reluctant to start taking it all apart unless there's some way of finding evidence.
Have checked throttle position sensor, air flow meter, vaccuum lines, etc. Would have simply replaced the HT side of things by now were it not for the reports that this hasn't solved it.
Do any of you fellas have a suggestion? Some experience of solving a low revs "load" type miss that didn't involve the HT leads, dizzy cap, rotor? Is there something else that I should be checking?
I know this kind of question is a bit vague, could be lots of things, but I'm always amazed at what this forum has been able to solve over the years...
cheers
Dave