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Low/Rough Idle After Head Replaced (2005 Sentra/Pulsar QG18DE) Forums > > Low/Rough Idle After Head Replaced (2005 Sentra/Pulsar QG18DE) Low/Rough Idle After Head Replaced (2005 Sentra/Pulsar QG18DE)
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  #1  
Old 05-11-2018, 10:49 PM
m4tto m4tto is offline
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Default Low/Rough Idle After Head Replaced (2005 Sentra/Pulsar QG18DE)

I am experiencing low/rough idle after replacing my cylinder head. The engine doesn't seem to be misfiring as it revs up well and drives fine under hard and normal acceleration. It just seems to idle low and rough when in "Drive" at the lights. No engine light on. I have replaced the spark plugs, all new gaskets with the head, cleaned throttle body and tried another temp sensor.

I have tried the Idle re-learn, throttle valve position procedures. I think they completed successfully but no change in the idle.

Has anyone experienced a similar issue after replacing their head gasket or cleaning TPS? I read somewhere that the dealer or someone with a decent scan tool needs to reset the idle or ecu?

Any help would be much appreciated. Cheers
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  #2  
Old 05-11-2018, 11:06 PM
Howard Bell Howard Bell is offline
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Why was head changed? An overheat? Often there can be various issues after that.

The work could have easily made a vacuum leak somewhere not found yet. Moving all the parts around can do it.
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Old 05-12-2018, 12:02 AM
m4tto m4tto is offline
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The head was weaping coolant extenally. The machine shop found a crack so i replaced it with a second hand low millage head after it was tested and cleaned up by the machine shop.

The car was driving and idliing fine before the head job. I suspect that it may have gotten hot by the previous owner, hence the weapage and crack. I only recenly just bought it off an old lady.

I cant see any obvious vacum leaks. The inlet manifold gasket is new and all duct piping and inlet manifold hoses look good.

Curious if the ecu or idle needs to be reset with a scan tool.
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  #4  
Old 05-12-2018, 11:24 PM
Howard Bell Howard Bell is offline
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'The car was driving and idliing fine before the head job.'

That screams to look close at the work there.
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Old 05-13-2018, 12:15 AM
m4tto m4tto is offline
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Thanks howard.

I dont know much about the internals of the second hand head or how it ran on the other car. I know it had a fair bit of carbon, the machine shop cleaned around the valves and i had to clean some from the spark plug threads.

Update: I sprayed water all around the inlet manifold and vacum lines but no change in the idle. Re checked inlet manifold bolt torque.

Disconnected each coil pack. Idle changed for each so definetly firing on all 4.

Im going to re check the timing marks tonight even tho im 100% sure it was right. Maybe it some how got a tooth out as i rotated the engine and chain took up slack. At this point i might need to recheck everything. 😔
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Old 05-13-2018, 03:15 AM
m4tto m4tto is offline
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Timing marks are spot on. Im starting to think the issue is with the second hand head. Might try get a comp test done and codes read.
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Old 05-14-2018, 02:55 PM
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bennyb53 bennyb53 is offline
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Try do the Idle Air Volume Learning procedure. You may need a clock or use your phone's clock. On Procedure 1 & 2, cycle the ignition switch On 3 seconds, Off 10 seconds 3X then on to #3. Hope this helps your idle issue.

https://www.nissanhelp.com/diy/sentr...e_learning.php
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  #8  
Old 05-15-2018, 01:19 AM
Howard Bell Howard Bell is offline
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I was going there next, compression check to determine if the head is doing it.

One does not take switching heads nowadays as lightly as before, too many variables crop up. Like did the head come with cams? If not then likely however the valve takeup was done may be at fault there. You don't just switch cams at the drop of a hat any more, the valves often need a set or if hydraulic then the lifters may not have been bled down and one is holding a valve open to slightly miss.
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