Yet another Idle / running issue, 1997 Australian Model

[andytork]

Hi All,

Before I start, I have been through just about every idle related thread on all Rav4 Forums I can find. So here it goes :-

Car : 1997 (april) Rav4 (of course), 4 Cylinder, Auto, 4/5 door
Location : Melbourne, Australia



Other Info : -

• Car has no EGR system - not fitted to Australian models (?)
• Throttle body has been removed and cleaned off the car and wasnt too bad anyway
• Car burns zero oil, loses zero coolant (never has)
• Plugs have been changed, old ones were correct colour etc
• Leads have been checked
• Distrubutor cap removed, cleaned, checked, rotor is OK
• There are no vacuum leaks (I have checked all lines, blocked most off to test etc)
• Recently passed an emission test for RWC (MOT)
• Car doesn't have an ODBII, shame as I have a scanner - and the CEL is not on anyways
• Car has no other running issues, gets little pinking noises under load, I read this is normal, I use 95+ fuel and have used cleaner etc
• Normal soot in exhaust, nothing too nasty, no smoke after until issue has occurred, then just a little as it cleans itself out.

Car starts great from cold, no issue, solid idle. Once warmed up get a click frrm the IACV and it stalls the car, won't restart until cold. When I say warmed up, could be 5 minutes into driving, engine temp at normal (just over 1/3rd guage towards 1/2). I am in Melbourne, Australia, its summer so it never gets "cold" as such, most moring temps are 20 deg c / 70 deg f. If anything idle is a little lower than I would expect, especially when cold

Here are my steps I have used for diagnosis so far, except of course for the checks above :-

1. So, If I disconnect the IACV once warm, it then runs OK for a while, but then after say 20 mins of driving it splutters from idle, runs OK when not at idle and will stall if not kept running and eventually won't restart until cold.
2. If I disconnect the coolant temp sensor, it runs good (except won't cold start of course) - Dont think this proves much ? Just changes everything the ECU thinks about? and of course wouldn't consider running a car like this long term. Disconnecting this also forces the CEL on until reconnected.

Sounds strange but when you think about it, it sounds like the IACV is working the wrong way round
Has anyone any ideas before I take it into a garage and hope they can find it ?

Hope someone can help, this is my daughters learners car and its not a good experience stalling on busy intersections and not being able to restart

Andy

[Ken Allistone]

You should have OBD1, have you tried reading for codes by jumping T and E1 in the diagnostic socket? Not all the sensors throw the CEL but will record a code.
More info can be found here Automotive Training and Resource Site (tech articles)
Is the click from the IACV or the TPS which will click when the throttle is closed?
The ECT (two wires) is very cheap to change it may be suspect, could be responsible for wrong signal to ECU causing it to pink
ECT easy to check if you dont want to change, if you have a multimeter, just look for change in resistance as it warms up (or not).
Could it be the O2 sensor? is it cutting out when it changes from open to closed loop? That said, it will run without the O2 so probably not.
Good luck.

[andytork]

Originally Posted by Ken Allistone

You should have OBD1, have you tried reading for codes by jumping T and E1 in the diagnostic socket? Not all the sensors throw the CEL but will record a code.
More info can be found here Automotive Training and Resource Site (tech articles)
Is the click from the IACV or the TPS which will click when the throttle is closed?
The ECT (two wires) is very cheap to change it may be suspect, could be responsible for wrong signal to ECU causing it to pink
ECT easy to check if you dont want to change, if you have a multimeter, just look for change in resistance as it warms up (or not).
Could it be the O2 sensor? is it cutting out when it changes from open to closed loop? That said, it will run without the O2 so probably not.
Good luck.

I will certainly have a read at that site, looks interesting.

I am sure its the IACV as the throttle is fully closed (and I am under bonnet) when it clicks

I suspect it may be temp sensor, I will warm it up with a multimeter attached, when good record reading, record reading when bad, if different I may just try diagnosing by replacing with a resistor of equal value to the good value. see if problems go away. The ECU appears smart enough to know when this one is out of range and thow the CEL on. Worth a quick check I suppose

As this happens when car has warmed up, even when not moving, I don't suspect the TPS as it has to be well warmed, not just warm. If you follow my logic there. I should have some freezer spray somwhere, so may blast it to confirm when problem happens

o2 as you say shouldn't cause such a dramatic failure

I will find a paperclip and look for codes.

Thanks
Andy

[andytork]

Ok, was Showing code 22 (Engine Coolant Temperature Sensor signal)

Which was because I disconnected it, I reset and retried and it went away

So,

I chucked my multimeter on the ECT, looked ok at first, then went from about 600 ohms out of range, so I changed range.. Was floating around 196K. Have a feeling the pins may be dodgy on it too. 600ohms looks about right for the 20c ambient here

From what I found online it shows 20k at -20c, dropping to about 0.5k at about 70-80c (probably thermostat range)

I found a 1k resistor, which is about 40c on the chart, the engine wasn't fully warmed when it cut out, probably 1/4 of gauge, added this, engine ran steady as a rock, once in correct temp range I could tell it was a little rich running from exhaust, but was still steady

Guess its off for a new temp sensor tomorrow (and a deep socket to fit it, I have read its a 19mm, but will test in shop)

Thanks for the help
Andy

[Ken Allistone]

Great news, allways good to hear what the problem actually was, the ECT is probably the cheapest fix in your situation too. You don't need a socket a ring spanner will suffice, a bit harder to get at I agree, I think I used a 19mm ring.
Save that autoshop101 link in your favourites, it may come in handy again!
Ken

[andytork]

Picked up a new sensor, genuine toyota from a dealer $97, lot cheaper for OEM in UK and US, however good news is that it is fixed now!

(I found my deep sockets in garage too)

Thanks for the help