HI Everyone,

This is my first post but I have been a reader of these forums for many years now. Also I'm not a newbie in Honda tuning.
This is my third Hatch and my previous build was a B20Vtec however I am currently facing an issue which I cannot seem to diagnose.
I hope perhaps some Honda wizard out there has experience with this and can help my further.

The Car:

1996 EDM EJ9 EK Hatchback with EG Subframe and EDM OBD1 B16A2, P30 ECU from Del Sol.

My issue is as follows:

When the car is cold it starts fine however when I start my commute and 10 minutes into my drive merge onto the highway. Not hitting VTEC but near 5k rpm. The CEL comes on.
The CEL prevents VTEC from engaging.

Once the engine has fully warmed up i.e after a 30 minute drive, I can restart the car and the CEL is gone.
VTEC works as normal and the CEL does not return.

The car runs perfectly fine. No roughness or misfires. Also I searched extensively and have replaced my distributor, checked engine timing with service connector plugged in.
Mechanical timing is spot on and dizzy has been replaced with a brand new one. My issue was the same before and after replacing my dizzy.
Once the car has warmed up completely is works without any issues revving all the way to redline and back smoothly.
Also VTEC engages without any problems since the CEL preventing VTEC engagement is gone.

The CEL code I get when checking with the service connector is code 8.

To me a wiring issue seems unlikely due to the car perfoming perfectly once warmed up. Same with ECU issues.
I do not see how engine/underhood temps can affect these elements.

Also just to clarify the car starts/runs/idles perfectly when cold. It is only when I approach the VTEC crossover point when the car isn't fully warmed up that I get this CEL.

Furthermore, I understand taking a car to redline when cold is bad. I do not rev or push the car hard when cold. But with the standard trans driving 60MPH on the higway in 5th is near 5k rpm and will trigger the code.

Any help is sincerely appreciated! If you have any experience with this issue kindly let me know how you fixed it!

Thanks!

CIVICADDICT314

 

From what I can see code 8 is the TDC sensor which in ODB1 I believe is in the distributor even on the B series. Just out of curiousity, does your EDM B16A2 have the crank fluctation sensor and sprocket on the the crank gear like the later generation D series do?

It is still possible it's wiring challenge. I believe all the sensor wires in the distributor are shielded wires. But the thought that occurs to me is a weak wire might sit right when cold, then as it warms up looses connect just enough to sporadically pass signal throwing the code until fully warmed up and then makes good signal contact again. The real bear with this scenario is locating it being it's an "intermittent" problem. The only hope I could see is finding that "sweet spot" warmth that throws the code and then immediately start testing wires from the dizzy to the ecu.

It's possible you got a second bad dizzy but I'd side with you of two dizzies, no change in behavior. Thus look at wiring, then ECU.

 

Hi TomCat,

My apologies for not being able to respond to you earlier. Have been very busy with my bnusiness.

Firstly, Thank you very much for taking the time to write me a response. Activity on this forum is lower than it used to be and you taking the time
To assist me in finding a solution is highly appreciated!

I might be wrong but I am fairly certain the EDM B16A2 do not have the crank fluctation sensor.
You are right, it is an intermittend problem which makes it a p.i.t.a. to diagnose for certain.

Due to the replaced Dizzy I am however very confident the problem does not lie there.

I checked basetiming again when the engine was fully warm and noticed that the mechanical timing had shifted during use of the car.
After setting it again correctly with my timing light the issues seemed so be gone for quite a while.

Up until yesterday when a pull to 8,5k rpm triggered the light again. it has since been coming on everytime I enter the "VTC Check rpm range"
even with a warm engine.

I will check the mechanical timing again later today and see if it shifted again. If it did then I have found the culprit.

Because it would mean the car it throwing code 8 due to mechanical timing shifting from driving the car.
Therefore changing the amount of timing changes the ECU has to make and making the TDC sensor read "incorrectly" accoring to the ECU.
That leaves me with the issue why my mechanical timing/dizzy position shifts from driving, possibly because I didn't tighten the dizzy bolts securely enough.

I have bought new distributor hardware and will change it all out tonight when I check the timing.
Also I will keep this thread updated as to if my timing has indeed again been thrown off.
That way we all know if it was the culprit and if resetting the base timing fixes the issue.

Thanks again for your help! Have a great day.

 

Just to clear up a little terminology for any future users. Your timing with the timing light is not mechanical timing, it is the ignition timing. Mechanical timing is done when setting the timing belt and is either correct or off by 1 tooth or more. If your mechanical timing was off you would have a difficult time setting your ignition timing. It would likely be at one extreme or another if you could get it dialed at all.

And just to be sure, when you set your ignition timing on OBD1 you have to short the service connector so that the CEL comes on solid when fully warm, if not when you try to adjust your ignition timing the ECU ignores it and fires where it had it's last setting. I believe but am not sure, that could be either advanced to retarded depending on where the distributor was set in the process.

Also, to check your mechanical timing you do what with the crank gear (and can be done with crank pulley usually) and the cam gears. Not with the engine running.

I honestly don't see having your mechanical timing or ignition timing off causing a code 8. I still believe it's either wiring between the Distributor and ECU or the ECU itself.

 

Alright. Yeah mechanical timing and ignition timing. My bad.
Mechanical timing is on point. It was set a while ago when I did my timing belt.

I am aware I have to short the service connector so that the check engine light stays on when starting.
Ignition timing was slightly off. I changed it to be spot on and so far have had no CEL coming on even with the car cold.

However this has happened in the past aswell. When I replaced the Dizzy I set the timing and after a few long/hard drives ignition timing was off.
I drive quite fast on the autobahn around 180/200km/h as I live in the German/Dutch border region.

It would make sense for the ECU to throw a Code 8 when the ignition timing
is suddenly changed without resetting the ECU. As the TDC signal is not where the computer expects it to be.

Therefore, I now have replaced all 3 distributor bolts and locked them down properly.
We'll see if this fixes the problem with the ignition timing changing.

If not it's on to wiring:

The biggest problem with checking this intermittend wiring issue is that the car does not do the VTC checks if the car is not under load or if the ecu doesn't register speed. So even when cold I can rev it past 5k and no light will come on.

If it's a wiring issue I would have to test for it on a dyno with cold ish engine temps or rewire the whole loom from the ECU to the dizzy plug.
The latter would probably be easier/cheaper as I have made full engine looms in the past. (this car stil has the OEM 1996 Loom)

Last option:

Furthermore, since the car drives fine I could always go into the HTS tune and remove the CODE 8 VTC check all together.
The reason VTEC is not working is due to the CEL preventing the car from completing all VTC checks, not a mechanical issue.

But I'm in general not really a fan of removing CEL's from the car's ECU using the tune.

Thanks again for your help!

 

One option to get the vtec working without car moving is to put the car up on 4 stands, then put her into 1st gear and vtec it.

This might allow you to throw the code for troubleshooting without the car moving.