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The issue I'd mentioned in earlier pages wherein there was a temperamental mystery leak somewhere near the back of the engine turned out to be the coolant bypass hose located on the rear of the 2JZ-GE cylinder head which extends to the Heater Control Valve. The twenty-four year old hose and clamp were leaking onto the rear of the engine, onto the transmission bellhousing and from there onto the ground. It had happened intermittently in the past but finally began showing signs consistently a couple of days ago.
And since it was also leaking, I replaced the hose the goes from one heater core connection into a secondary hose which eventually feeds into the metal coolant bypass pipe that extends from the 2JZ-GE water pump.
Also replaced due to leaking:
87251-24040 "Joint. Water" (<-- this one may be getting hard to find now)
90467-22011 "Clamp" x2"
The Toyota microfiche diagram's depiction of the cylinder head connection is not visually accurate but everything else is:
With that long lingering unresolved issue now being solved the only remaining thing related to the concerns on page one is now the very consistent rough startup issue which happens every time the engine has cooled down or is started from cold. After having replaced the fuel injectors, fuel pressure regulator and many of the main electronics and sensors I am left suspecting either the original 24 year old fuel pump or the 24 year old fuel pump ECU as best guesses.
The issue is only lessened by leaving the key in the full pre-ignition position and pausing as many as 10-20 seconds before initiating startup. I attribute this to... well... *something* getting electricity for quite a bit longer than a second or less before full electrical load is applied to start the engine. This is why I haven't ruled out the GE fuel ECU since it does have a big capacitor in there.
However I have no other driveability issues associated with the fuel pump or fuel ECU so time will tell of further diagnosis.
I will hopefully be resolving the final lingering issue within the summer depending on whether or not anything changes in this startup behavior. When and if I resolve that I will post my results here and that will have formally addressed everything that was listed as an issue from page one of this thread.
Last edited by KahnBB6; 09-10-16 at 01:21 PM.
Reason: Grammatical fixes and clarifications
I have still been living with the intermittent rough starting issue (but NOT all the other issues detailed earlier in this thread) I have noticed a slow but gradual deterioration of the condition. It is no longer showing up just when the engine is cold. That is still usually the case but I notice milder versions of this even when parking the car for only 15-30 minutes. Other times... no issue. A few times I have suspected some extremely brief hesitation when accelerating flat out to 70mph on the highway under full load.
Mainly I am feeling that the roughness during startup isn't getting any better. Sometimes it is worse than before. But it always clears up within 30-40 seconds.
Idle varies from glass smooth to not quite smooth at all. But idle in traffic long after warmup is nowhere near as bad as it is when initially starting up.
A small handful of random times I have noticed the car suddenly seem to misfire when it is allowed to idle untouched for several long durations of minutes at a time. Once during a smog pre-test months ago. Maybe 2-3 times since then under normal circumstances when I was just sitting in the car and stopped with the engine idling for a while. This particular observation has still been a rare one for me. A little revving seems to cure it without return.
I was choosing to ignore it since it seemed not to get any worse but now I think it is time to address it once and for all.
.....
So given all of that, I've researched these threads:
...And I've come to the hunch that since all other potential culprits have been previously addressed (check earlier posts in this thread) this specific startup symptom might have to do with my twenty-four year old, 243,800+ mile original-to-the-car fuel pump which was originally designed to last perhaps 18-20 years.
To recap, the injectors, plugs, cap, rotor, distributor, Coolant Temp ECU, TPS sensor, IACV, EGR system and fuel filter and many other parts and sensors were all recently overhauled. Other symptoms and conditions were cured from addressing those but not this original one.
I have tried the fuel pump ECU FP & +B jumper bypass test multiple times but that never cured the issue for me or caused a change in the rough startup roughness/misfire before it settled out until the next time.
I'm going to buy a Denso NA pump kit with a new screen and install that to see what happens. I'm saving my Denso Supra TT pump kit for later and frankly to avoid more complexity than I need to right now. If after that it turns out that I do need to either replace the NA FP ECU or run the +12V Mod w/relay then the car will be all the more prepared to accept it.
Final update and resolution to this thread soon I hope.
Totally random, but I was just reading up on hose ratings for various applications and discovered there are two sorts of fuel hose: ones designed for in-tank use (continual submersion) and ones designed for use under the hood. The latter isn't coated externally to withstand submersion, while the former isn't doesn't have the external layer to withstand heat, oil, ozone, and exhaust.
I'm not even sure where you would source the in-tank type, but as long as you're in there changing the pump, it might be worth checking that you have the right type of hose.
doing the jumper bypass test should fill the rail with pressure and then when you start it should be fine, so if its still rough on the start I think its something else.
Totally random, but I was just reading up on hose ratings for various applications and discovered there are two sorts of fuel hose: ones designed for in-tank use (continual submersion) and ones designed for use under the hood. The latter isn't coated externally to withstand submersion, while the former isn't doesn't have the external layer to withstand heat, oil, ozone, and exhaust.
I'm not even sure where you would source the in-tank type, but as long as you're in there changing the pump, it might be worth checking that you have the right type of hose.
I thought of that too so when ordering I picked up the Denso pump kit with a brand new strainer, clamp hardware and the special in-tank rubber hoses for the pump. I'm not convinced it's the original pump hoses but it can't hurt to replace them after nearly a quarter century.
Originally Posted by Ali SC3
doing the jumper bypass test should fill the rail with pressure and then when you start it should be fine, so if its still rough on the start I think its something else.
This is also what I've felt has been the case since I have tried the jumper bypass test more than once with no change in the rough startup behavior. If replacing my fuel pump first is an overkill measure I'm okay with that given the age of the original. If after changing it out the problem still persists even with the fuel ECU bypass then I think I'll be out of ideas.
Other than the fuel pump and FP ECU only the engine starter and ignitor have not been changed but I don't see those as being related to this issue.
I keep forgetting to report back to you on the similar issue I was having *rough start/idle on cold. I'm sure I posted about my symptoms somewhere, but for the life of me cannot remember where.
Previously, when cold - my car would crank longer than usual (2 seconds). Once running, the idle would be rough and lower than usual - it took a step on the gas to bring it to a "cold" idle, above/around the 1k rpm. It would do this when cold/parked for a long time. I especially noticed it in the morning, then starting again when going home from work.
As you know, I sent my ECU to have Tanin fix and completely did not get to re-diagnose the rough cold idle start due to my fuel pump dying a few days afterwards. It's all in my post here: https://www.clublexus.com/forums/per...missing-2.html
I am happy to report that after replacing the fuel pump, the culprit to my no start issue, along with other bits and pieces, I no longer have that rough cold idle start issue. It now starts right up at the typical cold idle. However, take all of this with a grain of salt, as it may or may not be completely similar to your problem.
Just to recap, Things I have replaced and to troubleshoot the dead fuel pump:
-ECU repair (Tanin)
-Fuel Pump (Walbro)
-Fuel Pump ECU
-Ignition Coil
-Coolant Temp Sensor
That certainly helps and puts the weight in favor of replacing my fuel pump. I haven't installed mine yet but I plan to this week. I do hope I have a similar result to yours at long last. What I have not been able to confirm is any incident of too little fuel output at higher RPMs under load. Other than the car having always felt underpowered (no turbo) I don't feel like I've had actual drivability issues at speed due to fuel pump malfunction.
So I will get the new pump installed. If symptoms still persist I may replace my ignition coil (one of the few components I did not yet replace). If I'm still getting symptoms I could switch to my other Tanin-repaired ECU for testing but both my ECUs have been serviced and I don't feel they are part of this issue. Last thing I will try if all else fails is the +12V Mod w/relay but I'm holding off on that for now since the FP & +B jumper test does not produce different results.
Hmm.... it could be similar to my issue but it sounds ever so slightly different in your case. I don't know that it's the same thing honestly. Mine sounds a little rougher than yours when it does happen and then it clears up with a few hiccups after about 30 seconds or less.
Hmm.... it could be similar to my issue but it sounds ever so slightly different in your case. I don't know that it's the same thing honestly. Mine sounds a little rougher than yours when it does happen and then it clears up with a few hiccups after about 30 seconds or less.
Sorry wrong video, This is after the fix. I'll try to find the video of when it was still acting up.
I finally installed a new OEM-spec Denso NA fuel pump kit w/new strainer (Denso #950-0109) and a new tank seal gasket (Denso #954-0018). Upon buttoning everything up and starting fully cold without leaving the ignition in Accessory before turning fully to Ignition (up until now I have been doing this on the hunch to reduce the incidence of the rough/misfire start condition)... I noticed NONE of the previous symptoms from before. The idle also appears to be smoother and acceleration feels slightly more consistent and unwavering than before.
It has been a cold night (50's-40's) so I'll have to see how it performs in warmer temperatures but even after leaving the SC to cool down for a couple of hours the startup is so far consistently normal again.
I'm going to monitor this for the next few days before calling every symptom I originally brought up in this thread solved but it looks like my fuel pump has been slowly wearing out over the last twelve months *in addition* to the other things addressed in previous pages.
It's looking like replacing the fuel pump has finally solved my last remaining symptom (actually it was the original first symptom before other symptoms started piling on one after another).
Even though I am getting closer to needing a Denso Supra TT fuel pump upgrade I wasn't ready to deviate from the stock fuel system just yet and buying these parts from Denso rather than Toyota and doing it myself made for a relatively inexpensive fix. The hardest part was simply finding the time to do it and getting into a slow week where I could drive around for a few days with a nearly empty fuel tank until I was ready to tackle it.
For anyone who is interested in the SC300/SC400 TSRM procedure for this, refer to pages 2031-2035
The new fuel pump did not clear up the occasional rough starting issue. It seemed to at first but the same symptom as before showed up again this evening after starting from full cold.
The car does however idle smoother and it seems to run a bit better as a result of having installed the fresh fuel pump.
I don't have any more ideas to try at this point so I will probably leave this part of my issues unsolved. I could guess that it is the igniter, a bad remanufactured injector what has an undetectable issue that ONLY affects startup sometimes or even something related to the ongoing internal coolant leak that I have to monitor closely now while I build my GTE engine. That issue alone is now addressed with 500 mile cheap oil and filter changes and regular checks of the coolant level in the radiator.
Altogether the SC still runs beautifully post-warmup and even after the initial 5-30 seconds of rough cold start idle.
Frustrating... but it's been going on like this for exactly a year now. Everything else has been fixed other than this issue that showed up in the beginning. C'est la vie...
Or maybe it is this as suggested by Ali SC3 in Post #8, Page 1 of this thread (see below). I hope not because if there is no way to know if a reman injector is leaking and only at startup then it sure doesn't bode well after having just recently spent a lot of money replacing both cats only to have them get eaten up like the last ones I replaced... which were also not very old themselves.
Certainly there is a slow internal coolant leak affecting the oil viscosity but so far the car is usable. Maybe the only cure for this short of throwing away $2k on a head gasket job is the GTE engine swap.
Maybe Ali's hunch has been right all along.... but it's worth noting that the startup issue predated my replacing the original injectors (which may have had other issues at the time) with remans OEM injectors.
I'm fresh out of ideas. The car is fine otherwise and I just need to to soldier on for now.
Originally Posted by Ali SC3
you wont be able to hear a bad injector always. sometimes they just leak when they are off and work fine when they are running.
our cars are designed to have pressure in the rail when its on, and then when you turn it off the pressure stays in the rail and the injectors for the next startup.
if you have a leaky injector, all that pressure causes it to push out all the fuel in the rail into that cylinder while it sits, the longer it sits the more fuel leaks in.
this fuel is not combusted really cause there is so much the plug does not fire and is "wet" so all that raw fuel gets pushed out into the exhaust and catylitic converter.
then the cylinder will start combusting after the plug sort of dries off (hence the hard start where it feels like its a cylinder down or so), and then when the exhaust heats up, it starts to burn up that fuel sitting in the exhaust and right on top of the cat, and after enough times it will melt right through the cats, so its good to sort out fueling problems sooner than later.
not trying to scare you lol, but raw fuel in exhaust it the number one ruiner of catalytic converters, otherwise they generally last the life of the vehicle.
...And it got me thinking about my car because it has been mentioned to me by more than one person that even after all of the replaced electronic parts, EGR replacement and cleaning, Reman injectors, ECU repair, etc. that I did up until the deadline for my last emission test... PLUS the new fuel pump and new plugs, cap and rotors recently... I was told on occasion that I was still running a bit rich sometimes. I didn't smell or see it myself but I figured that if at least three people who didn't know each other had the same comment it might mean something (plus... I hope that brand new #1 cat is still okay).
Anyway, the only part I HAD NOT replaced in the ignition system, emission system, fuel system, with electrical sensors was my original 24 year old ignition coil (aka igniter). This is due to it having been ruled out, supposedly after extensive diagnosis and after several other parts having been confirmed to have failed before they were replaced.
When I read through the linked thread above it did make me wonder if the same condition might be possible on a 3.0L 2JZ-GE which has the single igniter versus the early 4.0L 1UZ-FE's two igniters for its twin distributors.
Even though I have never noticed a glowing catalytic convertor during my troubles or at this time I decided to bite the bullet and order up a new 90919-02207 OEM Ignition Coil. Aftermarket versions exist and of course I didn't get it at MSRP which can be a bit ridiculous. Nonetheless I wanted the Toyota version.
It took all of two minutes to disconnect the battery, disconnect and unbolt the 24 year old coil, bolt up the new one and reconnect the battery.
Upon firing up the car I had no issues. To note, after I'd parked my car for a month and started it up before I also noticed no startup issue for the first couple of days of using it again... but I did a few days later (with the original ignition coil). After tonight I will still be monitoring for any resurgence of the rough startup symptom.
However I can report that idle, pickup, smoothness and responsiveness at all speeds felt MUCH better. Even more so than after I installed the new OEM fuel pump. It really wanted to move and hadn't felt this good in a long time. All my midrange and 5k+ RPM power had returned.
It seems a lot of these old parts were getting tired. Every time I replace one of them the car feels that much better than before. Each of them affected an aspect of the car's operation, feel, fuel economy and engine response but installing a brand new ignition coil really does seem to have cleaned up the performance of the ignition system as a whole.
So hopefully I will be able to report that THIS repair will finally pinpoint what my rough startup gremlin has been all along... in addition to the other worn parts that still needed replacing. It would make sense that if the ignition system were still putting out weak spark to all the cylinders I might not be running at full efficiency.
.......
My last indirect thing that I am still paying attention to is the health of my 243k+ mile original 80-amp alternator since I occasionally see the battery light come on at startup before it goes out within a few seconds (maybe that was the coil or maybe I need to be sure my alt's voltage regulator is still OK). That has only happened a couple of times so I am not very concerned but I guess it couldn't hurt to get the alternator checked again at a shop that has one of those advanced diagnostic devices for alternators and batteries.
But I have to say... after replacing this coil and waking up the ignition system... I am reminded of what a fantastic car this is! When it's really been gone through, tuned up and set up right you can't say an SC300 with a manual transmission even with the stock engine isn't one hell of a fun and refined practical muscle coupe. Unless you count fuel economy... but that's a given.
I guess if there is a takeaway from this post it is that usually replacing an ignition coil is not needed when tuning up an old stock SC300 but since they're all at or near 25 years at this point replacing the ignition coil on a 1992-1997 certainly cannot hurt.
....
Also, yes, I am still monitoring the coolant leak, continuing to change my oil every 500-700 miles to be extremely safe (cheap 10W30 now) and I'm still sending samples in to Blackstone to keep tabs on the data. However to drive the car right now you'd hardly know there were a major issue of concern like that.
Progress on the replacement engine is still ongoing but very, very slow so in the meantime I hope everything is fine for now.
my sons 93 sc300 just hit 80k miles today.not even broken in yet.
243k miles that is amazing!,and running great.
my 93 sc400 is at 112k miles.
i love these cars,LOL
09-09-16, 11:08 PM
