I have a 1992 manual D15b7 130K mileage civic that ran perfect for the 4 years I've owned it. The other night while on my way home it shuts off, I tried to start it but it will crank and not turn over... then after about 2 minutes of trying/waiting it started but idled at 1400 rpm with a CEL.

When I got home and got the error code from the ecu it gave me a number 3 for MAP sensor... I got 3 known working MAP sensors to test and had the same issue, high rev with CEL.

I've changed TPS, IAC-V, same thing... I tried my ecu in a friend's similar car, his was AUTO and V tec and the car started right up and went straight to the normal 700/800 rpm for idle... when I tried his in my car it started up but the revs were hunting between 700 and 1200rpm.

Had a place that works on electrical/electronic issues go through the car and tested the wire loom and they assure me that all the plugs and wires are good, they're suggesting that my ECU/ECM is "going bad" but couldn't explain why when I put it in someone else's car it works fine.

After a day of fooling around and checking all this out, I'm now getting an error 43-O2 sensor error and the car will idle high for about a min then go to the normal 700/800rpm idle range with the CEL still on for the O2 sensor. I've ordered an O2 sensor but what else could be causing this behavior?

ANY CLUES?? I'm particularly interested in what "txgreasemonkey" has to say.

. Clean the main ECM ground, located on the thermostat housing. Look for 3-wires going to a brass connector.

. Reset ECM by removing the 7.5A Backup Fuse, in the under-hood fuse box, for 10 seconds. Then, see if the Check Engine Light goes out and stays off.

. Perform K-Test on the ECM. Failing ECMs can throw bogus DTCs.

. Code 43 can also indicate a fuel supply problem. Because of the age of your Civic, I would replace the main relay and fuel filter. Do you hear the fuel pump run, when the ignition key is turned to ON?

. Replace ignitor and coil:

https://www.askmehelpdesk.com/cars-t...tml#post265896

Because of the age and mileage on the car, this should definitely be done. It would not surprise me if the ignitor is what caused the car to die and is responsible for the erratic rpm.

If Code 43 returns, after replacing the components above, replace the oxygen sensor (Denso). If the problem continues, I would focus on the ECM. MAP Sensors tend to be extremely reliable (and expensive).

Ok, I'll check and clean the ECM ground on the thermostat housing but mine has 4 wires on it instead of 3 so I hope it's the right thing.

What is the "K-test" for the ECM?

I doubt it's the fuel system as I have a kill switch that runs straight 12 volts to the fuel pump and bypasses the fuel relay. We also pulled the fuel supply line to the fuel rail and it's full of fuel and has tons of pressure.

I'll also try replacing the whole distributor as I have access to one.

I should be getting the new O2 sensor I ordered in about a week, it's a Denso too.

Txgreasemonkey, one thing puzzles me man... I just don't think it's my ECM because it works fine in a friend's car and idles perfectly but if I do all that you recommend and it's still having the issue I'll get an ECM as well and let you know what happens.

I agree with you--it's a possibility, not a probability. I really think installing a new ignitor (complete distributor, in your case) may solve the problem. Ignitors contain a very sophisticated computer that eventually gets fried from heat. When they are in the process of failing, all sorts of weird problems can occur.

The K-Test: Remove the MAP Sensor connector and turn the ignition switch to ON (not start). Using a multimeter, check for 5 volts going between the MAP Sensor connector's reference wire (+) and ground. As you look at the connector, this is the socket on the right. Really press the black test lead into a cleaned main ECM ground on the thermostat housing. If the voltage is low, it's probably indicating ECM failure. Most failed ECMs will record a fraction of a volt. To me, the K-Test is simple, elegant, and accurate.

Your modified fuel system wiring may be responsible for Code 43 being thrown.

Be sure to reset the ECM.

See if this link seems applicable to your situation:

https://www.askmehelpdesk.com/cars-t...tml#post260436

I'll do all you recommend and report back with updates.

I doubt my kill switch to the fuel pump is causing the 43 error code because I've had the kill switch for more than 4 years of driving and I only got the error since the car starting all this trouble.

One thing I noticed while reading through all the posts I could find on this site is that most people do not report back with updates on if all the help the received paid off and what the ultimate problem was. I'll definitely report back as soon as my car is sorted out so that my thread may help someone with the exact problem one day.

TX, I've called an Oreilly's in FL and they want $349.95 if I send in my old ECU, otherwise the price without my ecu is $449.95. Do you have any idea where else or what other branch I can get it cheaper with a lifetime warranty?

O'Reilly Auto Parts is the only outfit I know that offers a lifetime warranty. I bought one from them over 2 years ago and it has been great. That's not a bad price.

What leads you now to conclude the ECM is bad? Before, you thought it was good.

I just put in a brand new Denso O2 sensor and started the car up... same 41 error code. So now I'm going to put in another ECU and see if it still happens, would be logical to assume if I change the O2 sensor and the computer that it would be a wiring issue, no?

Do u know which pins in the wireloom that plugs to the ECU that I can test to see if the voltage is coming from the new O2 sensor and what voltage I should be testing for? By the way, it's a 4 wire O2 sensor.

No, I don't.

This is an update on my issue, I noticed most people don't update their original thread after they get the problem sorted out.

I changed my Main relay, my distributor and my ecu over the period of about 6 weeks and so far all is well. I couldn't be bothered with just changing one and waiting to see if that fixed the issue. My car is 140,000 miles so I just changed everything that needed to, including the O2 sensor and all is well with the car.

Want to say thanks to TX for all his help and insight, definitely going to be back here if I ever have any other problems.

What you did was smart. Once Hondas go over 120,000 miles, or 10 years, it's best to replace the ICM, coil, main relay, ECM, and distributor housing. It usually restores like-new reliability and performance. It's much cheaper than buying a new car.