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Discussion Starter #1 (Edited)
Y7/Y8 minime in '98 LX w/ high idle, uncheckable CEL, weird timing.

Car is a '98 Civic LX Sedan. Has y7 block, y8 trans, y8 head, z6 intake manifold and 2 wire IACV, manual y8 throttle body, y8 injectors(I think?), y8 fuel rail drilled for z6 intake manifold. Running an obd2a-to-obd1 ecu harness and chipped/converted P06 temp-tuned on neptune by a buddy until I can get the car to him for full tune. 3-to-2 wire IACV plug conversion done, and the ecu conversion harness was ready for that out of the box according to seller so no repin needed. Did pull unused orange wire from A13 and repinned to A8, and other end goes to VTEC solenoid. VTEC pressure switch is not plugged in and will not be used, it will be disabled in final tune and I think is already disabled in this temp tune.

Anyway, on start up and low coolant it started cold and ran at 1000rpm. I topped off the coolant and continued letting it run. Idle climbed to around 2000rpm and had a very slight/subtle roam to it that would come and go. If I turn on headlights and max heat I could get the idle down to around 1400rpm. Distributor is turned all the way towards the radiator(retard?) and turning it back towards firewall at all increases idle. Idle screw on throttle body is turned completely clockwise/in. I gave it plenty of time to warm up and even drove it, idle would never come back down.

Driving it around the block I found that it bogs/cuts out around 4000rpm. There is a check engine light, but jumping the blue 2-pin SCS connector by ECU doesn't blink the CEL when key is turned to ON position but not started. At this time the VTEC solenoid was not wired, did that and an ECU reset last night. Haven't started it yet since doing those things.

Any ideas? I've got this posted over on H-T and have thoroughly searched both forums for the last 24 hours, and even hit up every Honda friend I know. Everyone is stuck on getting the CEL code(s) pulled which I'm apparently unable to do for some reason.
 

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usually when it just stays on its either wiring or ecu (dont quote me on that its just what i heard) a buddy of mines had that problem rechecked his wires and changed out his ecu... apparently his ecu was bad and missed a few wires doing 3-2pin . popped in a new chipped ecu and it went away.
 

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Discussion Starter #3
Well I did just try running it without IACV, just dies unless idle screw is all the way out and timing is advanced a little. I could get it around 800rpm but it had a dropping roam and was getting close to dying every time it dropped.
 

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Discussion Starter #4
A12 and A14 on the OBD2A side of the conversion harness are pinned together to A9 on the OBD1 side, so it didn't matter that I moved A14 to A12 on my OEM ECU plug.

I did swap the IACV plug leads in case I had them backwards, didn't really make a difference.

None of my OEM wiring is messed up or modified. The car ran and drove fine and was my daily for a year with the y7 drivetrain, right up until I pulled the top end for this swap. The only problems I ever had were a CEL for downstream o2 due to it being unhooked after I installed my new exhaust system, and a rattle from the main input shaft bearing.

I'm completely stumped at this point. I have no idea why this issue seems to have persisted through a tb/im/iacv change, other than the roaming idle going from a long roam to a short/fast roam on the 2wire iacv. I also have no idea why the CEL is on and why I can't get it to blink, it's as if the SCS isn't doing anything because it also doesn't seem to level out the timing under a timing light when it's jumped.
 

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CEL on with no code is a faulty or poorly connected ECU. Check fuses and chips on your ECU.

Your bogging out at 4000, think about when vtec would kick in and then remember your solenoid was not connected......
 

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Discussion Starter #7 (Edited)
CEL on with no code is a faulty or poorly connected ECU. Check fuses and chips on your ECU.

Your bogging out at 4000, think about when vtec would kick in and then remember your solenoid was not connected......
Will check out the ECU when I get home from work.

The 4k cutout remained after getting the VTEC solenoid connected. I didn't drive it after hooking it up, but did rev up to 4k where it's still cutting out.

What is the target idle set at on the tune? What is the IACV duty cycle at?
I don't know either answer, but I have asked the guy that will be tuning it.
 

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Discussion Starter #8
IACV is set to 0 offset. Target idle is 800-900.

Inspected the ECU and found what looked like a tiny glob of solder bridging a lead of the new jumper to the lead of the new resister below it, not sure if it was making contact but I pulled it out of there. Threw ECU in, hooked up jumper cables, reset ECU while charging, car started at around 1100 and settled at 1500 with a very short/fast roaming idle and still had CEL. Shut it down, jumped SCS, turned key to ON, solid CEL. Shut off, clipped jumper in ECU to revert back to stock p28, still solid CEL. Didn't start it up yet after clipping ECU jumper because it needs to be jumpstarted again.
 

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solid check engine light is main processor crash (for whatever reason) running on backup processor/memory.

remove/cut jumper on j1 and see what happens. if you still have a CEL with j1 cut you have an issue with the computer. im assuming its running really rich at all speeds like this.

why would you redrill the y8 fuel rail when you could just bolt on a z6 fuel rail? boggles my mind.
 

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Discussion Starter #10 (Edited)
solid check engine light is main processor crash (for whatever reason) running on backup processor/memory.

remove/cut jumper on j1 and see what happens. if you still have a CEL with j1 cut you have an issue with the computer. im assuming its running really rich at all speeds like this.
After shutting the car off I cut J1 and turned the key back to on, there was enough battery power to cycle the fuel pump and see that the CEL was still on solid. I did not perform an ECU reset after cutting J1 / turning key to on...you think that mattered? Should I jump it again today, do an ECU reset, then actually start the car with J1 cut?

Tomorrow my tuner will bring another chipped ECU with him to work for me to try. We're both pretty much at the point of having ruled everything out except my conversion harness and ECU. We still don't know why the SCS doesn't seem to do anything for timing or CEL when jumped, but perhaps the ECU is bad in such a way that the SCS isn't working?

why would you redrill the y8 fuel rail when you could just bolt on a z6 fuel rail? boggles my mind.
Because the fuel rails are different lengths and use different fuel lines. My y7 fuel line barely reached the z6 rail and wouldn't fit it due to the two little prongs on the end of the line that keep it from trying to spin when on the rail.
 

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After shutting the car off I cut J1 and turned the key back to on, there was enough battery power to cycle the fuel pump and see that the CEL was still on solid. I did not perform an ECU reset after cutting J1 / turning key to on...you think that mattered? Should I jump it again today, do an ECU reset, then actually start the car with J1 cut?

Tomorrow my tuner will bring another chipped ECU with him to work for me to try. We're both pretty much at the point of having ruled everything out except my conversion harness and ECU. We still don't know why the SCS doesn't seem to do anything for timing or CEL when jumped, but perhaps the ECU is bad in such a way that the SCS isn't working?



Because the fuel rails are different lengths and use different fuel lines. My y7 fuel line barely reached the z6 rail and wouldn't fit it due to the two little prongs on the end of the line that keep it from trying to spin when on the rail.
if the CEL is solid and stays on even after cutting j1 you have a problem with the ecu and you will have the same problems with the jumper cut or connected because of that.

jumping j1 enables the programmed chip to be used, its common to see a solid CEL if you have a bad burn on the chip, or have installed the other components to chip the ecu wrong.

Its not common to see a solid CEL after cutting j1, that means there is a problem with the ecu itself.
 

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Discussion Starter #12
It was the chipped/converted P06 ECU. I hooked up my tuner's demon-board ECU that he threw my tune on and it had a solid CEL when turning key to ON until I realized the SCS was still jumped, removed jumper, then it worked fine. Started cold at around 1200-1300rpm and slowly dropped as it warmed up. Hooked up my laptop and got the ignition timed, idled at 900 once fully warmed up, no CELs, got her up to 5k+ a couple times on the test drive. Can probably drop the idle a bit more since the idle screw isn't turned all the way in.

Threw the P06 back in with J1 still cut and SCS not jumped, and just turning key to ON had no CEL anymore after fuel pump cycled. My last test of this ECU with J1 cut I forgot to pull the SCS jumper so it may just be the chip kit that was bad. I didn't run the car at this point, though, since the battery had died. Either way he's getting me another ECU so I can finish the car and get it to him for full tune.

It did feel like it had a slight misfire at idle which I'll have to troubleshoot, but it definitely had some pull past 3k that it didn't have before.
 

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It was the chipped/converted P06 ECU. I hooked up my tuner's demon-board ECU that he threw my tune on and it had a solid CEL when turning key to ON until I realized the SCS was still jumped, removed jumper, then it worked fine. Started cold at around 1200-1300rpm and slowly dropped as it warmed up. Hooked up my laptop and got the ignition timed, idled at 900 once fully warmed up, no CELs, got her up to 5k+ a couple times on the test drive. Can probably drop the idle a bit more since the idle screw isn't turned all the way in.

Threw the P06 back in with J1 still cut and SCS not jumped, and just turning key to ON had no CEL anymore after fuel pump cycled. My last test of this ECU with J1 cut I forgot to pull the SCS jumper so it may just be the chip kit that was bad. I didn't run the car at this point, though, since the battery had died. Either way he's getting me another ECU so I can finish the car and get it to him for full tune.

It did feel like it had a slight misfire at idle which I'll have to troubleshoot, but it definitely had some pull past 3k that it didn't have before.
if you have been driving this for any length of time with the cel solid you might have washed the cylinder walls and fouled the plugs as the ecu dumps fuel as a safeguard. i would check compression.
 
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