socialistic

iTrader: (2)

I have a '98 LX 5-speed Sedan and recently threw in a freshly rebuilt y8 trans and freshly rebuilt y8 head with y8 auto intake manifold, rail, injectors, tb. I re-used my y7 distributor, bought an obd1 ecu harness, and a buddy chipped/converted/temp-neptuned a P06 ECU for me. The plan was to get the car put back together and drive to him on the temp-tune so he can perform a full tune. Anyway, I can't get this car to run right at all and I'm at a loss trying to figure out what the hell the problem is.

With the P06 ECU it cold starts around 1000 RPM, then as it warms up it climbs and then sits around 2000 RPM with a fast and very short bouncing/roaming idle and the header glows a dull orange. With the timing light hooked up to spark #1 the single white mark on the crank pulley sits within the marks on the timing belt cover, with a slight bounce due to the roaming idle. This is with the distributor turned all the way clockwise/forward. If I turn it all the way backward/counter-clockwise, I get the 3 lines near the timing belt cover marks but my RPM climbs to around 3k.

With the OEM ECU and car already warm it had roaming idle from 1000 to 2500 RPM. With 2P SCS/service connector jumped and checking timing same way as above, the 3-lines are about half an inch to the right of the marks on the timing belt cover. If I turn the distributor all the way in the opposite direction(forgot which way), I can almost get the far-left of the 3 lines on the timing belt cover mark...but idle didn't seem to change.

I have set TDC four times now, and the most recent was this morning when I was putting the cam and rocker assembly back in after replacing a leaky cam seal...so I got a backside view of the cam sprocket so I could better see those little side markings line up with the upper head surface, and the single white line was definitely centered on the timing belt cover mark.

I can not find any vacuum leaks. There is a small hose from intake manifold to fuel pressure regulator, larger hose from intake manifold(lower front port) to PCV, large hose plugged on intake manifold due to EGR delete(upper front port), and large hose(back port) going to brake booster. The charcoal canister on the firewall is no longer connected to the engine at all, as there were no more small vacuum ports.

Turning the idle screw on the throttle body doesn't seem to do anything. Could be too subtle for me to notice due to the bouncing idles, though.

Any ideas? Car ran and drove fine with the d16y7 drivetrain, it was my daily for almost a year. Only had a noisy main input shaft bearing which led to the purchase of the y8 stuff.

chrysler kid

Automatic and manual transmission cars have different sensors on the intake manifold. So if you just slapped the auto intake manifold and sensors on there it's not going to run right

socialistic

iTrader: (2)

What sensors? It was my understanding the only difference between the two intake manifolds was the location of the IACV. Manual intake manifold has 2-wire iacv on back, auto has 3-wire iacv under the throttle body and is plug-and-play with my y7 harness.

eghatch9295

iTrader: (1)

yes, it is plug and play with the harness, but the ecu you are running looks for a 2 wire iacv.

socialistic

iTrader: (2)

Thanks for clarifying. I'll be damned, so it was the IACV the whole time haha.

Anyway I've sourced out a manual y8 throttle body and z6 intake manifold with 2-wire IACV. I'll slap that on with my injectors and that's all there is to it, problem should be solved?

TomCat39

What about the OBD2 Distributor (Y7 dizzy) run to an OBD1 ECU. Will this cause any problems?

I'm not familiar but thought I should toss the observation in the pot.

eghatch9295

iTrader: (1)

nope, itll work.

socialistic

iTrader: (2)

I brought home a manual y8 throttle body, z6 intake manifold, z6 fuel rail. Will install with my y8 injectors and y8 fuel pressure regulator, and re-use my y8 throttle body gasket and y8 intake manifold gasket...they were brand new, only started up the car and ran it a short duration a few times during troubleshooting so gaskets look well enough to reuse safely. I imagine this is all plug-and-play after the 3 to 2 wire IACV mod?

Also, is there any difference at all between IAT sensor locations? My IAT is in the intake pipe, but on the z6 it's on the lower back side of the intake manifold. I'm guessing it doesn't matter other than maybe getting a cleaner looking intake pipe later on, without sensor bungs in it. The z6 IAT needs to remain installed either way as it plugs the hole on the intake manifold.

eghatch9295

iTrader: (1)

iat shouldnt matter. wire the iacv correctly all should be well.

socialistic

iTrader: (2)

Now running d16z6 intake manifold and 2wire IACV, d16y8 manual throttle body, y8 injectors, y8 fuel rail(3 holes drilled for mounting on z6 intake manifold), and y8 fuel pressure regulator. TL;DR is high idle @ full ignition retard, very slight roam, CEL but can't pull codes, and possible ECU limp mode.

Forgot to top off coolant before starting, but anyway it started cold at 1000rpm and then I topped off the coolant just about all the way. RPM climbed to around 2k and had a very subtle/short roaming idle that would come and go. If I turn on headlights and max heater I could get idle down to about 1400rpm. Distributor is turned all the way towards the radiator(retard?) and turning it back towards firewall at all increases the idle. Idle screw in throttle body is turned all the way in/clockwise. I drove it around the block and around 4k it would bog and misfire/cutout so limp mode maybe?

I have a check engine light but obviously can't obd2 scan it anymore due to chipped ecu, and jumping the blue 2pin SCS plug by ecu and turning key to on doesn't blink CEL so I don't know what codes it is throwing. At this point in time my VTEC solenoid was not wired in, it now is but I haven't started the car since doing that.

3 to 2 wire IACV plug conversion was done per that popular diagram that always gets posted. My ECU jumper harness is pinned for A12 and A14 and not A13, and according to the seller is already set up for the IACV 2wire conversion but I don't know how to confirm that between the obd2a and obd1 side.

A13, the orange wire left over from the 3wire IACV, was repinned in to A8 and the other end is plugged in to VTEC solenoid.

VTEC pressure switch is not plugged in, my tuner will be disabling it in neptune.

The rear lower small vacuum port on the intake manifold(evap solenoid?) is plugged, rear upper large vacuum port goes to brake booster, front left small vacuum port goes to fuel pressure regulator, front right large vacuum port goes to PCV.

mk378

Unplug the IACV (*). The two-wire IACVs have a spring mechanism so they fully close with no electricity applied.

This should make the idle slow down to less than normal. If it still idles high with IACV unplugged, you need to find out where the excess air is getting in. The engine can't run fast without air.

If it does drop to less than normal idle with IACV unplugged, that means the ECU is commanding a high idle (usually because the ECT reading is wrong, and the ECU thinks the engine is cold), or the IACV circuit is improperly wired.

If there is a code set, you can jump connector with the engine running and it will blink out the code (at least, stock ECUs will do this). If ECU does not store codes with the key off, it is probably not getting the constant battery power for memory from the "BACK UP" fuse under the hood.

* Unplugging IACV while running will normally turn CEL on with a code 14.

socialistic

iTrader: (2)

Thanks, I'll give that a shot.

There is a chance of improper IACV wiring. As far as the plug conversion goes that should be right. But I did not move the black/blue wire from A14 to A12 on my car's harness because my conversion harness should have already had it done according to the product page. The conversion harness is pinned for A12 and A14 but not A13. I suppose it's possible that I still needed to do the A14>A12 swap.

As for the CEL, SCS jumped during running or key just turned to on doesn't blink CEL. The battery is almost completely dead and needs to be jumped every time I want to start the car because I haven't been able to let it run long enough, but it still has some power and I'd imagine enough to keep codes stored. Last night I wired up VTEC solenoid and pulled the BACK UP 7.5a fuse so maybe I'll see a difference when starting it today and trying the IACV unplug.

socialistic

iTrader: (2)

Moved A14 over to A12. Car started and then died with IACV unplugged. Idle screw all the way out and we could get it running, but it had a roam between like 400-800rpm. IACV plugged in, idle screw all the way in, distributor all the way retarded and it idles around 1500 with a 200ish rpm fast roam.

Reversed the wires on the IACV plug to rule out me having it wrong the first go around, no noticeable difference.

eghatch9295

iTrader: (1)

do you still have a13 plugged in?

socialistic

iTrader: (2)

Nope. Per the instructions from ff-squad I unpinned on ECU side and cut on IACV side. Since it was no longer being used it is now my VTEC solenoid wire and goes to A8.

I also confirmed that both A12 and A14 on the obd2a side of my conversion harness go to A9 of the obd1 side of the harness, so it didn't matter that I moved my A14 over to A12 because the harness would accept either.

I did reverse the two leads at the IACV thinking maybe I had them backwards, but I don't think that made a difference. Perhaps the IACV is toasted. Car does die if IACV unplugged or IACV hole in TB opening plugged, unless I have my idle screw backed all the way out and timing advanced a bit.

mk378

One wire of the IACV needs to connect to the 12 volt bus in the engine harness that runs various things like the speed sensor, purge solenoid, and O2 sensor heater. Both the 2 and 3 wire OBD2 valves have this as one of their wires. The other wire ultimately connects to pin A9 of the OBD1 ECU.

Next I would check the ECT sensor with a meter, and confirm that the IACV driver in the ECU is not blown (with all power off, A9 should not have much continuity to ground).

Up to 2000 rpm is designed to happen on a cold start (depending on how cold), you should warm up the engine before checking or adjusting idle.

socialistic

iTrader: (2)

The Black/Blue wire goes to A12 on my OEM plug, which through the conversion harness ends up at A9 on the OBD1 plug. I don't know exactly where yellow/black wire goes, but my harness wasn't modified in any way so it should end wherever Honda put it. As for the 2-wire plug, I got it from ebay so it has red and black wires on it which aren't the oem 2-wire IACV colors. The black/blue wire goes to the black wire(opposite side of plug from the release lever) and yellow/black go to red. Currently it is reversed because I wanted to rule out an incorrectly wired IACV plug.

I have a multi-meter, so what will I be checking on that ECT?

For A12/A9, should I be reading a certain resistance between it and ground?

I have been letting it reach normal operating temperature before messing with ignition timing and idle screw. At this point, with IACV connected, the lowest idle I can get is around 1500RPM with distributor turned all the way towards radiator and idle screw turned all the way in(clockwise). If I unplug IACV in this scenario the car will die. If I adjust idle screw back out and turn the distributor to about 50% towards firewall I can get it to start and idle below 1000RPM with a 100+/- RPM bounce.

mk378

Unplug ECT sensor and measure its resistance, compare to the chart of resistance vs temperature found in the FSM. Also confirm no leakage to ground. The IAT sensor can be tested the same way. Would be a good time to test the TPS voltage as well.

Make sure that no codes are happening.

Warm up engine, jump service connector and set timing with a light, and leave it.

With IACV unplugged, timing properly set but then connector unjumpered, set idle air screw to get 450 rpm and leave it.

socialistic

iTrader: (2)

I do have a code(s), but I can't pull them. My obd2 scanner won't work anymore due to the obd1 ecu. If I jump the SCS the CEL won't blink with car running or key turned to ON and car not running. It's quite possible the code(s) being thrown will tell me what's going on but can't get then pulled for whatever reason.

Also, jumping the SCS doesn't seem to level out the timing under a timing light. Doesn't seem to make any difference. It's almost as if jumping the SCS isn't doing anything.

socialistic

iTrader: (2)

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.

socialistic

iTrader: (2)

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.