1990 DX Weird Idle and Lugging

[jmar]

Hello,

I recently obtained a very cheap 1990 Corolla DX from a friend moving to Europe. (4A-FE, m/t) It was running a little rough, but changing the plugs, cap, and rotor has gone a fair way toward improving that. Now it idles right around 700 rpm when warm, but has a little bit of shaking/pulse at idle. When pulling out of a stoplight it bogs down until about 2000 rpm then really seems to clean out and pull hard. It feels like a turbo kicking in when it clears out and goes! I am not extremely mechanically inclined but did a basic check with carb cleaner for a vacuum leak and didn't find much (no whistling, either). Any suggestions for what to check next? This is an extra car, but I would love for it to run great!

Thanks,

Justin

[bakwoods]

1. Vaccuum leak would be prevelent and the car would bog down all the time, regardless of throttle position because the leak is just that before the TB.

2. When you replaced the cap and rotor did you accidentally move something? You do realize that it's position is directly related to timing. Mess with the cap and rotor and you'll mess the timing, messed up timing can cause the car to run out of wack.

3. When you say it bogs down until 2,000 rpms, I'm assuming that means that the car chokes. Sounds like a fuel cut issue. Have you tried checking the fuel pump and the filter.

[jmar]

As I continued poking around today, I gave the intake air temperature sensor a quick check with my multimeter and obtained a null value for resistance. The multimeter does work correctly, checked it on some wire. (As I understand it, this sensor is a resistor with varying ohm values at different temperatures?) Could a non-functioning IAT sensor be in any way related to my weird idle/shuddering initial acceleration?

Pretty sure that I didn't mess anything up when I swapped out the cap and rotor. I was careful not to bump them for fear of throwing off the timing.

I will look into the fuel pump/filter next.

[bakwoods]

IAT sensor getting no reading is strange. Car has a MAF sensor. Check the MAF for a reading too. For one check the TPS too. Somethign fishy.