atcfixer

iTrader: (1)

I've drove both a 95 T100 and a 96 Tacoma with the 3.4L stick and both seem to have weak bottom end power somewhere around 1500rpm they really take off. Besides the first start off (I haul loads etc with the trucks) they both run well. I've bought a rolled 99 tacoma with an automatic and it seemed to run much better for the bottom end and just figured maybe it's just setup better for automatics in general. However, I just recently bought a 98 T100 stick that had a bad ECU, I installed a 97 T100 Auto ECu in it (repin etc) and it runs just like the automatic tacoma.

To get to my question, does anyone know if the automatic ecu's programmed for better bottom end torque compared to the manual ones, of is it just a fluke that both manual trucks have some sort of issue (IAC maybe?). I tried to check the part number differences between trucks, auto vs manual etc, but it appears the cams and heads are the same part numbers for all of the 5vzfe engines so the only thing that is actually different is the ecu assuming there isn't a problem.

Co_94_PU

iTrader: (-1)

Toyota ECU typically have separate map tables for AT vs MT...

Way over our heads generally speaking. Lol have a look at the mr2, Celica, and Supra ECU threads. Several of those have identified identical code inside the MT and AT ECU, timing and fuel maps are selected by a jumper..

Malcolm99

1999 4R & Tacoma's got new 4 hole injectors for better atomization and a more accurate MAP sensor.

atcfixer

iTrader: (1)

Neat info to know. Forgot to mention my dad also has a 97 or 98 4runner that runs really well too which ironically is automatic too. Seems the mapping is backwards for application, better bottom end seems more ideal for a manual.

I do work with electronics, soldering etc, so if it's just a jumper inside, that would be an awesome mod.

For the 99+ injectors and map sensor, are they electronically comparable with the older ones by chance (if you know). I suspect service manuals would probably answer that question with wire count, signals, and in service resistance ranges. The 98 T100 I just got going does have a bad injector that acts up every once in a while on cyl #2 so if the injectors are a nice upgrade I might look into upgrading them. Also forgot to mention the mileage per machine is all over, the 98 t100 is the lowest at 216k and the 95 T100 is the highest at almost 300k, the 4runner has 260k and the rest are right around 240k. I have a 2wd pickup that has the 3.0L with 518k that still runs fairly well, but you can tell it could use a set of rings to up the compression, or it's the nature of the "3.slow" since I never really drove one on the road.

I guess I have a lot of searching to do, but I'm pretty tied up hauling wood ~12h a day. Taking today off to try to catch up on my ebay atv products I make since I'm 100% self employed currently.

As for the MT and AT ecus, I'll probably take the orig bad one apart from the T100, and compare it to an automatic T100. Hopefully I can see the spot where the jumper could be, and maybe a little googling to validate. I know it's probably over most people's head, but I'd like to repair the T100 ecu. I looked at the board and didn't see anything burned out, so I suspect it might just be a cold solder joint. If anyone knows what typically fails on them, that would be awesome to at least point me in the right direction.

Anyway, thanks for the info so far, it's at least very interesting and opens so many more questions lol.

Co_94_PU

iTrader: (-1)

Interesting and note worthy, but not entirely relevant to the question.

More info and insight on TCCS than most will ever need or want on the ignition and fuel maps buried HERE

Co_94_PU

iTrader: (-1)

Capacitors of this era were junk. There was a big ordeal over counterfeit ones based off an incomplete stolen formula for the electrolyte, mid to late nineties sometime. And of course even good ones will dry out, with increased odds the older they get.

There are some details Google might turn up, but I don't recall specifically which subsystem the repairs I am remembering were made on.

atcfixer

iTrader: (1)

Oh wow those even hit Toyota huh? I know the cheaper brands of TVs, Computers (Dell Gateway etc) were hit with that too and have repaired a few of those motherboards. Generally in their application (power filtering for the cpu, and power supply for the tv), they would bulge and leak electrolyte out of the top or bottom (brownish ooze). This gives me great details to research in my off time, maybe I can bring back a $250 ECU to life that's next to impossible to find on ebay (for the exact part number atleast). If I got it working again, it would be a good "ABA" test to validate that the ECU does make the fairly large difference at the bottom end. I did notice the OBD2 signal wire was a different standard auto vs mt so I suspect the internal chips are different too. I didn't dig into other years to validate if that difference is purely auto vs manual, or if it was just a change year to year.

Co_94_PU

iTrader: (-1)

details please.

It saves them time and money to integrate the variations into one code base running on a single platform. If the prototype guys brought the production team two seperate systems they would send them back to the workshop and make them integrate the two. In all but the densest of circuits this will be the case.

You have one open there a quick peek should show there are unpopulated components.

atcfixer

iTrader: (1)

I just got home where my EWDs are and such. Here is the terms used in the EWD, pin differences etc.

1997 Auto T100 3.4L ECU pin A18, signal SDL which goes to OBD2 pin 2 (tested working with my scangauge 2)
1998 MT T100 3.4L ECU pin A8, signal SIL which goes to OBD2 pin 7

The ECU is easy to get to in my T100 since there is a fender rust hole that the last owner claims caused the last ECU to fail (internally it looked great). Currently have the hole patched since I'm using the truck and haven't even put the glove box back in from checking the fuel relay (COR I think is the correct term). I have some packages to get ready, even though USPS is closed today. I'll try to get photos of the ECU internals. The MT housing is a bit different from the AT other other ECU's I've pulled from Toyota in general.

Co_94_PU

iTrader: (-1)

Obd2 pins..
Short version inconclusive..

#2 is j1850(sae), #7 is 9141-2 (ISO) known as K-Line
both could be running at 10400 baud, however j1850 can run at 41.6k also depending on the switching protocol..

The generic 8051 will run at megabit signaling speeds(I have very ancient network cards that run these from back in the xt/at/286 era for example). The Toshiba x8 is based on the 8051..


​​​​​​​Regarding housing difference, they wanted to keep the same basic profile and went to a two board circuit where the second board stacks on top of the other.

atcfixer

iTrader: (1)

Forgot to mention the 98 was a reman denso, I'd assume it's oem toyota that's been repaired but not sure.

For better google results, the PCM/ECUs are part numbers 89661-34342-84 for the 98 and 89661-0W030 for the 97. Both are 4x4 and for the 5vz, only two differences is the year difference and MT vs AT.

Kind of interesting the reman denso (japan) is the bad one while the good ones is Denso TN.

Anyway, giving a shot of uploading pics. The 97 I couldn't get all the screws out so I couldn't get a back side of the board, but there is a clear difference. Appears the 97 is a single chipset, while the 98 has missing spots where it looks like a 2nd chip set could have gone instead, maybe some sort of conversion year?

First 3 photos are of the 98 MT and the last 2 photos are of the 97 AT which looks like 90% of the other ECU's I've pulled from this era of toyota (cars and trucks). THe 97 board is around an inch longer, and both are only a single board.

If there is a chip you can't read the numbers on, let me know and I'll try to read it. I have quite good close up vision. Beware people scared of spiders, the last photo has one on the right side lol.

EDIT, the 2nd photo makes the HC401 black box appear cracked, it isn't, it's just how the camera picked up the silicone/epoxy line.

Co_94_PU

iTrader: (-1)

Looks like we have a good example of the Toyota JIT process. (JIT uses local manufacturing, the closer the better ECT..)

Your 97 ECU from ND Tennessee differs from the other example on the Toyota ECU wiki.

atcfixer

iTrader: (1)

Interesting, the board numbers are very similar, mine is prefixed TN, and the last 4 numbers are completely different though. I looked at the 98 ecu on the wiki and noticed it was a bit different too. I guess the main bulk of the number must be part type or something similar which is quite close to how I understand Honda part numbers, something like xxx-yyy-zzzz where xxx is part type/location, yyy seems to be source application for the design, and zzzz is the actual number to reference that exact part. If YYY is 000 then it's a universal type of fit (most bolts etc).

There seems to be a ton of ecu part numbers for the 5vz. From my understanding the 98 pickup was sold new in northern Michigan where I picked it up since it has the dealership tag painted on the tail gate and appears to be old. Both the 97 and 98 trucks didn't have EGR valves encase another ecu part number would be handy for those trying to do a 3.4L swap and pass SMOG.

Malcolm99

Interesting stuff guys and noteworthy.., looks like you'll have trouble determining the difference of performance between the ECU's on different 5vz-fe's, some might consider it relevant, but the injectors and MAP improve performance which is very relevant to the OP's concern about bottom end power. Caps leak and usually corrode the traces on the board, I guess you could call it "Drying up", so if your eyes are good take a look, leaky Caps also have a tendency to smell like dead fish, sorta like this thread.

atcfixer

iTrader: (1)

None of the caps appear to be leaking/bloating (in the pc world it's really easy to see). Some of the pins are corroded so might try to solder a couple wires to the pin thoughs on the board for the B+ and BATT, and the common ground pins and wire up a spare OBD2 connector to see if I can get any life out of it at all. With it installed in the truck it did the typical bad ecu sign of no check engine light when key to on.

Care to expand a bit more on the injectors and MAP changes? I checked with my dad and his 4runner is a 98, and the rolled tacoma I have over there is a 98 too, so none of the machines are 99+ as you stated before, so I don't see how that would be a common thing with which engines run better vs not. Is there a visual difference of the injectors besides the 4 ports? I assume with a MAP sensor it wouldn't have a MAS sensor (which all my trucks have).

A simple test I could do and pretty sure I know the results of would be to put the truck in high range and first gear at idle and let the clutch out slowly. The T100 idles around 600-700 rpm and my tacoma idles around 1000, the tacoma's rpm would drop to around 500 stumble and die while the T100 I've had down in the 250s-300s w\o the same "problem". Hard to compare ones with auto transmissions w\o the buttometer (ecomodder's term lol).

Just to jump ship a little, I have an 86 22R 2wd pickup with 3.58 gearing, and besides having to ride the clutch more to take off, it doesn't have the stumble and die at low rpm problem. Also have driven a couple 2.7L's (one auto, one stick) and both seemed to run exactly the same bottom end wise (very strong). I've actually been debating switching to the 2.7L because of the bottom end difference even though in higher rpm the 3.4L has more power. I had to take off a little fast with the T100 a couple of days ago and I had a hard time keep traction in 1st gear (maybe 1/2 throttle), in my 3.4L Tacoma I never really had that problem, I'd have to basically floor it to do similar and after it started moving it didn't have the guts to break the tires loose again (again lower rpm related). Seems the lighter truck with skinnier tires would have more problems with getting up and going but maybe I'm misunderstanding the physics behind it (smaller surface area = higher pressure = higher friction maybe?).

If there's a common failure or issue that causes low end power to decrease, I'd be intrested in hearing about it. I have a few parts engines I could pull parts from if it isn't too much of a pain to swap out.