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97 Corolla misfires under load

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New User

Sep 17, 2015, 11:14 AM

Post #1 of 4 (1175 views)
97 Corolla misfires under load Sign In

Hi, I have a 97 corolla with 187K miles, 1.6 and a 5 speed. My problem is this: at a certain rpm under load (I don't have a tach in the car, but it's around 60mph in 5th gear), the engine will intermittently misfire. The thing is, the problem goes away after about 10 minutes of driving, then I can run it as hard as I like. Now, the history: last winter, I came out one morning and the car wouldn't start. I tried the basics; cap and rotor, plugs and wires as it needed them anyways. Didn't help. I didn't feel like freezing to death in my driveway, so I took it to a shop. They mis-diagnosed it initially and replaced the coil. It ended up being the crank position sensor. So, most of the ignition system is new. Shortly after that, this problem started.

I haven't messed with it until now because I didn't really need the car over the summer, but now I do and it's driving me nuts. Here's what I have done: the fuel pressure is normal (~40 psi at idle, closer to 50psi when driving). I drove the car around with the fuel pressure gauge wedged under my wiper and watched it, the pressure didn't change a bit when the car would miss. I checked the injectors and they all ohmed out fine, and listened to them when the car is running and didn't hear anything unusual. I checked all the vacuum lines for leaks and found nothing. Even though I don't really believe in the stuff, I even ran a couple kinds of fuel cleaner through the tank (though not at the same time). The computer isn't throwing any codes, either.

So, I'm stumped. My best guess is that I possibly have a bad injector, but I can't confirm that and with new ones going for $120 each, I don't really want to guess and being that the problem only occurs under a load, I don't know of any way of testing them; short of laying on the motor while someone drives the car (no, I'm not really going to do that). The thing that is throwing me is the fact that the problem clears up after a short time; I can't figure what would cause that. Unless it has something to do with the engine warming up completely? Well, hopefully someone here has some ideas for me. Thanks!

kev2 profile image

Sep 17, 2015, 12:06 PM

Post #2 of 4 (1169 views)
Re: 97 Corolla misfires under load Sign In

did you scan for codes?
Do not ASSUME no light no code.
No miracle magnets, air filters, special thermostats, vehicle is stock?
claim 40psi - what is spec?
do you have a scanner- live data?
the term 'under load' is used to indicate hard acceleration ie WOT from a stop - is this the issue?
Have you cleaned throttle body?

New User

Sep 18, 2015, 2:31 PM

Post #3 of 4 (1141 views)
Re: 97 Corolla misfires under load Sign In

Thanks for the reply.
-Yes, I scanned for codes. As I said, there were none.
-It's a bone-stock Corolla I use to get to work.
-The manual I have says 38-42psi at idle.
-No I don't have any live data, or even a scanner with which to get it. Would the scanners they rent at Auto Zone be capable of this?
-When I say "under load", I mean just that - there is a load on the engine, as opposed to coasting or idling. Yes, it also does it if I put it to the floor, but it also occurs while maintaining speed at higher revs.
-Haven't tried cleaning the throttle body yet. Thanks for the tip.

kev2 profile image

Sep 18, 2015, 2:57 PM

Post #4 of 4 (1136 views)
Re: 97 Corolla misfires under load Sign In

Some ideas - a scanner would make simple BUT lets try easy checp first....
have you done a fuel filter?
PLugs are correct- don't go cheap, how do they look? wet, dry, black, tan? WHITE?
With carb cleaner have you checked for Vacuum leaks?

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