2009 Fit, 110,000 miles.
A few times my daughter's been driving it, and it suddenly drops to only going 5-10 mph. If she turns it off, waits 10 minutes, then it seems to run fine again.
Not sure how exacting her description is, but that's the idea.

I replaced plugs & ignition coils, but it has done this before & after.

Most recent code was cylinder 3 misfire, after disconnecting the battery for 10 minutes
Previously, there were 83-1 ecm/pcm relation malfunction, and also cylinder 3 misfire errors.

I wonder if the computer is the culprit, and not the the ignition system.

 

Is it a manual or an automatic transmission on a Base or Sport model? Mine is a '11 Sport AT and if the engine over-revs it goes into "engine protection" mode.

I was playing around with the paddle shifters while in "S" mode. It will automatically shift from 1 to 2 to 3 after a full stop but you probably can't drive at highway speeds while in 3rd gear and you "may" trigger the "engine protection" mode. In my case, I was driving two-lane roads around the house and over-revved 1st gear. That triggered it. Engine wouldn't rev, no speed, sounded like it was missing. I turned the car off and then restarted. Everything was back to normal.

Could the way the car is being driven (over-revving the engine) be triggering this "engine protection" mode?

 

Hi, It's a an automatic Sport.

She was driving through the neighborhood up a small hill. She never uses the shift paddles. Just normal driving, about 30 mph.

It happened a month ago on a flat road about 30 mph, and after restarting, it would only go 10-15 mph. We got it towed to a shop who recommended plugs & coils. I did the plugs and coils, but apparently I should have got iridium plugs instead of platinum.

However, suddenly crawling at 5 - 10 mpg would not be caused by the type of plug, I don't think.

The "slow drive" happened before & after changing plugs & coils.

 

Do I need a replacement ECU ?

If I buy a used one with matching part #, is "reprogramming" of some kind needed ?

 

Iridium vs. Platinum is not going to be a problem. As long as you used an approved set of plugs for your Fit.

If the plugs are not gapped properly or the new coils are rubbish, that could cause drivability issues. But since you had problems before & after the change, I don't think they were your issue.

Maybe a bit premature to consider that.

Randomly throwing new parts at a problem gets expensive fast. If you don't find a solution in these forums, one option is to go to a different mechanic or dealer and pay for a diagnosis.

 

So you can only go 5 to ten mph....

It would be good if you could actually experience this first hand........
Trying to recreate situations is very difficult.....
BUT,, If it happened to me. I would drive this like it is(5-10mph) and

See::::
If the vehicle is able to be put under load.......(meaning Can the vehicle travel up inclines - basically, drive up a hill of some sorts)

ALSO:::: The idea of "that she waits ten minutes and then the vehicle is ok!"
MAKES ME THINK&*&^*&^ Problem: has to do with an electronic part which overheats then malfunctions.... And then needs time to cool off...

I may consider looking at the "accelerator pedal sensor". (expensive part)
At least determine the APS's relationship to the vehicle and if there are other circuits involved. with vehicle acceleration.
At this time I have little experience with this particular vehicle regarding this topic... but, see if you can get others to chime in on this.....
Or start doing research on this topic.......... AND....... ask around and see if these APS's or related parts...... Fail........


Please keep us up to date on this and how it resolves...... Good for everybody to know about.....

Thanks, J

 

Killer suggestions so far. Based on what I'm reading here, well, it makes me think "loose wire".. im surprised to hear it moved at all on one cylinder. I assume the ride would be jerky to say the least. What kind of services were preformed on the car prior to this issue?.. has she ever heard a weird ticking while driving that seems to be coming from the engine bay, if only around the time the issue happened? It might be hard to distinguish from the regular dash rattles for an unfamiliar ear, but even so an electrical arc has a unique snap to its sound. Maybe describe it as a tiny mouse trap that keeps going off, hah.

 

Update: 2 local shops did not want to do a valve adjustment, so I had the dealer do it.
Everything seems fine after a week or so.

Thanks for all the replies in this and other threads.

 

What did the dealer say? Were the cylinder 3 (exhaust) valves were out of spec?