I installed the NGK Iridium IR yesterday. Yes it was very stupid of me, but I did not check the gap. When the car is in D at a light, the engine back fires. Could this be due to the gap? I also cleaned the throttle body. Could that have caused this??

thanks

 

The plug gap is supposed to be perfect right out of the box, so the gap likely isn't it.

You sure you didn't mix up the ignition coil connectors (connecting the wrong harness to the wrong coil), or leave one of the connections loose?

 

I did it one by one, to ensure i don't mix the coils. I would think if one of the coils is loose, it would be running on 5 cyl. while driving i don't feel the back firing at all. but i willl check to make sure the coils aren't loose. NGK web-site suggests to check the gap anyway, since the plugs are for many different cars..i might just pull all them and gap them.

 

What are the specific symptoms? (I'm not too familiar with backfiring, although I understand what it is, but not sure of all possible causes)

like, specific noises you hear, any jerkiness/vibration/etc

 

the engine jerks every 30 seconds for a second or two. can't explain how back firing feels..

 

i gapped all the plugs. they were .040. i gapped them to .044. but it's still misfiring. any ideas ...anyone

 

If this just happened after putting in the plugs, and you have checked that everything is connected as it should be, then i would put the old plugs in and see if the problem goes away. Maybe its simply the new plugs?

 

will try that tomorrow. it may also be the coils. she has 96k. maybe its time to change the coils..

 

Ya, I'm replacing my coils this week. Waiting for the UPS man to arrive

Usually, when the coils go you'll get a miss at startup,and the SES light comes on (code P1320). Is your SES light on?

 

no the light is not on. from where did you buy the coils and how much?

 

Six coils cost about $300 shipped. You need 3 of the "right" and 3 of the "left" (Front and Back of the engine).

Can get them from here:

http://www.nissan-auto-parts-dealer.com/

or, call David B. who works for Nissan. He is a great person to deal with according to many on this board:

888-254-6060

 

put on the old plugs and she is driving fine. no more misfiring. WTF i spent 60 bucks on those plugs. And i know for sure i did not damage them while gapping. I should have stuck to the oem ones....

 

Glad to hear you're up and running again. Bring the new plugs back and try to get a refund. Never hurts to try.

BTW, I have had my new coils in for two weeks now and the performance is like night and day. The engine accelerates and runs better than when it was new! I bet the coils were bad straight from the factory. I did find that one of them wasn't even connected correctly! Guess they did my assembly on a friday in japan.

 

i actually saw your thread about the coils. i checked all of mine and they are connect fine. i wanted to change those, but am getting wheels, y-pipe and some extras.......i am going to replace the MAF and get new plugs. i am also experiencing hesitation, and have checked the VIAS tsb....what can a man do. i am in love with her,,,i just can't let her go.....

 

Sometimes (especially on older "broken in" engines!) changing from the factory plug type/heat range causes weird problems. Example would be a hotter plug with a fatter spark, igniting carbon deposits in the cylinders that previously would not ignite due to the worn or colder-ranged plugs. This can cause the backfire-like symptoms you describe. In a true backfire the cylinder fires as the intake valve is open, (ignited air/fuel blows out the intake valve) or as the exhaust valve is open (blows out the tailpipe or detonates in the manifold/headers/pipes), instead of at TDC on the compression stroke. Severe backfires can bend valves and I have seen an air cleaner blown off its stud as the gases came back up the carb.

First thing I would do, make sure I am replacing plugs with correct OEM type and heat range. If you still have problem, it may be a good idea to run some combustion chamber cleaner through the system (a foamy goop that is sprayed into the intake.)

 

thx for the info. i am going to get the correct OEM plugs.

 

I installed NGK Iridium IR and my car performed much better afterwards...Up until I reset the ECU, then it started dropping RPMs when stopped, and transmission started slipping.

 

I would be willing to bet money if you look closely at the new plugs you will find that you more than likely the cracked the insulator when you were putting one of the plugs in. Did you make sure the you used a plug socket with the rubber insert? This will cause a missfire at idlle that my not be evident under a light load. Take a good look because it can be very hard to see. It will normably be a hairline crack running the length of the insulator.