I have a 99 plymouth voyager (w/ a replaced 3.8 engine) apprx: 100k miles, with check eng light on all the time; I can live w/ ck eng light on, but what scares me is that the ABS light comes on once in a while and when that happens all the gauges on the dash go off... the speedometer, gas indicator etc and thats not good. what can I do, please help...

Kind of sounds like a power control module.

The warning light is telling the engine oil pressure is below 10psi.
The problem could be a faulty pressure switch, or the engine could really have low oil pressure.
You can replace the switch, or check the pressure with a mechanical gauge and see what happens.

Take to local auto parts store and they will usually run codes for free and from there you can find the most likely source of the problem area.

No. But if your that far into the engine it is very little more that you need to remove to replace it. If it has never been replaced and you have more than 50,000 miles I would recommend replacing it.

if thi plymouth voyager as a 3.3l eng it does not have a timing belt it as a timing chain does not require any maintenace as all like the good ol days ..if it as a 3.0l eng then it as a rubber timing belt that control the valve timing that reqires replacing every 80 to 100, 000 miles make sure you know what engine this van as if its a 3,3l it wi say it on top of intake or 3.5l is the same they both have chain ...3.0l does have a timing BELT

HAVE CAR SCANNED COULD BE FAULTY IDLE SPEED CONTROL.FAULTY EGR VALVE OR BAD FUEL INJECTOR.

just because the check engine light is back on, it doesn't necessarily mean it is for the same problem. it could be, but would need to pull codes again to find out what its for. literally hundreds of different codes could turn on check engine light. also, was original code for "insufficient egr flow" or "excessive egr flow"? it makes a difference.

have you check your battery connections and the ground to the engine and body

Have you had your brake light sensor replace. They have a recall on it. Change out your drive belt and it should make the noise go away. As long as it's cooling(a/c) i would not change compressor.

My first instinct tells me timing chain or belt, but it could be a vacuum line loose, cracked or disconnected. Using a stethoscope, or a length of gasline hose held to your ear, and with the engine running, listen for a hissing sound. Be sure and wiggle all the hoses you can. You might make one hiss. If you don't find anything, get a timing light, and check your timing marks. They should stay in basically one spot. If it's jumping around a lot, you need a new timing chain or belt. Good luck.