coolchrisuk

- UPDATE - Problem Fixed...

Just thought I would make a note on this thread to say that I have finally solved all of my rough running/poor idle/stalling problems.

I have been at wits end trying to solve this one for some time now as some of you may know. The car finally threw a code for the IAT sensor at the weekend and this at least pointed me in some sort of direction after months of trying different things. Every sensor checked and cleaned where possible, valve clearances, ECU relearns up the ying yang etc etc.

I was content that the IAT was working correctly and with Honda wanting £60 for one I was determined to find the root cause of all my troubles.

When it came down to it.... as simple as it gets really. Wiggled my blue harness connector (the sensor feeds) on the back of my ECU with the engine running and hey presto the engine started going mental (threw a bad TPS code aswell)! Plugged in the OEM to rule out the harness, it seemed fine. Turns out the connections on the back of my Mugen ECU must have had some oxidisation on them (hardly noticible to the naked eye). I cleaned them up with some contact cleaner and a cotton bud, relearned and went for a blat.

Rock solid idle, it's like a new car! (I know everyone says that ) Im sure it never pulled like it does now!

My thinking behind this.... and possibly something anyone buying a second hand ECU should think about is: How long has it been out of the car.... unplugged..possibly in the back of a garage somewhere. Well worth giving the connections a good clean up before fitting one IMO. Sure the connections were made but surely when the thing works by the input of very minute changes in voltage, any corrosion/oxidisation of the connectors however small can cause all sorts of running problems as the resistance increases and hence changes the voltage.

Having ruled out everything in the FAQ ref hesitation/idle problems I noticed that bad ECU connections were mentioned wrt missfires. For months I have had problems without a single CEL. Thought it might be worth adding Cleaning of ECU connections to the Idle/hesitation FAQ.

Apologies for the essay but Im so happy to have my car back now

MB

I'd look at the voltage output siganl to the ECU.

It's 0-5v, so in this weather, with the ignition on i'd expect to see quite a low voltage. I don't have the sensor range to hand unfortunately, but i'd expect -20 to plus 50 or something.

Someone with a Scanguage could compare values.

coolchrisuk

Can i measure that with a multimeter MB? - On a side note I just disconnected the blue connector from the ECU to check the continuity of the cabling (jumper in place of the sensor) all good. HOWEVER - with the jumper removed and the ECU unplugged I checked resistance to ground for both the Signal wire (SG2) and the IAT wire.... IAT wire to ground = infinity so happy with that, SG2 gave me about 11Kohms? Does that mean I have an earth on the SG2 line, albeit not a great one at 11kohms? Surely this could cause a problem?

coolchrisuk

EDIT above - SG2 - sensor ground 2 - a bit of a clue lol

MB

Chris, yes, set your multimeter to read volts. Take a local ground and then put your other multimeter pin onto the output signal from as IAT. You can do it at the sensor or the ECu, wherever is easier to get contact with a wire.

coolchrisuk

Thanks, I'm on it

veehexx

from honda workshop manual:

Intake Air Temperature IAT Sensor
The IAT sensor is a temperature dependent resistor
(thermistor). The resistance of the thermistor decreases
as the intake air temperature increases.


test procedure: http://picasaweb.google.com/lh/photo/kqlGi...feat=directlink
page 2: http://picasaweb.google.com/lh/photo/Ik-zn...feat=directlink

coolchrisuk

Right - With IGN on measuring ground to SG2 I have 0.029V, measuring ground to IAT I have 5.02V. This would suggest all is well no?

MB

What's SG2?

What reading do you get from the singal out from the IAT, going to the ECU?

I'd expect it to be somewhere between 0.1 and maybe 1.5v in the current climate.

coolchrisuk

These were taken from the connector plug (unplugged) - SG2 is the signal ground - diagram as per veehexx's post shows connections - http://picasaweb.google.com/lh/photo/Ik-zn...feat=directlink.

So all ive taken so far is the voltage that the ECU is sending out to the sensor. Surely to measure the actual signal being sent back to the ECU im gonna have to tap into wires or use needle probes on the outside of the plug to the ECU?.... just v wary of prodding around the ECU when the IGN is on.

Running wise the error code P0113 has not popped up again. The car idles high (2k) on cold start and then falls a bit... up a bit, down a bit...lol... just sounds like crap, little pops here and there, judders.... give the throttle a blip and it stumbles. IACV possibly? Valve adjustment?

Thanks for all the pointers chaps, but its really getting to me! I want my car back! (preferably without having to resort to paying someone!)