Hey everyone, really weird problem here. Put together a b20vtec and threw it into my 94 eg sedan but right from the start it's had a problem. The car idles like trash, doesn't like to start and tries to die at every stop. It's almost like the car is misfiring and just sounds bad when you give it throttle. There's no power and afr's are all over the place. The car sputters and at WOT it hits a wall and pops and bangs out the exhaust. It's on a chipped p28 with a stock b16a base map from CROME. I'm getting a CEL when the car runs and when I jump the connector to check for codes the light stays illuminated. Okay so I figured it's maybe a bad ecu but after trying my friend's ecu it seems to run the same way. Except when I don't have the service connector jumped and put the car to on, the fuel pump primes and the engine light turns off. If the ECU was bad I'd imagine the engine light would stay on with the service connector jumped or not. I've double checked timing belt, tried a different working distributor and even repinned all the ecu plugs. Anyone ever have a similar problem? I'm getting extremely frustrated.

 

Is your friend's ECU chipped as well? If so, try cutting J1 in your ECU to revert to the stock maps and see if it will run. You'll need a stock MAP and stock sized injectors to do this. A solid CEL is usually an indication of a bad ECU.

Double check that you have everything plugged in correctly - that MAP and TPS are not switched. Are you sure the tune you have loaded matches the MAP and injectors you're running?

 

The next time the CEL turns on while the engine is running, retrieve the CEL code by leaving the engine running (i.e., don't turn engine off) while you jump the service connector.

If you unplug the O2 sensor, does the engine now run more smoothly?

 

Yes his is chipped as well. They're both P28s. What is J1? Is that one of the sockets on the board itself in the ecu? Yes I'm on stock map and injectors. TPS and MAP are plugged in correctly and injector firing order is correct.

It doesn't work. The engine light stays solid while jumping the connector when the car is in the on position and when the car is running. Engine light only turns off if service connector isn't jumped when priming fuel pump. I'm running in open loop and only have an aem wideband hooked up. No stock o2 sensors.

 

This^ sounds like an ECU problem.

If the wideband talks to the ECU, unplug it and check whether the engine runs more smoothly.

 

When I last tried with my friend's ecu it did the same thing though. His car runs perfectly fine. I just tried a new chip, checked over entire wiring harness and thermostat ground. Still no bueno.

I took the wideband off the o2 wire to the ecu. Now it's just running open loop with 0 o2 sensors hooked up to the ecu.

 

Given the cumulative information you provided, the problem is the ECU, the chip, or the software.

Is the engine now running more smoothly with the O2 wires disconnected, despite running in open loop?

 

J1 is a jumper on the ECU board. By cutting or removing it, you will revert your ECU back to the stock maps and it will not read the chip you have installed. If your engine runs fine, the problem is either with the chip or the solder job. How good was the soldering work that was done to install the socket and other components into the ECU? You can always solder a new jumper into J1 after you cut or remove it to make the ECU read from the chip again.

 

Well update! I decided to try burning my chip in HTS instead of Crome and the engine light is gone! Car still feels sluggish until 6k+ rpm but definitely a step in the right direction. However my afr gauge is still reading full lean but on decel will read for a couple seconds then lean out again. Is my sensor messed up or is my car actually running full lean? It certainly doesn't feel like it's leaning out when cruising around when the aem gauge says so.

 

Faulty wide band O2 sensor or running lean?

Have you swapped in a known good wide band O2 sensor to test whether engine runs more smoothly?

Also measure the fuel pressure and test the functionality of the FPR. Replace the fuel filter if it has not been replaced recently.

Have you looked for a small exhaust system leak near or upstream of the O2 sensor?

 

I'm not too sure but the engine isn't running off the wideband anyway. It's running strictly through open loop on the stock b16a map I loaded onto the chip in the ecu. Fuel filter was replaced recently but unsure if the FPR works properly. I have another to try, really hoping that's my issue because apart from that I'm not sure what it could be. I don't see it running the way it is on a stock map, it should at least drive somewhat smoothly for using the same map that matches the head (b16a head). Yes I potentially have an exhaust leak about a foot downstream the exhaust from the wideband sensor. Could this cause a lean reading?

 

Fix both the ECU/chip problem (indicated by CEL code 0) and the exhaust leak (O2 sensors can detect miniscule O2 levels produced by a leak). Also have your buddy test your wideband sensor in his car. Then go from there.