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4A-Fe Rough Idle At Warm Engine Temp


awrhodes

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I would even go as far as to, wake up morning to a cold engine, remove radiator cap, start car, and observe for ~20mins.

 

a detailed description of what happends to the temp guage, the idle quality, and the water in the radiator cap, will definately help in determining the dramas.

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Might be worth fitting an after-market temp gauge so you can see how hot the thermostat is running the motor

If you have a 0-100deg thermometer around the house use that. Before you start it up remove the rad cap, put in the thermometer an let it idle until hot. Check the thermometer against the dash gauge now and then.

 

If it is head gasket you should see it at the same time. With the thermostat in (in case you've taken it out!) fire it up without the rad cap and watch for flooding over and bubbles coming up over 5minutes. The moment the water gets warm to touch the test is over. What happens is the bubbles can't get past the closed thermostat very easily so expand downwards and push the water up from the bottom of the rad, then they come out. Once the thermostat opens they just bleed out. Not like the foam you had when you drained it at all, and if it was blown you would notice that you lost the top couple of inches of water but no more. If you filled the rad, you would lose it again, but then no more.

 

If it can hold the temp at the halfway mark then the cooling system should be fine.

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Things are better... I stopped by a local shop to see if they would run any diagnostics for free. They wanted $109 for a full diag. but they said they would test drive it and visually inspect it for free. I figured they wouldn't find anything but had some extra time so I let them do that. Of course just driving around the block and looking at it for five minutes didn't result in much other than the manager trying to sell me things. However the guy that looked at it happened to have the exact same car with 300k+ miles, he basically said it could really only be the TPS or IAC valve, which I've tried. But I asked him out of curiosity if his Corolla ran in the middle of the temp gauge and he said his always ran cool. So I pulled the thermostat, the gasket was torn and it was stuck. Picked up a new one and now the gauge reads a constant temp, about in the middle. It never has before, always fluctuated. So I just went ripping through the hills to get things nice and hot, then hit some moderate traffic and so far, so good. It never got to a point where I felt I had to hold the gas to keep it running. I won't know for 100% sure until I hit heavy traffic tomorrow, but things are definitely different, and better so far. So at least I've replaced another known-faulty component of this puzzle. I'm going to do the suggested tests for gasket leaks, and will report findings.

Edited by awrhodes
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My fingers are crossed as well! There might be something else going on, but hopefully this will buy me some time until I can see my brother, a few states away, who can give it the full shake-down. After another test drive, it's still pretty good. It's just a little bit rough, but I'm thinking that could be due to my very approximate installation of the salvage distributor. Hopefully everything will be good for a month or so, then he can get everything tip-top and keep this thing running another 200k! Thanks for everyone's input and help!

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This thread should be stickied as an example of how to ask for help so you get the answers you need.

 

If that would help others find solutions to their problems quickly, that would be great. For what it's worth the details of the engine (from the sticker on the hood) are: Engine Family - STY1.6VHGBFA - Evap. Family - STY1047DYM00 - MFI, 02S, TWC

 

If someone happens to come across this thread from a Google search and it saves some hair-pulling and wasted parts swaps, I'd feel better about the whole situation! I hope things continue to run smoothly and I will update if anything changes. Thanks so much!

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Another successful day in traffic, I think we might be good! I'm hoping I get a little more fuel efficiency as a result of the engine running at a constant, normal temperature. I've always thought it should be getting a few more MPG, but I'll know after running a tank through it.

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Wowo I would never have though a thermostat would have that great an effect on how it runs.

 

I still suspect the thing might present with another issue at some point, so let us know how you go over time aswell.

 

Must have been causing the fuel to vaporise in the lines or something to run like that.

 

Anyhow, glad all is well, and that it didnt cost the earth to fix. :dance:

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  • 8 years later...
On 4/3/2012 at 5:10 AM, awrhodes said:

Things are better... I stopped by a local shop to see if they would run any diagnostics for free. They wanted $109 for a full diag. but they said they would test drive it and visually inspect it for free. I figured they wouldn't find anything but had some extra time so I let them do that. Of course just driving around the block and looking at it for five minutes didn't result in much other than the manager trying to sell me things. However the guy that looked at it happened to have the exact same car with 300k+ miles, he basically said it could really only be the TPS or IAC valve, which I've tried. But I asked him out of curiosity if his Corolla ran in the middle of the temp gauge and he said his always ran cool. So I pulled the thermostat, the gasket was torn and it was stuck. Picked up a new one and now the gauge reads a constant temp, about in the middle. It never has before, always fluctuated. So I just went ripping through the hills to get things nice and hot, then hit some moderate traffic and so far, so good. It never got to a point where I felt I had to hold the gas to keep it running. I won't know for 100% sure until I hit heavy traffic tomorrow, but things are definitely different, and better so far. So at least I've replaced another known-faulty component of this puzzle. I'm going to do the suggested tests for gasket leaks, and will report findings.

Hi there brother.. Just taking chances if you're still active on this forum. I happen to have the exact same problem as yours. Just want to ask if the problem you are experiencing during the time you have your corolla did not recur after replacing the thermostat?

Thanks in advance..

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