Hesitation

[vcv10guy]

As the title says my '92 ES300 with 185k on the clock, hesitates when it's cold and it's been doing it for the past few months (it's now starting to bother me). The hesitation occurs when I am accelerating from a dead stop and the car shifts to 2nd gear (as well as any gear beyond first) and when it's going around 15mph it hesitates as if it's not getting enough gas. When I press harder on the accelerator, nothing happens really until the car suddenly has a surge of power. After 15mph, it hesitates kind of until I'm passed 35 mph or so. The hesitation fades until it hits normal operating temperature.

When I start the car, it idles fine and sounds fine. When it's in park and I rev the engine it doesn't hesitate. I even drove in L (first gear) to see if it hesitates and it does. It seems the car only hesitates when it's cold, and when it's going between 15mph to 35mph roughly. The hesitation is even more noticeable when I going uphill. No check engine light has come on or any warning lights when this occurs.

I recently had the car serviced in hope of solving the problem and it was also due for a 60k maintenance. The throttle body and fuel injectors were cleaned, replaced the fuel filter, replaced the rear brake pads/rotors and front rotors, replaced the spark plugs with NGK Iridiums, cap and rotor replaced, the throttle body plastic boot was replaced too (there was a 2 inch crack in it), replaced transmission fluid, coolant replaced, and one of hoses to the EGR was replaced too (started leaking air after service). Also put in a TRD air filter about 3k miles ago and replaced the PCV valve this past Monday. As far as the transmission goes, it was rebuilt around two years ago and the fluid was changed. The things done didn't help with the hesitation really.

I looked at other threads in this forum on the subject and it seems that some of the time it was solved by replacing the cap and rotor. Obviously that solution didn't help for me. I saw another thread in which a '97 ES300 owner replaced the EGR valve and it solved their problem. That may help my car, but I'm not sure. The car passed emissions, but I noticed that one of the numbers was relativately high may have been the Hydrocarbon index not sure (could this be suggesting I have a EGR valve in need of replacing?). Can anyone shed some light as what may be causing my hesitation problem or could advise me if it may be the EGR valve causing the problems? All advise is greatly appreciated. Thank you in advance for your help!

MORE INFO:

It turns out the car does hesitate in the first gear as well, if it's going over 15 mph. Earlier I said it doesn't, but it does, just checked it right now. In case if anyone is wondering I use 91 octane/premium gas.

[SKperformance]

I would suggest cleaning the ege as it sounds like it is having a problem moving the engagment valve to open and close ,alittle different from the 97 and ups since they are mainly contributed to their iacv for issues.

[ArmyofOne]

I would suggest cleaning the ege as it sounds like it is having a problem moving the engagment valve to open and close ,alittle different from the 97 and ups since they are mainly contributed to their iacv for issues.

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engagement valve?? forgive my n00bness, but i have never heard this term before...

[SKperformance]

an egr is a valve that controls flow of exhaust gases ,how did you figure it turned the flow of gas on and off ?

Just a metal flap controlled by a solenoid or vaume assist

[ArmyofOne]

an egr is a valve that controls flow of exhaust gases ,how did you figure it turned the flow of gas on and off ?

Just a metal flap controlled by a solenoid or vaume assist

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oh, i knew what an EGR was, but not an engagement valve LOL. thanks for clarifying.

off i go, back on the road.

[bartkat]

I would suggest cleaning the ege as it sounds like it is having a problem moving the engagment valve to open and close ,alittle different from the 97 and ups since they are mainly contributed to their iacv for issues.

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It must have been the ege typo that threw us off.

[SKperformance]

correct

[Lex3486]

At first sounded alot like a cracked intake...but I guess not since it fades away. One thing you might wanna try; probably won't do anything, but it's worth a shot and it only takes 1 minute tops. Check the clamps on the intake boot. One time after servicing mine, it drove funny and I'd had problems with this boot before. I dreaded looking but soon discovered that I'd neglected to tighten one of the clamps. Like I said, it's a long shot, but it's worth the second to check.

[vcv10guy]

hmm... I'll take a look at the boot. As far as the EGR valve goes, I need to have that checked still and I found out from Lexus that the part cost $170 to replace. If that's the problem hopefully they can clean it out instead. If anyone else has any ideas or ways of isolating the problem please share. Thanks.

[vcv10guy]

Okay I made an appointment with Lexus this upcoming Monday to have the problem diagnosed and I'm going to ask them to look at the EGR (per SK's suggestion). Hopefully they find what the problem is, and it won't cost too much to fix it. I'll update the findings when I get them.

[lex_mechanic]

The first thing I'd check is the Mass air flow sensor. That's the sensor in the air intake after the air cleaner box. If it is fouled you may be able to clean it. Usually if you have a sufficient vacuum leak to cause that kind of response it will throw a check engine light. You might want to check inside the intake boot though. If you have a lot of oil in the boot you most likely have a significant blow-by problem at the piston rings. It is a wise idea to have a proper diagonosis by a Lexus trained mechanic since they usually know all of the common problems and diagnosis for the issues. Good luck at the dealership.

[SKperformance]

a dirty maf won;t cause a hesitation only cold but all the time

[vcv10guy]

I took it to the dealer yesterday and they told me that the base timing at normal operating temp. was at 7 degrees BTC, which was causing the engine to run lean (it's supposed to be at 10 degrees BTC). They adjusted it and said the car was fine now. It helped a little bit, but I can still notice some hesitation still. Therefore I'm going to bring it back on Thursday morning. Oh ya it's funny too, the service advisor told me to never use Shell gasoline because it's terrible on fuel economy. He recommended Chevron or 76 Fuel. Well if SK and the service advisor recommend not to use Shell, then I'm convinced.

[SKperformance]

thanks for the vote of confidence

[vcv10guy]

Okay well I took the car back last Thursday and well sure enough they told me they couldn't find any problems with the car. They even told me the car drove fine. I find that funny because the car is still acting up. At least they didn't charge this time, but I had my distributor O ring replaced because it was leaking oil (still have to do the valve cover gaskets next). I guess I'm going to have to do my own trouble shooting on the car because apparently my car "behaves" with them.

It's weird though because ever since they adjusted the timing back to factory specifications, it seems the car's problem has changed a little. I'm not sure if it's called hesitation or stalling now. My reason for saying that is that the acceleration is not smooth, and around 30mph it acts like it's not getting enough gas and I have to nearly "floor it" on the gas to get it to continue to accelerate. It seems to be fine accelerating after 3000 RPMs or so. Of course it only does this when it's cold and when the car gets closer and closer to normal operating temperature the problem is rather non-existent.

Do any of you think it's the water temperature sensor, the fuel system, throttle position sensor, or something else? I would take it back to Lexus, but I feel I'm just going to waste my time. Again any input is greatly appreciated. Thanks.

[pgupta]

I am having the exact same problem on my LS400. If I find the cure, I will post for what its worth realising this is ES300 forum. However, mine started acting up in the peak of summer and has exactly the same symptoms. So, I wouldn't place too much emphasis on the "cold" part.

[vcv10guy]

I am having the exact same problem on my LS400. If I find the cure, I will post for what its worth realising this is ES300 forum. However, mine started acting up in the peak of summer and has exactly the same symptoms. So, I wouldn't place too much emphasis on the "cold" part.

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So your car acts like that no matter what the temperature is? Sorry I just want to clarify. To give an update, my car is now acting up more now. It appears that even though the use the car and I park it for roughly an hour or so, and when I try to restart it it makes a growling sound and stalls a little bit (once it almost died, dropped to about 500-400 RPMs). The growling sound disappears about 30 seconds later or when I put into drive and take off. I don't know if that's related to my original problem or what. Well hope you find out what's causing your/our problem pgupta.

[pgupta]

For what its worth, read the post by 95LS400Bob on LS400 forum titled:

95/96 Ls400 Low Idle, Engine Dies And Jerking Thre

Search for the above and see if this describes your problem. Given everything else that you have done on this car, this may be your problem.

[vcv10guy]

Oh also forgot to mention, last weekend I finally took a look at the EGR valve's filter and it was kind of dirty. I'm going to try to use some compressed air to clean it. Hey SK or anyone, do you think I should just remove the EGR valve and try to clean with some throttle body cleaner or what do you recommend I use to clean it with?

[pgupta]

So your car acts like that no matter what the temperature is? - Basically yes .. I will have to wait till next summer to confirm.

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Looks like my problem is related to the ECU per the link I just posted for you. I will start there first and will let you know if that works out for me.

BTW, also see KCTalker on SC400 forum post:

Sc 400 Hesitation...?, Normal at low revs?

Looks like the Engine Control Module / Unit or ECU in conjunction with the EGR Valve is acting up.

[SKperformance]

clean it with throttle body cleaner

or get a motorvac and clean the whole engine

remove the whole egr and clean all of it and

also clean the whole throttle body as well

[vcv10guy]

Wow, thanks for the information pgupta. Hmm that post from the SC forum is really starting to make me wonder about the EGR and the O2 sensor too. Oh ya thanks SK for telling me how to clean it. I believe the throttle body was cleaned already though, but ehh, if it's dirty I'll clean it myself. Ya I still need to get a motorvac, but I need to find a place who does this and also who I trust. Ehh...

[steviej]

Also, check the air intake hose. The black accordian like tube from the airbox to the intake. If there are any cracks or holes allowing excess air in after the MAF sensor, then this would create this problem too.

This is a consistent problem with Toyota and Lexus as the tubing becomes harder and brittle with age and prolonged exposure to engine heat.

steviej

[vcv10guy]

Also, check the air intake hose.  The black accordian like tube from the airbox to the intake.  If there are any cracks or holes allowing excess air in after the MAF sensor, then this would create this problem too.

This is a consistent problem with Toyota and Lexus as the tubing becomes harder and brittle with age and prolonged exposure to engine heat.

steviej

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Yep I replaced that part already and that didn't help (it was cracked though pretty bad too), and I also replaced the ventilation hose that connects from the front cylinder head to the intake boot (was cracked too). I wish those things solved my problem. Thanks Steviej for the suggestion though.

Man the more I think about those threads I read, I wonder if I have a lousy ECU too. I've noticed that the fuel economy on the car isn't that great either. I only get about 18-19 mpg (21 was the best I ever got). This is even after I got my 60k service done. Granted the car is old with a lot of mileage, but my '92 Camry V6 with 171k on it gets better fuel economy than the ES (at least 23mpg to 25 mpg). They are both driven under the same circumstances too.

[pgupta]

vcv10guy -- your posts are extremely helpful. They are eliminating all the things that cost a lot of time/effort and money and won't help with my basic problem as well. I bet its the ECU on my car that is flaking out.

The instrument cluster (dashboard) on all early Lexus cars has been notorious for bad transistors and capacitors - specially the electrolytic ones. They just flake out over time. Result - flickering lights, gas gage needle not coming up fully etc. till the cabin heats up. Its too early to tell on the late 90 models if they continued to use the crappy components. Takes about 8+ years for them to flake out. It is unfortunate that Lexus will use crappy electronic components. A 33 cent part results in a $1500 assembly being replaced. I can only hope that they are reading this and switch to tantalum caps on all their future designs.

However, on the ECU, it appears that the software flashed in the memory has a problem. Wonder if it is similar to what happened on the Mars rover -- over time it accumulates data and runs out of memory to hold it and then starts goofing up.

Next thing I plan to do is disconnect the battery overnight, perhaps over the whole weekend, and see if that resets the ECU. I know that disconnecting the battery for a short time does not do it.

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Yep I replaced that part already and that didn't help (it was cracked though pretty bad too), and I also replaced the ventilation hose that connects from the front cylinder head to the intake boot (was cracked too). I wish those things solved my problem. Thanks Steviej for the suggestion though.

Man the more I think about those threads I read, I wonder if I have a lousy ECU too.