queery about testing sensors etc

[Finnon]

When reading the manual quite often it mentions to check a sensor with a multi meter and it gives a range of temperatures. Im guessing this is the ambient temp? and 0 - 20 degrees c would be the ideal place to start in this sort of wether? (i live in uk and were experiencing a bit of a cold spell)

I need to check out my engine temp sensor. Along with isc and tps

im also gonna try a different ecu just incase the current one is faulty somehow (this is about my excessive high idle and fuel consumption issue)

[GrimJack]

Each sensor is different... the engine temp sensor, you measure the value from the sensor at various temps to make sure it's still within range. Or if you are having problems when cold, for instance, measure the value when it's cold - if it's still in spec, chances are your problem is somewhere else.

[Finnon]

ahh right.

ill give you a basic outline.

I thought i had a vac leak as i have a high idle speed etc.

i cant find a vac leak though (well a split in any pipe)

so i figured it could be a problem with the temp sensor making the engine stay in warm up mode permanently.

Also the temp gauge intermitently gets into the normal zone.

at first i thought it may be a seized fan clutch constantly blasting the rad with loads of air. but the fan spins no problem

i figure it could probably be a multitude of things so i guess working through each thing individually to narrow the problem down is a good course of action

no fault codes showing either btw

[GrimJack]

Gotcha. Sounds like you are on the right track!

Remember to check the silly small stuff - like the EGR connection at the back of the intake manifold, and the power steering idle up line...

I'm pretty sure you can check whether the ECU thinks you are warm or not with the heater control valve. If you put it to heat the cabin and the valve stays shut, the ECU thinks you're still cold. I think. It's been a while since I read that section of the manual.

[Finnon]

right, i found the original ecu for my car in a box in my shed.

I remember i swapped it over about 2 years ago when i was chasing about trying to find another daft fault. (it turned out in that instance to be a fault with the alarm. code 14 iirc)

i stripped out the glove box and removed the replacement ecu.

its part number is

89661-14120

and the numbers beneath that are

17500-0545

the replacement (the original ecu when the car was manufactured) is exactly the same bar the lower number which is

17500-0544

anyway i disconected the battery for about 5 minutes. (i have done this many times recently sometimes for a lot longer so i think that i can discount the disconecting the battery makes the car clear any codes etc)

i refitted the original ecu and reconected the battery and started the engine. Right away i noticed the idle speed seemed to be lower. I took it for a drive of aproximately 3 maybe 4 miles and when i got back home the engine was idleing at about 750 rpm.

the engine does seem a tad rough but i know i have to replace the rocker cover gaskets as theres a bit oil in the plug wells and also when i changed the plugs over recently i didnt have time to gap them correctly as the light was failing.

now this idle problem and high fuel consumption problem has been happening for a while. but not as long as the spare ecu was fitted.

there was a split vac pipe but i replaced that and cant seem to locate any further vac leaks.

[GrimJack]

Are you inspecting your piping for leaks by the Mark1 eyeball, or using a boost leak tester?

[Finnon]

just by look and touch mostly, the ones that are up by the top of the engine ive removed and inspected, the ones under the intake manifold ive only been able to feel around for any splits. I replaced the pipe on the pas idle up that runs from the hard pipe on the front of the engine close to the pulleys.

I wasnt sure where to start with a vac leak test.

Just seemed funny that swapping the ecu made it run much better. I supose theres a good chance it isnt the problem at all.

edit: iirc the uk cars have different vac systems than us cars. something to do with us emition control legislations or something?

[AJ'S 88NA]

Could have been the one you swapped was for a auto?

[Finnon]

both ecu's were for an auto. they are both exactly the same bar 1 number.

dont get me wrong. there is still some running issues with the car. its still runing rough. slight miss etc (im assuming thats to do with the oil in the plug wells)

its just its now running a lot slower.

I figure i still need to check out the other sensors aswell to make sure though.

It just seemed odd that this has dropped the speed right down.

ive since driven it again and its still idleing at about 750- 800

though it is stil fluctuating aswell so figure that there must be another vac leak aswell.

[GrimJack]

Try the other ECU again? If it still runs slow, check for corrosion on the wiring harness plugs?

[Finnon]

Try the other ECU again? If it still runs slow, check for corrosion on the wiring harness plugs?

yeah guess ths an idea. i built it up again so i could use the car but its easy enough to pull it all apart.

the ecu plugs looked fine to me no signs of corrosion

ahh i missread. ok man cheers will do