Engine/electrical problems in 2000 Toyota Sienna.

[cj123]

We have a 2000 Toyota Sienna XLE that we are having a series of charging system and engine issues with. The main symptoms right now are that the engine seems to be “dragged down”, ie.as soon as you let off the accelerator the tachometer almost instantly drops down to idle speed and you can feel the vehicle is losing speed unusually fast and isn’t coasting like it should. As soon as you put the pedal back down the tach jumps back 2000-2500 RPM. We’ve also noticed when coming to a full stop the tach briefly drops down to 600 RPM, nearly stalling, before coming back up to about 800rpm. Also, it seems that engine doesn’t have the power it used to and has to be revved higher before the transmission will shift. The other symptom we’ve noticed is that the blower fan slows down and the lights dim whenever slowing down to a stop and when sitting at idle.
In the 2011 we had spark plugs replaced and the fuel lines cleaned (not the fuel tank additives, but the actual pressurized solvent hooked up to the fuel rail), so we don’t think it would be either of those two things. Also, since the summer of 2010, we’ve have gone through roughly 5 different alternators in the van. We’ve had various problems that we linked to a faulty battery charge (car not starting, headlights getting dangerously dim, etc.) and replaced the unit hoping a new one would fix all our problems. However, after replacing the most recent one a month ago and still experiencing problems with the engine we are starting to suspect something else is going on.
We live in a rural area where the only dealership/garage we have any faith in is several hours away and we would like to avoid the cost of dealership repairs if at all possible, so any ideas on what could be the problem would be greatly appreciated.



Thanks!

[TierOneSupplier]

A couple of questions to kick things off:
1) how old is the battery?
2) what kind of alternators are you installing when you're buying replacements?

Like you, we've had more than one alternator replacement. The biggest disappointment came from a Denso remanufactured unit which failed in under a year.

Do you have a voltmeter? If so, it would be useful to know the voltage across the battery terminals at the following times:
1) after the van has been sitting for several hours, without running
2) while the van is in Park and idling.