mjbtn

I have a '94 ES300 with 303,400 miles and I have the same hesitation on pull off but I noticed that if I apply just a small amount of throttle for a few seconds (like jets do on take off) and then give it gas, it pulls off more on its normal power. But this can't always be the case in tight, got to move quick situations.

That said, my Check Engine light has been on and the OBD-2 code has been referencing an EGR problem. The first thing I changed is the vacuum diaphragm as the membrane was clearly cracked. Then, for about half a day, the Check Engine light went out on its own (no PCM reset) and I thought I was in the clear. But it came back on and the code was still the EGR. I rechecked the diaphragm but the replacement seemed OK still. So, I first removed the EGR valve and cleaned it throughly. That did not help, so I ordered a reman on Ebay (with new sensor), but that did not help. I also put on new vacuum hoses with the new diaphragm. What's left??? The EGR vacuum solenoid? It is still showing an EGR fault. based on how the hesitation is manifesting itself, is there some aspect of the EGR system that I might examine more closely? Once at speed, the car runs fine though I think its mileage is down (but that just may be 303,400 miles). :-)

I should add that the hesitation was minimal at first but has gotten gradually worse over the past year. Would fuel filter/pump/regulator problem manifest the same way or is there some aspect(s) where you would rule one out over the other? I suppose it could be a combined problem, but, I do know for sure the EGR is throwing an OBD-2 code. And I find it weird that the Check Engine light cleared on its own after putting in a new value actuator diaphragm. That was also on the original valve. So, perhaps the reman valve is faulty and now something else is triggering the EGR code.

92ES5sp

Does it behave the same while in reverse? Check your tranny fluid or better yet change it. Dexron 3.

GEORGE_JET

You did not mention what the code is, there are several different codes for egr.

mjbtn

George, it was a P0401 (EGR Flow Insufficient). What was weird was that shortly after I replaced the EGR Vacuum Modulator (the first step I took as my old one had clearly failed) (and I replaced it with a NEW one), the Check Engine light went off on its own for about a half a day and then came back on. I had the code checked again, and it was still the P0401. That was when I swapped out the vacuum hoses and got the reman'ed EGR valve (using new gaskets with that too). Could something be leaking?? I am wondering if the reman'ed valve is possibly the problem as the hesitation condition has been gradually becoming worse (and, though I have not yet tested for it, it appears my gas mileage has gone down too and I had read EGR issues can affect mileage). Thanks!

mjbtn

Not sure. Good point. I will check that today. Thanks!

mjbtn

This actually triggers another question I had had. I had read in more than one place that on high mileage vehicles where the transmission fluids had been more or less kept topped off (and not wholesale changed out as they probably should have been on a more routine basis), that a wholesale change out with fresh fluid can actually cause damage and/or transmission failure. Is there anything to this??

mjbtn

I tried this and it does NOT do this in reverse! Very interesting. It ONLY does this when trying to accelerate from full stop (or near full stop). If I give it just a little gas and let it get some forward momentum going then accelerate, it behaves (almost) like normal. At speed, it seems to be normal too. Shifting at low to high speeds seems to be smooth and normal too. I have not checked the levels yet, but will be doing that today.

Thanks and thoughts?

GEORGE_JET

Insufficient EGR will not normally cause a hesitation, excessive EGR could cause that symptom. Have you checked your vacuum lines for splits and cracks? How many miles since the last tune-up? Once you get up to highway speeds, does it act normal? Any signs of fuel starvation? Check to see if the fuel filter has been replaced, with that many miles you can bet that it is ready. Toyota does not recommend a replacement interval and some people mis-read this and assume that it is a lifetime filter.

mjbtn

Could insufficient flow affect gas mileage? I had replaced most if not all the vacuum lines immediately associated with the EGR valve and solenoid. And, at now approaching 307,000 miles, I must admit a proper "shop" tune-up was years and about 150,000+ miles back. Most issues I have been able to correct myself (and they have been luckily few). At speed it does behave normally except that I am pretty sure it is consuming more gas than it used to. I had read EGR issues can affect gas mileage. I have not observed anything that would make me suspect fuel starvation. It can still hit 100mph with not much effort. I am sure the fuel filter has not been replaced in quite a long time. I will check it as well.

I know this is an old car with very high miles and I am not expecting miracles. But I would like to eliminate the P0401 and address the hesitation issue if they are within reason. Fortunately, being a 1994 model, it falls below the radar for emissions testing locally which started requiring 1996 models and above (that have OBD2) to be tested by way of OBD2. Even though my 1994 ES300 has OBD2 (in the interior fuse panel) in addition to that proprietary interface Lexus has, being before 1996, I get tested the old fashion way *AND* I pass each time! If I had to be tested by way of OBD2, I would fail on the P0401. I got a kick out of one of the Autozone people when I stopped the last time to have the code read. They asked me the year. I said 1994, and all the way out to the car, they argued with me that no car before 1996 had OBD2. They kept on right up to the moment I popped off the fuse panel cover and we plugged in the code reader! :-)

ZGadson

If you haven't figured it out yet...

When I had my 92 ES, it had the same problem. No one could find the issue, not even the dealer. Then one day I was changing the air filter and noticed a huge crack in the ribbed/rubber air intake hose. I replaced the hose and it fixed my problem. Apparently when I revved the engine, or gave it gas to take off from a stop, the engine would shift just enough to pull the crack open further and let too much air into the intake (which led to replacing the engine mounts as well).

Lexus/Toyotas are extremely sensitive when it comes to air/fuel ratios. Too much (or too little) of one or the other will cause major problems, one of which is severe hesitation.

futures

Same thing happened to me - replaced it with a Camry intake hose and everything was normal ,no hesitation.

ZGadson

Exactly!

mjbtn

Well, the air intake tube turned out to be my problem too! I forgot to follow up here and just replaced the radiator last night and it made me think I had not posted my end result. In my case, I still had (and have) the check engine light. I had just assumed it was still the EGR (P0401). But just on a whim, one day while I was at autozone getting something for our other car, I asked them to check the codes again. Lo and behold, it was P0174 (an O2 sensor warning). The printout from Autozone suggested cleaning the MAF (mass air flow sensor - inside the air intake host). Since I had just gotten a P0171/P0174 code pair on our other car, and cleaned the MAF on it and clearing those codes, I figured it would not hurt to do it on the ES300. It was then that I discovered my *two* gaping cracks in the crevasses of the air intake tube. Even changing the air filter twice before had not alerted me to them. But to get at the MAF, I needed to remove the air filter cover, so, more bending was required. I was stunned. I quickly grabbed some duck tape and wrapped the tube on both cracks. Started her up and took off up the driveway. She burned a little rubber! I had gotten so used to the hesitation that when i punched it I was not prepared for the blast of life that had suddenly breathed back into her at over 324,000 miles! Short of it is $36 Dorman replacement tube at O'Reilly's and all better. I am surprised that this was not diagnosed much earlier in my efforts. Oh well, now I still have the P0401 EGR code and the high pressure line on the powersteering is leaking somewhere, but, I now hope she really will go the 400,000 miles I always heard Lexus engineered for.

afleitikh3

Thanks Zgadson, on the advice for the air intake hose, it seems to have fixed my problem right up,


Thanx man, Art.