My 1998 Toyota Corolla has 180 K miles. Two days ago I was putting the pedal down to get to work on time and it bucked, began chugging like a motorcycle and the check engine light (which was already on because of an emissions issue) began to flash. A mechanic looked at it and saw that cylinder 3 wasn’t sparking. He changed the plugs and wires but the engine was still chugging, especially when idling. The mechanic decided it was a stuck or burnt valve because he said he could hear/feel a lack of compression in the cylinder. I’m looking for a second opinion on the issue, and a first opinion on the mechanic!
A stuck or burnt valve is diagnosed by a compression test. These are easy, but it does not sound like your mechanic did this. Ask him to and post the results. Also post the code from the check engine light. It could be very important.
My car is doing the same exact thing. Is there any chance you figured it out. I just ordered a new catalytic converter and was hoping this may solve the problem. Thank you ahead of time!!
Assuming all the routine maintenance is up to date. If not, the fuel filter or air filter might be clogged, or a spark plug may have failed. Or the PCV valve isn’t working. If the compression is ok, and all the routine maintenance is up to date, I’d next suspect a stuck-open EGR valve, a clogged cat, or a faulty ignition component or O2 sensor. OP should post the codes here for a better diagnosis, and whether a fuel pressure test is in order.
Ths engine should have mechanical valve lifters and the valve lash should be inspected and adjusted as necessary every 30k miles.
It’s possible that a valve tightening up may have led to the CEL coming on. Ignoring the CEL eventually led to the problem becoming a misfire and then causing the CEL to flash.
The lash can be adjusted and it MAY bring the compression up to where it will run acceptably well. However, it may be a short term fix especially if an exhaust valve is involved. Tight lash is usually due to valve stem stretch which then holds the valve open a tiny bit and causes valve face/seat burning in the case of exhaust valves.
The best thing to do at this point is run a dry/wet compression test. If the wet test shows a valve problem then the lash should be checked and adjusted if needed; keeping in mind that any necessary adjustment may be a stopgap measure.
@Bombcar did your mechanic rule out a fuel problem.
Not all misfires are ignition related.
I’ve fixed MANY misfires which were fuel related.
Perhaps your mechanic’s “gut feeling” is correct, but you should ask him to back it up.
If he shows you that cylinder #3 has low compression, ask him to check the valve lash. If it’s out of adjustment, perhaps that cylinder can yet be saved by adjusting the valve lash (installing the appropriate shims, I believe)