Code 14 - AIC valve

Here's the deal. I have replaced...
The engine... All of it.
All of the sensors were swapped from the cx motor (that ran fine, but burned a LOT of oil) to the new engine, with the exception of the thermo sensor, AIC valve, MAP sensor, and Fuel pressure solenoid. The engine is from a 92 DX hatchback Automatic. I have a manual tranny.

All of my vacuum lines are straight, all of my coolant lines are straight. This engine doesn't leak a drop of anything and there is no air in the coolant lines. Every regular maintenance part in the motor has been replaced, including every bearing, seal, gasket, ring, piston, plug, filter, hose, belt, vacuum line... All check out fine. The only mods on the car are .020 over pistons, cold air intake, straight 2" exhaust with no cat or muffler.

My car idle surges like crazy. I've tried 2 different AICV's. Unplugging sensors, and plugging vac lines to see if anything changes. I've even gone as far as replacing my CX ECU with a DX ECU of the same model-year. No luck. CEL with a code 14. There is slack in the throttle cable. The throttle body closes completely. The screen on the AIC valve is clean. Everything on the motor has been through parts washers before I rebuilt it. Electrical parts were all inspected, and cleaned by hand.

When it's cold it will run on its own at 0% throttle, surging the whole time, but after it warms up, it will stall and die at 0% throttle. It surges even when it's warm. At a steady partial throttle, lets say around 3000 RPMs, the engine holds steady for about 3 seconds, then dies down to abot 1200, and kicks back up to a steady 300k for another 3 seconds before repeating again. It does this whether warm or cold. You can hear the AIC valve cycle open and closed so the electrical connector is good.

How TF does this AICV get regulated? I know the ECU tells it to open and close, but based on what values and signals from what sensors? How does it do the math and determine where it should be? Mine's pegging full-open/full-closed at 0% throttle, there is no in-between. Would a bad throttle body cause this? How 'bout the thermo sensor? Are the injectors any different between these motors (carparts.com lists the SAME injector for ALL U.S. and Canadian Hondas made between 92-95)?

There seem to be a lot of posts in different forums about this valve and idle problems, but nothing specific about what makes it tick and how the ECU knows what signal to send it. If I knew that, I'd be a lot closer to finding a permanent solution because it's not my AIC valve that's bad, but that's what throws the CEL code. Any insight from anyone who's tuned out a similar problem would be appreciated.

 

have you done a compression and/or leak down test? if so what are the numbers.

 

No, not yet. It's a brand new engine, .020 over, plastigauged all the bearings during a dry assembly, and it's in spec as far as oil clearances are concerned. The new pistons are 9.5:1 I think (I assembled it in November, so I'm a little foggy on that), and the plugs aren't burnt or fouled from fuel or oil. I rebuilt the head, grinding and decking the valves and new 3-angle valve seats, replaced the seals. The valves are all adjusted at .008 on the intake side, and .010 on exhaust. New head gasket and dowel pins to boot. Shaved .009" and it's flat.

The cylinder bores are fresh, and the block was decked.

I'm 99% sure the compression is right, but I'll check it this weekend. How would the compression numbers affect the idle or the function of the AICV? Would it still throw a code 14 on this ECU?

I'm a DSMer, so this motor's a little on the backwards tip to me. I'm used to having adjustable TPS sensors, BISS screws to adjust idle speed with, and an ECU that can be logged while the engine is running to check any sensor's parameters in real time. There's no connector on this OBD-I ECU for that. Just a 2-pin groundable connector to pull codes with.

 

I'm suspecting a major vacuum leak from the intake manifold flange. Even though all of the gaskets are new, I shouldn't assume they're sealing right.

I brought my turbo boost leak tester with me so I can check that out today. I don't want to spray any types of intake cleaner or fuels around the manifold (another way of diagnosing an intake leak) because everything has been painted and I don't want to damage the finish.

I'll post the compression numbers as soon as I get them.

Jafro
95 GSX
92 ?x hatch

 

maybe this will help you a little bit:
http://www.hondata.com/techidle.html

 

Thanks so much for that last post. It gave me the info I needed to rule several things out. I had not managed to find info like that anywhere doing google searches, and I wonder how the scan tool in the examples can be hooked up to my ECU. I don't have a connector that can allow ECU parameters to be sampled.

1. TPS was .453v at idle. That's in spec, and it's a good thing because these TPS sensors are riveted on; therefore, not adjustable. Just for giggles, I even took the old cx throttle body and plugged its TPS in (without bolting that TB to the manifold), started the car, and at idle, it still surged. I know THAT throttle body/TPS was good because the old motor didn't have idle problems. That ruled out the bad TPS sensor issue mentioned in the tech article.

2. Idle screw - this didn't change anything as far as the surging is concerned.

3. IAC - I had already tried the old cx IAC and even though it didn't fit right, I managed to make the gasket seal to the manifold using only one bolt and two big tire straps. It still did the same thing. That IAC is also known to be good, yet it's for a much different motor.

4. I've swapped ECU's (P05 A00 and a P06 A01)

5. Swapped thermo sensors (both of them). The one on the head, and the one in the thermo housing. Voltages changed on both of them as the car warmed up, so they work. The only time it seemed to normalize was when I pulled the electrical connector from the coolant temp sensor on the head. It still surged when my foot was on the gas, but the idle seemed better.

6. I grounded the o2 sensor (no effect).

7. I clamped and pulled every vacuum line, and even leak tested the manifold with my boost leak tester. All of the vacuum lines are new, so none of them are blocked.

I can't find anything wrong with this thing, yet it's rejecting this transplant. Maybe my car is type O- and this engine is AB-? No? I thought that would be silly, too.

I just printed out page #182 and 183 of the service manual which details the coolant flow of the D15B7 and the D15B8 motors. They're different. The water pipes are different. The flow path through the AIC motor is different. I'm pretty sure I have it right, but this is the last thing I have left to verify aside from the wiring harness. If it's all plumbed properly, I really don't know what to do.

Is there any reason a CX wiring harness shouldn't work on a DX motor? The only difference I can see is the length of the wires that go to the idle purge solenoid, and the cx uses a 1-wire o2 sensor instead of a 4-wire. The other 3 wires on the o2 sensor are only used for a heating element, so it shouldn't affect the o2 reading. There is no provision for using a heated o2 sensor on the cx wiring harness.

I do appreciate the help that has been offered with this so far. I'm sure I just have an oddball problem that would stump the most avid of mechanics. It's done that to 3 of them already, anyway. I guess this is what I get for swapping a car that already runs to start with. Thank God it's my car. Thanks again.

Jafro
95 GSX
92 cx hatch w/D15B7 transplant

 

I'd say check your TB and IM gaskets.

 

try to help anyway I can....lets us know the results

 

all: I just got back from the shop. All of the coolant lines are straight. I officially have no idea what's wrong with this bucket. I'm going to be paying someone to figure it out when funds allow it. There's a local shop that specializes in swapping motors that the Honda dealer reccommended that I call. My local Honda stealership's service manager said there's no way to log this ECU or the sensors except for grounding the ECU pins, so they couldn't do any diagnostics I haven't already done. They said they can only log '96+ cars.

qtiger: I already did. I did this by attaching a turbo boost leak tester to the throttle body inlet, crammed bolts in all of the vacuum lines (brake booster, fuel pressure regulator, pcv hose, idle purge solenoid) and pressurized the intake after spraying every square inch of the throttle body and manifold down with soapy water and checking for bubbles. Surprisingly, it held 10 PSI with no issues or bubbles whatsoever. It took about 10-15 seconds to leak back down to zero (normal, because the rings don't make a 100% perfect seal, and it hasn't run long enough for them to fully seat, either). If there were even a tiny leak, It would have foamed up where the leak is.

Details about this kind of tool can be found at...

http://www.vfaq.com/mods/ICtester.html

The one I made is a lot nicer than the one in that post. I have a 60 PSI pressure gauge on mine. it's really a tool for turbo cars, but since the throttle body inlet was basically the same size as the turbo inlet on my GSX, it worked just fine. This allowed me to test ALL the gaskets on the intake side exactly as they were, and without using caustic cleaners (like carb cleaner or ether) as a fuel source that would eat the fresh paint off of my manifold. I never thought I'd be using it on a NA car.

I will post a follow-up when I finally get something done about this. Money is tight right now as I blew it all on the swap. It will be hard to save money driving the GSX while gas prices are the way they are. I hope that whatever I spend on diagnosing the Civic helps someone else out someday.

Jafro
95 GSX
92 cx/dx hatch

 

There's one of those tools in the garage for testing a 97 GSX.