1993 Toyota Corolla 1.8L Mystery Intermittent Engine Failure - Dropping out & revving up & stall

Aloha from the Big Island of Hawaii! I have a 1993 Toyota Corolla 1.8L Automatic Engine model 7FAE conundrum I REALLY need your genius help on…

The car intermittently tries to stall. The engine drops out, like it is turned off, and then revs itself back up and increases the idle speed for a 30 seconds to a minute. On occasion it will die completely, usually when it does the drop out several times in a few seconds & then it can’t rev itself back up in time to keep running. 2 times it died & would not start at all for several weeks. This has been going on for MONTHS, and seems to be completely uninfluenced by the internal or external temp, the length of time the engine is running, stress (hills, etc) or if I hit the brakes, or if the tranny is shifting. I have lived with this by either revving the engine up or using the momentum of the car in transit to “help” the engine from completely dying out at speed. Usually it won’t die completely while running above 1500RPM, but lower than that (like at idle) it can. And then, sometimes it runs for a whole day & only does it a couple times. The check engine light will only sometimes flash on, but it isn’t holding any codes. Lately it has gotten so bad - dropping out every 3-5 seconds or so - the car is no longer drivable & is sitting on the side of the road @ some poor person’s property & must be moved. To boot, after the last mechanic “helped” me to the tune of $250 of diagnostics that didn’t go anywhere & I didn’t ask for, there is now while smoke coming out the tailpipe & the cracked exhaust manifold (this has been cracked the whole time I’ve owned the vehicle but hasn’t ever done this before.) The ONLY things I haven’t looked at (after much research on this site) are the ignition control module/relay (I asked the last mechanic to check that but he didn’t… don’t even know if & where this is on this model), defective IAC valve, or EGR (whatever that is) or throttle position sensor but I haven’t had a chance yet to see if these or an equivalent are relevant to this model.

Here’s the list of tests & work we’ve done on it. 5 mechanics and $1150 dollars in repairs & labor, and I’m now totally broke and can’t get anywhere. The car is only worth $800. Please PLEASE HELP!

2 new distributors
new spark plugs
checked spark plug wires
checked compression (great)
checked vacuum (drops out simultaneously with engine dropping out of course)
changed fuel filter
changed fuel pump
new fuel relay
checked & reseated top gasket
new OS
checked electrical system
checked battery
replaced the ECM (engine control module)
a couple new vacuum hoses
new air filter
pulled off the hose by the fuel pressure control module & nothing happened
opening the air filter makes no difference

Any ideas? This is complete torture. I’m going to start resorting to drugs to cope… ok, maybe not, but seriously, it is making me feel like I’m taking crazy pills. Thank you in advance for any suggestions!

I’m not to clear as to whether this is occurring while the accelerator is depressed or mainly when it is released. If it’s occurring when the accelerator is released it’s a classic case of a dirty, sticking IAC.

However, this wouldn’t explain the white smoke which may be a blown head gasket, although you say your compression is great.

Okay, I’m going to try to pick a logical place to start, and hopefully I’ll answer all your questions.

First, you do have an Idle Air Control (IAC) valve, It controls your idle only, and is totally out of the loop under any acceleration.
You also have an Exhaust Gas Recirculation (EGR) system that introduces a wee bit of exhaust gas under load to prevent the combustion chambers from getting too hot, preventing preignition and excess NOx production. If carboned up and stuck open, it’ll cause rough idling, but its failure symptoms are not typically similar to your description. I don’t think this is your problem.

Now, to that exhaust manifold leak… that COULD be a cause of your symptoms. Your fuel mixture is controlled by a number of sensors, one of which is from an oxygen sensor in the exhaust stream before the catalytic converter, known as the “upstream” oxygen sensor. It measures the amount of air in the exhaust and the computer “tweaks” the fuel mix accordingly. The manifold leak could easily be allowing air to be drawn in, creating a bogus signal by the oxygen sensor and causing the fuel mix to be all screwy.

Allow me to suggest that you buy an muffler repair kit at the parts store. It’ll consist of a wire fabric and a metallic “liquid metal” in a tube that hardens when released. With everything cold, access the crack in the exhaust manifold, follow the directions on the package, and patch the crack. NOTE: do NOT consider this repair permanent; it’s for diagnostic purposes only. If the problem disappears, you’ve found your culprit.

If that has no effect, you can buy vacuum hose dirt-cheap by the foot at ant parts store. Try replacing your vacuum hoses, one at a time so you can’t cross them up.

The white cloud is not good. It suggests a possible blown head gasket. If, with then engine cold, you release the radiator cap and turn the engine on and bubbles blow out the fill hole, you can suspect a blown head gasket. We can tell you how to confirm it at that time.

But, knowing that you’re cash-stricken, try the things I suggested for now. They’re dirt-cheap and should help you discover what you need to do from here.

Post back. We do care.

Hey, cheer up. At least you get to live in Hawaii. ;-]

I believe you have a map sensor on that year has it been checked? When it stalls out do you still have spark?

You do have an IAC. I would fix the leak like @the same mountainbike suggested. I would also clean the IAC.

I meant to post schematics for your sensors and ECM.

Wow, brilliant Auto-Genius Community! Thank you very much for the suggestions! And so quickly, too. I think you have more knowledge than the 5 mechanics I have been to so far who spent a lot of time just shaking their heads & poking at it with a stick.

It doesn’t make a difference if the accelerator is depressed or not, nor the RPMs. It will do it at 2500 & at idle.

Today I ran a check on the fuel pressure regulator. It appears to be working. At least, there is no gas leak in it, nothing in the vacuum hose, but it is hard to say if the amount of gas in the fuel line is the right amount. It is full of fuel at least. I tapped all over on the IAC & wiggled all the bits but got no response. I don’t know if I have the tools to clean it myself. Then I went around doing the “very professional technique” of jiggling all the connections, and the coolant temp sensor broke completely off. It is possible that I broke it with my manly girl hands, but it actually split in half, and the interior looks corroded, so I doubt it. I will get another one. I read that might cause fuel drops & surges. Do you think that could be the issue? Since I live in Hawaii, it is a week for any part to arrive before I will find out. Makes throwing parts at the black hole in the engine even more time-consuming, plus shipping, lol! Tomorrow I will get the patch kit for the exhaust manifold and try that out. I don’t really have tools, except for a few socket wrenches & screwdrivers, so that makes it tough to do much on my own.

I’d love to test the Ignition control module/relay. It keeps coming up on my research as a possibility. Any notions on how to go about that?

I’m not sure what a map sensor is? I haven’t had a chance to see if there is spark after stalling. Ran it for 45 mins today & it didn’t completely stall. It dropped out randomly at worst every few seconds and at best not for 10 minute stretches, as per usual. It is like a vampire, rising from the coffin with a rev & sputter right when you think it is over. I don’t have any electrical testing equipment, so I’d have to take it in somewhere.

Since it has had a compression test & all, you don’t suppose that is a blown head gasket, do you? Could it be a bad seating on a gasket somewhere or that cracked manifold or oil getting into the cylinders?

I really appreciate all your help!!!


Why pay those 5 mechanic’s to work on your car.

You could just send a couple of us tickets to fly there and help you out. We’d even bring some parts!!!

Sand , Sun, A little roasted pig, Dancing girls!!!

The IAC is easy to clean. unplug the wires, remove the screws/bolts, and it should pull off fairly easy.
Then just spray out the area with “sensor safe throttle body cleaner”.
Be sure to order a new gasket before starting on it though.

If you don’t know what a part looks like…like the Map sensor…just look the part up on-line and they should show a picture. Like thishttp://shop.advanceautoparts.com/p/bwd-intermotor-manifold-absolute-pressure-sensor-ec1645/18480847-P?searchTerm=manifold+air+pressure+sensor


Now that it’s clear this occurs also when the accelerator depressed I have to take back my original suggestion of a bad IAC.

After all of the work done, has anyone tried to establish if there are any fault codes logged by the engine ECU (computer)? Your 1993 is most likely pre-OBD II but a Toyota technician should be able to call them up from the memory. Please advise.

I’ve seen many things in my days.When’s last time you had timing belt replaced.Should be done every 100,000mi.along with front main seal.Maybe someone didn’t tighten the Crank pulley bolt tight enough and the keys that keep the timing gear and the crank pulley in position are getting sheared off.Make sure inside of distributor is clean and dry, you may want to change the igniter in the distributor.Let us know of outcomes.