Jump to content

Intake backfire


gareth29

Recommended Posts

Hi, complete z and forum newbie here! Recently bought a 55 plate GT car with 59k and a backfire thru the intake manifold from cylinder no. 6. The engine runs without the misfire if the lead to no.6 is pulled. The coil pack appears to be ok, I have changed all the spark plugs and the fuel injector, checked the compression (which appeared higher than no. 4) and am now puzzled.

 

Has anyone experienced anything like this on a zed or offer any thoughts? Apart from "why did you buy it?"

 

Any help appreciated.

Link to comment
Share on other sites

  • Replies 53
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

Put a intro post up (in the correct section and tell us a bit about yourself. (this post should be in technical but I'm sure the mods will move it)

 

Right, about your problem, more info needed.

 

You say backfire through intake? but then say misfire later. are you actually getting an explosion traveling into your intake? Or is it just misfiring until you remove no.6 from the equation?

Link to comment
Share on other sites

Sorry about the mistakes - it took me ages to work out how to post something.

 

Yes there is a pop back thru the intake, esp when the throttle is blipped. I've taken the top off the intake manifold and the tube down to no.6 is black.

Link to comment
Share on other sites

Think I would be tempted to do the compression test again. Maybe with a leak down test.

From the limited info you've given it does sound like it could be something fairly serious. I believe it is number 6 that is more prone to running lean and excessive heat due to the plenum design and location near the bulkhead.

 

Link to comment
Share on other sites

As you mention its plugs 4 & 6 - check out this thread and in particular the last 3 posts on the first page

 

http://www.350z-uk.com/topic/66607-changed-spark-plugs-but-something-not-right/page__hl__+coil%20+packs#entry989242

 

It is an easy mistake to make, if the leads have been taken off, and I'm just wondering if you might have got caught out ;)

Link to comment
Share on other sites

Thanks Dblock, but when i changed the plugs the one from no. 6 wasnt oily, just a bit sooty. Am now thinking sticking inlet valve(s) on no. 6. Wondering about taking the rocker cover off and trying to get some carb cleaner or similar down the valve stems, then draining/refilling with some flushing oil to try and clean it all out. Any thoughts anyone?

Link to comment
Share on other sites

If your getting ignited fuel coming up into the intake it does sound like a sticky or damaged valve.

If you take the rocker cover off and turn the engine over by hand you may see if its sticking.

Bare in mind you may not be able to get an oil tight seal on the cam cover after you've removed it and i don't believe you can get the seal as its attached to the cover, so it means a new cam cover. But that's the last of your worries ATM.

 

 

Link to comment
Share on other sites

Thinking it may have been a sticky inlet valve, I've tried a couple of engine oil flush products on it yesterday, with no result. Now thinking it must be a broken inlet valve spring - does anyone know if its possible to change the valve spring without taking the timing case, chain, etc,etc from the front of the engine?

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...