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Idling Problem


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HI GUYS,

i have a97 es300 the car is great in general,actually i had had the 95 modle before this one,now i have an annoying problem with my baby,when the car is idling or on the neutral gear,i find the rpm is dropping,and i feel like loosing pwwer,then the car resumes to its normal idling rpm which is under the 1000rpm by one degree- around 800 rpm; :mellow:

this also appears with the ac on at the drive gear while the car is stopped at a traffic signal,it never goes dead or shuts off GOD forbidden although when it does that looks like it.

i tried to clean the throttle body at a garage but it didn't help much.

any help from my fellow lexusiens would be highly appreciated. :)

thx

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Funny, that just started happening on my 94. Doesn't happen every time I'm at idle but sometimes it does. If it drops down below 500 rpms, the computer kicks it back up and it idles at 750 til the light changes.

I've been running w/ an 0171 code for months (system too lean bank 1). Could this be getting worse and causing the low/rough idle? I do know that when its idling, the fuel trim is pretty high (too much o2 reading at the rear bank sensor).

I've checked out everything in the FSM diagnositic that could cause that code -- detailed in a series of posts a few months back. I finally decided not to spend any more time on it as the car was running so well (25-27 mpg city, 30 hwy).

Time will tell.

LL

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HI LEXI,

thx for the concern, i see that you went by the policy that states that what couldn't kill me,make me stronger :P ,but i'm sure the cause of this problem is probably a minor flaw,which make me eager to fix it,and have my car in excellent running shape.

i just want someone to point the right path to walk,especially thanks to GOD,i have no codes at all.

thx again for the prompt and genrous response.

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It is good not to have codes!

According to my Haynes, in the troubleshooting section, "engine lopes while idling or idles erratically" could be caused by,

1. vacuum leakage

2. leaking egr valve

3. air filter clogged

4. fuel pump not delivering sufficient fuel to the fi system

5. leaking head gasket

6. timing belt and/or pulleys worn

7. camshaft lobes worn

The easiest is to check out the top 3, measuring fuel pump pressure requires a special fitting to connect to the top of the fuel filter, 5, 6 and 7 are fairly involved "checking"

LL

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HI LEXI

thx again for these generous and inlighting infos,it is really an analysis study,and i'll start working on it :D ,i had had a vaccum leak before and i fixed it,maybe it's reoccuring,also i ruled out the iavc anf the tb as i cleaned 'em myself with the help of my mechanic friend,also i recently have cleaned my air filter along with my iavc and tb ;) ,so that leaves us the other two first possibilities according to your detailed scheme;anyway million thx for your replies and generosity.

c u at the garages ...........i think :lol or on the interstate i hope :cheers:

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HI LEXI

thx again for these generous and inlighting infos,it is really an analysis study,and i'll start working on it :D ,i had had a vaccum leak before and i fixed it,maybe it's reoccuring,also i ruled out the iavc anf the tb as i cleaned 'em myself with the help of my mechanic friend,also i recently have cleaned my air filter along with my iavc and tb ;) ,so that leaves us the other two first possibilities according to your detailed scheme;anyway million thx for your replies and generosity.

c u at the garages ...........i think :lol or on the interstate i hope :cheers:

You're BOTH wrong! If cleaning your Idle Air Control Valve doesn't fix your idle concern, you will need to replace it. Lexi's p0171 code is a failing Mass Air Flow Meter.

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Death,

you seem sure that its the maf sensor, can you say how you know? Aside from the illogic of the code only showing up on one bank (vrs 2) for a device that is way before the intake splits, i did 1) check out the electricals on the maf, voltage and resistance and these were ok and 2) cleaned the sensor pick up wires with spray electrical cleaner (twice)til they glowed in the dark (almost...) I'm reluctant to spend $150+ on a new one, or $35 used just to "hope" that this would fix the code, given the lack of probs.

Altho the rough idle may be an indicator of the 0171 getting worse.....

LL

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hi all,

thx lexi and death for your replies,i want to break the good news for both of you,i finally got it :rolleyes: ,here is what i done:

- checked for vaccum leaks result:none

-cleaned all the tb area again,i mean hoses switches and valves as i cleane iavc and the tb itself before.

-[b]injectors and here the devil revealed himself,they were messy,that's the least to say.

-to make sure i vaccumed my air filter

-checked the fuel filter.

and now thx to GOD ,my idle is tammed as calm lion.

i don't know what really solved the problem,but considering i have 210k on my odometer,you can imagine my joy.

i would like evevryone having the same problem to look for the thread of how to tkae care of your iavc and nourish it,i found it very helpful.

thank you guys again and lexi i guess i c u on the highways now B)

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Death,

you seem sure that its the maf sensor, can you say how you know? Aside from the illogic of the code only showing up on one bank (vrs 2) for a device that is way before the intake splits, i did 1) check out the electricals on the maf, voltage and resistance and these were ok and 2) cleaned the sensor pick up wires with spray electrical cleaner (twice)til they glowed in the dark (almost...) I'm reluctant to spend $150+ on a new one, or $35 used just to "hope" that this would fix the code, given the lack of probs.

Altho the rough idle may be an indicator of the 0171 getting worse.....

LL

I've seen it a hundred times. I don't imagine you have access to a Techstream. If you did, you would see fuel trim way out of range. Indicator that the ECU is trying to increase fuel mixture to compensate for a false signal from the MAF sensor. It thinks it's getting too much air. Usually caused by cheap aftermarket air filters with too much oil content contaminating the sensor. I've heard of guys getting away with cleaning them but it's never worked for me. Don't buy a used one. Don't buy one aftermarket(usually just used ones cleaned and resold). Buy new from the dealer. You should notice an increase in fuel economy and throttle response. Flush out your IAC Valve and throttle body while you're at it.

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My fuel consumption increase even having a known good MAF sensor. We found a small hole on one of two rubber hose after the MAF sensor before the throttle body. There was more air mixture going into the intake. When there is more air draw in at a faster rate, surely the indication is to signal the ECU to increase fuel flow. Or is my logic off?

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Guys,

Thanks for the feedback. Death, you're one of the few who has responded to my threads on this issue (system too lean), and I appreciate an oppty to discuss this w/ someone who may know more than I (being a backyarder...). I get the cause of 0171 code (system too lean bank 1) in theory. Either there's air coming in from the intake side diluting the air/fuel mix creating a "real" problem for the computer to respond to, or an exhaust side air leak (manifold to block,egr pipe, poorly seated o2 sensor) making the computer think the a/f mix is too lean. And of course any of the electronics (i.e. MAF), that help the computer tell if the a/f mix is too lean (or rich)can malfunction leading to that code (0171).

In my case, I've only been getting the bank 1 side being too lean, so I've deduced on this basis, that there is a leak vrs an electronics problem (low chance of computer malfunctioning as this is my 2nd one with the same code). Otherwise, too lean codes should theoretically be seen on both sides/banks. I've been thinking the exhaust side, given the wrangling I did to get it off initially distorting the lower egr pipe, making it a bear to get back on. Not the easiest place to work on/in (behind bank 1)

I'm not eager to shell out $200 for a new maf sensor, but I agree that buying used is not a good idea.

So my plan is to just wait, so far the car is functioning well (aside from ac needing an expansion valve, and occasional drop in idle speed) getting 25 mpgz in city, 30 on hwy.

I am gonna go look for air leaks again, maybe today.

LL

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