kinvid22

i have a 00 b20 in a 98 ek. i was running obd2 LS and it was idling fine. I decided to convert it to obd1 with a 95 LS ecu. On cold starts, it revs"up and down" until it warms up, it idles fine at 700rpmish. how can I fix this problem? how can going obd1 from obd2 that was idling fine go wrong from the conversion?

I have no CEL, does anybody know what can be the problem? Bad 95 ecu?

Unjockable

when you go from obd2 to obd1, is it just plug and play? did you have to do anything with the distributor wires?

kinvid22

that's what i thought...i didn't touch the distributor nor anything else. testing this after the car being sit for awhile, and properly resetting it, i plug back in the obd2 ecu and it will rev just fine. Then i plug in the obd1, reset it, but it'll go back to revving "up and down" between 1500-2000rpm...man this is amazingly weird, the idling is best at obd2.....could it be a bad obd1 LS ecu?

Adam.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kinvid &raquo;</TD></TR><TR><TD CLASS="quote"> On cold starts, it revs"up and down" until it warms up, it idles fine at 700rpmish. </TD></TR></TABLE>

I'm not sure this is a problem. On cold starts my 99 ex does the same thing, no engine swap, obd2b. Other than that after about 2 minutes of driving it's fine. Is the revving that noticable? Depending on how cold it is my engine will rev between 1k and 2k to warm up.

mntuner2

Before condemming the ECU I would check: #1 IACV, functioning, wired right. #2 EACV, Functiong, Adjusted properly, wired right. I would also go buy an OBD1 shop manual for the computer you put in there (95 DC OBD1) Then make sure all your wires go where there supposed to and make sure the resistance values aren't different for obd1-2. Paraphrase: GET A MANUAL

kinvid22

ok, not a bad ecu. The IACV functions and is wired the right way. The engine idles like it supposed to on a cold start up with the obd2 ecu. Like i said, when i switch to obd1, the cold idling is all jacked up.

Could it be a vaccum leak that the obd2 ecu doesn't detects but the obd1 does?

I'm using a '97 obd2 intake manifold and TB, but i've heard on obd1 TB's, it uses the "fast idle valve" in conjunction with the IACV to idle correctly on cold start-ups. Is this true on 94-95 DC LS that it utilize the fast idle control valve?

As we know the more advanced obd2 ecu only needs the IACV to idles steadily.

Kataku2K3

The things that everyone has mentioned are the things I normally check for first... IAC, FITV, etc... It really sounds like it's electronics as it changes when you swap ECU's, however I doubt it is the IAC since it too worked fine with the OBD2 ECU... With no CEL it makes this a little more difficult but oh well (you're sure it isn't burned out right, when the ignition is off and you click it to ACC does it come on for a second?)... I also highly doubt it's a vacuum leak, something mechanical like that is going to happen all the time and swapping ECU's shouldn't change a thing... Do you know for sure that your ECU is a manual one? I've come across this problem in the past but you normally have a CEL up... If you could take a high resolution pic of the internals of the ECU down by the 27256 ROM (basically directly opposite to plug D on the board down by the barometric pressure sensor) I could tell you if it's an auto ECU if you're not sure... The easier way if the tags are present is to read me the one off the side... Should be something like 37820-P75-XXX... Sorry I can't help you more right now but I'll keep thinking, Good Luck

kinvid22

It should be a manual ECU. I got it from ebay
The number on there is: 37820-p75-a51 AX

check out the ecu i won on ebay, http://cgi.ebay.com/ebaymotors...33596

The IACV isn't burnt, it operates correctly with the obd2 ecu.

Is it because the 97 TB doesn't have the fast idle thermal valve that obd1 ecu's operates in conjunction with?

hmmm..let me correct what i said on my first post, after the engine is fully warm up, it idles at 500 rpm..i thought it's at the 700 range but it's not.

Maybe i need to bump up the idling at around 750 rpm? I haven't mess around with that yet

Jaker

A51 is an auto ECU.

kinvid22

darn, i got jibb for $50 on ebay.

Kataku2K3

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jaker &raquo;</TD></TR><TR><TD CLASS="quote">A51 is an auto ECU.</TD></TR></TABLE>
Yup, Jaker is right... I'm willing to bet you that's your problem... If are comfortable open it up, find the auto/manual selection (resistors and jumpers) directly below the 27256 external ROM slot, cut or desolder out the resistors in RP17 and RP18, then resolder a JUMPER back into RP18... Hopefully this will fix your problem, Good Luck again

kinvid22

thanks man, you really helped me out..did what you told and now, no more cold irratic idling....thing is, after the "auto to manual" conversion, will the ecu run like the original ecu? is gas mileage the same...is there any difference from an "auto to manual" converted ecu from a manual ecu...let me know because i'm bidding on a manual p75...and don't want to win it if i won't need it.

Kataku2K3

Good I'm glad to hear that, as you converted it to manual it'll act just the same as it did before... If anything changes there's something wrong (gas mileage, performance, etc.)... Also something to note, if you were to activate your CEL right now (even with the auto/manual selection on manual) you'll still get a code 19 (automatic transaxle lockup) this shouldn't however make your CEL come on alone... If I were you I wouldn't waste my money on another ECU, it's not going to make any difference... Just my $0.02, Latez

kinvid22

ok the "converted" ecu should function like a manual ecu, right?
what do you mean if I were to activate my CEL? the CEL will come on itself if the ecu detects something wrong. So how and when will this code 19 come on?

The reason I converted to obd1 is to rid all those sensitive CEL's on the obd2. If driving around with code 19 on will happen, it's just going back to obd2

Kataku2K3

Okay first off, your ECU is technically a MANUAL now and will act just as a normal manual would... Do NOT worry about the CEL, what I am simply saying is it shouldn't be lit up unless you're shorting the SCS... As long as everything else is wired correctly your check engine light should work just as it normally would, BUT if you jump the connector you'll get a 19 (tho it's not hurting anything)... Leave it at this, YOU'LL BE ABSOLUTELY FINE...

Jaker

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Kataku2K3 &raquo;</TD></TR><TR><TD CLASS="quote">
BUT if you jump the connector you'll get a 19 (tho it's not hurting anything)... Leave it at this, YOU'LL BE ABSOLUTELY FINE...</TD></TR></TABLE>

I have converted MANY ECUs from auto to manual, and I have never experienced this!

Kataku2K3

I have too, and everyone has still thrown an auto transaxle lockup code... It's not a big deal tho!

kinvid22

then that's cool. I don't have any CEL's. As i found out when i let the car to warm up all the way, it will still does the "hunting" revs, but at a minimal range from 1000-1500 rpm for about a min or so, then it stops at the normal operating temp. It's not so bad as before to get me annoyed. Probably because I dont have the fast idle thermal valve as obd1 tb does.

Hybrid

refer to https://honda-tech.com/zerothread?id=718018

apparently this is a common problem when doing the obd2 to obd1 conversion and is a result of the fitv, but you can re-route the coolant from the fitv which solves the problem (only recommended for warm climates).