2001 Elantra Cylinder 4 misfire

My daughter drives an 01 Elantra that started w the minor symptoms you describe. We had numerous conversations with various mechanics and found many suggested possible remedies on forums such as this. We replaced numerous different sensors, plugs, wires, etc., that had seemingly worked for some others, but to no avail. In fact the driveability continued to get worse until it misfired so badly under any kind of acceleration that the car barely made it up shallow inclines. Fortunately, we stumbled across a suggestion for a diagnosis that apparently is quite common for this car, but strangely is rarely mentioned in forums and the like. Often, the original intake manifold gasket dries out, becomes brittle, and deteriorates, resulting in vacuum leaks causing a 'stumble' & a misfire in the cylinder closest to the failure in the gasket. Long story short, I replaced the intake manifold gasket, as well as the valve cover gasket, (as a result in having to remove it to get to the intake manifold) and my problem was solved. The car runs perfectly with no misfire whatsoever. As soon as i saw the condition of the gasket when I removed the intake manifold, I knew that was my problem. There are several ways that you can check for a bad gasket, although I'm not certain that these tests were conclusive in my case, rather it seemed that the descriptions of the symptoms I found more closely matched mine after trying seemingly everything else. Google for an image of a bad intake manifold gasket & you will see what I mean. I performed this work outside during cold winter weather, and it was not as daunting a task as it appears at first glance. If you have done any of your own simple maintenance in the past and have basic mechanical skills and sockets, you can save yourself substantial money by performing the repair yourself. There are videos and step by step instructions available online, & I found the most difficult part to be fitting my hand in a couple of tight spots for bolt removal. Tight, but doable. I hope that this helps you as I am all to aware of the frustration in not being able diagnose a mysterious condition, or having other posters fail to report back when they finally find the solution to their problem. Good luck.

*all too aware

'02 Elantra w/ similar issues...EVAP system issue (1 clogged fuel valvue). All for the most part is well, and check engine light went off.

Had a similar issue w/ my '02 Elantra. Check Engine light had been on for a while, was told it had to do w/ oxygen sensors. Most recently the car would stall, idle at very low RPMs, and did not have much power and would sputter through turns. End result was only a clogged fuel valve, and that seems to have done the trick. A lot of these issues posted regarding older Hyundai Elantras seem to all relate back to the fuel source...good luck...

my 2002 is went like this but now it wont start we thought it was fuel pump but its still working but my car just sounds like the fuel just wont get through ? any ideas we thought maybe sensors

if replacing the o2 sensor make sure yo get he right one for your car I didn not know Hyundai made 4 ,5 & 6 prong fittings for the same year car ---- I ordered the wrong one ( an MTK 25606 and it was supposed to be a 23403 ) now the Whitney catalog is giving me a hard time about returning it,

BSling's answer was the solution for my 2002 Hyundai Elantra. Cylinder 4 misfire code. Rough idle. Stumbling at both high and low speeds, especially during acceleration. Prone to overheat on hotter days, or after the car had been driven for a while. I first tried replacing the spark plugs which seemed to help a little bit, but did not fix the problem. I then found and read BSling's answer above. I figure I'd take a chance and replace the intake manifold gasket. The gasket had no cracks or missing pieces, however, it was very firm and brittle. I got a replacement at Autozone for $10. Installed it, torqued the intake bolts to ~16 ft-lbs, put everything back... Car seems to be fixed and working well now. Thoughts: Metal expands when heated. If the metal within contact of the gasket expanded in hot weather or when the engine got hot, perhaps it caused the very firm gasket to shift around and allow vacuum leaks. The new gasket, being very pliable, is able to compensate for the expansion and retraction of the metal.