SirRevvs

I have a 94 Civic Ex with a obd0 Ls engine. The guy who I bought my chipped p75 ECU from originally put a VTEC program on the chip and I was geting codes 15, 21, and 22 from my ECU. The car ran ok for a while it was real hesitant after about 5000 rpms or so but today I got him to rechip it for me. Now the engine pulls really hard all the way up to about 7000 rpm but under partial throttle, driving normally, i'll press on the gas and it feels like the cars bogging but when I floor it it takes about 3 seconds and then it takes off like it should. Also since the ECU was re- chipped my idle will fluctuate between 1000-1200 rpm back and forth. I have no CEL now, but what would cause that hesitation and rough idle only after installing a new ECU? Also ever since I did my swap I've had really bad gas mileage and I know it's a bigger engine but it seems a little less than average. Thanx.

SirRevvs

Bump. Anybody?

Greasemonkey

Try this:

Reset you ECU and let you car idle for about 15-30mins with out the headlight or radio on. Everything is off accept for the engine running so you ECU can learn the car Idleling.

If that does not help, try to adjuster you TbS sensor. That's what my mechanic did.

SirRevvs

cool i'll try that and let you know what happens. is there a way to reset the ECU other than unplugging the battery? If I jumper the diagnostics plug will that reset it?

TheIntegraGuy

Check your IACV. Also, it might sound weird but sometimes even the coolant temperature sensor has part in it.

When I had my SR20, I had the same problem. I found out that it was the IACV AND miswiring of the o2 sensor. WOT would be perfectly fine, but when I'm driving "normal", it woudl hessitate and the idle would flucuate between 700-1500 constantly.

Look up "Irratic idle" on google and see if that helps. My guess is it probably has nothing to do with the ECU unless something is wired incorrectly. My thoughts are that it's most likely your IACV. It's either faulty, or it has to be adjusted.

SirRevvs

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TheIntegraGuy &raquo;</TD></TR><TR><TD CLASS="quote"> My guess is it probably has nothing to do with the ECU unless something is wired incorrectly. My thoughts are that it's most likely your IACV. It's either faulty, or it has to be adjusted. </TD></TR></TABLE>

My first guess would be the ECU because it only started to have erratic idle after I re installed the ECU with a new chip. But thanx for your input. I think the IACV is probably functioning correctly.

I reset the ECU car has been running about 15 minutes now...... the first 5 minutes the idle was really rough and it seems to be getting better now.

But what about the bad gas mileage? WHen I did my swap I pieced together header/downpipe from 2 LS headers and niether had an o2 bung so I had one welded in about 6 inches from the cat and used the 02 sensor and wiring harness from my d series dc 4-2-1 header.

Greasemonkey

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SirRevvs &raquo;</TD></TR><TR><TD CLASS="quote">

But what about the bad gas mileage? WHen I did my swap I pieced together header/downpipe from 2 LS headers and niether had an o2 bung so I had one welded in about 6 inches from the cat and used the 02 sensor and wiring harness from my d series dc 4-2-1 header. </TD></TR></TABLE>

That should be fine..

The reason you let it idle because the the OBDII ECU like to learn the car idle so it can adjust itself..

SirRevvs

But isn't it an obd1 ECU? It's a 94 civ w/ stock wiring harness.

Greasemonkey

Are u running OBDI or II? cause OBD I does not need the seconb bung on the cat..