Hello, I am having a problem with a new to me 1990 civic hatchback with a b20 swap. The car is running off of a chipped P06 ecu, not sure of the tune on it, but when it runs, it runs amazing!

As I am driving sometimes the car will bring up a check engine light and act as if all fuel or spark is cut to the car, this can also happen many times within a span of a few seconds. I hear a relay clicking under the dash when this happens, both when the CEL turns on and off. So to add to that, when I bought the car the owner stated that the cars idle would surge. When I arrived the main relay harness had been cut and there was an attempt to "wire" in a new relay, the new relay being from an eg civic 1992+. I bought the car none running. The original relay was in the car, but upon further inspection was toast because a spring was missing so the connection would not be good. I bought a brand new relay from AutoZone and wired it into the harness using information from this forum. After replacing the main relay and two fuses, alternator and ecu, the car ran fine. My wife was driving it to work the next day and the car cut out on her when it had barely warmed up, when I arrived the car started and ran fine for me. Then it did it to me a few days later, it was cold, and this time I was able to get CEL code 3 for the map sensor, I believe. The weird thing here as well is the CEL and relay would go crazy until it gave me the code clicking and lighting like crazy. I have since gone through the wiring which was a chore because it was done very poorly. Butt connectors and horrible soldering skills included. I have double checked the wiring and have soldered correctly and replace all butt connectors, cleaned and connected all grounds and adjusted the TPS as well. It ran fine for the last two days and now it has done it to me again on the way home from work. I was able to switch the key from ACC to ON and the car ran fine the couple miles back the my house no problems at all even started back up fine.

If anybody has any ideas please let me know.

Thanks,
Mike

 

The bad wiring on the map sensor could have damaged it

 

The map sensor wiring was not messed with at all. The wiring that was - Distributor, IACV, Two injectors (2,4), and the dpfi to mpfi ecu wiring were cut rather than moved. All of these have been fixed (soldered properly). On top of that all grounds, including grounds on thermostat have been cleaned. I am kind of at a loss as it is so intermittent. Nothing is adding up cause it could happen cold or warm, one hour of driving to two - three days of driving.

 

Failing knock sensor? We need to think about how you can gather more information here. I think you need to find out if this is an intermittent problem or if it's caused by a specific scenario. Have you noticed a pattern? Can verify the compatibility of these chips?

Couldn't the relay and fuse signals mean a lot of different things? You need more information and so do we. Fuel and/or spark can be cut for all sorts of reasons. Are you pretty sure that what's happening? A sudden cutoff would feel like a hard jerk and would be noticeable under throttle. Even though the engine and chip swaps are highly suspicious, I would look into the fuel/spark cut off a little more. Do we know all the situation that can cause this? It could even be a failing knock sensor for all we know.

 

No knock sensor. It is the "low" compression b20b I checked and there is no knock sensor to be had. I am trying to think of what could be happening to narrow it down and I can't seem to come up with anything on my end. A lot of it sounds like a grounding problem with the grounds on the thermostat housing. I have cleaned that connection along with every other ground.

The car did it to me again when I left work on Friday. It started fine then when I pulled out on the main road the CEL kept coming in along with the clicking of the main relay. After fiddling with it on the side of the road it had an idle surge with the relay "buzzing" then after another couple starts was running fine, until a little down the road when the relay clicking and CEL kept flashing on and off. Switching between ACC and ON seemed to do the trick every time and eventually the car ran great fortunately. It did this for about 5 miles after that the car ran great, I had to pick up some groceries, came back out and it ran fine the rest of the 15~ miles home.

I drove it today, to and from work, and had no hiccups whatsoever. Again a lot of the symptoms sounded like it was a bad thermostat ground according to some of the forum threads I have read through especially with the "buzzing" main relay.

So what I have done so far
-New main relay, Had to get this because the car did not come with one.
-Cleaned and mounted all grounds (battery to transmission, transmission to body, body to valve cover, and thermostat housing)
-Went through and properly soldered all the wires that had been cut and spliced by whoever did the swap. This is any wire that had been touched to go from dpfi to obd1.
-Re-seated all connector plugs to the ECU.

 

I would try throwing a new (junk yard) map sensor on it and double check the map is getting good vacuum. Could be a continuity issue at the map plug its self on the engine harness or just a map sensor going bad. As for the knock sensor comment, p06’s don’t have a knock sensor board, never came to run a knock sensor so that’s not a possibility. The map sensor is the single most important sensor on the whole efi system. It determines load indexing to tell the Ecu how much fuel and how much spark you need for the given rpm.

 

I have tried the firewall mounted map and a two maps that I grabbed at the picknpull in town although one came off a 6 cyl and I haven't ran that one just used the o-ring used it as a block off. I assume they would have been different anyway.

I am thinking now it may be a fuel pump issue. I gassed it up and haven't had an issue since. It just seems so weird to act in that way. I am waiting on some funds an should be putting a new one in soon. Thinking a Walbro 255.

 

Had the issue again tonight while sitting at a light. The CEL flashed real quick while the car was running, went to go take off and the relay started to click again. Bumped the key from ON to ACC and back and it ran fine the rest of the way home. I am at a loss. If the map was bad the car would go into limp mode correct? The car does not go into limp mode the CEL flashes randomly and the car wants to die, or depending, will idle surge for me with the CEL staying solid. When I check for engine codes the car gives me nothing.

 

Ok. Drove to work and the car ran great. No problems. Then I went to leave and I got a solid CEL with a buzzing sound going on. I thought it was the relay again, but lo and behold its coming from under the hood. I tried to feel for it and couldn't find it. The only thing is it was coming from around the intake and more on the passenger side of the vehicle. I placed my hand on the fuel rail, iacv, fuel filter. But I couldn't feel anything. The car would start and instantly die. I pulled the map sensor to put the car into limp mode to try and get it home. I made it 10 miles and the CEL turned off. Pulled off to the side of the road hooked up the MAP and the car ran great the rest of the way home. I did try and check for CEL but it didn't work.

What could that buzzing sound have been?