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If it's not the timing belt, what can it be?

First, never name your car. You get too attached. Well, we got very lucky pulling into a parking space when the first timing belt went at 140,353 (we’re third owner so had no info on previous belt replacement). Now at 201,406, (just at the standard 60,000 mi. replacement period), started to have an occasional shudder while idling. Then started to stall at stops maybe once a day. Battery seemed done so replaced it. Ran fuel cleaner through it. Still had occasional shudder. Replaced power packs. Made it two miles and faltered at a light. Stalled pulling into another parking space and didn’t want to start even with new battery. Dodged “catastrophic engine damage” once. Drove it home and had it towed to excellent mechanic (also listed with Car Talk). We suspected timing belt slipping (per friend’s suggestion). Mechanic has had it three days today and so far all I get is it hasn’t done it for them yet. Says there’s no codes. Don’t know what my take away from this is. Can’t be safely driven. Are they trying to say they really don’t want to fix it? Are there other possibilities beside timing belt we haven’t looked at. I drive cars. I don’t diagnose them. Kinda stranded. Any help welcomed.

Is it reasonably up to date on things that are scheduled maintenance like spark plugs and their cables if it has cables, clean air and fuel filters, etc. That’s the first place to look. There are lots of sensors that can create this kind of stumble, but they normally make the check engine light go on and set a code.

They would give it back to you w/No Problem Found (NPF) if that was the case. The fact they are still looking is evidence they are interested in fixing it but haven’t yet had any notable issue to work against. It’s fairly well known that both cars and humans stop acting up when the mechanic or surgeon is looking…

Appreciate the advice. New plugs and wire cables but we didn’t change fuel
filter. Wouldn’t that be nice. Husband would have set the idle up (not the
real solution) but was over his head. Heading over to mechanic to see what
he says. Jon will suggest fuel filter - Thanks again.

If a timing belt breaks then the engine won’t run period. They are either working or not…no in-between.

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Most OPs here don’t speak Gearhead and “broken” to many means needing to be fixed and not necessarily a violent separation. If the timing belt’s tensioner becomes weak and results in the belt skipping a tooth causing a driveability problem many would consider that something is broken. But in this OP’s case the timing belt doesn’t seem to be the cause of his complaint.

I wonder if a coked up throttle and IAC could be the problem? Many drivers who grew up with EFI have no inclination to step on the accelerator to get the engine to start when extended cranking occurs.

I agree with Rod_Knox about an IAC problem.

Crankshaft and camshaft position sensors come to mind.

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Timing belts do not cause intermittent problems. If they break, the car won’t run. Since they have teeth, they don’t slip. It is possible but rare for it to jump a tooth,but if it happened, the car would run poorly if at all and it wouldn’t come and go.

Everyone’s input was very helpful. Mechanic wasn’t going to “just throw parts at it” and couldn’t get it to fail so told me to come and pick it up - no trouble found. He wanted me to go for a test drive and I asked if it could be the “IAC” as suggested by you and agreed on by ok4450. He said it didn’t have other symptoms of that. I asked him what they were and he mentioned a little trouble starting at first. I had told the intake person that it did that occasionally but the info didn’t get to the mechanic. So… we took it home for the weekend to drive (back road) and he wanted us to check if the rpm’s dropped when it faltered. It did drop and the plan is take it back on Monday for the IAC replacement. So at least there’s a course of action thanks to your suggestion. Will let you know how it goes . Squishy thanks you and so do I.

Let us know how it goes. I’ve had two Accents (a 2005 and a 2009), and as long as the basic maintenance is done, particularly the oil and timing belt changes, these are very tough little engines.

At 200K miles, those symptoms could be caused by a number of things. I think you should focus on being happy your car made it to 200K before they started :wink: It doesn’t sound like the timing belt, but if the timing belt is due for replacement, make sure to get that scheduled. Espeically important to do it quickly if the belt is over 7 years old.

hmmm … as far as the rough idling, stalling … if I had that problem on my 200K miles Corolla here’s where I’d be looking

  • Read out the list diagnostic codes current and pending
  • A full systematic set of tests for vacuum leaks . Leaks can occur in the hoses, or the devices they hoses connect to. One common vacuum leak source is the power brake booster. Another is the PCV system. If you want to replace something on a guess, replace the PCV valve, an inexpensive guess and sometimes works.
  • Check all fluid levels, including transmission, and bring all recommended engine & transmission maintenance up to date.
  • Throttle body, IAC service. This usually is best done by removing the throttle body rom the engine and cleaning it and the IAC on the bench. The gunk from the EGR and PCV systems can gunk up the back side of the throttle body over time and cause the throttle valve to stick at undesirable angles
  • Check the EGR valve & system for proper operation. A sticking EGR valve can cause this.

Thanks for all the good clues to this mystery. Should know something

I don’t understand the mechanic’s comments about the symptoms not being an indicator of an IAC issue.

Stumbling at idle or randomly dying at idle are exact symptoms of an IAC problem although there are a few other things that could cause a problem like this. That would be a vacuum leak or possibly an EGR hanging open.

It’s also quite common to have an IAC problem without setting any Diagnostic Trouble Codes.

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When a car is towed in and the customer states that they think the timing belt slipped but the car runs this initializes a mystery for the technician. How many hours should he drive the car before the car dies?

That further confuses the problem. How was this engine operated that would result in damage?

The additional details about poor idle quality and stalling suggest that there is a problem with the idle control mechanism, the actual part involved depends on the model year of the vehicle.

Well, Squishy got a new IAC yesterday. Later stalled at a light. Guess we’re looking maybe at the EGR and PCV. Our mechanic is kinda stumped because he says there are no codes to show it is stalling. He hates throwing parts at the car, but I have to give him the news.Any ideas?

Got the new IAC and it stalled on the way home. Talked to the mechanic’s wife and now hearing there was a code for catalytic converter. Don’t know when that appeared but it would have been nice to know before the IAC. We decided to continue to drive it with the occasional stall. Ran some Cataclean in it the next day. Drove about 20 miles on 1/4 tank. Went to fill up the tank and it wouldn’t start at all. That could have been a good thing since what we kept hearing from the mechanic was he couldn’t find a problem because it wasn’t doing it. But then it started and I drove it home revving the engine and using brakes at lights and stop signs. Got us home - Died in my driveway Today it started right up. We’re looking at getting another car but, with all the new stuff (battery, power coils, IAC) we’d like to figure out what Squishy needs. It would be worth it down the road to replace catalytic converter for a car that my husband can drive to the store while I’m at work. Just don’t know what the odds are that if we get the cat done it still has this stalling and not wanting to start problem. Would like to say, “Squishy Rides Again,” but not yet. Thanks to all who have given of their time and expertise. Until it will act up “reliably”, we’re just stalled…

When mine was doing that (except the stumbling) a fuel pump was in my future. Sometimes the pump but once freshening up the connector to the pump.

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