Leeroy

Hey guys/gals,

I am enjoying this forum a lot. Please excuse my ignorance if it has been mentioned/asked in another thread, but I have researched and haven't found an issue quite like mine, or so I think. Anyways, about 2 months ago, I purchased my 2000 LS with 130,000 miles off of a gentleman on Craigslist. The car's body is pretty beat up but the interior is perfect. It was running pretty rough when I bought it. It seemed to be running rich and I was getting intermittent P0420 codes, but the price was right and I had to have it. I went ahead and changed the oil and the trans fluid. The car was shifting weird and had a heavy vibration from 40 to 50 MPH. After the fluid swap, I went ahead and replaced the trans mount. It was completely separated. This fixed the vibration issue. I changed out the air filter (which was nasty) and replaced all four o2 sensors. Also, I removed the MAF and sprayed it down with some CRC MAF cleaner. I also ran a couple of tanks of 93 octane fuel with some CRC complete fuel system cleaner through it.

When I bought the car, it was making a kind of whirring/droning noise, almost like a power steering pump that was running low on fluid, however, the pitch didn't seem to change much when I turned the steering wheel from side to side, which I believe was due more to the RPM drop instead of the load itself. The noise does change pitch with the RPMs of the engine. The noise is louder inside the car vs. outside. When inside the car, it almost sounds like the noise is coming from inside the console. The car has an intermittent issue with a low idle around 400 RPM at stop lights. After driving around for a while, both city and highway driving, the idle goes up to around 600 to 625 RPM.

So after some more research, I decided to clean the throttle body intake plenum and the 2 big holes and 8 small ones under the vacuum plate. I did not, however, really go wild on the 2 big holes. Also, I went ahead and replaced the engine coolant temperature sensor with an OEM Toyota part. The low idle condition is still present, and I still get an intermittent P0420 and P0430 on my scan tool, but it doesn't throw a check engine light. The car doesn't show any other codes at all other than those two.

So fast forward to a week ago, I dropped off my car with an independent shop beside my workplace that refurbs used cars for all of the big dealerships around town. I know a few of the guys who work there and we repair/replace car audio systems for them. Needles to say, they usually take good care of me. So when I dropped the car off, I told them about the low idle and the noise. I explained that it sounded like a PS pump, but I didn't think it was the problem. I told them that I thought it could be a vacuum leak or an exhaust leak at the Y-pipe, pre-cat. I also told them that I wanted to change out the PS fluid because it was black and change out the serpentine belt and tensioner pulley. They called me and said the PS pump was leaking and needed to be replaced. They replaced the pump, but the droning noise is still present. The low idle condition is still present and intermittent, but for the most part, there.

So when it is all said and done, I am thinking it is either an exhaust leak at the cats(hence the intermittent P0420 P0430 codes, or a vacuum leak (EGR maybe? Does this car have an EGR?), or I didn't spray enough carb cleaner in the two big holes in the throttle body. What do you guys think I should try next? Take the air intake back apart and get at the two big holes on the throttle body some more? Drop the car off with an exhaust shop and have them check the seals at the cats? Check for vacuum leaks? Ultimately, I am pretty confident that it is an exhaust issue, but I'd love to hear some feedback from some of you LS400 Jedi Masters on what you may think it could be. Other than that, the car is awesome! It blows the doors off of my Cadillac Deville, and it rides better, despite being an older car.

timmy0tool

iTrader: (7)

in summary, you're experiencing a low idle issue. you did right in cleaning the passages, replacing the ECT, and basic routine maintenance. when you replaced the trans fluid, what did you use? how much was replaced? drain and fill or full flush?

the whine could be your fan bracket or idle pulleys. the PS leak is a common issue with usually is fixed by a simple $3 o-ring at the bottom of the reservoir. your car does NOT have an EGR (last year that had it was 97).

Leeroy

I had the pan dropped, cleaned, new screen and new Type T-IV fluid put back in. I don't believe it was a full flush, but about a month later I had the plug pulled and some more fluid swapped. I think it's pretty clean now, but I could be wrong. I will probably do it again in a few days. What is a way to tell if I am having an issue with the fan bracket or idle pulley? BTW, when i turn the A/C on, the RPMs go up to a little over 600 when the low idle condition is present. Thanks for the help timmy.

timmy0tool

iTrader: (7)

idle always goes up when the AC is triggered, that's normal to compensate for the extra load on the engine. a simple drain and fill, in your case pan drop, is only good for about 2qts of fluid. the system capacity is much larger (over 8qts if i am not mistaken) so you will benefit from another DandF. glad you are using type-IV as it should be!

reason why i am asking about the trans fluid is bc when in gear at idle the car is under load and if the trans is not in good condition, the engine will strain further. i am unsure what else to do other than changing the spark plugs. if the car does not stall, i would not worry about it too much but that's just me. it's a common thing on our cars, and something i've learned to live with.

of course take care of those CEL codes which could be contributing to the problem. i hope it's not your cats, and it's just a simple exhaust leak as you stated.

Leeroy

Also, when I am in park and the noise is present it will drop in pitch while I press on the brakes and go back up in pitch when I let off of the brakes. I haven't had the car stall out completely, but there have been a few occasions where it came close. I was driving earlier and the car started lurching and acceleration was weak. I applied the brakes and the car was still shaking, RPMs dropped way down and I came to a stop at a light. the RPMs evened back out at around 400 and off I went. No more weak acceleration all the way back to work. When I got back to work I grabbed a ratchet and wrenched the battery terminals down to ensure that they weren't working loose.

Leeroy

Here is a video I just took of the noise.Sorry about the poor quality, my phone's camera sensor is failing. It's kind of hard to hear because of the background noise, but if you listen closely, you can make out a droning noise that sounds like a nest filled with a thousand wasps. It's a little easier to hear it when I put the camera under the car.

djamps

Trans fluid pump? Hard to tell without revving it a little at least. Is it louder when it's cold?

Leeroy

Hey djamps,

The first thing I thought when I got the car was that the trans pump was starving because of contaminated fluid in the system. I took it to someone to change some of the fluid out. Since then, I have done one more fluid exchange. There may still be some gunk in there. I am going to order some more fluid and drain and fill again. It does seem to be a little louder when the car is cold. Funny thing is, when the car idles down at a stop light, to around 400 RPM, the noise isn't there.

djamps

I have a noise on mine but it's more of a whirring that only starts happening when it's warmed up, the warmer the louder. I think I've narrowed it down to either the fan bearing or idlers and wrote it off for now unless it gets worse. But in my research I found if the noise is louder when cold and either goes away or gets quieter when warn it might be the trans fluid pump. I doubt changing the fluid more would get rid of it either. I also think if the pump is no good you should be looking for a new trans ($cost to repair > $used trans) but maybe someone else can correct me.

Leeroy

I hope I don't need a new trans. the car only has 131,000 on it now and the trans seems to behave pretty well. It doesn't seem to shift crappy, but I am pretty sure the guy drove the car with a broken mount for a while. And it's only marginally noisier when cold. And, might I add, the car idles around 675 RPM when cold starting and in closed-loop mode.

fixmiester

ANYTIME you experience this type of droning/humming sound that varies with engine RPM, the most effective troubleshooting step is to remove the serpentine drive belt, start the engine, and see if the symptoms change, or go away. If they persist, then you likely have a transmission issue, of possibly WP or timing belt. If they go away, the problem is in one of the belt driven components: idler/tensioner bearing, alternator (bearing or internal diode fault), fan bracket bearing, PS pump, or AC clutch bearing. Those can each be listened to individually with a stethoscope, etc. Not foolproof, but it certainly gets you looking at the right area.

Leeroy

Thanks for all of the replies everyone. In the next few days I will remove the belt and see what happens.

Leeroy

So I start the car this morning and begin my commute (30 degrees outside). I turn on the heat and the rear defrost and begin driving. All of a sudden about one mile down the road, the car starts shaking violently. I increase the engine RPM which seems to go up smoothly as does the car's speed, but with heavy vibration. I pull over and park the car and the droning noise is pretty loud. I try to turn off the heat and none of the buttons respond. So I start changing modes and it begins responding. After doing that and pressing the off button a few times, it turns off. I turn it on and off several times without an issue and continue my drive in to work with no vibration. But the low idle is present at red lights.

Leeroy

So I just did the newspaper test on the engine fan. It stopped the fan quite easily. Also, I noticed that fan in front of the radiator does not turn on when I engage the AC.

LexFlexTex

Did you ever find a solution? Mine started making a similar noise. I havent checked the belts yet but was wondering if you had any tips.