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I had updated my post when I wrote the first one I thought 71 was for the vsv then I remembered 71 is just a general code and can be all 3 things. check the edited post of mine above above for what I wrote after, didnt think you would quote it that fast. there is a good chance if you have over 150k that its fully clogged, that is basically what it does over time. it would be worth cleaning it out to fully overhaul the egr system but its a task to say the least. I think there are a few tests you can do with the vsv but start by looking inside the tubes and seeing if they are clogeed, but I think most people have the tube get blocked then the egr temp raises and trips the temp sensor and the code comes on. the vsv failing and the modulator failing are less common but also definite possibilities.
I just re-read your post, Ali. Thanks for clearing that up! So it is just one code for the entire EGR system. I guess I was up early when I quoted you.
Good to know that 150k miles is a good general number for our EGR systems to need some checkup. I had no idea about that when I first got the car.
I know it will be a big task but I have to do it. I shudder to think what even independent shop labor would be for the cleaning. I've looked up some of the tests for the electronics. I need to double check how to set my multimeter for the resistance measurement functions with its internal battery.
So I should check:
--EGR VSV and vacuum lines to it first. Then the +12V and vacuum pump test to make sure it works.
--EGR Modulator. I followed directions to check this and it seemed OK but I think I should do it again to be sure.
--Modulator vacuum lines
--EGR Tube, Valve, EGR plenum passages, plenum carbon buildup
--EGR Temp sensor electrical resistance test with multimeter
Now by "tube" do you mean the metal pipe going from the cylinder head to the valve or the internal passages inside the "Y" intake plenum? I assumed I'd need to check and possibly clean both, plus the EGR valve itself once it's off the car.
I've got a can of cleaner, a plastic tub and a hard nylon brush to get at the carbon buildup. For the passages I was going to pick and chip away at the (assumed present) clogging with a plastic fine straw and fine screwdriver picks.
But you're saying there are two changes in direction for the EGR passage? It looks like only one straight shot from the EGR valve mating area and then a 120-degree shift into the interior of the manifold. There's another bend inside there?
...
I looked at a youtube video showing an interesting trick: take an electric variable speed drill and an old metal mechanical speedo drive cable, put the cable end into the drill like a bit and once the intake cleaner has already started to break down the top carbon surface, snake the bit in the clogged EGR passage at moderate drill speed and keep feeding it deeper and let its flexibility navigate those bends.
Not long after I posted that the IACV seemed to be the culprit with my mystery cold start rough idle... it came back, same as before.
Additionally, the Code 71 EGR issue has been difficult to diagnose, plus a hesitation issue seems to have come up by the time I hit almost 40mph and above 40mph. I had initially been concerned that this was related to the break-in period of my clutch but it just doesn't present itself until at least 35mph and above when I want a bit more acceleration. The new clutch is fine so far.
I became curious today if it might in fact be a sign of my fuel pump beginning to fail-- that maybe it's not operating well in +12V mode. Completely unsure on that, since I already did the Fuel ECU bypass test.
What is for sure is this, in regards to the EGR issue:
1) Last week I took off the intake "Y" plenum and got into it with two cans of intake cleaner, scrubbing carbon deposits and laboriously cleaning out the EGR passage (which did appear to be clogged at first) until I finally got it to drain cleaner out of the valve mating side. I didn't get it all perfectly clean but I think I made a major improvement in both the main intake tract and by scrubbing and scraping inside the EGR passage and saturating the crossover tube with cleaner until I could see it drain out the other side.
Result: After that, I reset the ECU and drove the car. The CEL Code 71 came back on in about 39 miles.
2.) My mechanic re-tested the EGR Vacuum Modulator and demonstrated the blow-test. We confirmed the diaphragm was bad. He tested the EGR valve directly (on the car with it running) and he did not at that time think it had gone bad since it did react to the vacuum test.
I bought a new EGR Vac Modulator from Toyota and put it in. I also replaced any loose EGR vacuum lines with new, tight ones. I did an ECU reset again.
Result: The car SEEMED to idle and drive a bit better right away (but the 35-40mph+ hesitation was still there) but the CEL light came back on after just under 50 miles of driving. That was tonight.
3.) Frustrated, I checked the EGR VSV again to be sure I had a pressure reading from BOTH hose connections. One side registered no vacuum reading at all.
I pulled off the original EGR VSV and found that the original P/N is actually 90910-12125-A... NOT the discontinued 89470-24010 I had been told was the correct number for that location. Holding the two together to compare and there was no question... they are completely different VSVs. The diameter of the nipples on the incorrect one are also larger and won't fit the same hoses already on the car.
I've picked up a used one from ebay and I'll see if that does anything. I also tried ordering the part number new-- why not at this point?
Tomorrow I get the system looked at again at my mechanic's.
......
Based on what he said, an EGR valve that isn't operating correctly at the right time can possibly cause the hesitation I'm experiencing. Possibly.
However if that hesitation is not related to my EGR then it does make me wonder about the last few items that I HAVEN'T replaced to solve my original rough cold start idle issue:
--Fuel pump ECU?
--Fuel pump?
--TPS sensor?
--Send out the 1992 SC300 M/T Cali-Spec ECU I have to Tanin, have that rebuilt, get it back and see if... perhaps... the pricey Toyota Reman ECU is in fact not in such good condition after all?
I'm not so certain about the very last one but I am going to have that recent ECU find serviced by them anyway. And once I have it back I will have no need for the incorrect 1995 M/T Cali-Spec ECU I've also got set aside.
Last edited by KahnBB6; 03-18-16 at 12:30 AM.
Reason: Corrections/additions
That 35-40 MPH hesitation is the exact range where my SC400 struggled until I figured out it was the ignition coils. I can't remember if you already addressed that, but it seems like a big coincidence.
Had the shop test the EGR VSV. They say it's okay. Maybe I tested it right the very first time. Still, a correct spare is not something I'm unhappy about.
t2d2, no coils on a non-VVTi 2JZ-GE. The plugs, cap, rotor, wires and distributor are new. I assume if the ignitor were bad it just wouldn't fire at all.
It's probably time to take off and clean the EGR valve and tube at this point.
Last night I took off the EGR tube and original EGR valve.
That tube is a doozy to get to. It requires a 12mm socket, some very short extenders, then a flex joint, then 2-3 long extensions poking out near your fuse box before you connect your torque wrench (the two bolts are 15ft-lbs. Loosen or torque them carefully with all those extensions). The huge pipe nut is 47ft-lbs and requires a 32mm open end wrench or, to be accurate, a 32mm crows-foot socket (looks like the just the "C" of a wrench with a 3/8" opening at the end) connected to a torque wrench. I believe there is a minor torque correction factor when you use a crows-foot socket with a torque wrench.
I kept trying from the rear top of the engine until I discovered this very helpful thread which explained how to get to the lower EGR pipe bolts from the rear SIDE of the engine:
Anyway, there was some carbon buildup in the pipe which I cleaned but the majority of carbon clogging was in the EGR valve itself. The valve worked fine when connected to vacuum but there was buildup in the chamber which had to be cleaned away.
Also in the section that connects to the 32mm nut, in the temp sensor area and finally what I figured was the culprit... total blockage in the port area and tiny removable metal tube that connects to the EGR vacuum modulator. This has a small phillips screw that you remove before you can carefully pull out the tube with a pair of pliers. Both the little tube and the port it fits into were totally blocked with carbon. LOTS of cleaning last night.
Once I cleaned all of that I also got rid of a little bit of the carbon buildup on the cylinder head port but there wasn't much I could do there with the head on the engine.
New gaskets were used and the system reassembled and all vacuum lines checked.
I started the engine and let it warm a bit. (The rough cold start was still there but as always it went away within a few seconds. No hesitation with the starting as per usual... just rough idle for 3-10 seconds).
On the test drive for the first seven miles I still had that hesitation but after that everything ran much smoother. I did not notice the hesitation any longer at all, idle was SMOOTH again and engine response was much better again. I was very happy.
I intended to drive for fifty miles just to be sure the EGR CEL wouldn't come on but right at 29 miles, there it was again...
So the car does appear to be running much better than before after all the cleaning but I still have a code 71 issue.
--Cleaned intake "Y" plenum and EGR port which seemed to be clogged (although I did not punch out the freeze plug looking part directly allowing access into the plenum's EGR tube area)
--Tested EGR VSV and it's working fine. Bought another one just in case.
--Replaced the apparently failed EGR vacuum modulator with a new OEM part
--Replaced any loose vacuum lines in the EGR area
--Removed and carbon cleaned the EGR tube and EGR valve and removed total carbon blockage in the modulator port area
--New EGR gaskets at the valve-to-intake-plenum and tube-to-cylinder-head mating areas
So I'm a bit confused now. A lot of cleaning has taken place, at least two blockages cleared and one major component has been replaced. The car is definitely running better now.
Since the EGR valve responds to vacuum pressure tests I don't think it's that.
All I have left are:
--EGR Temp sensor (ordered an OEM from Amayama)
--Removing the "Y" plenum again to gain access to the tap-in "freeze plug" that allows direct access to the manifold's EGR tube and clean anything I find in there too.
Here's a Celica-Supra DIY article showing a very similar (but located in a totally different way) plug area for the internal EGR tube inside the intake plenum. This is the only thing I did not think of removing to clean directly:
And.... I'm still wrong. Last night after at least twenty straight miles of good acceleration without any bucking or hesitation at all, tonight that symptom is back again, albeit in a milder form.
The idle (after cold startup of course) is still smooth and most of the engine's acceleration characteristics do feel smoother but I'm still getting the occasional hesitation for some reason.
I'm going to guess that this means there still is a flow restriction somewhere. I don't know where else that could be at this point except the intake manifold passage that I already cleaned. I'm already looking for the "plug" part that I plan to tap out to access the deepest part of the intake EGR path. In case I damage or deform my original one taking it out I want to have a spare to replace it but the Toyota online ordering system doesn't list this.
If it's not that or the EGR temp sensor causing the Code 71 and the (now diminished) acceleration hesitation then I can take out the old EGR valve and install the aftermarket SMP valve... but since cleaning and testing the old valve with a vacuum pump gauge I still don't think that's the problem.
What's so surprising about all of this is that there was NO warning and a few months prior I passed an emissions pre-test I'd done just to make sure I would be OK for my smog in May. Then all of a sudden it's a wild goose chase with the EGR system. I'd have expected warning signs prior but NOPE.
A used correct type EGR VSV arrived today in the mail. I hooked it up to two test leads and followed the TSRM procedure to see if it held vacuum and released when +12V was applied. It clicked when it should have and did hold and release pressure correctly.
I performed the same test to the car's original EGR VSV with the engine off this time. No click. Nothing. Dead. I'm not sure what the one mechanic at the shop I use tested with that VSV but he clearly wasn't doing it right. My initial diagnosis of a failed EGR VSV was correct.
I replaced it with the used VSV and reset the ECU. I'll see if a CEL comes back on in 30-50 miles.
The hesitation upon acceleration at 40mph+ is still there and I've turned my attention to a possibly misadjusted or failing TPS sensor... even though I have no CEL code for that and even though my idle isn't hunting (although it's around 800-900 currently).
I'll go through the TSRM adjustment procedure for that tomorrow.
I've tried ordering a new 2JZ-GE EGR VSV in the correct part number to have as a backup and will see if Toyota comes back saying it's discontinued. I've also ordered a new TPS sensor.
It would be magic if the TPS sensor has been what's caused my cold start rough idle all this time. Will see.
Ran the resistance test with a multimeter on my TPS with some clamp leads and noted the values for the idle circuit and VT1 circuit with the throttle at closed, idle, part throttle and WOT positions. The idle function seemed to be within range but the VT1 only gave the lower range of its signal. Advancing the throttle position during the VT1 test did not really produce any varying resistance values for the first few millimeters and right before the part-throttle position... it just goes to zilch. It started at .417 or .418 and only momentarily gave .5xx to .8xx readings inconsistently before showing virtually no figure at all. Most of the time the only reading I could get was .417 at the full closed position.
It didn't matter when I tried adjusting the sensor from the marked position. The VT1 resistance range seemed to be nearly shot. I'm not sure why there hasn't been a CEL Code 41 for this yet.
Since the idle circuit test seemed to show me the ranges the TSRM demands but the other test was completely off I'm going to guess it's a good idea that I ordered a new TPS sensor. Possibly this is what's been causing my hesitation at part throttle.
I haven't used full throttle yet since the new clutch has been installed. I still have 125 miles of break in left before I can do that.
The replacement EGR VSV did the trick! The CEL Code 71 did not return after 54 miles from the last ECU reset! And it turns out that the part is in fact not discontinued (yet). My order for a new one went through. Most of the Toyota EPC's will give you an incorrect part number for the 2JZ-GE EGR VSV. It is 90910-12125, same as the number on all factory 2JZ-GE EGR VSVs from 1992-1997.
So with that code I had:
--clogged intake plenum EGR passage
--clogged EGR valve port-to-vacuum-modulator
--bad EGR vacuum modulator
--bad EGR VSV
--carbon buildup (but not clogging) in the EGR valve and EGR pipe
--probably a couple of vacuum hoses to the modulator that weren't sealing
......
With the Code 71 solved, next up is to replace the TPS sensor, calibrate it and see if that cures both the intermittent acceleration hesitation and rough cold start idle.
To note, the factory 89452-33010 TPS sensor has been discontinued and now supersedes to TPS sensor 89452-32060 which is a bit more expensive than the original.
Edit: I also learned that TPS Sensor 89452-22090 works as well. I threw that on the car since I had one already stored away for my GTE swap. Issue still seems to be present. Since my current fuel filter has 44,000 miles on it I am going to try getting that replaced as well since most sources recommend changing those around 30k or so.
Last edited by KahnBB6; 03-24-16 at 01:27 AM.
Reason: Additional information/update
Driving this evening a CEL came back on again. When I could pull over and check it, sure enough, it was another Code 71. This time it took 80 miles to show up. Some of these fixes must be doing something.
I checked the EGR valve directly again with a vacuum test and as before, the engine doesn't really respond or sound like it's stalling out all that much after 5 Hg or even 10-20 Hg of direct vacuum pressure. Even though I was assured the valve was okay I am beginning to think this was about the same as my original EGR VSV being "okay" when it was actually dead.
The used replacement EGR VSV still checked out when doing the battery +12V and input air test.
So for the EGR system this now leaves me with:
1) Take out the original thoroughly cleaned and checked original OEM EGR Valve, replace it with the SMP AC425 / Intermotor EGV867 aftermarket EGR valve
2) Replace the EGR temperature sensor. I assume OEM is what I should use but there are Standard Motor Products and an Airtex/Wells aftermarket versions available for not too much less than a factory sensor.
3) Remove the top aluminum intake "Y" pipe and clean the EGR port all over again, this time punching out the "freeze plug" area to directly clean the internal metal tube.
Great timing, this. I just got my registration renewal bill in the mail directing me to a STAR Test Only smog station. I still have time but... holy hell, car.
...
I installed the spare new TPS sensor I had. Something seems slightly better but the hesitation and startup issue did not go away. Since I noticed my OEM fuel filter has 43K miles on it I've ordered a new one to put in and I'm currently waiting on that.
I did the Fuel ECU bypass test again (at the Diagnostic port) and startup wasn't any different, nor did the hesitation go away. Although today it wasn't so bad as before.
So if a new fuel filter doesn't cure that problem I am going to have to assume I'll need a new Denso SC300 fuel pump. Thankfully they aren't too expensive.
Edit: Currently I'm trying to figure out if I can order a replacement "freeze plug" in order to have a standby replacement to directly access the intake manifold "Y" internal EGR tube. Hoping I don't have to do this but I also don't want to pop it out only to find I can't seal it with the original plug again.
Last edited by KahnBB6; 03-26-16 at 05:08 AM.
Reason: Grammatical correcton
Great timing, this. I just got my registration renewal bill in the mail directing me to a STAR Test Only smog station. I still have time but... holy hell, car.
Assuming its' a sensor issue and not an emissions issue, does the 30->40->80 mile increasing range between CELs give you sufficient time to get it through the test? Maybe leave a few minutes early, stop a couple blocks from the test site, pull the EFI fuse to reset the codes, then let 'er rip.
And if that assumption is correct and it actually is an emissions problem, I imagine you can retest without too much added difficulty, once getting it sorted out?
t2d2, I think it just depends on how many miles it takes for the ECU to relearn its cycles after you reset it. I think it should be no more than 50 miles required but it could be as little as 25-30 miles. Not sure. The CEL is coming on for some reason though and I've narrowed it down to only a couple of things at this point.
I do see the increasing intervals of miles between repairs before the CEL 71 comes back as a good sign though. Things were defective.
Even with an OBD1 car you have to let the ECU get through that first 25-50 miles after a reset for the emissions test to work. I don't want to risk failing and then retesting. They ding the car's permanent record here with, basically, sending you to Star Test Only stations (which are much more stringent) for the rest of the life of the car.
I have until May to get the smog test done but since this is a step by step troubleshooting process when I have free time I've wanted to find the problem(s) sooner rather than later.
I suspected the EGR temp sensor last night so I got out the manual and looked at the K Ohm figures it's supposed to read at different temperatures. On my multimeter mine didn't get anywhere near the correct ranges after a good long drive. 58 K Ohms to 65 K Ohms at the start (TSRM states that's about the range for 120F) but only 81 K Ohms lowest reading after my drive. Seems to suggest it's not operating within range to me since it's supposed to be something like 15 K Ohms resistance at 302F.
That sensor also has 239K miles on it so reluctantly I ordered one of those pricey things from Toyota.
I hope that does it. If not, it's one more EGR component that had failed anyway. The only options left after that are installing the new aftermarket EGR valve and/or re-cleanining the intake manifold EGR passage which would be the most difficult.
...
Also I'm continuing to monitor how the throttle acts under acceleration. Last night I noticed no hesitation but I also had the EGR temp sensor temporarily disconnected for testing purposes. I'm going to see if that really is/was a separate issue unrelated to the EGR or not.
Edit: Hesitation around 40mph+ or third gear again earlier tonight (EGR temp sensor plugged in this time). Still keeping an eye on that.
The new fuel filter and new EGR temp sensor won't be delivered for several days. The new clutch is just about at the 500 mile break in point. I'll give it a bit more before easing into any full throttle or 4000rpm+ revs. I'm going to throw in a new air filter too to see what happens.
This thread so far best describes what I've been experiencing with the part throttle hesitation issue:
Even with an OBD1 car you have to let the ECU get through that first 25-50 miles after a reset for the emissions test to work. I don't want to risk failing and then retesting. They ding the car's permanent record here with, basically, sending you to Star Test Only stations (which are much more stringent) for the rest of the life of the car.
Dang, they make that difficult! The areas up here with DEQ, last time I had to go through it many, many years ago, it was a joke of a process. It's amazing how much more stringent CARB is in every detail.
The EGR temp sensor sounds like a very plausible culprit. If it's reading faulty, and possibly inconsistent, as it warms up, that could explain it taking a good number of miles to trip the CEL.
^^ Until you have an issue like this (or modify the engine, ha ha) it's actually a pretty routine and simple process when you get tested. Even a basic fix like a gas cap or evap part isn't all that complicated.
It's when you have an emissions control part somewhere in one of the subsystems go bad and you have to hunt for the issue that it gets hairy because, as you pointed out, CA wants everything to work no matter what. Although there is some leniency after you've proven you've spent $500 or so to fix a failed smog issue. However I'm pretty sure that just puts your car into the "gross polluter" list which means you'd be more likely to be "randomly selected" for a smog out of your normal 2-year interval. They have been known to do that sort of thing in some cases. Better to figure out the issues and avoid the ire of the ARB. Keeping a classic car maintained out here is enough trouble as is. Oregon not being all that stringent is surprising actually. Then there's the total opposite: Florida
I hope you're right about the EGR temp sensor. I also bought this neat tool which is a flexible super long drill bit that is used to snake into EGR passages and bore out the carbon deposits with a variable speed drill. If the EGR temp sensor doesn't cure the issue, out comes my intake manifold "Y" a second time to use that thing.
It makes me wish I'd known about the tool weeks ago when I first did the intake passage cleaning. Hopefully that's not the issue but if it is I think this bendable drill tool is my best bet.
I'm now wishing I'd just bought a new fuel filter locally. Waiting on the part to be shipped out was a poor decision on my part.
With my hesitation I'm currently thinking it's the fuel filter, fuel pump or possibly the fuel pressure regulator. Hopefully just the first of those.
Yeah, it's surprising, with Oregon's eco-friendly reputation for most stuff, that we only have DEQ for the Portland Metro area. And last time I went through that, it was nothing but a tailpipe sniffer test that required a quick tweak by the mechanic to pass.
Are you still on the original fuel filter? I wouldn't wish changing that on anyone... Be prepared to cut the fuel lines off and bond new ones in! And get a siphon pump to completely empty the tank. (I didn't know at the time, my gauge reads ~3 ga low, so I had like 5 ga of gas flowing down my arm for hours while I wrestled with that nonsense. Damn the pre-purchase inspection mechanic who listed that as a recommended maintenance item!! My skin was blistered for weeks.) It's the biggest factory screw up on the car, and since the filters are supposedly considered a lifetime item, I would put it off until you're out of alternatives. That or take it to an unsuspecting mechanic who you don't plan on working with in the future, and have them do it as a flat fee...
03-06-16, 08:52 PM
