Head Work

dannyboyau · Post by **dannyboyau** » Fri Apr 28, 2006 2:43 am

what year apprentice are you ?

try and eliminate the easiest possibilities first.

EG ; you think it is on the front bank, so get a cheap NGK spark plug and swap it with the new ones to make sure that you have not got a new plug that is miss firing when cold.

If you have access hook it up to an ocilliscope type diagnostic/tuning machine when cold you should then be able to see which cylinder has a differant electrical signal on the scope.

I have heard of guys striping a motor down trying to find a problem and it turned out to be a dodgy spark plug or lead.

Check your wiring and electrical plugs for damage or dirty contacts.

khunjeng · Post by **khunjeng** » Fri Apr 28, 2006 8:56 am

start with the spark and move backwards....coils, leads, plugs....half the time its an issue with these if u have the "splutter" effect.
eg hair-line fractures in the coil pack stop u from getting full spark...thats why sometimes with better plugs witha smaller gap it works better...just talk to anyone with a skyline about that...the coils are old now...this is a common problem with the nissans.

dyno...always a good tool...costs u about $70 and they can also check all the afr ETC to elimnate that side also...plus u will see how it runs and at which RPM its failing.

just my suggestion.

u can easly check the spark...not going into to it here...most workshops have the tools and will do it for u.

when i got my FTO Imy mechanic changed my plugs...whihc distrubed 2 fauly leads...took them a while to work it out...I peronally when and had some new leads made..I think 8mm ones...they are fully sick now. U only have 3 leads for the rear in an FTO..

bigpitty1 · Post by **bigpitty1** » Fri Apr 28, 2006 11:08 pm

I'm a second year apprentice going to 3rd year in a couple of months.

I have narrowed it down to the front bank because you can hear it, I don't think I will go with the plan of replacing everything because basically I don't have the money.

I know it ain't the spark plugs because when it started happening I replaced the spark plugs, nothing happened, I swapped the coils around and still the same thing.

I don't really have access to a ocilliscope type diagnostic/tuning machine, I got a mate who is a auto electrician, at his work they have a diagnostic computer which can be hooked up to most types of cars, I got him to connect it up to my FTO and found no fault codes.

I got a can of upper engine cleaner because I thought there might of been a build up of carbon in the combustion chamber but that didn't do much but made it run smoother.

The only thing that come to my head now that might be the problem is the tappet, one of my tappets has that little plastic bit that sits around it damaged, that maybe the problem but I got to ring Nihon car parts 2morro and order one, hope that is the problem...The only weird thing is my car runs fine once it has warmed up.

dannyboyau · Post by **dannyboyau** » Sat Apr 29, 2006 12:02 am

you adjusted the valve clearences after the coughing started?

Did you do the compression test ?

Does it cough when idling or when accelerating ?

Is the engine under load ?

how long does it take the coughing to stop ?

Can you put an air/fuel meter on to it and check the air/fuel ratios when cold ?

You seem to think it is one of the front cylinders causing this, so that eliminates faults that would normally effect all cylinders. So you need to determine which cylinder.

Internal combustion engine basicly requires 3 things to run.

Air, Fuel, Spark

When it dosent run properly one of those things is being affected.

Some examples
Air fuel ratio could be out because of inlet manifold leak, dirty injector, faulty spark plug, false reading from O2 Sensor, Burnt valve, etc.
In your situation burnt valve can be eliminated because that would still effect the car when hot. O2 sensor would effect more than just one cylinder.

Spark relates to plugs, leads and timing

Something is not performing its job when cold but once the car warms up that part of the system has been bypassed or the faulty parts works ok when warm.

The hardest job for a mechanic is diagnostic work you need to understand each system in the car to be able to figure out why it wont work. It helps if the car is infront of you and you have the right diagnostic equipment.

bigpitty1 · Post by **bigpitty1** » Sat Apr 29, 2006 1:49 pm

I did check the valve clearance when it started, it was all OK

I haven't done a compression test yet, I will bring it to work and get it done next week.

It only coughs at idle when cold, if I accelerate its fine till it gets back to idle.

Its not there when the engine is at load, except if I have the AC on when its idling on the spot.

The coughing stops once it has warmed up, so around 5 mins.

I don't think we have a air/fuel meter at work, I will have to ask.

I haven't really narrowed it down to which cylinder, but I think its the middle one, I think it is cylinder 4, only a guess because thats the one with the tappet with the little plastic thing damaged.

It doesn't have a inlet manifold leak, I got the vacume gauge on there and it seems fine, I even put oil around the gasket and it didn't blow any smoke.
I ran injector cleaner when I first got it, it won't be the spark be cause I swapped spark plugs around and coils.

The O2 sensor I haven't checked yet, I cleaned it when I fitted the extractors, it was covered in carbon, I was also thinking about the injectors, I should get them looked at, I can test duty cycle and that at work but with flow I might have to sublet them out.

dannyboyau · Post by **dannyboyau** » Sat Apr 29, 2006 2:45 pm

have you checked the stepper motor ?

it is on idle and the coughing is probably caused by a miss or air/fuel mixture change. What is the main control for the air/fuel mixture on idle.

With the previous post the last half was just to try and get you to think how the problem is occuring.

Also have you got a noid light or test light that can check the injector pulse

bigpitty1 · Post by **bigpitty1** » Sat Apr 29, 2006 11:35 pm

The stepper motor, I don't know what I would test for, I know it controls the idle, is there something on the motor where I can make adjustments.

At work we got multi-meters that we use to check injector pulse and duty cycle, I think we also got a TECH 31 which is basically a $10,000 multi-meter, it can display it all in a graph for you.

dannyboyau · Post by **dannyboyau** » Sun Apr 30, 2006 1:55 am

you could try cleaning the stepper motor and checking the wiring to the plug, but probably best to replace it. It is a common problem with the FTO and causes idle problems when it is not working properly.

khunjeng · Post by **khunjeng** » Sun Apr 30, 2006 11:57 am

yeah lots of examples on this site about the stepper motor and idol problems. WR has a turbo and had major dramas....in the end it was also the stepper motor.

but also check the leads..not just the coild and the plugs...these are a common source of failure.

anyway Danny has covered basically everything u should do...one by 1 until u find the problem.

KJ

bigpitty1 · Post by **bigpitty1** » Sun Apr 30, 2006 10:22 pm

I will take my stepper motor off next week and give it a clean, but it seems to be working fine, when cold it is idling just over 1000rpm and once it have warmed up it idles ound 700rpm, but anyways I will take it off and look at it, it maybe whats causing the problem.

Thanks for you help guys, when I get it sorted out I will tell you what the problem was.

dannyboyau · Post by **dannyboyau** » Sun Apr 30, 2006 10:30 pm

you said before that it only coughs while idling when cold. ?

When you say cough does it sound like a flat spot, a miss, over fueling, fuel cut.

what was the colour of your spark plugs when you changed them?

Does it blow any smoke when it coughs

bigpitty1 · Post by **bigpitty1** » Sun Apr 30, 2006 10:57 pm

The cough doesn't sound like a flat spot, miss or fuel cut, probably more towards the over fueling.

The old spark plugs looked pretty good, Lucky I still got them sitting around.

Left 3 spark plugs were the front bank and the right 3 were the rear bank.

bigpitty1 · Post by **bigpitty1** » Sun Apr 30, 2006 11:00 pm

Oh and it doesn't blow any smoke.

dannyboyau · Post by **dannyboyau** » Mon May 01, 2006 12:14 am

the photo is not very clear but the plugs from the front bank look like they were not burning that clean. The ceramic should look like the rear bank plugs

Would be nice to know what a compression test shows

Have you checked the timing ?

bigpitty1 · Post by **bigpitty1** » Mon May 01, 2006 4:56 pm

I haven't check the timing yet, I will have to go dig the timing light out of the shed.

dannyboyau · Post by **dannyboyau** » Mon May 01, 2006 6:44 pm

need a clearer pic of the spark plugs but it looks like the whole front bank is running rich.

with your spark plugs that you put in are they correct spec, not a colder or hotter plug.

when you did the valve clearences did you check the timing for the cams. ?

something is causing it to run rich on idle on the front bank, or conversly the rear bank could be running lean. might be a manifold leak on the rear bank. try spraying soapy water on all the places that parts come together, and get a bit of vacum hose on a bit of metal brake line or metal fuel line and put the hose to your ear and use the metal end like a stethescope

I am still leaning towards the stepper motor though

bigpitty1 · Post by **bigpitty1** » Mon May 01, 2006 10:38 pm

I will try to take another pic of the spark plugs, that pic was taken by my phone, the front plugs were NGK BKR7EKC-N and the rear were NGK PFR7M, but now I just use the PFR7M for both front and rear.

I did have a look at the cam timing, all the marks line up.

khunjeng · Post by **khunjeng** » Mon May 01, 2006 10:41 pm

bigpitty1 wrote:I will try to take another pic of the spark plugs, that pic was taken by my phone, the front plugs were NGK BKR7EKC-N and the rear were NGK PFR7M, but now I just use the PFR7M for both front and rear.

I did have a look at the cam timing, all the marks line up.

yeah they both have the same temp. ratings...the BKR7EKC-N are stock plugs though...

bigpitty1 · Post by **bigpitty1** » Sat May 20, 2006 9:12 pm

I got a couple of the mechanics at work to have a look at my car, we hooked up the A/F meter and found it was running a bit rich and reacon the O2 sensor maybe dead.

bigpitty1 · Post by **bigpitty1** » Sat May 27, 2006 9:14 pm

Yep my car is running rich, my cat converter is clogged, would anyone know how much a O2 sensor would cost.