QuestionQUESTION: i have an Hyundai elantra 2004. i recently skim the head of the engine due to over heat. after i install it back, the engine having difficult time to start and obtain a stable idle time. once i done an engine diagnose, the error code say that there is a problem with its manifold air pressure sensor. however, i erase the code to make sure that it is truly the problem. since then there is no more error detected by the ecu but the problem still persist. the timing is still a problem but the check engine light did not light up. can you help?
ANSWER: Hi, Zulanders. Unless you have an engine management system on this car that isn't available in the United States, the ignition timing is not adjustable. I'm left wondering whether I understand the question properly.
Are you having an issue with the ignition timing, specifically that it is not steady preventing you from adjusting it?
Do you mean that the idle speed (engine rpm) is abnormal?
I can say that anytime I've seen a beta engine cylinder head damaged by overheating, the cylinder head needed to be replaced. Usually, there was not only excessive warpage on the surface, but the valves no longer seated properly.
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QUESTION: your assumption is correct.it is quite clear to me that you have suggested that the head need to be replace. there is still one more question i need to ask... if the timing is not correct/stable/normal, why the check engine light did not light up? the situation is like this... in idle mode, the engine vibrate abnormally and when i check the spark plug in cylinder 2,3 and 4, the plug has turn black at the tip. is there any thing else i can do before resulting to change the head? before i skim the head, engine work normally after replace the head gasket. after 2 day, the engine overheat again.
ANSWER: If the engine was running normally after replacing the head gasket, then I hesitate to tell you that the cylinder head is the culprit, unless it was damaged again by the second overheating.
As for why the check engine lamp is not on, I'm not familiar with Australian self-diagnostics, which could be different than those here in the U.S. For example, your description sounds like you may have a misfire, and the Australian spec ECM may not attempt to monitor misfires.
I'd recommend normal misfire diagnosis, starting with checking the secondary ignition components (plugs, wires, coils). Since we know you've had engine mechanical issues, I'm not really expecting you'll find any issues there. Presuming you don't, I'd next suggest performing a compression test to see whether any cylinders are just blatantly weak.
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QUESTION: may i ask what is the default value or normal pressure reading at the cylinder? can the manifold air pressure sensor (MAP)have anything to do with the current problem? actually the car spec is 2004, 1.6L, asian spec.
AnswerUnless I can determine you have an engine that is also used here in the U.S.-- all of our 2004 Elantras use the 2.0 Beta engine-- I won't be able to give you the compression specification. Can you tell me whether this is a Beta, Sirius, or other engine? My suspicion is that you'll find a large variance from cylinder to cylinder, making it obvious in which cylinder the problem lies.
I doubt the MAP sensor could cause this issue. The ECM applies data from the MAP sensor equally to all cylinders. Unless I misunderstand your symptoms, you're looking for something that can affect one cylinder but not others.
