Strange Idling And Dying

[95LS400Bob]

Got some strange idle issues that suddenly occured on recent Phoenix trip. Thought I would post them here as we figure out what the deal is.

The car has always idled normally. Fast idle when cold and then about 600 when warm. Totally smooth.

We leave Reno and drive freeway 70, 75 mph to a town about 60 miles away. Stop at a light and engine dies. Restart instantly and idling smooth at 600 rpm.

This occurs various times on the trip. Watching the tach...I even catch the engine idle at 200 rpm. Shut the engine off and restart and back to 600 rpm.

Short freeways runs 60 mph or less and all is normal. But 70 or better on freeway for a while...engine dies at idle. No surging or unsmoothness...just verrrry low idle speed.

First place I will go is the Idle air control, remove it, clean it and try to test it. Mystery is why this never happens around town..only after long running 70 mph or so. And once it is restarted..all comes back to normal.

26.6 mpg average on trip tells me it's running fine.

We do have a check engine light and 2 codes I have no definition for:

C 13

C 34

Anybody know what those codes are?

[92Lex]

I'll throw in intermittent MAF sensor malfunction.

C = chassis

1,2 = fuel and air metering

3 = ignition system or misfire

4 = auxilary emission control

[95LS400Bob]

I'll pull the codes again when the wife gets home. I'll also have a look at that mass air flow sensor.

[VMF]

this is a known issue with the engine ECU and you might be eligible for free replacement under recall, when engine dies after driving over 20 mins on highway and then pulling from the highway to slow speeds or complete stop.

this recall is for 95 and 96 years only. and yes it starts back u right away no probs.

so ask ur dealer, have ur VIN number, if he will refuse, call the lexus america.

[95LS400Bob]

I removed the mass air flow sensor and the idle control unit. I did some ohm meter testing and everything checked out.

Seems to me that all idle speed air is controlled by the idle control unit. So if it was not working properly then I would think fast idle when cold..etc would not be working either.

I drilled out two roll pins and took the idle control assembly apart. I put in back together with unit screwed closed and letting in no air. I put everything back together and started the car.

It went cold fast idle..about 1500. Then tapered down as it warmed up to about 600. Turning on air conditioning raised the idle to about 850.

Apparant to me the pcm is controlling the idle through that idle unit and evidently the idle unit is working.

I tried to disconnect the air hose from the idle control unit to the mass air unit...but the engine would die.

The car has always had one other thing...sometimes when you let off the throttle and get back on the throttle....the car bucks or acts like a slight hesitation. Just happens once in a while.

Maybe this is PCM related and I will check out that recall for sure. By the way...a new idle control unit is $600.

[92Lex]

Hey, does this only happen after a freeway trip? Does this happen on short distances from block to block?

[95LS400Bob]

Won't happen around town. Seems you have to be doing freeway driving for at least 20 minutes. Then it happens. It's just like the idle control valve closes nearly completly and lets no air in. After I knew it was doing it...I kept my foot slightly on the throttle to get through towns. But if I let off completly..it would try to idle near 100 rpm and then die. Start immediately back up and idle normal 600.

Trouble with these Lexus cars...you can't feel them idle and the only way you know it quit is all the dash warning lights come on.

[92Lex]

It might be ECU like VMF said. It could also be your MAF sensor breaking down under heat...do you have access to a digital storage oscilloscope? My sister had the same problem before she sold her 92 Camry, I checked the MAF sensor with a pack of ice on top of it and also heated it up...it only malfunctioned when subjected to heat.

If your ECU might be replaced under a recall then you should definitely look into that.

Do you have a K&N?

[95LS400Bob]

Has stock air filter. I have a laptop with diagnostic software but no scope.

[92Lex]

Which program are you using?

[95LS400Bob]

Auto Engenuity software. OBDII. http://autoenginuity.com/

Works pretty good but I haven't played with all of it's features yet.

[VMF]

Bob, just like i said, go and get a brand new ECU from the dealer:)

this is definetly the ECU problem, its been discussed here and i also received a letter from lexus regarding this issue, i didnt pursue changing the ECU since mine is working fine but if i ever will get the problem this is first thing i would do.

its free!!! and you have definite simpthoms of that problem since its happens only after prolonged highway driving.

[bartkat]

You can look up the TSB's here. There are like 85 of them listed for that car.

http://www.alldata.com/recalls/index.html

[bicol-ini]

hello, with regards to the ECM RECALL there is a TSB issued on it covers only early production vehicles for 1996 with VIN before JT8BH22F3T0041045, so if your vin is before this you might be covered for free replacement, but then again TSB says 4 years or 50000 miles, the TSB NUMBER is EG002-97 issued FEB 28, 1997 the OLD PART no for the ECM is 89661-50302 the new ECM part number is 89661-50303,good luck and contact lexus for more info,

[92Lex]

Hey Bob, it appears that the program you're using it all that bad...it works like a scope. It also allows you to see freeze frame data and allows you to run functional tests on monitors...plus a whole lot more. It has a bunch of extremely useful features and almost everything you need to help you diagnose problems.

[95LS400Bob]

Bob, just like i said, go and get a brand new ECU from the dealer:)

this is definetly the ECU problem, its been discussed here and i also received a letter from lexus regarding this issue, i didnt pursue changing the ECU since mine is working fine but if i ever will get the problem this is first thing i would do.

its free!!! and you have definite simpthoms of that problem since its happens only after prolonged highway driving.

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I sure hope it is free. I am sure gonna try it. But I have 151,000 and change so there may be some arguement.

I do have to read up on the scan tool. Is a nice unit with a lot of features.

[mehullica]

code 13 is a bad camshaft, or crankshaft signal. Make sure the wires aren't cut by the serpentine belt.

[95LS400Bob]

hello, with regards to the ECM RECALL  there is a TSB issued on it covers only early production vehicles  for 1996 with VIN before JT8BH22F3T0041045,  so if your vin is before this you might be covered for free replacement, but then again TSB says 4 years or 50000 miles, the TSB NUMBER  is EG002-97 issued FEB 28, 1997  the OLD PART no for the ECM is 89661-50302  the new ECM part number is 89661-50303,good luck and contact lexus for more info,

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Now you have really got my wheels turning. Mine is a 95...yet I see this applys more to 96's. My vin is way earlier than the one listed.

Further digging around for pcm info I find the following. These are used pcms in case the dealer won't cooperate.

1995

California pcm#89661-50231

49 state pcm #89661-50220

89661-50221

89661-50224

89661-50234

1996

pcm # 89661-50302

89661-50303

89661-50304

1997 pcm # 89661-50340

89661-50341

So if I don't get cooperation from a dealer or Lexus then a wrecking yard pcm might be the ticket. I believe more and more it is a pcm issue as all else checks out. I'll pull my pcm tomorrow and see which one it is since I have to fix the lights in the radio anyway.

Update:

After some further digging in the threads here I found someone who tried the new 96 #89661-50303 in his car and got an immediate check engine light.

I also did some searching part numbers and found the following:

From Park Place Lexus:

Latest PCM for a 95 Federal emmisions car is 89661-50224

California is 89661-50235-84

Update Nov 28,2004.

I've done about 3 days of searching for info and what I have found is all complied in this thread. I'll make a seperate thread when I get the final info but for now...take a look. http://www.clublexus.com/forums/showthread...threadid=142055