Rough Idle on Cold Engine

[AllanL]

mismatched MAF may be a reason for the poor fuel economy, 'matching' it with the current ECU can be done but this requires a re-socket and a re-program of the EPROM.

mine used to run 22mpg [approx 8km/l], considering no o2, no knock and just the rich/lean adjustment knob set correctly.

i'm curious how he adjusted for 70/30 A/F mix with the knob...

system reboot happens when the (-) pole of the battery is removed, and not while pumping the accel pedal.

for the diagnostic port, there is a way to check directly from the ECU.

get well soon. while your 'down' read up on how to get your engine in good running condition.

and try to get a second opinion, as Rich recommends. i'm afraid 'system reboot' @ accel pump is not a good indicator of a good mechanic for your GTi...

by the way, does your 'check engine' light still turn on with the ignition key at ON, then turns off after approx 5seconds?

 

[microserf]

Hi AllanL
Thanks, i managed to google a galant service manual, am trying to read it to familiarize myself with the car

- by re-socket, you mean convert the native 7 pin to the 6 pin of the Eclipse MAF? yes i think the mechanic did that, i will ask if he re programed the EPROM - is this simply accessing the ECU and configuring it ?

- as for adjusting the A/F mix, he tweaked the knob and i saw him probe some parts with the volt meter.

- "system reboot" is incorrect, i asked him what conditions do i create if i pump the gas pedal before starting, and his exact word get the system ready. I see Paul's point - it will produce a richer mix by adding more fuel, right?

- yes when the ignition is ON, the check engine lights up and then goes out after a few seconds.

- still no reply from your brother, does he check the ECU - to check if the MAF is matched, and other diagnostic problems



Thanks again AllanL

 

[AllanL]

great!

study the items for 'on-vehicle inspection' in the service manual.

 

[cheekychimp]

Actually Jonathon, thinking about it I'm not sure pumping the accelerator will do anything to be honest. It won't have the same effect that it does in a carburettor controlled vehicle.

 

[Fish]

^^ From my experience with some early American efi vehicles (mostly tbi chevy), pushing the accelerator pedal to the floor before starting puts them into clear flood mode. This cuts the injector pulse way down and has about the same effect as wide open throttle on a carburetor.

So if the car has a rich condition this may actually be somewhat compensating for it if this system works about the same way.

When the op said runs rough cold and poor fuel economy I instantly thought coolant temp sensor or coolant temp sensor wiring. This seems to be a very common problem with our cars and an open in the coolant temp sensor or circuit would cause the car to read very cold temperature (about -40*F) and run extremely rich.

Hope this helps
Branden

 

[microserf]

@ Cheekychimp - thanks paul for the thought. I was pretty mystified about this myself, that is why I kept asking the mechanic about it. All he said is clears the system....maybe this is what Fish was referring to?

@ Fish - hmmm i will keep the temp sensor in mind, and or its wiring. but i recently change the temp sensor to a new one, maybe i should get it tested.

Thanks Paul, Fish for another round of inputs, the good news is i am seeing new mechanics this weekend, so lets hope they find the culprit.

 

[iceman69510]

Keep in mind a new temp sensor does not mean the wiring is good. It may be cracked or brittle from age.