vebong

Recently replaced my alternator since lost power a few weeks ago and car was fine for a day or two when oil pressure red light flashed periodically; when the light flashed, RPM dropped when at stop light below the normal approx 750 RPMs to around 500 and car shakes a little; took her to mechanic and dude just added two quarts or so of oil and told me to keep oil on hand since engine leaks and was running low. The good thing was that the light went away for all this time, but started to experience symptoms again; the engine RPMs drop when at stop signs, and the car is not accelerating as smoothly as before. Wondering what the issue may be(fuel pump failing??). Also, I once attempted to start the car, it came on for a minute or so, and then RPMs dropped to zero, and engine went off while all the lights{electrical) stayed on. Took the key out and restarted, and the car operated as normal with the periodic drops in RPMs at stop lights. Sidenote, already changed my fuel injectors last year so assuming that is not the issue. Just wanted a few ideas before taking her into the shop again for diagnosis so I'll have a baseline of speaking to the technician.

Thanks

03_GLE

If nothing was experienced like this PRIOR to getting your alternator changed, then perhaps the "new" alternator you put in is defective, or it's not wired up properly or securely enough to emit enough power to keep the entire vehicle running smoothly. One way to check is to start your car, and then unplug the battery once it's idling. This would show what's providing the car power. If the alternator is good, the car will continue running. If not so good, it'll sputter and shut off shortly thereafter. I've never performed this personally (observed others on their cars troubleshooting this method), so I would recommend having someone knowledgable enough to tackle this with, or have a mechanic help you to avoid any electrical shock/ shorting of the car.

What other work have you done to the car during this time leading up to the experience you're describing? One thing that's easy to rule out by checking is the butterfly piece controlled by when you give the car gas to go. The name of the part escapes me - Throttle Position Sensor? -(waiting for my coffee to brew ) but I recall on my '01 the screw unwound a bit, and was causing my car to idle low similar to the range you've mentioned. It's next to the throttle body. BE CAREFUL! There are two screws/wires that BOTH look identical. One is for the actual throttle, and the other is for the cruise control cable. IIRC when engaging with the appropriate one, it'll supply power to the engine as though you're mashing the gas pedal. I think the proper one is engaged by itself, and the cruise control one (when engaging it) couples both cables together for cruise control purposes -- in order to possibly help distinguish the two. Simply screw the piece until your RPMs hover where they should for idling purpose; this would help having a friend or someone gauge the RPMs while the other performs the aforementioned. I am not 100% certain this is your case, but one area that can be ruled out if this is not the culprit.

Another option would be to either check how dirty the throttle body is as it can choke the engine if it's severely dirty. OR the MAF sensor may be causing theses symptoms (when was this changed, if ever?). A failing MAF rarely throws a code and a vehicle can function if not too damaged. My '01 I must've driven with a failing MAF for about a year before realizing its being defective, and changed it. The power difference was literally night and day. Off the line launch was "a thing" since before it felt like the car needed a bit of momentum to build speed from a dig. Downshift WOT was not even existent, and I figured it's the way the car was engineered. Was I wrong.

Assuming your oil has been low and the engine is burning oil for some time, this could vault out other gremlins that none of my prior assumptions point towards. Rear main seal leaks are popular depending on how high your vehicle's mileage is, coupled with how great of care the vehicle was shown. What's your oil change/service interval like?

vebong

I bought the car last September 2018, and I haven't put much miles on it yet; the only changes so far are alternator, fuel injectors, velocity sensor(TPS). Have only added oil, but will go ahead and conduct an oil change. Also, will look into the alternator issue. Haven't driven much lately causes worried about it stranding me if I eventually lose power. Thanks for the suggestions

User1

You replaced your alternator. Cool. What are your charge and resting voltages?

vebong

Finally got a "service engine soon" light when attempted to start this evening; the tach popped to 2000 RPMs when initially started the vehicle then settled; then as soon as I shifted to reverse, the car died and all the lights came on the dashboard; gonna get her towed on Monday or get a mobile mechanic to my place

User1

Okey dokey smokey. Let us know how it goes.

scotty64

coil or coils intermittently failing? low idle could be the Idle speed control-FI pot p/n is 161822Y011, this sits on the throttle body its a diaphram which works on vacuum. if the internals of this have failed it can mess with idle. low idle when cold, high idle when at operating temp. throwing this out there as possible reasons.