1992 4-cylinder sputters and dies at idle

[fancypants]

My '92 4-cylinder with 139k miles has been having some sputtering under load and dying at idle issues.
It idles fine above 1100 rpm and it's been idling around there a lot lately, but will begin to sputter if it drops to 800rpm. If I don't give it any gas it will die anywhere after a few seconds to a few minutes.
Sometimes, usually when the engine is warm, it can be hard to start (have to crank the starter for ~5-10 sec and then give it some gas to keep it from dying). Other times it starts up just fine.
What's been done so far:
-new plugs and distributor cap
-new plug cables and rotor
-intake cleaning and a can of injector cleaner in the gas tank
I saw an improvement after each of the above (much less sputtering under load), but the problem is still there.
After reading through the forums I also looked at:
ECT sensor
-measured the resistance on the engine coolant temperature sensor, values appeared reasonable and stable (2.8kOhm cold, 0.5 kOhm after ~5 min of idle).
EGR valve
-disconnected the EGR valve when engine was cold and then started the engine, still sputtered during idle. I'm not sure if that's enough to rule out the EGR.
I also want to take a look at the coil, but I'm not sure if that's beyond my skill level. Does this sound like it could be a coil to anyone?

Can anyone recommend other things to check?
Any thoughts would be appreciated.

[97toyotacam]

Do you change your oil enough? I had the same problem but after i changed my oil it went away. A strong battery and alternator also help to ensure your car won't die at idle.

[93celicaconv]

It could be a coil. I believe on your 92 5S-FE, that was the first year Toyota put the coil in the distributor body. There is a test procedure for the coil, but they sometimes act differently depending upon if they are cold or hot. Not knowing what your abilities are, it might be best to take it to a trusted mechanic to take a look.

[fancypants]

Thanks for the replies

I change my oil every 5-6k miles, most recent was in Jan this year (though I did use Mobil's high mileage conventional for the first time...).

I made an appointment with my mechanic tomorrow to check it out, with some specific attention to the coil. He asked if he can't find anything wrong anywhere, should he change it out anyway. I know throwing parts at a problem isn't the preferred way to go, but it feels different when it's your car and you're feeling desperate. I think I've already read on the forum that sometimes a failing coil will still test OK, or is it more straightforward?

[93celicaconv]

All I can tell you is that distributor mounted coils on these engines have been trouble-prone and some exhibit the symptoms you are experiencing. There are a lot of other things that could cause it, and you checked some of them already, but not throughly (such as an EGR valve that isn't closing completely, an idle air control (IAC) valve that isn't functioning well, etc.).

If your mechanic has capabilities of checking all these and other potential causes out, you will know a lot more. I really can't advise you to replace a part that, when tested, doesn't show a problem. You have to make that call. If this car is your primary means of transportation, you may have to take some risk in changing out parts more so than if this is a second car and you have more time to diagnose it more thoroughly.

[matrixmaster]

Have you had anyone suggest the idle air control valve on the throttle body? This part is a common repair for yor complaint. Also you should check your air intake tube from the air cleaner to the throttle body for cracks or pin holes. This is also common for this car.

[matrixmaster]

You need to take your car to a repair shop and stop throwing parts at it! After a second read of your complaints and your attemted repairs you have two issues, your idle and your egr system.Th egr could be the valve itself or the modulator and or the vsv that controls the egr.Your idle problem? Is it only when it's cold, or does it idle fine when warmed up.if so you need an EFI temp sensor. If it idles bad all the time then it's either the Idle Air control valve(IAC) or the air intake tube has a hole in it.Take it to a repair shop-all of the parts are not cheap and are dealer only.

[fenixus]

Originally Posted by fancypants

After reading through the forums I also looked at:
ECT sensor
-measured the resistance on the engine coolant temperature sensor, values appeared reasonable and stable (2.8kOhm cold, 0.5 kOhm after ~5 min of idle).
EGR valve
-disconnected the EGR valve when engine was cold and then started the engine, still sputtered during idle. I'm not sure if that's enough to rule out the EGR.

what catches my eye is reading of ECT after 5min idle ... 0.5k ohm is low temperature actually (still cold), ~60-70C (140-160F), check this graph:


if engine cannot reach warm operating temperature (or ECU thinks it cannot) it will do crazy things. make sure engine is warm after 30 min driving then measure ECT again on running engine, it should read somewhere around 0.2-0.3K ohm (around 180-190F). if it still shows 0.5k then i would suggest replacing ECT for EFI sensor (green connector, correct?) as it might be sending false info into ECU. mind that disconnecting ECT on running car will throw up a CEL and trouble code related to ECT for EFI sensor malfunction (safe to reset, it won't come back).

Easy way to test EGR valve is to allow a warm car to idle, then use your fingers to push up the membrane on bottom of EGR (under the "dish" part), car should stall almost immediately when you do that. if it dies then most likely EGR is fine and your problem is elsewhere.

also as suggested by others, make sure TB & IAC are clean, IAC affects idle speed heavily:
How to: Cleaning Throttle Body -4 Cylinder Engines- With Pictures

also just on a side note. 5-6k OCI for dino oil no matter what kind is too much! stick to 3k dino OCI. 5k is good for synthetic, dino will start turning into a black crap after around 2.5k miles. your engine might also be sludged IMO.

[fancypants]

Thanks again for all the replies everyone

This morning I inspected the air intake tube for cracks and pin holes, looks fine.
I let it idle for 30 minutes (sometimes it was rough, even from the start, but it never died) and measured the ECT resistance, it was 0.2 K ohm.
I forgot to try pushing up on the EGR membrane, will do that soon.

After idling for ~45 min I drove it to my trusted mechanic who performed most of the above mentioned work on this car.
He performed a simple coil test by dumping half a gallon of water on the engine/distributor cap while it was running and it didn't falter. He suspects it's the IAC valve even though it's been cleaned. Due to the cost of the part he recommended I wait until it gets worse to make sure that's the problem before replacing it, makes sense to me.
I'll follow the throttle body cleaning how-to of marc780's (thanks fenixus) this weekend and see if that makes any difference.

Thanks too for bringing engine sludge to my attention, I had been going with 5-6k miles based on my manual and my type of driving. I'll definitely be sticking with 3k from now on.

[fancypants]

The problem has become a little more consistent. The car starts fine cold, idles ~1000-1100 after warm up, occasional hesitation under load. After driving for 20 min and shutting off, it will often start up with the sputtering idle that will die without giving it throttle. Shut if off again and then it's a real pain to get started again, have to let it cool down completely.

I tried cleaning out the IAC valve in place by spraying bursts of sea foam deep creep into the IAC hole. First did it with the engine off, then with the engine running and in between squirts I triggered the IAC valve by disconnecting and reconnecting it's electrical connection. After reassembling everything I tested the IAC valve according to my Haynes by bridging TE1 and E1 terminals of the check electrical connector, I heard the engine speed increase for ~ 5 sec and then go back down. According the Haynes this means the IAC valve is ok. However, after driving around a bit, turning the car off and on again, the problem was still there.

Today, almost ready to take it in for a new IAC valve, I thought I'd take a look at the coil first. To my surprise I found oil in the bottom of my distributor cap!!! I wiped it out, pulled the rotor and coil cover, and the measured the coil's resistance, which seemed fine (primary - 0.5 Ohm, secondary - 12.45 k Ohm, cold). I did notice a small crack in the plastic on the side of the coil, where the dust cover latch clips on.

Could an oil leak be causing my problems? Does anyone know if the seals are difficult to replace?

[fenixus]

Originally Posted by fancypants

The problem has become a little more consistent. The car starts fine cold, idles ~1000-1100 after warm up, occasional hesitation under load. After driving for 20 min and shutting off, it will often start up with the sputtering idle that will die without giving it throttle. Shut if off again and then it's a real pain to get started again, have to let it cool down completely.

I tried cleaning out the IAC valve in place by spraying bursts of sea foam deep creep into the IAC hole. First did it with the engine off, then with the engine running and in between squirts I triggered the IAC valve by disconnecting and reconnecting it's electrical connection. After reassembling everything I tested the IAC valve according to my Haynes by bridging TE1 and E1 terminals of the check electrical connector, I heard the engine speed increase for ~ 5 sec and then go back down. According the Haynes this means the IAC valve is ok. However, after driving around a bit, turning the car off and on again, the problem was still there.

Today, almost ready to take it in for a new IAC valve, I thought I'd take a look at the coil first. To my surprise I found oil in the bottom of my distributor cap!!! I wiped it out, pulled the rotor and coil cover, and the measured the coil's resistance, which seemed fine (primary - 0.5 Ohm, secondary - 12.45 k Ohm, cold). I did notice a small crack in the plastic on the side of the coil, where the dust cover latch clips on.

Could an oil leak be causing my problems? Does anyone know if the seals are difficult to replace?

i think that hair line crack in distributor's coil is your problem. you should get a new one. that oil leak is probably only a bad seal. get a new OEM one.

[Mike Gerber]

^ I have to agree with fenixus. That cracked coil is probably the problem. This is a common problem as these cars rack up lot's of miles. It surfaces as the car and the coil itself heat up. Replace it.

Mike

[LittleWhiteBubble]

Dumping water on a car does not test a coil. Mine went bad and had the same symptoms as yours until it wouldn't start at all one day. I bought a coil at a junkyard for 25 bucks and now it runs like a champ. Its easy to do yourself and took about 20 minutes. Even new the coil shouldn't be over 50 bucks or so, and thats cheaper than an hour labor at a mechanic

[fancypants]

Thanks again everyone for the input. I picked up a new coil this morning and should have time (and better weather) to install it tomorrow.

[fenixus]

good luck! keep us posted.