KahnBB6

iTrader: (5)

ECU arrived at Tanin today. I spoke to them briefly and they will recondition anything they deem as amiss and replace any potential problem capacitors they know are likely to fail and cause damage even if they haven't yet.

I've also ordered a new OEM Denso distributor from Japan. FAR cheaper than any available in the USA ($550-$700 is a bit of a double take) but not sure if I'll get it in time to install before the holidays. That's perhaps overkill but given the severely premature wear on the plugs, cap and rotor, the strange cold start misfiring that cures itself, the warm idle misfiring, and the small oil leak on the underside metal plate that's ben present for at least three years now despite a new O-ring I just decided to rule that one out too. The distributor is as old as the car and not hard to replace once I have it.

Having the same relative symptoms with two different ECU's, even if one seems a bit less symptomatic than the other, and after new injectors and after a new plugs/cap/rotor/wire tune-up still made me think it had something else to do with basic ignition timing. And given all I've already done, in a GE that makes me think of the distributor.

If I'm wrong... but I really don't think I am... oh well. I'm still not sure when I'll have the GTE swap ready to convert the existing short block and I'd rather the car be fixed or future proofed for now as my DD.

But this has been some expensive trial and error of diagnosing symptoms.

In retrospect, at least one mechanic warned me about possibly replacing the distributor in the past.

As long as the original distributor holds out for the next ten days, I'll be happy.

t2d2, I know you've kept telling me about cleaning my IAC-V and I will. This just seemed like the next last logical chance to take since ordering parts takes a while. I may end up being wrong, but I won't mind too much once all is said and done if I am.

t2d2

iTrader: (8)

No reason you can't take apart the IAC and clean/service it while waiting on all the sparkly new parts.

KahnBB6

iTrader: (5)

^^ That's true!

Looked it up the other day and fond this image online. If accurate, that's a very easy sensor to get to. Hard to believe some places want $700 for it.

t2d2

iTrader: (8)

Yep, that's it. The part number is shown as the same 2-piece, serviceable one on the '92-94 SC400, so you can take it apart for inspection without removing it from the intake. There should be three phillips screws holding the black plastic housing onto the metal base. Remove those and the whole thing pulls apart. Use caution in disconnecting the electrical plug, as it can be a pretty tight fit and the lock tab is less sturdy than the rest of it. I always use a flathead screwdriver to gradually pry it free while holding the tab down.

Even by crazy OEM pricing standards, the only way I can see them justifying the $700 price tag is the stepper motor and however complex that setup is to turn the bearings. The valve itself is something that could be built with scrap parts for a few cents.

KahnBB6

iTrader: (5)

^^ I've looked at mine and my electrical plug has begun to deteriorate in the plastic areas. It's in snug and tight and isn't going anywhere but I won't need to worry about the plastic tab-- the outer shell has disintegrated Not sure if I would find a part number to reference for replacing that connector on the harness with the surrounding area gone.

Question though... and sorry if you already explained this in your DIY thread for the IAC-V... why wouldn't I just want to remove the whole IAC-V from the engine to dismantle and clean it?

.......

Update:

The day before yesterday I began noticing some odd temperature gauge behavior while driving home. At first I worried about the worst case scenario (headgasket). After the car cooled down I checked the radiator and it was running low. Had to wait until morning to buy more coolant.

I also noticed that the old hoses at my HCV and heater core had been leaking. They weren't actively but maybe with enough heat and engine speed their age has begun to show. I cleaned up the dried coolant overspray on the firewall to check for further leaks under stress later.

I have all the OEM hoses in storage to replace them except for the two-piece connection from the heater core to the engine. That's the one I'm most suspicious of (picture below).

I topped off the radiator, burped the system and while that lingering start idle issue was still there, I now had no more temp gauge issues and far fewer misfires at idle. Initially I thought I had another coolant leak but it appears that was just some spillage from my refilling and burping.

But now I will keep an eye on those heater core hoses and get the new ones installed next month and I'll continue to monitor the bottom of the engine in case there actually is some other leak-- but that doesn't appear to be the case.

Looking back over the whole thread so far, perhaps many things were all becoming an issue around the same time. And perhaps I do have a slowly/intermittently leaking original heater core hose or at least a bad original tension clamp. Lots of curveballs this month :P

-Still waiting on Tanin to mail back the original ECU
-New distributor on the way later from Japan
-IAC-V cleaning to do
-Little round filter under the throttle body needs to be replaced (it fell off)
-Need to or just should replace those hoses at the firewall

Hoses I have:

87245-24290 -- Hose, Water (Lower HCV Hose to heater core, SC300)
87245-24300 -- Hose, Water (upper back of GE head to HCV, SC300)
87251-24040 —SC300 Heater Core to Block Hose 1 (Upper)

And I need to order (these numbers *should* be right):
87245-24270 —SC300 Heater Core to Block Hose 2 (Lower) -- Jan 2016 Edit: Confirmed that this hose has been discontinued.

t2d2

iTrader: (8)

That disintegrated connector sounds like a very likely culprit. Mine felt snug, too, but with the broken lock tab, it's deceptive.

The only reason not to remove the entire IAC assembly is convenience. But, since you're already investigating coolant leaks, draining the coolant to get the metal housing off the car isn't a deterrent. There's not really anything to do with that part, though. It's basically just the coolant routing and a chunk of metal that directs the valve's head at the hole it plugs or opens into the plenum.

I took my Dashpot out of the car yesterday after toting it around for a few days, just in case. I've yet to notice a difference under any conditions.

gerrb

iTrader: (34)

Craig - send me the shipping cost and I will send you an IACV from the SC300 or SC400 which ever you need . I have a couple of those from the SC300/SC400 junkpile I have.

btw , the sc300 I was bidding on for parts was taken out off the market by the insurance company so we will not get it .

scblackout

iTrader: (2)

Looking forward to hearing if the distributor fixes the issue as I have a few threads here describing almost the exact same problems I've been fighting off and on for months now. I have replaced EVERYTHING except the iacv and the distributor itself and still have the same problems you describe. The ecu fix from tanin did nothing for solving the problem.

KahnBB6

iTrader: (5)

gerrb, thank you! Though I haven't even gotten around to cleaning my original IAC-V yet (sorry t2d2. I haven't had the time to get in there yet other than refilling the coolant the other day). Let me see what I find first before you go to that trouble. It would be the SC300 version unless as t2d2 suggested they are the same part.

As for the insurance car... that sucks. More for your loss of the interior. Thanks for letting me know.

Interesting. Would you mind linking to the threads you mentioned which describe the same symptoms?

I won't have the distributor in hand until January. Right now I'm still waiting on Tanin Auto to let me know the prognosis. But for what it's worth, most of the issues were solved with the reman injectors and plug/cap/rotor/wire tune up. My low coolant issue appears to have been caused by old heater core hoses which only leak some of the time. Will be replacing all of them. I'd consider that unrelated to the main issue at this point.

Thanks t2d2. I will try to replace that connector if I can identify the number. It looks similar to the same harness connector used for the GTE IAC-V.

Noted about the IAC-V servicing. Apologies, I just haven't been able to have a free afternoon to tear into it yet as I'm up against a time crunch this week. Today I get to repair a tripod mounted camera slider.

Good to know you also haven't noticed any appreciable difference with the "Dashpot" off. That's been my experience too. I'm leaving it alone for now.

TaninAuto

Hello,

Have you contacted us about your continued issued? We are now replacing drivers in the ECU in addition to the capacitor replacement. The cost will be slightly more going forward, however we are offering this service free (less shipping) to anyone who purchased our ECU capacitor rebuild service in the past and are still experiencing issues.

So contact us and we will get this squared away.

TaninAuto

The ECU is in queue for repair. It will ship out Monday. We were waiting on components because going forward we are replacing all drivers in the ECU's that come in for repair. See the quoted reply above. You are the first to receive this new service at the same low price.

KahnBB6

iTrader: (5)

Thanks for chiming in! And for updating all of us on the new policy. I actually do not know what the "driver" in the ECU is but if you folks have deemed them a universal problem I am very glad you've taken the extra time to wait on those parts. More so than the current issues I've had I have wanted to future proof my factory ECU as much as is possible so I'm happy your company has decided to go even further your standard repairs now.

And slightly unrelated but I called a couple of weeks ago to ask if you can offer the same reconditioning/repair service for USDM Toyota Supra Turbo ECU's. I was told that you do not since these issues haven't been observed but everything I have read about Toyota capacitor failure suggests that even those engine computers can develop similar issues to the 1UZ and GE and even 1JZ ECUs.

Would it still be possible to send in a 1993-1995 Supra Turbo ECU as a special request for the same reconditioning repairs?

Thanks!

TaninAuto

We offered a low price service in the past because that's what people wanted to pay for in competition with everyone else on the internet. We were recently called out on a facebook group and put on blast by someone slamming what we did or didn't repair in our stated service. We also have customers that never contact us after the fact if they have issues. We can't help people that never reach out to us with issues.

None the less, we now offer the same "full" repair as some competitors which has an added cost in time and parts, but also includes replacement of these components related to the injectors/misfiring.

I don't believe we have ever had an inquiry or ECU sent from a Supra. The boards and design is nearly identical across the board with Toyota's and Lexus. If you want to send it in we can surely take a look at it and perform the same service as the Lexus ECUs.

The cost going forward is $129.99 vs the old $89 price which only included replacing capacitors and cleaning up any spilled mess. The price on our website has been updated.

Any other questions please ask.

t2d2

iTrader: (8)

It's the same connector used on a lot of Toyota products, and not just IAC. I've seen it under part #22270-46080 and #11144, and the listings aren't always consistent which model it pertains to. If I remember right, the same connector is also used for EGR and TRAC.

My replacement one came off the parts car, so who knows how long it'll last before the tab breaks. I'll order one of these as a spare next time I have a few things I need from Drift Motion:

http://www.driftmotion.com/Idle-Spee...r-p/dm1681.htm

When I hear "drivers" in conjunction with computers, I think firmware. What does it mean in this context?

gerrb

iTrader: (34)

Craig - NOT ALL SC300 IACV are same thus NOT ALL SC300 IACV are same with that of the SC400 . Thus NOT ALL SC300 IACV have same part number with the SC400 IACV !

It all depends on your 2jzGE throttle body , they are not all same since some have traction control.