Engine surges on hard acceleration

[g_force58]

Mt 2000 ES has been doing this since I bought it but seems to be getting worse. As it accelerates the engine seems to step up power in stages causing a surge effect that is very noticable and sometimes is so bad it will bob your head back and forth. Has never been this bad before. Cleaned the throttle body, iac checked for vacuum leaks, changed the plugs and wires, rechecked plug gap, inspected tps wiring all with no luck. Anyone have ANY idea what is going on here. The car has no codes stored and gets 28mpg in town and 36 on the highway. Normal driving doesn't cause the problem only on aggresive acceleration.

[occasional demons]

Have you checked the TPS voltage in the WOT position? It might be bad in that last bit of travel, causing the voltage to fluctuate. As long as the voltage isn't too high, it may not set a code. On an NGC set up, probably, but an '00 maybe not. Might try cleaning the MAP sensor end also, or possibly replacing it.

Your parts are 11 years old, so anything is possible. But overall, they do seem to hold up well. AFAIK, all of my sensors are original. The only thing as far as general engine management that has failed me, is the IAC, but it is an actuator.

Your IAC prolly wouldn't have much influence at/near WOT. If stuck open, it will give part throttle response a bit of a boost, as it is giving some additional cfm. But WOT will provide little vacuum to pull a significant amount of air through.

[g_force58]

Ok Bill, didn't think of that one. I did have thoughts of the problem being the tps, have no idea why I didn't check it before. Can you tell me how to clean the map sensor, or is that even possible?

[occasional demons]

Basically just remove it, and check for sludge built up on it. IDK if spraying a solvent based cleaner on it will damage it or not. As oil is mainly what collects in the IM, moisture mixing with it could gunk things up. If anything, I would spray it down with WD40. I doubt there is anything in there that would harm it. It is basically non toxic, so it shouldn't do anything worse than it's current operating environment.

[g_force58]

thank you sir for your input. I will try this and see what happens when the rain stops in about 3 days. Be careful up there Bill, I hear you are about to get another round of snow.

[occasional demons]

That's why I haven't rid myself of the XJ. It might be a fuel sucking pig, but it does prove useful for neon deep snow. Unfortunately, it just means another day of shoveling snow at work.