I just bought a 99 ford explorer, there are couple issues here.
The car makes clicking sound, i don't know if it's the timing chain(if it's a chain and not belt) slacking
or hydraulic lifter... anyways, the real problem lies in the actual driving.
The car will rev high when it's in neutral but when i'm driving, i'll floor it but
will not get any decent acceleration outof the car. The top speed is pretty much like
120km/hr, and when i floor it it feels like the car jerks stops jerks stops jerks stops repeatedly
instead of a continuous acceleration... The previous owner claimed that there is a new transmission so
i really don't know what this is... Does anyone know?

 

High miles? - get a new converter. The clacking is your valves and can be caused by the converter. When a converter clogs with carbon and oil ejected by a high mileage engine the exhaust backs up into the engine block and your oil gets high amounts of exhaust deposits making the oil black and ruining seals in the engine (like the small ones in hydraulic lifters). Therefore they clack because they're failing (or beginning to). After you change the converter (if that is your problem) change the oil and filter. It's either the converter or an electronic sensor - and sensors are harder to diagnose without a code reader (and even so code readers have been known to be wrong). If it were a timing chain or belt it would not run, more than likely. Although if you have high miles (over 100,000 ) you may want to get it checked if it's a belt. Chains last 150,000 - 200,000 miles or more (which is whylots of companies aretrying to phase them out). P.S. always buy the highest quality belt or you'll be sorry when you have to do it over a month later.

 

Thanks a ton, your explanation makes perfect sense.
The car is a high mileage car, 160,000 miles.I will get right on it before i damage any more seals. Do you know if there is any way to diagnose whether it's the catalytic converter or not? It makes sense that clog can cause the car to shake, jerk and stuff upon acceleration + check engine light...but if there is a way to diagnose catalytic converter before replacing that'd be perfect.

 

Wait until it's very well cooled off and start the engine. Immediately go to the tialpipe (it should be cold) and clamp your hand firmly over the end. If your hand isn't easily blown off you have a problem. You can also try this when it's hot - just replace your hand with a small flat piece of board.

 

wait i just thought about this.... the car revs fine when i put it in neutral or park though...
i'm left quite confused now... hmm... is the exhaust heavier when it's actually driving? but then again
i can't see how it could be more pressure upon actual driving

 

Revving tells you nothing because the exhaust can back out through the engine by blowby and intake exhausting if your converter is clogged. It can run fine - just lose power gradually until it reaches it's worst point. If the motor oil gets dirty and black that is a sign of it. The difference between revving in park or neutral is that the transmission is not engaged and the engine isn't powering anything therefore it has extra power left over from doing nothing to expend on keeping running. You mentioned a new transmission - you may want to check (just to be safe) that the shop didn't do a dum dum and forget to put the trans. fluid in.

 

P.S. Don't forget to check the fluid the engine must be warmed up fully and in Park.

 

It sounds as if you are having symptons that sound similar to old carb engines misfiring through the carb. You may also want to check ingition coil packs. A Chilton manual will tell you the resistance specs for the coils. Failing high mileage coilswill also tend to have these same type of symptons, as well as dirty fuel filters.