_Endless_

The problem keeps getting worse and I think I have tried everything to troubleshoot it. My brother was using the car one day and after parking it for only a few minutes the car doesn't want to start. He lets it rest for about half an hour and it started right up and he was able to drive home without stalling again. I thought it was the main relay but after a few days, he used the car again but the car stalled while he was driving so he lets it rest for a while and was able to get home.

We suspect it was the ICM because the same thing happened to our CRV. On the CRV, it got worse before we were able to check that it was the ICM. So we didn't wait for the civic to get worse and replaced the ICM right away.

The car didn't have any stalling issues after replacing the ICM until one day when I was driving the car. I was just cruising down the road when the car suddenly stalled. I pushed the clutch in and step on the gas and then let the clutch out but to no avail so I had to coast to the side of the road. I tried starting it but it would just turn over but not start. I have to let it rest for about 20 minutes and it started again. However, around 2 kms to my home it stalled again. I tried starting it again, sometimes it started for 2 seconds then die so I think it's not the ICM anymore since the tach needle is moving. I removed the rear seat to check if the pump is priming and it's not. I had to check every 5 minutes if the pump would prime. Sometimes it would prime but it will stall again after 2 seconds. I had to keep trying until it primes before I start her up again. After successfully starting it up again, I drove less than 100 m and it stalled again. I let it rest for 20 minutes and I made it home.

I checked the main relay using the steps on the Helms manual and it checked out ok. I decided to put in the stock pump thinking that the walbro pump was the problem but it's not because after I put the stock pump in, it was stalling repeatedly again. I decided to reflow the solder joints in the main relay and I was able to test drive the car for less than 100m with no problem. At this point, I found out that moving the ecu changes the idle speed erractically. Sometimes the car will stall. So I thought it was a simple problem of locating which wire is causing it to stall when being moved.

The following day, I started the car up and suddenly the idle is loping and rpm is only at 500rpm and there was smoke continuously coming out of the tailpipe. I didn't shut the engine down but instead I started moving each wire of the ECU using a wooden barbecue stick. By the way, I'M USING AN OBD1 P28 ECU and I use the jumper method instead using an OBD2 to OBD1 conversion harness. I found out that touching SG1 or Map sensor ground would affect the idling big time and would actually stall the engine. The other one was SG2 or sensor ground which only had a slight effect on the idling speed. I also got a solid CEL with no codes at this point. For some reason, the problem got worse overnight.

I decided to repin SG1 and SG2 so I bought another "D" connector. I thought that it's a simple fix but after repining both of them, it actually got worse yet again. When I started the car, rpm shoots up to 2000rpm and stays there for a while before it starts to surge then drop then stall. Sometimes it will just surge but not stall. I'm still getting a solid CEL. I was so frustrated and didn't know what to do anymore. I decided to resolder the solder joints of the main relay AGAIN but still the same problem.

The next day, I removed the obd1 ecu and put the stock ecu in. The high idling persist but now I get 2 CEL codes - VTS and MAP. I connected back the VTS and MAP to the obd2 ecu socket but this time I get a solid CEL while the idling speed is still 2000rpm which is still too high. I'm perplexed why the stock ECU wasn't able to solve the problem. I then swapped in a working MAP sensor from our CRV as well as the main relay but problem still persists. I even put the Civic's MAP sensor to the CRV and it runs well with no CEL.

Next step, I decided to wire the MAP sensor directly to the ECU using separate wires in order to bypass its stock wiring. The solid CEL completely went away however I got a loping idle at a low 500rpm and smoke was coming out of the tailpipe. I touch the ECU wirings but idling speed didn't change. Then I removed the stock obd2 ECU and put in the obd1 ECU and still using the separate MAP sensor wiring and the solid CEL also went away BUT the idling speed was at a high 2000 rpm then it will creep up to 2500rpm. I shut the engine off and start it back up again the engine will idle at 2000rpm again then drops to 1500rpm then jump back to 2000rpm over and over again like there was an invisible person pumping the gas pedal. I tried removing the IACV plug and the idle drops to 500rpm but runs more smoothly and with lesser smoke but when I put the back IACV plug the rpm cycles from 1500 rpm to 2000 rpm again.

So now I'm at a lost already I don't even know when to work on tomorrow. Has anybody had this kind of experience? Nothing was done to the engine after it began stalling due to the pump not priming. The stalling was caused by the fuel pump not priming but now it gotten worse like the car is possessed by an evil spirit. I'm planning to have my tuner re-burn my rom to the chip in case the program got corrupted. will it help? By the way, I'm still using crome and I have been using it for many years without any problem.

Any help will be appreciated.

_Endless_

Still no luck with the car. Today I put in the stock ECU. The idle speed was low at 500rpm and you can hear the sound from the exhaust isn't smooth and a lot of smoke coming out. I decided to give it some gas and the idle stabilized at 1000 rpm during warm up. The engine is idling fairly steady but the sound of the exhaust is loping. I guess the stock ECU can't control the 450cc injectors I'm using hence the smoke which smells of fuel and stings my eyes. I let it idle until the radiator fan turns on. At that point, the idling speed is at 700-750rpm. It's not possible to drive the car with this set up and I need to give it more gas just to back up in the garage.

Next, I swapped in the chipped P28 ECU running crome and idle shoots up to 2000 rpm again then it will cycle from 2000 rpm to 1500 rpm like somebody is playing with the gas pedal. I tried to give it some gas by pushing the gas pedal in but when it decelerated the rpm shoot up again and went back down and died. When the engine stalled, the CEL came on and the main relay starts buzzing. I pulled the code but it's just solid cel. I started it up again it revs up and then stalled and CEL lights up and main relays starts buzzing. I also tried wiggling the keys in the ignition while the car is idling to see if it's my ignition switch but it made no difference. This is driving me nuts. I haven't re-burn the rom since my tuner is busy and right now I'm not even sure if it's the ECU or the program that's causing the problem.

mk378

Check the ECU ground wires on the thermostat.

A false reading from the ECT sensor will cause the ECU to command a fast idle as if the engine has just been cold-started in winter. Ohm test the ECT. Also test ohms through the sensor from the ECU end of the wires to confirm the harness is OK. Check that the cooling system is full. Coolant sloshing around on the ECT will cause reading to vary, and idle speed will also.

_Endless_

Thanks. Yes I have checked and clean the ground wire on the thermostat housing.

I have fixed the problem. Since I've done every test that is on the Helms manual I decided to look at the components inside the ecu. I didn't notice any leaking actually but there's one cap that doesn't look right because the markings on the cap seems to have come off and it can be rub off easily. But there's not electrolyte coming out of it so I'm guessing probably it is overheating. Another cap near the "D" connector has not visible problem and the pcb below it seems normal but after wiping it with a cotton swab I see traces of brown stuff on the cotton swab. I also replaced the C14 cap because I read somewhere here that it's a major cap. So all in all I replaced 3 capacitors and after that, the car idle like before. I let it warmed up until the rad fan turned on twice and then I reset the ECU and no stalling, weird idle or solid CEL anymore. Tomorrow I'm going to put the walbro fuel pump back in again.

Nave43

Even though you have replaced the caps with with a quality equivalent. Remove the board and get it re-flowed at a professional computer repair shop. They can ultrasonic clean it and re-flow all the solder to clean up any all of those cracked and corroded solder connections. I would do this just for piece of mind.

mk378

Best to replace all the electrolytic caps. They're 25 years old. They weren't intended to last that long.

You can wash the board under plain hot water to remove the corrosive capacitor residue. The important thing is to make sure it is ABSOLUTELY dry before trying to power it up.

Nave43

I would not run that board under tap water! There are unknown quantities of metal, minerals and other contaminants in it that could easily short the board. If you insist on cleaning it yourself only use pure distilled water. Then make sure to dry it for multiple days, up to a week or more in a bowl of rice.