7AFE Runs rough when cold, Until the car gets close to warmed up, the engine runs poorly Options

[GriffGirl]

When I go to start my car, particularly in the morning after it's been sitting all night, the engine feels like it's kind of "chugging" or "hicupping" until it's warmed up. I noticed this right when I bought the car, about 6 weeks ago, and that the temperature gauge was taking forever to go up into the "warm" position.

So naturally, my thermostat must be sticking, right? Well I replaced the thermostat last weekend, and while the car warms up at a normal rate now, it still does this weird "chugging" thing from the time that it begins to warm up until it's about 2/3 of the way to temp.

I did notice that the day after I replaced the thermostat, the car didn't do this. I also noticed that there was a slight leak from where the upper radiator hose goes into the engine block (my fault - I took the wrong thing off in search for the thermostat housing, and didn't use enough sealant when I put the mounting back on). So when I fixed the gasket seal and put everything back together, it resumed it's chugging thing.

Could this be because of air in the line? I'd think it would overheat if there were air though. Bad coolant? It's almost as if there's a vacuum leak, but I can't find one anywhere, and it just seems directly related to the cooling system since the duration that the car does this has also decreased with the proper warm up time in place now.

Any ideas? Thanks!

[95CelicaST]

is the chugging like sputtering? Like its running on 3 cyl for a bit?

[Bitter]

i had this problem, i dont know if i ever fixed it tho. clean the throttle body and IAC well and see if that helps.

[CelicaST_CALI]

ya id bring it to a garage and leave it overnight and let them figure it out,u might have blown a valve....

[GriffGirl]

ya id bring it to a garage and leave it overnight and let them figure it out,u might have blown a valve....

It's weird though, it only does it when it's cold. Once it's warmed up it runs great. It's not sputtering like it's running on 3 cyl; it's kind of chugging like a vacuum leak. It doesn't make any noise when it does it though; no backfiring or anything. If the car could "hiccup", it would feel like what it's doing.

[Bitter]

i had the same symptoms as well, felt really rough like it was missing intermittently across all the cylinders and ONLY when the engine was stone cold too. i'll see if it does it this winter and look more into it. seemed like 30 or below it did it. now the other morning when i went out and it was cold the engine started just fine. but it was only about 40. when its colder i'll see if it still does it or not and if i solve it i'll try to remember to post up what i did to fix it.

[Harold_Fastwaker]

Are there any codes thrown?


Sounds like a starvation for either oil or fuel. As in the fact that the ecu is unable to figure how much it should supply on startup.


Just as a side note. When was the last time your radiator fluid was changed?

[K-ESD]

Check your coolant sensor, if it isn't working correctly (ie: loose connection) it will mess up your ECU and it might not set the correct fuel trim for cold idle.
Also, you might benefit from a IAC and throttle body clean aswell.

[daphreakda]

Check your coolant sensor, if it isn't working correctly (ie: loose connection) it will mess up your ECU and it might not set the correct fuel trim for cold idle.
Also, you might benefit from a IAC and throttle body clean aswell.

x2

[GriffGirl]

Don't know exactly when the radiator was flushed, I do know that in April a new engine was put it (before I bought the car) so fluid was replaced then. I think I'm going to start by checking those connections and also thoroughly flushing out the radiator, and see where that gets me. The temperature sensor thing makes sense.

Could just be there's gunk in the radiator clogging it. I know it's rarely that simple, but sometimes simple is a good place to start, eh?

[GriffGirl]

Check your coolant sensor, if it isn't working correctly (ie: loose connection) it will mess up your ECU and it might not set the correct fuel trim for cold idle.
Also, you might benefit from a IAC and throttle body clean aswell.

x2

How exactly do I get to the coolant sensor? My understanding is it's under the valve cover? Is that correct?

[K-ESD]

Look on the side of the head, around the coolant outlet. It's a dark gray connector with 2 wires (green and brown).



This post has been edited by K-ESD: Sep 24, 2007 - 3:25 PM

[GriffGirl]

Sweet moses (sayeth the nice jewish girl)! Thanks!

I'll post again once I get this underway and hopefully resolved!

Hey, where'd that image come from, and where can I get more like it? That's way better use than anything in any Hanes or Chilton manual.

This post has been edited by GriffGirl: Sep 24, 2007 - 3:31 PM

[K-ESD]

right here: http://www.celicatech.com/imagearchive/bgb...95ewd/95ewd.htm

enjoy

[Bitter]

Check your coolant sensor, if it isn't working correctly (ie: loose connection) it will mess up your ECU and it might not set the correct fuel trim for cold idle.
Also, you might benefit from a IAC and throttle body clean aswell.

however when the car is at running temp she would also have runnablity symptoms like very poor gas mileage and the engine would feel sluggish, also it would fail emissions badly with very very high HC

not to mention if it were 96 or later it may also set some OBD2 codes for the engine being cold for too long, but i dont think that the obd1 has codes for that.

This post has been edited by Bitter: Sep 24, 2007 - 9:29 PM

[GriffGirl]

Check your coolant sensor, if it isn't working correctly (ie: loose connection) it will mess up your ECU and it might not set the correct fuel trim for cold idle.
Also, you might benefit from a IAC and throttle body clean aswell.

however when the car is at running temp she would also have runnablity symptoms like very poor gas mileage and the engine would feel sluggish, also it would fail emissions badly with very very high HC

not to mention if it were 96 or later it may also set some OBD2 codes for the engine being cold for too long, but i dont think that the obd1 has codes for that.

Gas mileage is phenomenal (considering my last car was a 4Runner, and I drive 40 miles a day commute). Averaging 400 miles to a tank. Runs great once the car is warmed up, has no symptoms whatsoever. As for DEQ, I haven't had to run it through, tags are still good, but I'm guessing considering the condition other things were in on the car when I got it, that this has been a fairly long running problem, likely existing at last DEQ inspection. I feel very strongly that if I had to run it through DEQ today, it'd pass. I'm going to check the connections on the coolant sensor, and poke around for maybe any vacuum leaks, bad hoses, that sort of stuff this weekend. I'll follow up with any findings.

This sucks! It's getting colder in the mornings, and once it starts to rain, I think this is really going to be a problem. Ugh!

[K-ESD]

If you want to eliminate the coolant temp sensor as a suspected problem you can do this:

-engine cold - note aprox outside temperature
-grab a multimeter and set it on 20k ohm range
-disconnect the CTS plug
-measure resistance between the two pins on the sensor, take note
-plug it back in and start the engine, let it warm up until gauge is at 1/2
-turn it off, unplug the CTS and measure the resistance. note

this is the table of a working sensor
-20*C -4*F = 10K-20K ohms
0*C 32*F = 4K-7K ohms
20*C 68*F = 2K-3K ohms
40*C 104*F = 0.9K-1.3K ohms
60*C 140*F = 0.4K-0.7K ohms
80*C 176*F = 0.2K-0.4K ohms (typical running temp)

ideally you'd want to check these readings at the back of the ECU, but it involves getting to it, which is harder than at the sensor. Doing this would give you the actual reading that the ECU sees, if there was any problems with the harness or connections it would show up here.

Hope this helps

Good luck

[GriffGirl]

This is a great start for me, thank you. I will follow these directions this weekend and see what I can come up with. It's at least a good way for process of elimination.

I just don't have the money or time to leave it with a mechanic overnight. That's often the case, which is how I've learned to do my own work on the cars I've owned. I figure if you're gonna own it, you should know how it works, right!? Especially as a woman... I'm amazed at how many times I've had mechanics try to b.s. me about stuff that they thought I knew nothing about. But then I love the look on their face when I get all technical in proving them wrong! Most of the mechanics I've dealt with are usually really stoked that a woman wants to learn this kind of stuff, but there are those few shady ones who just think it's simply a man's job. Eh, whatever.

Thanks again!

[GriffGirl]

If you want to eliminate the coolant temp sensor as a suspected problem you can do this:

-engine cold - note aprox outside temperature
-grab a multimeter and set it on 20k ohm range
-disconnect the CTS plug
-measure resistance between the two pins on the sensor, take note
-plug it back in and start the engine, let it warm up until gauge is at 1/2
-turn it off, unplug the CTS and measure the resistance. note

this is the table of a working sensor
-20*C -4*F = 10K-20K ohms
0*C 32*F = 4K-7K ohms
20*C 68*F = 2K-3K ohms
40*C 104*F = 0.9K-1.3K ohms
60*C 140*F = 0.4K-0.7K ohms
80*C 176*F = 0.2K-0.4K ohms (typical running temp)

ideally you'd want to check these readings at the back of the ECU, but it involves getting to it, which is harder than at the sensor. Doing this would give you the actual reading that the ECU sees, if there was any problems with the harness or connections it would show up here.

Hope this helps

Good luck

Okay, I don't have access to the necessary tools needed to check the sensor. After researching this, I've found that for the same amount of money it'd cost me to get this checked out, I can just replace the sensor myself. Process of elimination, and a new sensor to boot.

Has anyone used Niehoff sensors? Are they any good? Money's a factor here, they cost less than some of the others, but I've also found that they are owned by the same company that owns Borg Warner, a brand I understand to be decent.

Prices on the sensor range from $29.99 to $61.99, ranging with Niehoff to ACDelco. Anyone know anything?

[GriffGirl]

Replaced the coolant temperature sensor on Friday, no luck at all. Someone else told me he had same problem with entirely different car, had to replace air flow sensor. Looking it up online, I found there's a variety of parts that somewhat fit this description:

Air Charge Temperature Sensor,
Air Cleaner Temperature Sensor,
Air Flow Meter/Mass Air Flow Sensor.

Something tells me it'll be the MAF, since it costs the most, but I thought I'd ask anyway just in case.