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2006 Toyota Corolla Hesitates and Delayed Starting

I have a 2006 Toyota Corolla LE with 157k miles. For a while the starting has gone from firing right up to a slight delay when starting every few times. There is also a little hesitation and it feels like it idles a little low and sluggish.

So I have found everything I can about similar issues and I have replaced the battery and I just tested it and it was fine 13V+ and cranked down to 11V+. I replaced the intake manifold gasket, PCV valve, throttle body gasket and cleaned the throttle body with cleaner. I replaced the fuel pump module in the gas tank. I replaced the spark plugs (for the second time also did it around 80k miles), and also the ignition coils.

It isn’t throwing any engine codes, but it isn’t running like it used to. I am a bit out of ideas.

I have a crankshaft and camshaft sensors coming. My only other thought was oxygen sensors.

Any thoughts?

My answer is a bit conflicted… normally I’d say throwing parts at a problem hoping to fix it is a fools errand but… With 157K on the clock, these are the kinds of things that tend to need replacing.

Except, I wouldn’t change O2 sensors just yet. There are cheap scan apps for your phone that allow you to look at OBD2 O2 data while the car is running. I would not replace an O2 sensor until I could see a lazy sensor or an O2 sensor code.

But if you want to find out the issue(s) at hand… start with a vacuum test - steady, strong vacuum at idle. Do a balance test… Boost idle to 1500 rpm or so and disconnect each fuel injector for just long enough to note the rpm drop. Compare cylinders by rpm drop. Pull the spark plugs and do a warm, dry and then wet compression test. Compare wet-to-dry readings of each cylinder and then across all cylinders.

This will likely set codes you need to clear but… It is the best way to uncover the cause of “sluggish.”


Thanks for the reply. I have a Bluetooth and stand alone scanner. I will see about the O2 data.

I also hate to just throw money and fix random parts, but most were probably around due for change anyway. I will try some of the tests you suggested before I try anything else.

Thanks again.

I hope you get it figured out and post the solution to the problem. Another possibility, a clogged or damaged catalytic converter, can produce hesitation as well.

If this starting problem occurs when the engine is cold, forget the O2 sensors.

The O2 sensors don’t come into play until the engine warms up and the computer goes into the closed loop mode.

I would look more toward a dirty/faulty IAC valve.,2006,corolla,1.8l+l4,1432846,fuel+&+air,idle+air+control+(iac)+valve,6072


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Well it has been a while. I replaced the fuel pump module a while back. Worked fine for a bit and then the gas gauge stopped working. However it didn’t really change how the car ran/started. I finally broke down and contacted the manufacturer to replace the fuel pump module under warranty. Got it, installed it, and now the car is having lots of trouble starting. It doesn’t start on the first crank. If I crank it a second time it starts roughly sometimes and normal other times. My assumption is the new fuel pump is bad. It did fix the gas gauge and that works correctly now.

My last ditch effort is going to be to see if I can take the pump off of the other module that I still have in my possession before I send it back and put it on the new module with the working gas gauge.

Any thoughts?

Well I replaced the fuel pump module again and am back to it starting normalish. Still running about the same as it was prior to that though.

I purchased a IAC valve, but I can not for the life of me find it. All of the non-electronic throttle models show it on the right side of the engine attached to the throttle body. I removed the throttle body and several other parts on the side by the throttle body and I never saw anything that looked remotely like the part. I can’t find a single picture, diagram or anything that shows where it would be on the 1.8L Toyota Corolla LE.