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rough idle after timing belt change?

 
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  #11 (permalink)  
Old 25 Feb 2011, 05:03 pm
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Default Re: rough idle after timing belt change?

The bottom mark on these crankshaft gears are very deceptive. The marks will appear to line up when peeking in from the wheel well, however it is best to look from the top, or let the engine wayyyy down so that you can actually see the tooth that the mark is in front of on the gear, and line up the center of the tooth with the arrow on the block. I have made this mistake myself, with the same effect that you are having. Also, the marks on the cam gears should be lined up, but they are angled, not straight across. Use a straight edge, like a ruler and use all four marks on the cam gears with the up arrows facing up! I am a mechanic, and have done over 30 timing belts on these engines in the past 6 years. I have to admit, the hanes and chilton manuals are confusing if you are using these to assist with the job of changing one of these timing belts. Always rotate the engine over two revolutions to recheck the timing marks before putting it back together!!

Also, check your vaccume hoses on the back side of the upper intake and hvac. I have had those weather check and get broken or cracked when raising and lowering the engine. These will make the engine miss, surge, or idle irratically.
Hope this helps, and good luck. I know I was pulling my hair out when this happened to me.
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Old 26 Feb 2011, 01:00 pm
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Default Re: rough idle after timing belt change?

expert advice is always to the nines! could the erratic idle be due to the alternator disconnected from the pcm circuit? also will not go back together until i get it right, to much work! all appears right on. i am mechanic by trade as well. this one confused me? not my first rodeo! read that there is cam/crank synch process with drbIII that is required after this repair? any thoughts are appreciated all the best.

Last edited by 508713; 26 Feb 2011 at 05:20 pm. Reason: missed info
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Old 26 Feb 2011, 02:43 pm
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Default Re: rough idle after timing belt change?

Done this job, I already mentioned my troubles.

Here's cams: Note the 1/4" hole on the cast in collar on the nearest cam:

Here's another view, installed: (NOT MY ENGINE!)


The 2.4 side of gears have two marks each.
I didn't realize this.
Each time I check the rolled the engine a few time to check; the cam marks'd
be different.

I then ONLY checked the marks with the drilled 1/4" holes pointing straight up.
Ding! Ding! Ding! That did it.

As aforementioned:
-ensure you have a good line on the lower mark, also note the arrow is CAST
into the oil pump, there's some variability.
- Use a machinist's rule etc to put across the cam bolt center.

With Neon, dunno if it holds true with PT:
1. There is a re-learn procedure, only necessary if gears were set wrong from factory.

2. If intake (cam sensor doesn't know anything about the exh cam) cam is
off significantly, it will trip a CEL.

3. This is an announcement only, it didn't change any engine inputs.
Re-learn ONLY shuts off the CEL.

You can do old-school timing, if you want assurances: (This IS my engine)





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Old 27 Feb 2011, 09:45 am
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Default Re: rough idle after timing belt change?

reset timing again and it would not idle by it self, pressed gas pedal and it fired right up! however the idle is still in question? timing must be right? appears to be flooding with fuel? like iac is not working? with gas pedal apllied its smooths out, did not have this problem before, iac valve is new, is there a reset for the iac? confused! ????
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Old 27 Feb 2011, 11:58 am
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Default Re: rough idle after timing belt change?

if it has/ MAP senses low vacuum, it pukes in fuel. Add some 22 cams, it'll do
the same thing.

Massive vacuum leak?
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Old 27 Feb 2011, 04:17 pm
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Default Re: rough idle after timing belt change?

It will take a few minutes of the car running to clear the overloading of fuel and misfiring that has been dumped into the cylinders from the previous misaligned timing. This is common on 2.4s, especially when the timing belt has broken. They will often not idle correctly until the engine has had a chance to clear out which can take a few minutes. Aic is controled by the ecm, and is not adjustable that I know of. Let the engine warm up and clear out. It should pick up and idle on its own. Is there any kind of smoke coming from the tail pipe?
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Old 27 Feb 2011, 04:56 pm
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Angry Re: rough idle after timing belt change?

no smoke! black residue a tail pipe, still no idle, as long as the gas pedal is partially pressed say around 2k rpms it continues to run. when released it shuts off, it was mentioned that a large vacuum leak will do this?but where to look? its as if some thing is out of synch and loading up with fuel? removed # 1 plug its black, air/fuel mixture is whacky. i connected the alternator and tested and made no difference. i find hard believe that it still could be out of time! before all this occurred it started and ran well until it warmed up and it began rough idle, thats when the consensus was it out of time. I read where there is cam/crank sensor synch procedure, after doing this repair with the drb3. any solutions are appreciated. thanks,
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Old 27 Feb 2011, 05:20 pm
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Default Re: rough idle after timing belt change?

no smoke, just black residue at the tail pipe. like its choked! remove foot from gas pedal and it dies. is it possible that the tps is faulty? or the pcm at fault? no cels, has new iac, map, egr, plugs and wires as well as water pump and timing components. hard to believe it still out time? read where after this repair a cam/crank sensor synch procedure was needed, a DRBIII is required to do this. does this make sense? thanks again.
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Old 27 Feb 2011, 07:44 pm
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Default Re: rough idle after timing belt change?

got 2 dtcs p1682 and p1684 but do not appear to be related to idle issue, first is low chg. voltage and other is batt. disconnected. still confused.
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Old 28 Feb 2011, 12:00 am
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Default Re: rough idle after timing belt change?

You say it's in time.

You say it ran reasonably well before the time belt R&R.

You say the plugs are black.

You are talking of the alternator for some reason.

It sounds like it's running very rich.
Multiple things could cause that, focus on items that could have been
changed/broken during the latest work.
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