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Discussion Starter #1
Hi!
My 1998 Corolla CE only has 101,000,but for the past two months or so it's developed an annoying habit of intermittent stumbling, hesitation, and sometimes even stalling. I really don't want to get rid of this car and a new one isn't in the budget, but I am running out of ideas. Have taken the car to two mechanics and they were unable to find anything. One mechanic said "it could be the car's computer." How would I even find this out, and how likely it is that the car's computer would be failing at this low mileage?
Here's what has already been done:
Starter is relatively new
Alternator, battery and ECT sensor test fine
IAC valve new
Throttle body clean
MAP sensor new
PCV valve new
Spark plugs and wires new
Stalling/hesitation is almost always when relatively cold and/or at low rpms. Sometimes happens when putting a load on the engine.
I have pay-per-mile car insurance, which requires a dongle in the OBDII port to track mileage. I had it about four months before the trouble started-doubt this would have anything to do with it. Problem is intermittent and there are NO codes-just the occasional check engine light.
There is some oil in the intake manifold, but we are not sure if it was just sitting there from before the PCV valve was replaced.
Any help would be appreciated!
 

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2006 Corolla XRS
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Let's go back to the beginning.

What was the car's condition prior to having all this work and parts done to it? This should give us a baseline and hopefully some direction.
 

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Discussion Starter #3
Thanks for the reply! I am the second owner of the car-I bought it in 2016 at 85,000 miles. I obviously don't drive that much, as the car is only at 101,000. It has been a great little car. The previous owner got all the factory scheduled services. My boyfriend replaces parts as needed, and it did get a new starter solenoid in 2017. We regularly check the oil and coolant levels. Absolutely no problems until very late August of this year, when the car stalled at a red light. The problem is VERY intermittent-maybe 15 stumbles or stalls since then. Car stalled twice when the wheel was cranked all the way when backing up. Restarting is never an issue.
Let me know if you need any other info!
 

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2006 Corolla XRS
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You have a vacuum leak somewhere in there. How does it feel while idling? Is it hunting or just surging?
 

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Discussion Starter #5
Hi, that is actually something I have thought about. My bf tested for a vacuum leak with starter fluid, but maybe that is not a reliable test? I would say hunting more so than surging.
 

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2006 Corolla XRS
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Disconnect the hose from the brake booster and use apply vacuum to see if the engine stalls or stays running.

I would look at the intake manifold gasket.
 

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Discussion Starter #7
Thanks! We are not sure what is meant by "use apply vacuum"-could you please elaborate? We have been trying to figure out what is going on with the oil in the intake manifold. I so appreciate the help!
 

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2006 Corolla XRS
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Its a vacuum gauge and it has a trigger. It takes around 8-10 inches of Mercury to get the engine to stumble.

If the engine stumbles, then there's no leak. But, if it does not stumble, there is a leak in the system.
 

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Discussion Starter #9
Thank you so much for all your help! It is pitch dark when we get home from work now, but we will do this over the weekend and I will report back. I am hoping this is the fix-the other thing I have been told is crank sensor, and that looks like a nightmare to replace on my car!
 

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2006 Corolla XRS
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Also, verify the mark on the crankshaft pulley is aligned with the stamped markings on the engine.

This may be hard to see, but with the help of a timing light, you should be able to see how many degrees timing is set at. Not sure what the spec is on your Corolla, but timing may be off and can also be a cause of idling issues. Check this after you do the vacuum leak checks.

I forgot to say, you can also use soapy water to check for leaks also. Idle the engine and only spray the vacuum lines in the engine bay.
 

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Discussion Starter #11
Thanks! We DID test for leaks with starter fluid, but maybe that is not the best way to do that? (Of course we used very little as the stuff is so volatile.) During the test we REALLY noticed the "hunting for idle". My car has a timing chain-I understood those usually outlast the car?
 

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2006 Corolla XRS
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Yes and possibly no.

If the PO maintained the Corolla properly, it should last you a while. But, if not, you can pull the valve cover and check the tension on the timing chain. Also, wouldn't hurt to inspect the timing chain guide inside the timing cover.
 

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Discussion Starter #15
Yep! My car insurance will show you stored codes, as I have the mileage tracker, and we also have a code reader. Nothing. When the car stalls it's almost like someone reached over and turned the key.
 

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98 Corolla Conquest
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You have been amazing! Thank you so much! We will try everything this weekend and report back!
Hello. I may be late with this reply, but my other car which is a Ford Probe GT was doing the same thing as you described, as well as popping from the exhaust, and an overly rich mixture. At first I thought it was the distributor, so I fitted a new one. It ran fine fore about five minutes, then did the same thing. Had the codes pulled and the result was a faulty crank angle sensor. Replaced it and now it's running perfect like before. If you engine warning light has come on, have the fault codes retrieved to make sure that is your problem.
 

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Discussion Starter #17
Thank you for the reply! Was just going to post-the steps above did not solve the problem. I am completely afraid to drive the car, and my partner has run out of time to keep working on it. As much as I hate this option, going to the stealership Saturday to see if I can get an answer and not have to buy a new car. Crank sensor DOES seem a likely culprit-however, we have already replaced multiple parts to no avail. No codes are being thrown, nor do they come up on a code reader. I get a check engine light when the car shuts off, but it's just like someone shut it off with the key. I would give anything if the car would just throw a code! It WAS running rich when I started it in the driveway the other day. Idle sounds like garbage-the car sometimes 'hiccups" like it's going to shut off.
 

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98 Corolla Conquest
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Thank you for the reply! Was just going to post-the steps above did not solve the problem. I am completely afraid to drive the car, and my partner has run out of time to keep working on it. As much as I hate this option, going to the stealership Saturday to see if I can get an answer and not have to buy a new car. Crank sensor DOES seem a likely culprit-however, we have already replaced multiple parts to no avail. No codes are being thrown, nor do they come up on a code reader. I get a check engine light when the car shuts off, but it's just like someone shut it off with the key. I would give anything if the car would just throw a code! It WAS running rich when I started it in the driveway the other day. Idle sounds like garbage-the car sometimes 'hiccups" like it's going to shut off.
That definitely sounds like a crank sensor, given that it it governs timing advance, fuel metering etc. Shame you have to take it to a dealer. I hope you sort it out one way or another.
 

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Discussion Starter #19
That definitely sounds like a crank sensor, given that it it governs timing advance, fuel metering etc. Shame you have to take it to a dealer. I hope you sort it out one way or another.
Ha, if I was the least bit mechanical I wouldn't be doing that, but I have already used up a lot of my boyfriend's time and I really want my reliable little car back! That sounds like a reasonable hypothesis-I will for sure report back once I get a diagnosis. Thanks! Jen
 

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Discussion Starter #20
Ha, if I was the least bit mechanical I wouldn't be doing that, but I have already used up a lot of my boyfriend's time and I really want my reliable little car back! That sounds like a reasonable hypothesis-I will for sure report back once I get a diagnosis. Thanks! Jen
BTW, I do have a crank sensor for the car. It just sounds like a project to replace without a hoist, and I don't want to put ANOTHER new part in and have it not fix the problem. If I can get a clear diagnosis of the issue my bf would likely put the sensor in for me.
 
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