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Discussion Starter · #1 ·
Ok, so my car has developed a slight miss in the timing at idle. I've replaced the cap & rotor, wires, plugs, EGR & PCV valves but I still have a slight miss which would appear to be coming from the passenger side. I even took apart the throttle body and gave it a good cleaning and replaced all the gaskets. I've also been replacing suspect looking vac lines, as well as a new EGR and PCV valves with new tubing. Motor has somewhere around 130k to 150k (odometer burned out :( ) Was looking at replacing the fuel pressure regulator (fuel filter is fairly new) since it looks original and very oxidized. My Dad keeps mentioning a "weak" valve / "sticky" lifter but the car runs really well other than the miss at idle. Can anyone give anymore insight? I think at this point it's either in the fuel system or inside one of the heads.
 

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Did you double-check (Even triple check) your spark plug wiring order? It's really easy to get one crossed (especially on the passenger side). Make sure they are all snapped in place at both ends also.
 

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Discussion Starter · #3 ·
Did you double-check (Even triple check) your spark plug wiring order? It's really easy to get one crossed (especially on the passenger side). Make sure they are all snapped in place at both ends also.
Yeah, I've double double double double checked those plug wires ;) At one point pulled them and checked the resistance and traced them using the meter. No the miss was there before I started, it's just a VERY slight miss at idle.
 

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if you had wire mixed up you would not have a slight miss, it would be a full miss, since 1 miss placed wire = 2 mixed up sparks.

:D

if its @ idle you can count our the egr , i would look into the ICA
 

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Discussion Starter · #6 ·
if you had wire mixed up you would not have a slight miss, it would be a full miss, since 1 miss placed wire = 2 mixed up sparks.

:D

if its @ idle you can count our the egr , i would look into the ICA
ICA? Advertised Intake Closing timing (angle)? You're loosing me fast, if that is what you're talking about how would I go about checking that? Sounds serious.

Ok, maybe some more info will help narrow this down. Car also has a 95 ECU with a PCM4Less tune, however this tune was done years ago with a slightly different setup. Since the tune, I've removed cats (spare me the lecture) and added Headers. Less back pressure in the exhaust wouldn't affect the timing though would it?
 

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Discussion Starter · #7 ·

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ICA? Advertised Intake Closing timing (angle)? You're loosing me fast, if that is what you're talking about how would I go about checking that? Sounds serious.

Ok, maybe some more info will help narrow this down. Car also has a 95 ECU with a PCM4Less tune, however this tune was done years ago with a slightly different setup. Since the tune, I've removed cats (spare me the lecture) and added Headers. Less back pressure in the exhaust wouldn't affect the timing though would it?
ica is under the TB,

its a valve that allows air to flow into the intate while @ idle.
 

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Discussion Starter · #10 ·
ica is under the TB,

its a valve that allows air to flow into the intate while @ idle.
Oh you mean that sensor I didn't bother removing before I hosed it with TB cleaner? cwm6

Thanks for the help.

SEO9C1 thanks for the vacuum diagnostic info, I'm definitely picking up one of those gauges.
 

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question...

if it was something wrong like the valve or something with the head, would it not be @ all rmp, not just idle?

thats what make me think its the ica, since its only idle..

anyways keep us posted.
 

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Discussion Starter · #12 · (Edited)
question...

if it was something wrong like the valve or something with the head, would it not be @ all rmp, not just idle?

thats what make me think its the ica, since its only idle..

anyways keep us posted.
Will do but I just went to lunch and went to parallel park my car and when I went into reverse I thought I was dragging a muffler. Guess I'll be doing rear end work this weekend. :rolleyes:

Anyways, my Dad seems to think that as the engine warms the lifter starts working but admittedly he's not for sure and he's an old school guy that doesnt like/understand modern GM.

I'll try resetting the IAC position (not ICA) and see if that helps. Something I should have mentioned it does idle faster and longer at the initial startup than it did previous to the tune up.
 

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Will do but I just went to lunch and went to parallel park my car and when I went into reverse I thought I was dragging a muffler. Guess I'll be doing rear end work this weekend. :rolleyes:

Anyways, my Dad seems to think that as the engine warms the lifter starts working but admittedly he's not for sure and he's an old school guy that doesnt like/understand modern GM.

I'll try resetting the IAC position (not ICA) and see if that helps. Something I should have mentioned it does idle faster and longer at the initial startup than it did previous to the tune up.
smart ass...you knew what i was talking about :)

keep us posted
 

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Discussion Starter · #14 ·
smart ass...you knew what i was talking about :)

keep us posted
I think you may be on the right track. Doing some further reading and rumor has it that that longer/faster idle I was mentioning is a symptom of a dirty IAC sensor. I knew I should have pulled that sensor when I was cleaning. Thats what I get for ignoring my Spidey-sense.
 
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