Intermittent stalling on warm starts, No issues with cold starts. Options

[jordisonjr]

Hey guys, looking for some advice on an issue that arose on my car. Ill start off by saying its a 95 GTS (Canadian car) with a 5sfe. Motor is completely stock aside from a short ram intake, which I've just replaced with the factory air box.

From time to time, when the car is warm, it'll give a tough time starting. Ill start the car up cold and it gives no issues, drive it untill its up to temperature, and then turn the car off. I'll let it sit for 10-20 minutes, come back and the car will give difficulty starting.

It'll fire up to about 1000 RPM (regular idle) and then drop right back down to 0. If i give it some throttle I can get it to run if i hold the RPM at idle for 30 seconds or so, and then it runs and drives fine. However if I don't give it throttle it just stalls out again. This problem is also very inconsistent, majority of the time it will start and run fine, but when it does give me problems, its always under these circumstances.

It occurred once this week where i had to give it a significant amount of throttle(1/4 to 1/2) to force it to start, and then held it at idle for 30 seconds or s, and then it idled fine.

I posted this on the facebook page, and also did some researching on other toyota forums, and have a very very rough idea what could be causing this, and I'm hoping someone could provide some insight as to what could cause this. Its a difficult thing to diagnose, as it doesn't happen extremely frequently, but I'm also hesitant to drive it, as I don't want to get stranded somewhere with a vehicle that doesn't start.

Any help or advice would be greatly appreciated.

[richee3]

How does the distributor look? My guess is cap or rotor.

[Bitter]

Check the coolant temp sensor resistance against the chart in the BGB when it's acting up, sounds to me like an intermittently failing CTS, likely reading very cold when the engine is very hot which causes it to inject WAY too much fuel for starting with closed throttle, opening throttle allows in more air and leans it out enough to start and then when you hold open throttle it clears out the over fueling. Why it doesn't continue to run rich, I'm not sure, but I would be sure to inspect wiring and connectors.

[Box]

I would check the ignition coil along with the cap and rotor. IACV and EGR would be next places to check.

[jordisonjr]

Thanks everyone for the replies!

How does the distributor look? My guess is cap or rotor.

Distributor, was replaced a few years ago with a used one, which I also replaced the cap and rotor on. There's also no CELs being thrown.

Check the coolant temp sensor resistance against the chart in the BGB when it's acting up, sounds to me like an intermittently failing CTS, likely reading very cold when the engine is very hot which causes it to inject WAY too much fuel for starting with closed throttle, opening throttle allows in more air and leans it out enough to start and then when you hold open throttle it clears out the over fueling. Why it doesn't continue to run rich, I'm not sure, but I would be sure to inspect wiring and connectors.

Where is this located? and how would I check this (Sorry, very unfamiliar with electrical things like this) The explanation you provided does make sense to me though.

I would check the ignition coil along with the cap and rotor. IACV and EGR would be next places to check.

Where is the ignition coil located? And how would I go about checking this? What should I look for in the cap and rotor? It was replaced a few years back, but could be due to be changed again. I've read more than a few times that it could be IACV related.

A member on the facebook page also mentioned this could be a bad MAP sensor as he was having similar problems. When this first arose, I was thinking it was more fuel related than electrical/sensor related.

[Box]

The engine coolant temperature sensor:

You would need to measure resistance across a range of temperatures, can do it with it in the car still. Just do it with it cold and then up at operating temperature, just have to find the resistance values out of the service manual.

The ignition coil will be connected to the center ignition lead off the distributor cap, to actually test it you'd need to find the testing procedures from a Toyota service manual to get the proper resistance readings. Normally you measure resistance of the coils but if I recall correctly the ignition coil on my 7A was sealed in epoxy so I'd imagine it'd be the same for the 5S. The easiest way at that point would be when it doesn't want to start pull a plug out and put it against the intake manifold and have someone crank it and see if it sparks weak or at all. As far as the cap and rotor goes you're just checking for corrosion or burns on the contact points.

Usually a MAP sensor acts up all the time but it could be tested as well. Let me try and find testing procedures for everything.

[Box]

K here's a graph for the temp sensor I found:


Also apparently on earlier 5S the ignition coil is on the side of the distributor, found a PDF out of the service manual:
http://bgbonline.celicatech.com/93celica/i...pection5sfe.pdf

Then for the MAP:
0.3 to 0.5 voltage drop @ 3.9 in-Hg
0.7 to 0.9 voltage drop @ 7.8 in-Hg
1.1 to 1.3 voltage drop @ 11.8 in-Hg
1.5 to 1.7 voltage drop @ 15.75 in-Hg
1.9 to 2.1 voltage drop @ 19.7 in-Hg

Measure voltage with ignition on but the car off to get you baseline reference voltage.

[jordisonjr]

Holy crap, that was a serious amount of information. Thanks a lot for providing that. I've borrowed a multimeter from a buddy last night, and will post back with what I find once I check everything out.

A couple last, newb like questions, as I've never done something like this before. When I'm checking the resistance of the IACV, and Coolant Temp sensor, I should disconnect the plug/wiring harness running to the sensor, and connect the multi meter to the sensor itself, correct?

And if that's the case, this won't require the ignition to be in the "on" position right?

Thanks again for all the help.

[Batman722]

Make sure you're igniter is grounded properly.
Check to see if there are any cracks on it.

[Box]

On the coolant temp sensor and ignition coil you'll test those with the power off, the MAP the car will have to be running and you'll also need a vacuum gauge to connect to the intake so you can get pressure readings to go with the voltage readings.

[jordisonjr]

So I did a little bit of poking under the hood today, and this is what I've found:

Pulled off the cap and rotor, found that there was a bit of oil at the bottom of the cap. It seems that where the distributor assembly mounts on the motor is where the leak is. There's a few hoses as well as a harness directly below the dizzy with significant amounts of old, built up oil, and it seems to be a little cleaner near the dizzy mount. Its hard to get an eye in there, so i was mostly checking the condition of the oil by feel. See photos:

Bottom of cap:


And here's the hose/line below the dizzy, the harness/wiring is farther below that. I don't think this would be the source of the leak, as this looks to a be a coolant/water line to me. If you look just above that, the dizzy mounting bolt is wet with oil.


I don't think this oil could cause the problem, as its not interfering with the electrical connections, however its concerning. Would this simply need a gasket/o ring to be replaced? Or would this require entire dizzy replacement?

This next photo is the inside of the cap. Looks like there's a slight bit of corrosion on the contacts. I'm not sure if this is something that can be cleaned, or if that would require replacing. Or if thats even how it should look, its been a while since i've seen a fresh cap.


Rotor:


Dizzy with dust cap removed:



While I was in there I checked the resistance of the Ignition Coil, based on the link Box provided, and everything seemed to be in spec. The next time this issue arises i'd also like to check by removing a plug and checking for spark, however being intermittent, I need to wait for it to come up again.

I also checked the Resistance of the IACV, and that also seemed to be withing spec (19 - 23 ohms, based on this link: http://www.toyotanation.com/forum/103-camr...eaning-iac.html which is a great article on how to remove and clean the IACV). So that can rule out a damaged/malfunctioning IACV I would think.

I also checked the Igniter wiring for cracks, and there was no signs. All of the wires seemed intact. I tried to trace this back to where it would ground as Batman mentioned, however it leads back the main harness, at which point I lose it. Is there a way to test this with a multimeter?

Next was checking the resistance of the coolant temp sensor, however, when I went to do this, my sensors were slightly different than the image box posted:



Based on the image posted by Box, I would assume the sensor on the right side (Lighter grey) would be the coolant temp sensor, but this sensor only had one wire leading to it, and one terminal on the inside of the plug which I found odd. So I wasn't sure if this was the correct sensor, or how to go about checking its resistance. I couldn't really do much else with this.


After this was all done, I drove to the parts store, and picked up some injector cleaner (long shot) as well as some Seafoam deep creep to clean out the IACV while its still on the car. I thought this would be worth a shot. I drove it there, and the car was at operating temp, came out and it stated up fine, drove to the gas station filled up, and it started fine once again and then I drove home. I feel like this issue is going to be a pain to resolve due to being so inconsistent.

I sprayed down the IACV and also ran fuel injector cleaner in the gas, but I'm not convinced this will resolve anything. I've also removed the short ram intake, and put the stock air box back it, but I doubt this will have any affect on it either.

As this is an intermittent issue, Ill try and keep this thread update as frequently as possible, but it may go some time without posts, depending when the issue arises.

[Bitter]

2 wire is temp sensor for computer, 1 one wire is sender for gauge.

[Box]

What Bitter said. Also cap doesn't look too bad, but the rotor could probably do with replacing. You can clean the cap contacts and the button with some metal polish on a Q-tip.

[jordisonjr]

When I was in there, I did try and check the 2 wire sensors (Coolant Temp Sensor, thanks Bitter) and for some reason I could not get an accurate reading. The numbers were all over the place. Now I'm not sure if this is perhaps because i couldn't get a proper connection on the sensor, Or would this be a good indication that this needs to be replaced?

I as able to get a proper reading off the IACV, and followed the same procedure for the Coolant Temp Sensor.

[Bitter]

Could be either a bad connection or a bad sensor. Best way to tell is to clip on with lil gator clips and heat or cool it to make sure it runs the range correctly. It's too bad you can't get live data, that could make it easier for sure.

[jordisonjr]

Could be either a bad connection or a bad sensor. Best way to tell is to clip on with lil gator clips and heat or cool it to make sure it runs the range correctly. It's too bad you can't get live data, that could make it easier for sure.

Yea definitely.
I'm going to take another crack at the sensor later tonight after work and will report back with what I find.

Also drove to my girlfriend on the weekend (20 min drive or so) and we went out about 30 min after I got there. And of course, it was acting up again. Seems like 20-30 min may be the ideal time of not starting. I took a video of this as well, I'll post it up later when I have the chance.

[jordisonjr]

Forgot to update this. But I re-tested the Coolant temp sensor when cold.
Had quite a bit of difficulty getting a resistance reading, and when i did, it jumped up and down between 143 to 180.

Based on the graph Box posted, it should read between 2 and 4 at about 15 degrees Celsius. So I'm nowhere near that. I'm not sure if this is a sign that the sensor needs to be replaced. Or if I'm simply doing something wrong with the multi meter, such as wrong settings or something like that.

[Box]

Those are kilo ohms, so x1000 on those numbers. So 2-4 kilo ohms, or 2,000-4,000 ohms.

This post has been edited by Box: May 30, 2017 - 1:22 PM

[jordisonjr]

Those are kilo ohms, so x1000 on those numbers. So 2-4 kilo ohms, or 2,000-4,000 ohms.

Totally missed that on the chart, thanks for pointing that out.

So I guess if my readings are accurate, those are significantly lower than they should be reading, and could be the cause for the issue?

[Box]

If the readings are accurate then yes it needs replaced.