2005 Corolla RPMs dropping suddenly while driving - Help!

toyota
corolla

#1

I have a 2005 Corolla (4-1794; 1.8L engine) that is well and truly freaking me out. In September (about 4 months ago) I was making a left turn off of a stop sign when the RPMs completely cut off and the power steering quit - no warning lights and the radio, A/C, lights, display all stayed lit - it just stopped driving. I turned it off and turned it back on and it started up immediately with no problem. Made it home, but the next morning it struggled to start, and cut out several times while driving to the mechanic. The mechanic ran diagnostics, cleaned a bunch of crud out of the compression system to restore to factory settings, replaced the spark plugs, cleaned the fuel system, and got it back up and running.

It hasn’t shut off while running again (nor do I think it’s having trouble starting), but the engine seems to be “blipping.” When I’m driving, the tachometer will suddenly drop (usually from just under 2k rpm to just above 1k) and then come back up very quickly. I can feel the car sort of…rock, a bit, but it’s very quick. It never happens while I’m actually accelerating or going up hill, only while I’m maintaining speed on a flat stretch – usually at about 35mph – and especially while I’m attempting to maintain speed going downhill. In a 20 minute drive to work, it maybe does this 5 - 10 times. The RPMs never surge up unexpectedly - only drop and then come back up to the original level.

I’m not sure if it matters, but this is a really low mileage vehicle for its age - only about 68k on it. The vast majority of its driving has been done at city street speeds and it doesn’t get much highway driving - above 55mph - at all.

I never thought of myself as a nervous driver, but this problem is really freaking me out. My stomach knots up every time I take the car out, at this point. I want to take it to the dealership or a mechanic, but I don’t want to just turn them loose with this vague of a problem because I’m really tight on funds. Does anyone have any suggestions about what the issue might be? Am I going to die a horrible, fiery death if I don’t get it taken care of right away?

Thanks!


#2

While you didn’t mention it, I would find it hard to imagine that the Check Engine Light isn’t lit up.
Is the CEL illuminated?
Or…worst case scenario…is the CEL blinking/flashing?

:confused:


#3

The problem might be caused by a faulty crankshaft position sensor.

https://www.rockauto.com/en/moreinfo.php?pk=942174&cc=1433059&jsn=364

This sensor has many functions.

It informs the computer if the engine is rotating, it detects for misfires, and it sends a signal to the tachometer to display RPM’s.

If the computer loses the signal from the crank sensor, and tach drops in RPM’s, the engine will shut down momentarily until the signal returns from the crank sensor to the computer.

Tester


#4

No, it’s not lit up at all right now - that’s mostly why I haven’t taken it back in. :confused:


#5

There is a recall for the Powertrain Control Module on certain 2005-2006 Corollas;

Background
The ECM for certain 2005 through 2008 Toyota Corolla and Corolla Matrix models equipped with the 1ZZ-FE
engine and two-wheel drive may have been improperly manufactured. There is a possibility that a crack may
develop at certain solder points or on varistors on the circuit board. In most cases, if a crack occurs at certain
points or on certain varistors, the engine warning lamp could be illuminated*, harsh shifting could result, or the
engine may not start. In limited instances, if cracking occurs on particular solder points or varistors, the engine
could stop while the vehicle is being driven which may increase the risk of a crash.
*Please note the engine warning lamp may illuminate for reasons unrelated to this condition.
Remedy
Toyota dealerships will inspect and, if necessary, replace the ECM at no cost to the vehicle owner.

Enter your VIN in the Toyota site to see if there are any incomplete recalls on your vehicle;

http://www.toyota.com/recall


#6

All good ideas above. Could also be clogged fuel injectors or just that the throttle body needs to be cleaned. This car hasn’t ever been in an accident, has it? If so, since it occurred during a turn one time, you’d also have to consider a wire being pinched in the engine compartment somewhere.


#7

I am not a car expert by any means, but this whole story sounds awfully familiar. Do you have a lot of stuff on your keychain?

upd: ah, crap, Tester did it already. :slight_smile: I was gonna go for a more mysterious approach.


#8

The keychain/ignition switch idea above is a good possibility too. OP could try driving the car with just a single key in the ignition switch, see if that helps.


#9

My first car was a 1994 Corolla, which did exactly as described above. I was commuting for 75 miles every day on I-55 and it was properly dangerous. A few times I thought it was the end of me. My mechanic, who was a dirty piece of garbage, milked me for about $1500 in “repairs” (I got the car for 2K) until I took it to another one, who replaced the crank position sensor for like $60. Taught me well.


#10

Thanks, all! I’ve got an appointment with the dealership to get the ECM looked at - the recall hadn’t been satisfied, so thank you @Nevada_545! If that doesn’t fix it, the crankshaft position sensor sounds like it might be the culprit, although I have a pretty light load of keys.

I appreciate it!


#11

[quote=“awaznis, post:1, topic:98688, full:true”]
I have a 2005 Corolla (4-1794; 1.8L engine) that is well and truly freaking me out. In September (about 4 months ago) I was making a left turn off of a stop sign when the RPMs completely cut off and the power steering quit - no warning lights and the radio, A/C, lights, display all stayed lit - it just stopped driving.[/quote] The fact that the Check Engine light didn’t come on when the engine stalls makes me think the ECM is involved, and hopefully, the recall will take care of the issue.

[quote]The mechanic ran diagnostics, cleaned a bunch of crud out of the compression system to restore to factory settings, replaced the spark plugs, cleaned the fuel system, and got it back up and running.[/quote]If your mechanic used this terminology, he/she is blowing smoke up your tailpipe. I hope you are paraphrasing!

[quote]It hasn’t shut off while running again (nor do I think it’s having trouble starting), but the engine seems to be “blipping.” When I’m driving, the tachometer will suddenly drop (usually from just under 2k rpm to just above 1k) and then come back up very quickly. I can feel the car sort of…rock, a bit, but it’s very quick. It never happens while I’m actually accelerating or going up hill, only while I’m maintaining speed on a flat stretch – usually at about 35mph – and especially while I’m attempting to maintain speed going downhill. In a 20 minute drive to work, it maybe does this 5 - 10 times. The RPMs never surge up unexpectedly - only drop and then come back up to the original level. [/quote]This could simply be the transmission upshifting or the torque converter locking. At that speed, this would only happen under very light loads, like going downhill. But monitor this after the other problem is fixed.


#12

To clarify, the crank position sensor possibility is unrelated to the key/ignition switch possibility. Two different and independent theories to explain your symptom.