Hvactechgreen

I have recently purchased this car. Drove great for a week, then idle jumped up to 1500. When I would try to accelerate it would stutter unless i gave it a lot of throttle. Pulled the code. P0505. Cleaned IAC and throttle body, replaced vaccum lines and searched for leaks around intake manifold and injectors. Confirmed TPS is reading correctly. Reassembled. Same problem. Replaced IAC and throttle body gasket. Yay no problems, until 2 weeks later. All of the sudden check engine light comes on, does not idle high but starts stuttering around 1500 when trying to accelerate. Pulled into a gas station, cant find anything. Cleared the code. Runs fine for 3 trips. Same thing happens, clear code, great for a few trips, same thing. I can clear the codes immediately and it runs fine. Still cannot locate any vacuum leaks. Now I have noticed its almost always thrown with a P0450, and P0453 which is for the Fuel Tank Pressure Sensor from what I can tell. Issue is this car does not have one. I spoke with Honda and determined I am supposed to have a P2E-337 ECU, but my ECU is a P2E-L32. No clue why it was replaced, but its looking for sensors that don't exist. I am trying to find a correct replacement ECU. In the mean time I have been clearing the codes and carrying on. Yesterday however, I was stuck in traffic. Idle jumped to 1500, pulled forward a few feet, 2000, pulled forward, 2500, and finally 3000. Still no codes. I broke through the traffic and after driving for a few minutes came to red light, idled normal. The last 3 times it has thrown a CEL i took pics of the freeze frame. Im sharing these freeze frames and hoping someone has dealt with this and can point me in the right direction.

Hvactechgreen

Ran flawlessly yesterday. Found a broken ground wire last night. Repaired it. Purged the coolant system. Took about 30 minutes to get the bubbles to stop, but it ran for 10 more without any. Cranked it this morning and immediately threw all 3 codes and idle jumped to 1500. Cleared the codes, Ran great the whole 80 miles to work. This is going to drive me crazy.

tony_2018

I would suggest you download the FSM and verify that you don't have that sensor. The ecu seems to be the correct one for the 96-98 model civic. You'll need a digital multimeter to verify voltage and continuity to the wires going to these sensors.

Hvactechgreen

I work in HVAC so I have a abundance of Fluke meters to use. This is a Canadian model and from the diagram I have it does not appear to have the sensor, and I crawled under the car and could not locate it. The P2E is correct for the model and age. But from what I have been told the Canadian and JDM versions did not require these sensors for emissions and so the ECU did not look for them. I may be completely misinformed. I understand LV wiring but have never worked on a cars electrical system therefore I have no clue what I am looking for. I find it odd that my P0505 is almost always coupled with the other 2 and from what I can tell the problems should be completely unrelated. Being intermittent though, how do I determine where the issue lies? Is it in the harness, the ECU, a sensor? Why is it on startup sometimes, and after I've driven for 30 minutes others?

tony_2018

Well you have the wrong ecu if its looking for that sensor.

Hvactechgreen

Unless I have been misinformed that is. Is it possible I have a faulty ECU though causing the idle issue as well, and if so, is there a way to confirm that? We have pretty straightforward diagnostic procedures on AC equipment to determine if its a control or component issue. I'm assuming its the same for a car. I cant find what sensors inform the ECU to control the IAC, what they should be reading, and what pins they report in on. I was hoping the freeze frames would give me an idea of what is happening but I have not. I am hoping to pick up a replacement ECU next week and pray it resolves the issue. But I wanted to see if there was anything else I should be looking at in the meantime to rule out other faulty components.

Hvactechgreen

Hvactechgreen

Still clearing codes just about daily. Will be replacing the ECU this weekend. The random high idles were getting more common. I finally got frustrated and pulled into a church parking lot and opened the airbox. Pushed down on the baffle and it closed, idle dropped. Throttle cable was not tight, but not loose either. I loosened the throttle cable. Haven't had that issue again thus far. Probably need to lubricate the throttle body. I cant remember if I did it after cleaning it so I will just assume I didn't. Also adjusted base idle per instructions in HSM. Idle screw is almost completely closed and idle wont drop below 850-870 no load, 870-910 with radiator fan running. Checked again for vacuum leaks, still none found. Radiator fan is cutting on at 205 degrees, TPS is reading correctly. Still have been unable to find any data showing what the MAP sensor will read on the scanner at idle. Its showing 7-8"hg at idle, draws down to 5-6"hg as I give it throttle up to 1500-2000rpm.

mk378

The TPS should be 0.4 volts at idle. I think that should show 0% from the ECU.

If the ECT sensor tells the ECU that the engine is cold, it will idle fast, as it is supposed to on a cold start. This is why it is important to purge the cooling system fully. Also ECT sensors can go bad and give readings that are wrong, but not wrong enough that the ECU throws a code.

Hvactechgreen

This is what was in the manual. I show 9.8% at idle and right at 90% at WOT

Hvactechgreen