awrhodes

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.

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!

Now, if I can just fix this pesky dome light! :-)

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!

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.

Ok, so I got curious as to why you would ask if there were bubbles in the coolant, so I quickly googled "foamy coolant". I'm seeing mixed information, but I'm not sure I like what I'm reading! I already had a friend take it to be disposed but now I'm wondering if I should have kept it. I also should have paid more attention to what kind of bubbles and foam, I just thought to myself, "hey this is kind of foamy." Shows you what I know! Apparently this is an indication of a BHG and I saw something about test kits to check for gases and so on. Maybe it was just really old and nasty, I'm thinking positive here. I also just checked my oil and it is at the halfway mark. I change my oil every 3k and it's right at the 3k mark since I last changed it last. It's not milky or white or anything, but I don't leave behind drops of oil so it must have gone somewhere. So since I've already disposed of the old coolant, if there is a BHG will the bubbles/foam reappear relatively soon? Could I have a minor leak that's not even related to this current problem? Man, it's a 7th gen Corolla with just over 100k, I shouldn't be having these problems! (but I wasn't responsible for the first 90k, so who knows) Considering I'm practically broke at the moment, I think this will be my plan of attack. Please feel free to suggest anything else. 1.) Try to track down a salvage or borrow an air temp sensor since it did randomly throw that code once. Maybe this will make the ECU happy and we'll have a fairy tail ending. 2.) Pull out the thermostat while the engine is cold and see if I can tell if it's stuck in the middle. If not obvious, run the car without the thermostat to determine if it is faulty. If either are the case, go to Toyota and get an OEM thermostat & cross fingers 3.) Give up the DIY, and go get a coolant pressure and compression test, or general professional diagnosis whenever I can afford to and hope I'm not looking at a major repair. If there's anything else I can cheaply try, I'm all ears. Thanks everyone for your input.

Do you mean if it is going to halfway quickly it could be a more serious problem? From a cold start, it will climb to the middle in about ten minutes at idle, then the fans will hold it there (cycle on/off), but it will run rough.

Yes, the fan does hold the temp steady at the middle of the gauge. I don't drive the car much since this started happening. When I do, I keep it idling by holding the gas a little (a bit tricky on hills using the clutch, gas, brake, and handbrake!), but I've never seen the needle go above halfway.

I could certainly try that. I pulled them off one at a time when it was running normal and no particular cylinder seemed to be any worse than the others. I didn't think to try it while it's running rough, it probably will die. I can also try your advise on pulling the thermostat.

Well, I never flushed or changed the coolant until yesterday, I've only had the car less than a year and have only done routine oil and changed the plugs as maintenance so far. The car always ran so cool it never seemed like a priority. When I talked to my brother about this, he said Toyota factory coolant is red. What I drained out of there was a nasty deep purple/brown color that looked like it might have been red 15 years ago. I'm just running water in there now. I did notice some bubbles, almost foamy, so I flushed it out about 3 times with water until all the traces of the old coolant were gone. Then the only bubbles were from the air purging. I've never noticed a white residue under the oil cap. How would one pressure test a cooling system, or is that a job for a shop? Hypothetically if a thermostat were stuck halfway would that cause the engine to run hotter than usual, but not overheat? My [non-professional] theory is that it could be running hotter than it should, or used to, which could be sending bad information from the various temp sensors, sending the wrong air/fuel ratio, messing with the 02 sensor, etc causing a rough idle. Sounds good in my head anyway :) Hoping it's not a head gasket, I'm relatively mechanically inclined, but that's probably a little beyond my skills and tools (and budget!)

That's what I was thinking as well. When the one that I've replaced is disconnected, the gauge still functions so I'm assuming that is the more important ECU signal. Regarding the thermostat itself, am I correct that it will usually just get stuck open or closed, resulting in either running very cool, or running very hot?

I think I've ruled out ignition coil, I've tried two with the same result. Ignition wires seem okay. I've also tried two coolant temp sensors, with the same result. I'm trying to track down a salvage air temp sensor, or see if the local parts store will let me borrow one to test in the parking lot :)

Thank you for the reply. If I approach a light after moving for awhile it will be fine because the temp has cooled enough for the gauge to not reach the middle. If multiple lights, or stop and go traffic the temp will reach the middle and problem begins. It's like flipping a switch, once that gauge hits the middle it begins to idle rough. To recreate the problem in my driveway I just let it warm up to temp and lightly rev the engine, as it drops back down to idle the rear view mirror will vibrate and almost stall. I don't remember it getting to the middle of the gauge before, even if I let the car sit and idle for an extended period of time. The fan does kick on but it doesn't help the situation. From what I understand about thermostats they usually just get stuck open or closed, right? Or could it be possible that the thermostat is now opening a different temperature than before? Also wondering what the sensor is on the thermostat housing. I've replaced the coolant temp sensor (2-wire), but there's another sensor on the housing (1-wire). I'm not even sure if this is a cooling issue, there just seems to be a direct correlation between the engine temp and when the problem begins.

Greetings, I am having a problem with my 95 1.6L that I can't seem to figure out. I have searched many forums and tried many things that resolved others' similar problem with no luck. Basically, the car runs absolutely fine while driving along or for short distances. Once the engine temp gauge reaches the middle, at red lights or in traffic, the engine begins idling very rough and almost stalls. Once you're moving again and the temp cools, all is well. Here is what has been done so far. The fuel pump was replaced a few months ago due to a no-start issue. While troubleshooting that problem I swapped a few things and kept the originals, along with some other maintenance items which I have tried in solving this problem including: Distributor, Ignition Coil, Cap & Rotor, Plugs, TPS, Coolant Temp Sensor, IAC Valve. While trying to figure this out it did once throw a code for the air intake temp sensor, but my brother, a ten-year Toyota tech said he has never seen one go bad on this engine and doesn't believe it would cause this condition. I'd hate to throw another $40 part at the problem and I can't seem to find a salvage or donor part in my area. The condition is the same with this sensor plug in, or not. Thoughts? Also the condition is the same with the O2 sensor unplugged. It may be due for replacement but not sure if that would cause such behavior? One other thing that might be worth mentioning is that when the fuel pump was replaced about 3 months ago (I gave up trying to figure out the problem and took it to the dealer), the technician showed me something very strange. The pump went bad because the one of the five pins on the connector had actually shorted and melted the pin out of place. It would intermittently cause me a problem until it finally gave out entirely. What's more, he pointed out that someone, at some point, for some reason, had cut and spliced the two power pins of the harness and put spade connectors on. Exactly why someone would do that we're not sure. There must have been some other problem with the fuel pump in the past, or perhaps these two problems are somehow linked? I checked the harness again and nothing indicates that the pump problem is reoccurring, just thought this information may be important to disclose. One last thing I find interesting is that when I purchased the car about a year ago in Florida it didn't seem to run as warm as it does now. It's not overheating but I remember noticing that even in the dead heat of summer the temp gauge wouldn't even reach the middle point. The car was a one owner with 87K when I bought it, 103k now. I have no idea of the maint. history. I just flushed the coolant and it was pretty nasty but that didn't help. This is such a great car but this problem which seemed to develop suddenly about a month ago is driving me crazy! If anyone has had a similar problem or suggestions, that would be greatly appreciated. As with most of us these days, money is tight, so trying to resolve this as inexpensively as possible :) Thanks in advance! -Alex