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Yeah, I wouldn't touch anything else before the test if you don't get any more CELs or drivability issues. With how many seemingly unrelated but interconnected things you've just changed, you wouldn't want to open pandora's box again!
It doesn't make much sense that it would, but maybe... Isn't the sensor's function simply to tell the valve when to operate? The valve itself doesn't affect drivability in any way that I can think of. It's just there for emissions (a controversial topic, to be sure). Unless maybe a bad temp sensor is telling the valve to open at the wrong time, allowing exhaust gases into the manifold at a time when they have an adverse effect, if that's even possible?
All the drivability issues being solved now I wouldn't be worried about changing plugs and doing more cleaning. Those things just don't seem to be needed any longer.
The EGR temp sensor is supposed to just tell the ECU if the exhaust gas flow (temperature) is within certain pre determined ranges at different overall engine temperatures. But this result may suggest that when the ECU sees the incorrect temperature range (from a faulty EGR temp sensor) it makes the EGR VSV operate weirdly, possibly leaving the EGR valve open while accelerating... which it should not be doing.
I've already replaced the EGR VSV, EGR modulator, vac lines and cleaned 90% of the EGR system prior to testing and replacing the EGR temp sensor so my guess is that may have been what was happening. Parts can wear out after 24 years. Although in the case of my car's EGR valve it just needed to be cleaned out. It's own operation and pressure holding when in the open and closed positions seem to be fine. The rest of the system components needed replacement. And a couple of passages also needed cleaning.
Anyway, it's running the way it should again. If it turns out I still have a blocked passage at least I have a plan to unblock it now. But I think everything is fine now
I was feeling good and planning to get the car tested on Monday but... of course... on a normal drive tonight the CEL came back on 91 miles after the last ECU reset.
SO then...
The "Y" intake will get removed and its manifold EGR port will be drilled like crazy. Spark plugs will be inspected and possibly changed.
Honestly, I was looking forward to all of this being completely over with since I am getting ever closer to the registration renewal deadline.
The moral of the story is, when solving your car's EGR Code 71 issue, the answer is always "everything".
Sigh...
Last edited by KahnBB6; 04-10-16 at 03:04 AM.
Reason: Grammatical correcton
Last night I did the entire "Y" intake removal again and went to clean out the EGR passage all over again.
This time I did manage to clean up the accessible EGR valve side of the passage and removal all the buildup there... but I was still unable to get very far with a coat hanger OR the flexible Snake-Bit drill bit. That tool did bore in a little and it did bring out some crud but it proved to be incapable of making the second bend into the EGR tube area.
I used nearly a whole can of cleaner on both the tube side (using a straw attachment to push cleaner directly into the tube's pinhole exit) and on the passage side. I still feel like there is significant clogging in there because the cleaner didn't flow easily and I am fully expecting the Code 71 to come back on.
I put the car back together and, again, it drove just fine.
I am going to schedule an appointment with Carson Toyota take care of this. I am fully convinced that the only way to unblock a '92-'97 2JZ-GE's manifold EGR passage is to pop out the small freeze plug that allows direct access to the internal EGR tube... and have not damaged that plug or have a means of replacing it... which I've confirmed Toyota doesn't sell or have a measurement for.
And yet there exists a small screw (not pictured below but it IS there) that looks like it allows the tube to be slid out of the intake manifold once the freeze plug is out of the way.
Frustratingly, as popular as the 2JZ-GE is and as many of them are rolling around in emissions counties across the country I have found ZERO guides on how to correctly deal with that little EGR freeze plug passage.
I'm over trying to clean this out myself. I've diagnosed the entire EGR system, tested every component, replaced anything that tested bad and cleaned everything I possibly could.
Since I am concerned I will damage that plug and not be able to find a replacement for it I am taking it to a dealer that services Lexus vehicles so that someone there can use whatever method Toyota hasn't disclosed for cleaning this critical part of the intake manifold. That port obviously exists to access the place I haven't been able to get to but there is no TSRM procedure or replacement plug for it.
I'm not looking forward to the expense right now but I figure a Toyota dealer that has had a lot of experience with Supra MKIV's ought to be able to handle this properly. I'm absolutely amazed that it's been this difficult.
I have a month to get this solved now and I haven't even doubled-checked any other parts of the emissions system.
Craig what else haven't you replaced to resolve your problem and I may have ? I have that Y pipe and a lot of SC300 / SC400 parts am about to throw in the trash bin I can send to you ... just send me a shipping label to put in a box .
Craig what else haven't you replaced to resolve your problem and I may have ? I have that Y pipe and a lot of SC300 / SC400 parts am about to throw in the trash bin I can send to you ... just send me a shipping label to put in a box .
Gerry, that's kind of you!
I've replaced/serviced:
-EGR VSV (with working used, but have a new one also as backup)
-EGR Modulator (with new)
-EGR Temp sensor (with new)
-Various vac hoses
-EGR Valve fully cleaned/unblocked and tested for pressure holding (have a spare new aftermarket valve in reserve)
-cleaned EGR pipe from block
And:
-partially cleaned EGR passage in USDM intake "Y" plenum but that still has blockage internally where I cannot get to the "pipe" area with any cleaning tools.
It's the entire "Y" manifold section I'd need, Gerry. Specifically one that has a fully free flowing EGR passage without carbon obstructions.
I've thought of buying one used but I'll gladly take one off your hands if you're throwing one out
I don't know if these manifold sections ever changed from 1992-1997 but I'm sure an OBD1 version would be the same as mine.
Edited for accuracy after trying again: That, or I just need to figure out how to replace the little freeze plug I posted about after it's tapped out. A 12mm socket fits onto the CENTER and a 13mm socket fits near perfectly onto the OUTER diameter of the plug as an evenly placed tapping tool. 14mm is too large for it. The actual measurement may be slightly different than the outer diameter of a 13mm socket but it's pretty close from what I can tell.
More telling information that this "freeze plug" EGR passage method some manufacturers use is not limited to Toyota. Here's a thread for EGR system diagnosis on Suzuki Sidekick and Chevry Tracker 1.6L engines:
NOT a Toyota engine below but the same concept. Interestingly the thread poster does not recommend removing the EGR freeze plug in this example... but I have to wonder how on Earth all that carbon buildup would be completely removed without getting at the plug.
And here's a Celica-Supra 5M, 6M or 7M thread where buried in the middle of the posts, a one person asks if the OP removed the EGR freeze plug area and replaced it with a new one:
I double-checked the TSRM for the SC300 and I still found no mention of a specific manifold EGR passage cleaning procedure outlined by Toyota or any mention of this plug. As specific as these factory manuals usually are it's a very strange thing to leave out on their part.
This doesn't really help you, other than possibly to ease some of the frustration you're dealing with, but I'm of the opinion that EGR systems were a band-aid to meet non-JDM emissions requirements and very little planning was given to longevity. Who in their right mind thought it was a good idea to pour exhaust gases back into the intake? And knowing how bad the carbon buildup would be, not provide an easy means of cleaning it??
Maybe try soaking it in the strongest solvent you feel is safe? Gas, diesel, simple green, industrial cleaners...
A lot of people feel that way and I do agree that on the 2JZ-GE and 2JZ-GTE it seems to have been a secondary R&D consideration the way it's designed... but a lot of US manufacturers and plenty of foreign ones used EGR for years.
Generally it was phased out in many gasoline engines after variable valve timing technology came onto the scene. VVT and far better fuel control can in most forms can accomplish many of the functions EGR used to do as a separate system. However these weren't available technologies for Toyota until 1996 at the earliest.
EGR does a job and I don't mind that. There is a good reason for it for many engine designs from the 2JZ's era. EGR is still commonly used on modern turbo-diesel engines to clean up NOx emissions before the two other exhaust system cleaning catalysts. It does have a purpose. Generally it's also not supposed to bother 2JZ-GTE performance until you start getting into some big horsepower numbers and heavy duty modification beyond BPU.
Anyway, out here in CA it doesn't matter if it was a poorly designed EGR system or the best such system in the world. It also doesn't matter if it's inferior to a better NOx reduction system that could be upgraded from a newer engine. Unless you change your entire engine to the one the "improved" system comes from, California wants to see everything exactly the same as it was for the year your car's engine was designed. It can even pollute MORE than an improved system for a version of the same engine a couple of years newer (which I don't think exists for 2JZ's but that's beside the point) and they'd still want the original emissions hardware for THAT year. Even if that hardware is discontinued and hard to come by.
I don't fault this EGR system itself so much. What I find very annoying is the lack of manufacturer documentation on cleaning the intake passage of carbon and the lack of a direct replacement freeze plug for the access port.
Craig - answered your PM. I really doubt that Y-pipe is your problem.
If you blow into that opening .. do you feel the air coming out of the "pipe" holes in the middle of that y-pipe. As long as you do , that is not your problem.
But still you are free to have the parts you need that I have if you want to experiment .
On second thoughts , stop wasting money on that GE... throw in the GTE ... lol.
Craig - answered your PM. I really doubt that Y-pipe is your problem.
If you blow into that opening .. do you feel the air coming out of the "pipe" holes in the middle of that y-pipe. As long as you do , that is not your problem.
But still you are free to have the parts you need that I have if you want to experiment .
On second thoughts , stop wasting money on that GE... throw in the GTE ... lol.
Unfortunately what's happening is that there is little to no flow of air... or cleaner... from the little exit holes in the intake tract :/
I'd like to take you up on the GE manifold you have. Thank you! Maybe yours is cleaner than mine is :P
I completely agree with you about the moving on to the GTE. I'd love to right now. The timing of my very close DMV registration renewal deadline requiring a passing smog test before they'll clear me are the only reasons I'm going to all this trouble with an engine setup I do not plan to keep indefinitely.
ok.... then your egr passage to the y pipe is clogged . I just tried blowing in one of what I found around ... there was strong air coming out from those pipe holes.
sent you text messages ... I can get it out tomorrow if you want.
EGR does a job and I don't mind that. There is a good reason for it for many engine designs from the 2JZ's era. EGR is still commonly used on modern turbo-diesel engines to clean up NOx emissions before the two other exhaust system cleaning catalysts.
I wasn't aware of that, but looking around a bit turned up a number of informative pieces.
It would be interesting to see how the '90s EGR systems compare to that research in terms of % recirculation and load. And, of course, how choked your percentage is!
It would be interesting to see how the '90s EGR systems compare to that research in terms of % recirculation and load. And, of course, how choked your percentage is!
^^ That is a very in-depth study. I'm going to take a closer look at it later. Farm and construction equipment traditionally hasn't been emissions controlled but in recent decades I do think at least EGR and some kind of exhaust catalyst have been used for some industrial diesel engines used in such vehicles. The newest types for sure but farm and industrial vehicles have such long lifespans and cost so much you're usually seeing more older machines than new in use.
Especially on diesels, just a working EGR system and a DOC (Diesel Oxidation Catalyst, which is a passive filter requiring no special additive or "regen" cycle for cleaning) does plenty to take away the common impression of sooty, black and pungent exhaust. Pretty simple to maintain, too when you compare those setups to the new complicated systems that use diesel exhaust fluid.
As applies to JZ engines, I've seen these figures printed elsewhere but I found this interesting:
"The US and UK market Supra featured bigger injectors, steel turbines and bigger inlet cam and had emissions in the range of 259 g/km CO2 despite the addition of Exhaust Gas Recirculation (EGR). The Japanese market Supra had CO2 emissions in the range of 224 g/km.[citation needed]"
And here's the well known white paper Toyota released on their "new" 1JZ-GTE VVT-i engine many years ago... I assume in 1995 or 1996. There are no emissions numbers listed but the paper does discuss how the VVT-i technology and other changes reduced HC's and significantly reduced NOx.
I've been strongly suspicious for some time that the 1JZ VVT-i might have burned at least as clean as a stock USDM 2JZ-GTE or at least very close. And it has no EGR system. Nor do 1998-2005 2JZ-GE VVT-i's.
Another reason I really like that engine and would love to try one sometime. It's always sounded like it really could have been sold in US market SC's and GS's if Toyota had wished to with very little additional R&D to make it pass our emissions at the time. It makes the exclusion of it from our shores more irritating.
For new gas engines with the newest technology (direct injection turbocharging with high compression, VVT on all cams, modern OEM cats that flow well, and sometimes even switching between Otto and Atkinson cycles (like the RC-F's V8 engine does) EGR is a technology of the past.
Diesels seem to need it because... well... compression-ignition has great advantages in power and fuel economy but it's pretty dirty combustion on its own.
"The US and UK market Supra featured bigger injectors, steel turbines and bigger inlet cam and had emissions in the range of 259 g/km CO2 despite the addition of Exhaust Gas Recirculation (EGR). The Japanese market Supra had CO2 emissions in the range of 224 g/km.[citation needed]"
That's depressing, but not at all surprising. So much of what [little, compared to you] I've read points to the benefits of '90s EGR being mostly theoretical. I'd love to take an EGR-deleted car to a sniffer test and see if it matters... Just for fun, of course, not one that I needed to pass.
The part that troubles me the most is Japan not using EGR on their own domestic vehicles, despite being way ahead of the game in terms of awareness of that sort of environmental stuff, usually. The only explanation I've seen given is that it cost too much, but it seems like a minimal add-on compared to all the other tech on a car. My semi-educated belief is, they knew it was a gimmick and only put it on to meet requirements in other markets.
Its just a freeze plug, you can remove it and clean it out and then have a new one reinstalled by like a machine shop. problem could be finding a new one the perfect size, but Gerrb has the right idea just replace whole Y with one that is not clogged. My stock original one was not clogged, but like 2 others I had were completely clogged up, it just depends on usage.
one of the Y pipes I cut out the EGR pipe (sawzall from throttle body opening) to mate up the ls400 throttle body, and it was solid caked all the way through when I took it out in 3 pieces (cut a center piece out and you can pull the side pieces that are left out). It was like solid full of Carbon I would not have wanted to clean that out, but from the freeze plug would be the only way to get a hard drill bit in there that might do the job.
04-09-16, 03:42 PM
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