2001 S Is Jerky When Maintaining Speed - Toyota Corolla, Chevy Prizm (1998-2008)

I've got a 2001 Corolla S (5-Speed) - had it since new - I've done all the required maintenance and oil changes etc.... recently, while driving on the freeway it has started a very disconcerting jerking, almost like skipping. It doesn't do it while accelerating. Only while maintaining freeway speeds - 60mph to 70mph - while in 5th gear.

I noticed a slight jerky feeling while going about 40-45mph in 4th gear.

Those speeds are at about 2000rpm or so.

If I press the accelerator, the jerkyness goes away.

If I let off the accelerator, it goes away as well.

Only when maintaining that speed does it go into what I can only describe as a hiccuping jerkyness. Also, the hiccuping isn't in any sort of rhythm. It's very random.

I'm at a total loss... any thoughts??

Hmm. Do the RPMs fluctuate when the car is fluctuating at cruise? Is the jerkiness present when you are coasting in gear, in neutral? If you tap the brakes, does the car still show signs of jerkiness?

Could be a number of things. First, I'd double check the plugs, make sure that they are in good shape. Read the plugs (ie. note any gross visual differences from plug to plug, noting which cylinder the plugs came out of). Ideally, all the plugs will look the same - same amount of deposits, same color, etc.

Second, I'd look into getting the throttle body cleaned (couple of DIY writeups in this forum) and cleaning the MAF sensor in the intake. Fairly common for these to be overlooked during "routine" maintenance. Same with the PCV valve and associated hoses.

Then I'd look for potential vacuum leaks, more so if tapping the brakes causes a significant change in jerkiness behavior. A quick visual inspection can catch the obvious issue - cracked, loose or missing hoses.

That will pretty much cover the "simple" stuff that can cause this behavior, aside from normal maintenance. Also couldn't hurt to add a bottle of injector cleaner in the gas tank on the next fillup. Redline SI-1 Fuel System Cleaner is the one I like to use, others are Chevron with Techron Concentrate Fuel System Cleaner, Valvoline Complete Fuel System Cleaner, and Gumout Regane Complete Fuel System Cleaner.

If these don't change the jerky behavior, then it will require some further diagnosis, hopefully with a data logger to see exactly what is going on when the jerkiness is present. Could range from an exhaust leak, to a bad sensor, to a VVTi issue, to electrical noise issue.

Thank you so much for your response. I'll try to answer all your questions -

Do the RPMs fluctuate when the car is fluctuating at cruise?

Nope. Not that I've noticed anyway. I'll keep a closer eye on that.

If you tap the brakes, does the car still show signs of jerkiness?

No. I tried that - wondering if it was a brake issue as well.

Is the jerkiness present when you are coasting in gear, in neutral?

Well, here is some new info I tried to glean after reading your reply. Took the corolla out on the freeway and paid very close attention to what I was doing/not doing when the jerkiness happened. I stated earlier that it happens when I'm cruising at a steady speed - but actually, I noticed that it only happens when I reduce pressure from the throttle in order to maintain the same speed (like if I'm coming down a slight hill). Very jerky then. Not at all when I put more (or normal) pressure back on the throttle.

There is a check engine light on which is reading PO420. It's been on for about a year now (the dealership wants about $1500 to replace a cat converter) -- but the jerkiness is new. The plugs were changed one year ago and the MAF sensor was "cleaned". At that time the check engine light went off for about a month, then came back (that's when the dealership stated that they needed to change the cat converter). I'll take a look at the plugs though - and grab some injector cleaner. Couldn't hurt. I didn't even think about vacuum leaks... I'll take a look at the hoses etc.

Thanks again.

Yeah, that P0420 code is pretty common for this generation of Corolla, just search for it on this forum and on the net - lots of people have this issue. Fortunately, doesn't really hurt the car's operation or drivability, just that the downstream O2 sensor "thinks" the catalytic converter is not doing its job. What you'll find is that 90% of the time, the catalytic converter is function perfectly, it is usually an exhaust leak or bad rear O2 sensor that is causing the code to pop up.

Hmm. So when you back off the throttle enough to maintain speed, jerkiness is present. Have you tried just coasting in gear - slight engine braking?

I'd double check the simple stuff first. See if that help smooth out the jerkiness. Then I would double check the torque mounts (engine mounts). I've noticed that when my mounts started to get worn out, every time I unloaded the transaxle, I'd get some jerkiness in there. Gets worse as the slop increases inside the gearbox, driveline, axles, etc. Probably couldn't hurt to take the wheels off and inspect the axle boots - see if they are still in good shape, nothing leaking or torn down there.

I tried the 'coasting in gear - slight engine braking' and the jerkiness wasn't present if my foot was all the way off the throttle... It was smoothly coasting.

This afternoon, though, the car seemed to start 'skipping' while at a red light (first time that's happened) ... so I finally just took it in to my mechanic. He probably won't get to it until thursday or friday, but I'll be sure and post back on some details just in case someone searches this problem in the future.

I sincerely thank you for your help, fishexpo101.

Cheers!

Might check your throttle position sensor (TPS).

In case anyone searches this topic - here's the culprit on my Corolla:

Leak at the timing chain tensioner (O-Ring)... causing the slipping/timing/jerkiness/skipping feeling.

Also, the valve cover gasket was leaky. Several plugs were fouled (replaced them all).

Engine code caused by a bad O2 sensor. Catalytic converter is fine, no exhaust leaks.

Thanks you guys for helping.

Cheers!

Thanks for posting back a solution to your issue. Interesting that a leaking timing chain tensioner caused that jerky behavior - good to know.