Dear Tx,

You have done good logical repair work so far.

Go to hmaservice.com, and register.
Enter Service Information
Enter Elantra
Enter 1999
Enter 2.0 liter engine
Enter OBDII tab
Enter Fuel System
Enter OBDII P0302
Enter Code Description P0302

This says your ignition coil is likely failed or failing.

Ouch! $118.99 at Autozone for the repalcement, but cheaper than the dealer.
Product Part No. Price



Duralast / Coil - Ignition
C1119 $118.99

Byron

 

considering your high mileage and the fact that you say your miss-fire is at idle and low revs. you have a classic possible symptom of a burnt valve. before you do anything else get your compressions checked, what you have done so far is sensible and shoild rule out all the obvious things but you may well be missing out the basic problem so get the compressions checked out before you spent any more money

 

Ok, thanks. I've got it in the shop right now for the recall repair .. had to have it towed because the condition suddenly degraded yesterday to the point where it was risky to drive it.

A mechanic at shop near where it died thinks that maybe the converter is clogged, and the resulting exhaust pressure is backing up into the cylinder causing the misfire. He cited the popping and knocking sound it was making when I finally nursed it into their parking lot. If that's the case, and if nothing else is wrong, I'll know in a few hours.

The misfire codes expanded yesterday to include P0300 (random misfire) and P0303 (cylinder 3 misfire). It also had a P1586 (AT/MT encoding malfunction, Communication error) and a P0501 (speed sensor range/performance).

The latter sounds serious, since it can range from a short circuit all the way to a failed ECM, but reading through the possible causes I think it was just a side effect of the misfire. I had Cruise Control on when it first started losing power, and so in spite of the system's best effort the vehicle's speed dropped while the engine revved. On of the options on P1586 is a reduction in speed with no brake switch change (Cruise Control) ... so I'm going to chalk it up to that for the moment.

Anyway, if it still misfires after the converter (actually the exhaust manifold, but the two are one piece) is replaced, then I'll get a compression check ... but I'm hoping this fixes it ... especially since it spread from cylinder 2 to random in under an hour yesterday morning. Valves don't burn to the point of malfunction that fast, do they?

Engine coolant temperature was normal the whole time, and airflow seemed to make a huge difference in performance. That morning, it was lacking power, but did much better if I could keep it above 30MPH. Below 30 it would lose all power. I'm just a Saturday mechanic, but this seems consistent with the idea of resistance to exhaust passing through the converter.

More air entiring the engine at higher speeds would put more fuel and air in the cylinders, overcoming any residual exhaust more often, thus fewer misfires. I still had a significant power loss, about the best it would do was fifty on level road, and I had to nurse it to 35 or 40 up hills, which I'm told is also consistent with a clogged converter.

I didn't drive it to the shop, even though it started and ran a little better that evening, because it still lacked consistent power (it would rev, but only with persistent coaxing) and I was cautioned that driving with a clogged converter (if that is indeed the problem) could blow your cylinder head. Better safe than sorry, a tow costs less than a new cylinder head/engine, free with AAA.

 

Had the system diagnosed, including a compression test, which checked out fine. Mechanic believes it is the fuel pump, since fuel pressure at the injector's was low ... I hope that is the only problem. I'm letting him do that particular replacement ... since it is arguably the most dangerous of all repairs. One spark and your next ride might be a black Cadillac.

I'm sure there is a way to reduce or eliminate the risk, probably by draining the tank first ... but it was nearly full and I don't have anything that will hold 10 gallons of gas, or a way to transfer the fuel if I did.

It certainly fits with Friday's sudden power loss, since it still existed after replacing the converter ... but I'm not sure if it explains the original cylinder 2 misfire or not ... we'll see. If cylinder 2 still misfires after replacing the fuel pump, that pretty much leaves that fuel injector in my mind as the only possible remaining source of that problem.

 

if the problem returns after the noted repairs, start checking the sensors. personally, I don't believe that it is a fuel filter problem, and here is my reasoning:

the fuel filter (filter) supplies fuel to the entire fuel system. knowing this, it doesn't make logical sense (to me anyway, and I am always open to hear someone else's thinking on this) that the filter would only be causing a problem with one cylinder. it makes more sense that you would be getting a more random missing problem.

it seems more plausible (once again, this is my personal belief and I am open to others' opinions) that you could have "dirty" valves. it is not uncommon to have a "chunk" of something, usually carbon, stuck onto a surface within a firing chamber. this item will begin to glow red hot as the engine starts working, increasing with temperature with every power stroke of the cylinder. this red-hot ember is hot enough to cause pre-mature detonation within a cylinder and this may be causing your problem code(s). I'm not sure if this is true, but if you woudl like to rule this out, try using a full bottle of concentrated fuel injector cleaner, or even fuel system treatment. i woudl recommend you add this to your fuel tank when you have a short amount of distance or time before you have to re-fuel. this will send a higher-concentrated dose of cleaner through your fuel system. when you get to the gas station, fill up with the highest octane gas you can. some people say that the higher octane won't help any, but I figure it can't hurt not to try it. the higher octane is usually a little cleaner and better for your engine anyway. (note: the higher the octane number, the less chance you have for pre-mature detonation, as the octane has a higher combustion point). I'm sure that if you go to a shop or a dealership, you can get some sort of "magic potion" that will claim to do the same job better and more efficiently than anthing else on the market, but I have found that running this cycle of cleaner and gas every 10-20,000 miles helps keep my gas milage up and my car running smoother.

anyway, if you would like to do that, I woudl highly recommend that. it may have some time by narrowing out one more possible cause. after that, i'm not sure where to go. let us know if the shop says anything different.

good luck!

 

I seem to be having the exact same problem as this. I'm wondering what the resolution to your problem was if any?

Rick