Brandonallen97

I have a 99 dx sedan I replaced the engine and did a swap to a 5 speed. Everything there is good. But the engine I am told was out of a 98. Both were d16y7 so no issues there. I have been chasing an idling issue along with once the engine is up to temp it idles itself up to 14-1500 rpm constantly and any acceleration between 14-2000 is a very bad surge. Trying to drive it shakes the whole car when going slow. So far I have replaced the intake manifold gasket twice. Currently using y8 IM. Blocked off the y8 iac. Using the iac on the y7 tb. I have sprayed down for vacuum leaks and putting my hand on the tb does stall the engine so that clears up the question of vacuum leaks. I have replaced the tps with a known good one. I have replaced the iac twice with used one from automatics and both times it runs very high and surging on its own no matter what. So now back to the 5 speed iac I got online. Still running the y7 automatic Ecu that was in the car when I bought it. Have tried using a standard ecu but the whole idling issue only is worse. Also have replaced spark plugs, spark plug wires and distributor and cap. Do not suspect timing as anything over 2k rpm the engine runs great no issues whatsoever. I was wondering if possibly It could be the oxygen sensor or me needing a different iac. Any ideas?

muellersfan

1) Post all CEL codes.

2) Match the IACV to the ECU.

3) Bleed the cooling system.

4) Then go from there

Brandonallen97

P1768 is the only code because I’m still using the auto ecu. I did bleed the cooling system. I’ll try to locate the correct Iacv for the ecu. Any insight on that would be great

muellersfan

You obviously need a manual 99-00 Civic P2E ECU.

The D16Y7 ECU and engine use a 3-wire IACV.

How did you bleed the cooling system? Provide details.

Brandonallen97

I am using a 3 wire Iacv the 2 wire Iacv on the back of my y8 manifold is blocked off. The 3 wire Iacv is built into the throttle body. I have a large funnel that has a built in radiator cap I put on the radiator so it could burp. Ran the car for 20 minutes with the heat on so it could circulate and massaged the hoses during the process

muellersfan

Warm up the engine.

Remove the air intake system.

Start engine and let it idle.

Cover hole leading to IACV inside throttle body with your finger.

Does idle speed drop and remain steady?

Brandonallen97

The idle does drop with the passage to the iacv plugged but seems to idle rough. But definitely drops it down to where it “should be”

muellersfan

Start here:

Brandonallen97

Okay thank you. I’m assuming the Iacv is operating as it should since the idle dropped when plugged? And the surging issue only happens when the engine is “high idling” when it puts itself up to 1500 and only does it until you accelerate past 2000 rpm

muellersfan

It means the IACV is bypassing too much air to the IM. Start by adjusting the idle speed exactly as shown in the diagram.

Brandonallen97

Plan do to that tomorrow. Can I use the tach on my cluster or do I need a more specific one ?

muellersfan

You need some type of external tachometer because the cluster tach does not accurately read low rpms. I use my OBD2 code reader that also reads live data.

Brandonallen97

The idle screw is not making any difference

muellersfan

Details?

Brandonallen97

It’s like the Iacv is overriding the adjustment screw. It’s not lowering the idle at all

Brandonallen97

Update: attempted idle screw again. With iac plugged in and unplugged. No change. Replaced tps and calibrated to 0.5v with the throttle closed. Found a small coolant leak. Replaced the hose and rebled cooling system. Sprayed again for vacuum leaks, no luck. Starting to get lost here. Other than running a 99 ecu with 98 motor so I don’t have a fitv. Maybe that’s an issue? I can’t run an earlier ecu due to the obd2a-obd2b difference

muellersfan

If the idle speed dropped to normal when you covered the IACV hole inside the throttle body, then you don't have a vacuum leak or an intake air leak.

Ohm test the 2-wire ECT sensor under the distributor.

Brandonallen97

306 ohms at operating temp

Brandonallen97

I’m assuming the miss when it high idles is from the Iacv letting air in along with the throttle blade when I’m trying to accelerate so it’s making a very lean condition. Like I said anything above 2k rpm is great. Like driving on the highway when I get off at my exit it idles down for a few seconds then idles up to 1500 and then any throttle above that idling point up to 2k is a miss. If I restart the car it’s fine until it idles up again. Runs great down the road. Any more suggestions would be awesome. It’s gotta be something to do with the temperature, since it only does it when the engine is hot

muellersfan

Post pics of Y8 IM where the injectors are located. Was the Y8 IM taken from a 99-00 Civic EX?

muellersfan

Also install the standard P2E ECU in the car to eliminate the current transmission-ECU mismatch.

muellersfan

Can you give an approximate rpm value to "should be"?

Do you have a stock Y7 IM and throttle body?

Brandonallen97

I Believe the Im was from a 98 civic. I used my y7 injectors on it because it’s a y7 ecu. 750 is my “should be” rpm. And I’m trying to
lpcated the correct ecu but I do not have one of those fia valves on my thermostat housing

muellersfan

How many 3-wire IACVs do you currently have? Are any brand new or are all used?

Do you have a stock Y7 IM and throttle body in your possession?

The 99-00 Y8 IM has a nipple at the red circled location in the diagram below. The 96-98 Y8 IM lacks this nipple. Does your Y8 IM have or lack this nipple?

Brandonallen97

I have 3 used 3 wire iacv I ohmed our all 3 and the resistance on all respective terminals are nearly identical. I do have the y7 throttle body and manifold. The throttle body is on the car with the y8 manifold currently so I can use the 3 wire Iacv. I had this same exact issue before I swapped manifolds. My y8 manifold does not have that nipple