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!

[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