Hi guys,

I just got a '95 GX ej18 recently and am having a power hesitation problem once I drive 2km down the road. The car starts well, and runs well when cold, but as soon as i drive a certain distance (always the same distance) and go to accelerate from stand still or low speed the engine hesitates for a few seconds for the next 10 seconds or so, beofre going back to driving well.

I suspect this to be related to the onset of closed loop control. How is the open loop enrichment controlled (end point) on these engines and what could be the culprit of this do you think? Engine block temp sensor? Crack angle sensor?

What would be the best way to diagnose this? I have just changed the oxygen sensor (and reset ecu) thinking that this could be the culprit due to its slugish response.

Thanks Dan

 

what is a GX?

 

The '95 GX here in Australia was a one up from the basic flavour Impreza LX. The '95 GX basically recieved AWD, cruise control, full electrics and an 1.8L over the '95 LX's 1.6L

If you'd like to read more
http://www.redbookasiapacific.com/au...s.php?id=99071

 

i'm guessing you don't have any DTC's or else you would of said so. do you have any type of diagnostic equipment where you could look at the real time display? that should show you loop status. and you should be able to see if you have any sensor issues. there are so many different things that could be wrong, its hard to pinpoint any one thing.

EB Turbo

 

I checked the OBD I codes and it didn’t come up with anything

I checked the old oxygen sensor output with an oscilloscope and it was very sluggish that's why I replaced it with a new one witch is responding much much faster, but the problem persists.

What makes the ECU decide to go into closed loop control? Mostly water temp?? Anyone have resistance/temp data for the sensor?

Is there are good way to monitor when the ECU goes into closed loop??

 

it should be coolant temp, time, and oxygen sensor. an easy check would be referencing the gauge on the cluster. are you sure you dont have a clogged catalytic converter? your symptoms sound similar to those of a clogged cat.

EB Turbo

 

Thanks for the advice EB turbo, I’ll check the cat out.

The car has relatively high mileage (270,000km/170,000miles) so you might be right.

The fuel economy is a little higher than I expect at 9km/L (11L/100km for people in marketing ) which might be pointing at the cat as well.