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By SnowFish
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#6252
Are these 2 ECU’s compatible?

This one marked “Tuned ECU” now has a stock chip. Still doesn’t work right.
Image
Diagnostic doesn’t work. CEL always one. No code flashes with fuse installed.

Would like to try this one.
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Want to get the engine running like it should, have diagnostic mode, and turn off CEL.

Are these 2 compatible?
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By SnowFish
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#6258
jamalspelling wrote: Wed Aug 28, 2019 11:13 pm

Does it start and run?

Yes, but very poorly.
Check engine light is always on.
Diagnostic is not functioning. Will not flash codes when diagnostic fuse is inserted.

This is T3RapTops Twin Cam conversion convertible that allegedly was dialed in at one time.
Richard said the check engine light was due to the Rally chip. Said CEL was not on with standard chip. That’s why I installed the standard chip. No change. CEL still on, diagnostic still not working, car still runs very poorly.

Compression is 240, 240, 240, 220 when checked last week.
That’s why I’m searching for a different ECU to see if my current one is partially corrupt.
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By jamalspelling
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#6263
This may or may not help, but I recall after one head swap my
MIL light was on steady and no start.
Knowing all was well before, I knew it wasn’t the ECU but swapped one
to verify and still had the same issue.
Long story short, the computer ground(s) had not been bolted back to
the intake manifold. There’s a series of ring terminals on MK1 that
are mounted to the intake manifold, one of these being the ECU ground,
if these are not secured it will make the MIL light on steady.
Unrelated, there’s more grounds near the headlight well that will
also produce a no start if not secured.
Since you mentioned the steady CEL, it made me think of that time
where the ground wires were unattached in the engine bay and my
CEL was steady.

Of course for you the easy diagnosis would be to swap the ECU, but
doesn’t sound like you have that luxury of a spare at the moment.
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By rmprob
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#6265
GhostntheMachine wrote: Wed Aug 28, 2019 10:53 pm

they are Not compatible The “F3″ is for a 1.0 ltr
You looking for a 16 13 or I6 I3

This is out of my 91 twin cam that ran perfectly for years. Im pretty sure its not a 3 cyl ecu..
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By macuserman
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#6266
rmprob wrote: Thu Aug 29, 2019 10:04 am
GhostntheMachine wrote: Wed Aug 28, 2019 10:53 pm

they are Not compatible The “F3″ is for a 1.0 ltr
You looking for a 16 13 or I6 I3

This is out of my 91 twin cam that ran perfectly for years. Im pretty sure its not a 3 cyl ecu..

Can always crack it open and take a look inside, they are quite obvious when open if it is a GT/GTI or not.
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By macuserman
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#6271
Teeth is still busy moving, but should be around soon to shed some light. In the meantime I dug up this old topic from the archive: http://ssgtirep.com/tsarchive/viewtopic ... 61555.html

Here’s the interesting bit:
Teeth
"Yes there are differences, however, it doesn’t matter which one you use, they will all plug and play unless you have an automatic–or a CA car with EGR, I guess.

The later ECUs, I2 (92-93) and I6 (94 only) make slightly more power, probably due to a slightly more aggressive timing map and faster processors. Unfortunately, offsetting that advantage is a bug in the code that can prevent the ECU from enrichening properly with the throttle until well after warmup–don’t try to run one of the later cars hard until you’ve been driving 15 minutes or so.

Don’t forget there are Euro-spec ECUs that are expecting input from a trim-knob rather than an O2 sensor (but will accept that too).

Even a Cultus ECU from those years will run an export-spec motor, but it wouldn’t be a good idea as the maps would not be optimal and you’d get a code for a missing knock sensor."

So still not sure what the lettering is on the 89-91 ECU, I can pull mine if needed and have a look at it. But I think I’ll be able to dig it up given just a little more time rooting around in the archives.
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By SnowFish
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#6274
Thanks Mac!
I’m learning more everyday.

T3RapTops twin cam convertible Does run better when fully heat soaked. But still down on power compared to others stock twin cams.

TurboGTS22, who drove the car from Ohio to the Minnesota meet, commented that it is down on power. He has a couple stock GTi’s of his own to compare.
1DcGuy, host of the Minnesota Meet, commented he same. He has a stock GTi as well.

I drove it home, 4 hours, and noticed the same low power compared to the other GT’s I’ve driven. Sad thing is, my 3 cylinder cruises 70-80mph similar to this twin cam. Somethings going on.

Starring at a check engine light, not having diagnostic mode, and lower power than it should have is my main issue.

Thus, wanting to try a different ECU to see if I can at least get diagnostic mode back. Then I can build from there.
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By GhostntheMachine
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#6295
macuserman wrote: Thu Aug 29, 2019 1:12 pm

The later ECUs, I2 (92-93) and I6 (94 only) make slightly more power, probably due to a slightly more aggressive timing map and faster processors. Unfortunately, offsetting that advantage is a bug in the code that can prevent the ECU from enrichening properly with the throttle until well after warmup–don’t try to run one of the later cars hard until you’ve been driving 15 minutes or so.

.
this rule should be adhered to for al GTI/GT cars because of the weak Exhaust valves
in these engines
They are expensive if you can find good ones
.
……GnM
.
.
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