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2005 chevy trailblazer_ls
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Discussion Starter · #1 ·
I have an 05 Trailblazer with about 85,000 miles. A few months back I had misfire code at cylinder 4 and the idle was far rougher. Changed out the plug with an AC Delco and it went away. However, i still have a rough idle but it is far less substantial and most people don't notice it. However I do. Anyways, so I been reading on here and trying to figure out what to do. So I went through and changed all plugs with AC Delco's. Some of the original plugs were oily, engine was hot, just got home from my 25 mile work commute. However, the idle problem is still there. So next I took off the throttle body, cleaned it thoroughly and removed all of the buildup. But to no avail, idle problem persists. So now I'm wandering what to take a look at next.

Please let me know what your thoughts are on this.

Thanks,

Blake
 

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2002 olds bravada
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Cylinder 4 misfires are very common due to the fact that water can get past the hood seal and leak right onto the coil. Your coil may have gone bad because of it. It would be easier to confirm this if you still had a code, but just a guess for now. Still, codes can be present even when the light isn't on, they can be pending. Have them read and see if you have any pending codes. :thumbsup:
 

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2003 chevy trailblazer_ls
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if you know the code- it will indicate which coil.
what other members do- is find out the offending coil--- then swithc it around with another coil...

if the new code that is set follows the coil... then the coil is most likely the offender.
 

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2005 chevy trailblazer_ls
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Discussion Starter · #5 ·
Alright......scanned today and no codes were read. Hmmmm? Any other suggestions on what to check out with this issue?

Blake
 

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2004 chevy trailblazer_lt
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Did you remember to disconnect the batt for an hour after cleaning the TB?

Also, I forget if MAF was introduced in 05 or 06, but if you have a MAF sensor, it could be dirty/faulty.
 

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Discussion Starter · #7 ·
Battery was disconnected for an hour and then changed as it was near gone. Also, not sure on the MAF. Where could I find it if I had one?
 

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Also, compared to park and neutral, the idle will be moderately rougher in gear. That happens with any vehicle. In case you think its the same :suicide:
 

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Discussion Starter · #10 ·
I will check for the MAF when I get home.

As far as roughness in idle, I understand this, there is no load on the engine when you are in neutral or park.

The idle is not normal while in Drive or Reverse. The vehicle definitely has developed a rough idle that sometimes seems like it will kill, but hasn't.
 

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Discussion Starter · #11 ·
Checked for the MAF. I do not believe my car has one. Hmmm? The only protrusion is a set of wires with what looks to be a temp probe / sensor. Any ideas?
 

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check all your hoses for vacuum leaks... especially at the intake manifold and throttle body

recheck the bolts to the TB and make sure the gasket is sealed correctly



run the truck and use a soapy water solution and rub it on all the hoses and see if you can see any air bubbles

a vacuum leak is a cause of missing at idle

also do a compression check
 

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2002 olds bravada
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try unplugging the number 4 coil with the engine running and see if the idle changes. if it does, coil is good. if not, or even if it changes just a little bit, the coil is bad. check for spark if you can.
 

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Discussion Starter · #16 ·
I'll try the coil trick tomorrow after work.

How bout the vacuum lines? I tried checking them tonight quick but it was basically dark already. Where do I find the lines and which ones shoild I pay attention to?

Thanks,

Blake
 

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I'll try the coil trick tomorrow after work.

How bout the vacuum lines? I tried checking them tonight quick but it was basically dark already. Where do I find the lines and which ones shoild I pay attention to?

Thanks,

Blake

big curly dude going from Brake Booster to Intake Manifold (you cant miss it)

dont forget to recheck the throttle body and the bolts and gasket
 

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2002 gmc envoy_sle
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I just had to have my 2nd coil pack replaced in my vehicle. When it would rain out it would start to act up about an hour after driving in it. It would skip and chuggle when sitting at a red light and you could feel it skipping on acceleration and set off the SES light saying #3 cylinder misfire. It was still doing this a day after the rain stopped and the weird thing is that sometimes it would be a major misfire like the coil pack was completely dead and other times when I would stand on it, like on the highway, it wouldn't skip. I tried to swap the coil packs between #3 and #2 but the code never changed so I took it to the shop and they confirmed the coil pack was bad. They changed it and it's fine now.
 

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Discussion Starter · #19 ·
Alright, checked the vacuum hose going from manifold to brake booster. Good connections at boths end and no leaks found.

Also, pulled of each coil one by one to see if any were bad. From what I could tell each time one was pullled it ran a little rougher. Hmmmm?

In addition, I notice something that may or may not be correct. At the front passenger side of the engine there is a vacuum hose that connects and it turns and then ends, not connected to anything. Is this correct?
 

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2002 olds bravada
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I think you're talking about the fuel pressure regulator hose. One end connects to the intake resonator, the other connects to the fuel pressure regulator itself.
 
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