Just seeking clarity for now. So when you start the engine cold, it will stall unless you keep your foot on the accelerator pedal - got that. Can you get the engine to normal operating temperature doing this? And if so, after the engine reaches normal operating temperature, do you still need to keep your foot on the accelerator pedal? Or will the engine idle properly without using the accelerator pedal? Also, after the engine warms up, does the engine run smoothly when driving, in all driving situations?

 

Hi everyone, and thank you all for your help !



I did it. The engine vas hot (very hot : fan was turning quickly ! 20 min to 2500 rpm...) but stalls when I release the accelerator pedal. It seems I can drive normally (just on my property to go in my garage). I don't feel any power loss.

OP, in your place I'd start by checking the condition of the rotor and the contacts in the distributor cap. Also verify that the O ring in the distributor body that forms a seal with the cap to keep out dust and water is intact and not missing.

I'm quite sure it not that. Engine is running well, with no misfire or anything, as long as I keep my foot on the accelerator pedal. But thanks for the idea !

Your engine ECU can tell you what is ailing it by using the attached .pdf below.

Tell us what code you get and that will help a lot.
Norm

I forgot to say that I had already tested the error codes. There isn't any error code. Engine light is flashing quickly and continually.

First thing I would check for a fast easy free check is the intake boot between the MAF and the throttle body.


If there any cracks / tears in it (which these develop a lot) then the motor will run like you described. Remove the boot and carefully inspect the bellows for rips tears / holes. Tears like to develop inbwetwen the folds and are often hard to see.

If you have a rip / tear you can temporaryily use duct tape to seal the boot up.

I've already checked that. It's in good condition. Not new but no cracks or anything.

Now I can exclude cold start injector. Maybe I need to check all vacuum system ?

 

First thing I would check for a fast easy free check is the intake boot between the MAF and the throttle body.


If there any cracks / tears in it (which these develop a lot) then the motor will run like you described. Remove the boot and carefully inspect the bellows for rips tears / holes. Tears like to develop inbwetwen the folds and are often hard to see.

If you have a rip / tear you can temporaryily use duct tape to seal the boot up.

 

First thing I would check for a fast easy free check is the intake boot between the MAF and the throttle body.

If there any cracks / tears in it (which these develop a lot) then the motor will run like you described. Remove the boot and carefully inspect the bellows for rips tears / holes. Tears like to develop inbwetwen the folds and are often hard to see.

If you have a rip / tear you can temporaryily use duct tape to seal the boot up.

How would the misfires be only on the firewall side (the old number cylinders) with this as a possible cause? What you suggest would cause all cylinders to misfire - it would not cause only one side of the engine to be misfiring while the other side has no misfires.

 

OP, in your place I'd start by checking the condition of the rotor and the contacts in the distributor cap. Also verify that the O ring in the distributor body that forms a seal with the cap to keep out dust and water is intact and not missing.

 

Your engine ECU can tell you what is ailing it by using the attached .pdf below.

Tell us what code you get and that will help a lot.
Norm

 

How does it run when you need to give it gas? Does it run fine / like you are just revving it or does it run poorly / stumble as you give it gas?


When you let off the gas does it just die immediately like you cut the key off? Or does it kind of stumble before dying? Likwe it tries to idle a bit but dies.


A few things yo ucan do:


You could also have a vaccum leak somewhere. Trace all vacuum lines / gaskets / hoses from the MAF back to the engine. Cylinder heads down.


If everything is running ok though id suspect that the IAC valve has failed despite "testing" ok. if you can get a used one maybe off ebay or a junkyuard you can try that. They are usually ok but I have had not one but two fail n toyotas. Sooo they DO fail.




A bit more involved but if it hasn't been done, you may want to give it a good tune up. itd have to be done anyway....Plugs, wires, cap totor....since the plenum has to be removed to get the back plugs, you can pull the throttle body and give it a good cleaning front / back.

 

Hello everyone,

I'm sorry, I've been busy the past few weeks and didn't have time to take care of that car.

How does it run when you need to give it gas? Does it run fine / like you are just revving it or does it run poorly / stumble as you give it gas?

It works very well.

When you let off the gas does it just die immediately like you cut the key off? Or does it kind of stumble before dying? Likwe it tries to idle a bit but dies.

It tries to idle, but it stalls quickly.

A few things yo ucan do:

You could also have a vaccum leak somewhere. Trace all vacuum lines / gaskets / hoses from the MAF back to the engine. Cylinder heads down.

All is ok.

If everything is running ok though id suspect that the IAC valve has failed despite "testing" ok. if you can get a used one maybe off ebay or a junkyuard you can try that. They are usually ok but I have had not one but two fail n toyotas. Sooo they DO fail.

I'm sure the first one is working, but I've tried another one (after I tested it), it's exactly the same.

A bit more involved but if it hasn't been done, you may want to give it a good tune up. itd have to be done anyway....Plugs, wires, cap totor....since the plenum has to be removed to get the back plugs, you can pull the throttle body and give it a good cleaning front / back.

I'm sure all is ok with these parts.

Was your battery disconnected recently?

Yes but when I tested the issues codes, the battery wasn't disconnected yet, and there was no error code.

This might be an air leak. when engine is on, spray carburetor cleaner around the intake manifold, hoses, etc. If engine Idle changes while you do that, you got an air leak. 2nd, replace the idle control valve. In many cases that is the culprit in many cold start issues. Lastly, replace your spark plugs. Worn out plug with incorrect gap will not spark when cold.

All is ok with all of these parts.

I've found something today and I took a video (need sound)
It's here :

So maybe the throttle sensor is dead ?

 

the throttle body, with the throttle position sensor : works as specified in the technical document. All is clean, each hole is free, vacuum can be generated

Was your battery disconnected recently?

 

This might be an air leak. when engine is on, spray carburetor cleaner around the intake manifold, hoses, etc. If engine Idle changes while you do that, you got an air leak. 2nd, replace the idle control valve. In many cases that is the culprit in many cold start issues. Lastly, replace your spark plugs. Worn out plug with incorrect gap will not spark when cold.

 

What does that hose go to? I can't recall what it goes to, but removing vacuum lines while the engine is running could make it stall.... its a rather small line though.


Seems to be idling fine with that line attached

 

That hose goes to the little dashpot under the throttle body:

 

It is the Throttle Opener. According to the shop manual, you disconnect the hose (and plug its end) and if the idle speed goes to 900~1950rpm the throttle opener is working.
Then you reconnect the hose and the idle speed is supposed to return to the target 700 +/-50rpm.

Perhaps there is a trouble code? Take a paper clip and short the terminals in the data link connector (DLC2, located below the fuse block in front of the driver's left knee) "E1" and "TE2", then count the blinks of the "check engine light" on the instrument panel. Use the attached .pdf guide to see what that code means.

 

Anyone else notice its a 5 speed and nobody s stepping on the clutch to start it?


Slightly tired / sleep deprived but that's what I think i saw.

 

Anyone else notice its a 5 speed and nobody s stepping on the clutch to start it?
Slightly tired / sleep deprived but that's what I think i saw.

I wonder if the French destination spec perhaps did not require the clutch start switch?
First thing I did with my '93 V6-5MT was disconnect the switch on the clutch pedal so that I could start without having to press the clutch pedal down.

 

Not in the FSM - when I had issues w/ "throttle linkage" (cutting off) idle in the past on other vehicles (not a Toyota) - it wound up being a bad TPS / Throttle Position Sensor. - Just tossing this possibility out there for the OP.

 

In France there's no clutch start switch. You can start the engine with a gear engaged. Dangerous sometimes, but it can help in some cases.

 

Today, I made a new video, the best is to see it, I made some comments inside.

I really don't know what is wrong. IAC valve is able to close, but it seems not able to open, very strange. It was exactly the same with another IAC valve, which was running well on another car.

 

It seems for the most part to be operating correctly......... when you are disconnecting and reconnecting that vacuum hose, the ECM is compensating for air etc.. and ten you reconnect it, it has to again compensate....

the ecm is reacting to the increased air and then decrease of air at around a low idle so that's probably why it stalls. Its compensating but the idle is so low that it fumbles trying to find the right idle and stalls.


Your cold start with the lower idle and what not makes me think your coolant temp sensor, maybe even the cold start injector sensor is bad... but Id go with the coolant temp sensor... its probably old anyway and could use a fresh one... .


Ive seen it where the CTS tests correctly etc... yet when in action, it sends tHe incorrect info to the ECM.... its working but giving the wrong info.



Its fairly cheap.. id give that a try. Theres a bunch of other posts recently that Ive seen that seem to have the CTS as a culprit but I cant recall if that was already covered here or not though.

 

If the coolant temp sensor is bad there ought to be a code from the ECM (code #22, when mine went out and I could not start the engine - the check engine light didn't go on, but that code came up when I used the instructions provided above, it saved me a LOT of time searching in vain for why it wouldn't start!).

Be sure to only buy Denso / Toyota sensor if that is the issue for you.

The coolant temp sensor is the dark green one on top of the water bypass assembly on the LH end of the intake manifold:

Visible in the center of the below photo:

 

If the coolant temp sensor is bad there ought to be a code from the ECM (code #22, when mine went out and I could not start the engine - the check engine light didn't go on, but that code came up when I used the instructions provided above, it saved me a LOT of time searching in vain for why it wouldn't start!).

Be sure to only buy Denso / Toyota sensor if that is the issue for you.

The coolant temp sensor is the dark green one on top of the water bypass assembly on the LH end of the intake manifold:
View attachment 423514

Visible in the center of the below photo:

Not aways. I didn't have any codes when mine went out, It just gave improper readings to the ECM. Ive had a few others too that acted weird idle wise and a CTS fixed the issue.


Throwing on some OBD 1 live scan tools showed that the CTS was giving improper readings for the given temp to the ECM....

ex. its 60 degrees but the CTS was telling the ECMthe coolant is 110 degrees... basically its working "correctly" but not in the correct range / scope... so its basically deceiving and would not always throw a code.

 

A good way to test the coolant sensor while in place is to measure the resistance across its terminals.
There is a graph in the shop manual, at room temp it should be around 3.6kOhms at 55F, 2.2kOhms at 68F, and around 0.2kOhms at 212F (100C)

 

What part is the barrel circled above connected to on, (or in) the Throttle Body?

Throttle Opener (dashpot) ?
Throttle Position Sensor ?
--
This is the part you pushed / moved in video #1 causing stall, and it shows same behavior in video #2, causing low idle.

That part seems "loose" to me, if it is shaft-driven. You should clean your linkage (including all return springs, there is some grime on the inner spring by the butterfly valve.).

+1 w/ Norm & 1990toyota on replacing the Engine Coolant Temp sensor, as part of your diagnostic.

 

Hello,

Sorry, I haven't had time lately...
I have just checked the value of the temperature sensor: 2.09 kohms at an ambient temperature of 27°C (80°F)

This seems very close to the reference values. I will test when the engine is warm, tomorrow maybe.

 

Hello,

Here are my observations for today, ambient temp 24°C (75 °F) :

- Before any try, temperature sensor value is normal : 2.20 kOhms (engine cold)

A) When all is plugged as normally in the engine, cold start don't work --> cause IAC valve was totally closed.
B) I opened manually IAC valve (electric wires as mentionned in the shop manual) --> cold start is perfect now
C) Engine slows down gradually when it's warming --> IAC valve can close gradually, controlled by the ECM
D) As long as I don't touch anything, engine is running perfectly even it's hot. I let the engine warm up for about 30 minutes, it didn't stall at any time.
E) If I try to speed up the engine, it works just fine. When I release the accelerator, it's close to stalling but I was lucky this time. The 2nd time I tried it, it stalls after trying to idle (I can upload a video if you want to see, but it's like the one I put last week)

- After that, engine was very hot, fan motor was running quickly, and temperature sensor value was normal : 0.260 kOhms

Facts I'm sure at 100% :

• There's no air leak or ignition malfunction, there's no vacuum leak, engine condition is good and there's no error code
• IAC valve can open electrically : I can open it with electric wires according to the shop manual (S4-S3-S2-S1)
• IAC valve can close electrically : ECM do it, because engine slows down after cold start, and if I look at the IAC valve after tries, it's closed
• Temperature sensor values are good, as cold as hot

I agree to change the temperature sensor, but I'm not convinced that the problem comes from there since the values are good.

It acts exactly like the ECM wasn't able to re-open the IAC valve, but why ? I'm pretty sure that's the problem. Is there another sensor I can test ? Maybe the ECM is malfunctioning ?
To be sure: is it the role of the IAC valve to regulate the idle any time ?

Thank you for your patience with me, but I'm a quite lost with that.

 

To be sure: is it the role of the IAC valve to regulate the idle any time ?

That is correct. Cold start logic in the ECM uses the ECT sensor to default to IAC valve fully open (fast idle): then based on coolant temp., ECM starts to close the IAC pintle, in stages .. until coolant temp. reaches above 160 F (normal idle).

Maybe the ECM is malfunctioning ?

It's possible w/ a 25 y/o+ part - you are able to simulate ("restore") normal operation, by manually opening the IAC valve. The ECM should be doing this automatically, on cold start. Or some possible (?) issue w/ wiring, or in the IAC pintle (coils).

 

Its just a magnetic rotating device if i recall... unlike other IACs. I can imagine that 25 years with engine heat etc... that damage / inefficiencies can occur.


I think Id personally go for a nice used OEM unit and see how it acts with it.



Off the top of my head there are no IAC reset prcedres for these unlike GM cars.. .not that I can recal lfrom this era anyway. it should be plug and play..... I personally never had to replace one / never experienced them go bad but the OE units would be the best replacement vs a tempting cheap aftermarket repalcement.

 

Here is everything I could find in the Toyota shop manual on troubleshooting the IAC:

 

One month later...

After checking most of the sensors and values I found this in the documentation :

So, if the IAC valve does not open, it is because this power supply is no longer supplied after switching off the ignition.
From that moment, I was almost certain that the ECM was faulty.

I found another ECM (mine is 89661-33150 for a manual transmission, is it the same in USA ? ), and now it works perfectly !
Out of curiosity I opened the ECM box but found nothing resembling a relay (Main Relay Control Circuit), even a compact one...

So... Thanks everyone for your help and your patience with me ! Now we can mark this subject as "Solved" !