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Discussion Starter · #1 ·
___When engine is cold (Florida climate)____

- As soon as the car is turned on I get a really rough idle and/or vibration, then it smooths out
- Turning on the AC and/or putting the car in drive make the car idle very rough (about twice as hard as it used to 3 months ago)
- If I turn on the AC and then turn it off, I will feel a slight jolt and then the car shuts down. Its quick and easy to restart as the battery is only a year old.
- Stepping on the brake to go from park to reverse, to drive, to park then the car will eventually shut off on one of those shifts (can really feel some movement in the car when shifting)
- If I start the car then turn on AC and drive around, the car will shutdown at a stoplight (engine still cold while AC is running)

___When engine is at full operating temperature____

- When in park I barely even know the engine is running its so smooth (until I turn the steering wheel)
- Park + Drive = very rough idle (dashboard vibrates a good bit, coins start to rattle a bit)
- Park + Drive + A/C = the idle is just plain ridiculous :(
- Park + Drive + A/C + Turning steering wheel = the idle is so rough it feels like the car is about to blow up or toss me out of it! :eek:

___My attempts to fix the problem___

- Installed NGK platinum spark plugs
- Installed NGK wires
- Installed both the rear and front motor mounts (one screw stripped on the front mount as I was installing because the holes didn't exactly match up)
- Installed new MAP (mass air pressure) sensor (car was giving a check engine light)
- Installed new IAC (idle air control) valve (idle was much better when car in park and nothing else)
- Changed oil at every 5,000 with Mobile1 5w-30 (synthetic for cars with over 75,000 miles)

___Possible next steps?___

- Change the fuel filter in the gas tank (my friend mechanic said it never needs to be change)
- Change the top motor mount (guy at Tirechoice said it looked quite a bit worn and could use changing, but would cost $400 to do it) - 'Attached Photos'
image001.jpg image002.jpg image003.jpg image004.jpg image005.jpg
- Check vacuum hoses for leaks (have no idea how to do that)
- Definitely open to suggestions

I'm guessing I may have to fork up the $400 to have a smooth ride again. Any ideas? I'm totally stumped :tongue:
 

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I'll just throw out what happened when my car started shaking like crazy until it wouldn't even start any more.

Crankshaft position sensor was cracked
coil pack was bad (causing misfire)
vacuum leak

When the car was starting hard and a bit shaky(nothing too alarming) then would stall after trying to gas it.

Misfire(spark plug wire arcing to block)
clogged primary cat
bad o2 sensor(cannot remember if o2 sensor 1 or 2)

Usually when I have a vac leak it doesn't shake or throw a code for a few start up cycles, just really sluggish.

Hope that helps.
 

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Discussion Starter · #4 ·
Wow! Thanks for the run down on this. That seems pretty extensive along with a rather BIG bill!

Didn't think about a possible clog, but definitely something to check out. The coil pack had crossed my mind but then I thought probably not because I have a smooth idle without all the equipment turned on. I could be wrong and I guess it wouldn't hurt to change it. O2 sensors I had not thought about either. Do you know how one would go about finding where the leak might be coming from?


I'll just throw out what happened when my car started shaking like crazy until it wouldn't even start any more.

Crankshaft position sensor was cracked
coil pack was bad (causing misfire)
vacuum leak

When the car was starting hard and a bit shaky(nothing too alarming) then would stall after trying to gas it.

Misfire(spark plug wire arcing to block)
clogged primary cat
bad o2 sensor(cannot remember if o2 sensor 1 or 2)

Usually when I have a vac leak it doesn't shake or throw a code for a few start up cycles, just really sluggish.

Hope that helps.
 

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Discussion Starter · #5 ·
So yesterday I decided to install a new coil pack. I reset the ECU and then drove it around multiple times. Unfortunately this did not work either. So on to plan "E", changing the side engine mount. The guy at the shop is asking $400. I looked around for a DIY and did not find one. Is there a way to do this myself?

So far today i've tried only1db's method of checking the intake manifold for leaks by spraying throttle body cleaner around where the manifold attaches to the engine block. Unfortunately this did not work as the car did not smooth out )=

Another guy in the forums said he took it to the dealership and the found that the electrical connector to the IAC (idle air control) valve was bad. Looks like I may have to go ahead and take it into the dealer, at least for a diagnosis. Also took it to Advanced Auto and there were no codes which just makes things even more difficult. Really hoping this is not cause by low engine compression as this is already starting to get expensive!

Current thoughts...
Connector to IAC?
Engine Mount?
Something in the fuel line (injector, regulator, or filter)?
 

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if there is no codes i would prob rule out sensors, on the other hand a blockage somewhere is quite possible... that or a vacuum leak
 

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Discussion Starter · #7 ·
Thanks sammech. I was thinking a vacuum as well but could not locate any leaks.

I installed a new strainer in the fuel filter and afterwords put 93 octane in the tank, then cleaned out the fuel injectors with seafoam through the vacuum lines.

One thing I did notice however was that there was A LOT of smoke coming up from under the hood of the car when sucking in the seafoam. Im guessing a cracked header.

Question is would a cracked header cause a significant amount of power loss in the engine? Enough to shut off the car at a stop light with the AC on?
 

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If you had a cracked header I think you'd both hear it and smell it when you were driving. What I've heard (take this for what it's worth) is that most common place for a header crack is between #3 and 4 cylinders, if you care to poke around. In any event it'd probably be a tiny hairline. Also it'd probably throw codes like crazy. How well does it run on the open road? Is your mileage suffering?

I can't see how a worn out engine mount would affect the actual running of the engine, I suppose maybe a totally broken one could contribute, but it's gotta be somethin' other than that. Seafoam smokes like a 5 alarm fire, I've run it through a motorcycle. It's hard to tell what's just rolling back out of the intake & what's curling back up from the exhaust. What do your plugs look like? If they all look about the same (whether that's good or bad) or if one or two look significantly worse than the rest will help clue you into what might be wrong.

One other thing, just throwing out ideas here. could be your a/c compressor. Usually they make a hella lotta noise when they die, and it's pretty obvious. But if the thing is locking up on you, it can reduce power while the engine fights its locked-up butt to keep turning over. If the A/C is really going in the tank, it could be that even when it's not turned on, the bearings are binding up & putting excess strain on the engine. It wouldn't cost you anything to pull the A/C belt & see how the compressor feels turning the pulley by hand: does it turn easy and free, does it crunch, is there any lateral/up and down play? Take it for a drive with the A/C belt removed and see what happens.

Just a thought. Good luck man! And please let us know how it turns out.

Jim B.
Grove City, OH
05 Elantra

Forgot to add-- even a dying ac compressor will often still work for a long time. Mine made horrible noises & made the car buck occasionally, and it went on for over a year before it made a final "whoosh" and the refreshingly brisk air stopped blowing. I don't know what goes on inside a compressor, but it has an electrical clutch and a bunch of bearings, so either one can actually (temporarily) lock up an engine if it's defective.
 

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Discussion Starter · #9 ·
Hey Jimmy thanks for the reply, did not want to reply till had something solid. Cannot really say its the compressor. I was thinking the same thing, but the car does this with anything else that I do.

Just changed the ECT (Engine Coolant Temperature) sensor. It made almost no difference at all.

The 2 symptoms that most single out this problem are ...

1) Engine is cold - Turn on AC - Car stalls and dies when I turn OFF the AC

2) Engine is cold - Driving in store parking lot at slow speed - Car stalls and dies when making sharp corners.

Even when I turn on the headlights I can feel the engine bog down a little bit )= . When warmed up its a really rough idle.

If any knows anything or experienced a similar issue then I could REALLY use the help. Am totally frustrated by this!, sigh...
 
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