<SOLVED> Car Stored 5 years, Cylinder 4 not firing at all

[Recap]

Hopefully someone on this forum can help me out.  As stated in the subject, I have a sick GN.  I have been trying to sort this out off and on for the last 2 months.  Below is what I have done to date.

-replaced plugs (twice)
-checked full pressure
 -replaced plug wires
 -new O2 sensor
 -new fuel filter
-checked resistance between engine and battery negative post
-checked exhaust manifold temps with infrared temp gun
 -new Coil Pack (Accel)
 -new ignition module (Standard LX338)
 -checked compression and all within 5psi
 -verified signal to injector 4 was present (node light)
 -had injectors backflushed and flow checked (checked out OK when he received them)
-moved injector that came out of cylinder 4 to different cylinder, no. 4 still not firing

I am not sure where to go from here.  Any and all suggestions welcome!
 
 

[gbsean]

have you verified spark....did you change coil pack because there was no spark or just because you wanted to

[Recap]

Replaced coil pack due to checking header temps and having a cold cylinder.  When that did not work, I replaced the ignition module.  When that did not fix the issue is when I pulled the injectors and sent them off to be checked and serviced.  Tried to put the list in chronological order as to what I have done since trying to diagnose the problem.  Regarding checking spark, have ordered a little tester to do just that, so have not done so yet.

[Steve Wood]

As I suggested, pull that plug wire and put a plug in it while it is laying on the valve cover.  Start the engine for a second while watching the plug gap to see if it is sparking properly.

Normally, a firing problem that is associated with the coil and/or module, will affect two plugs at the same time because we have a waste spark system so both plugs on an individual coil pack will fire, or both will not.  So a single cylinder is usually a bad plug, or a bad wire.

As the noid lite was blinking, that would mean the injector harness was okay.

If the problem stayed on number four even after switching the injectors about, then that should eliminate the injectors.

Now, the only thing that could account for a truly cold cylinder would be a lack of compression and that would be most likely due to a valve train problem unless there is a big hole in the piston. 

I hate to assume things, but, I hope you cranked the car up, let it warm up a bit, and then disconnected one injector lead at a time to demonstrate that the engine started to miss on each cylinder except for the number four cylinder which stayed the same.   If you have anyone to help you, have them sit in the car, foot on the brake, car in drive, while bringing the rpms up against the converter to add a little load.  This should make the miss worse and easier to discern.   I am not disputing that number four is colder, but, I have been fooled a couple of times using that as my sole determiner. 

[Scoobum]

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[SuperSix]

I was thinking valvetrain too/lack of compression.

Can you do a compression test on that cylinder? You seem to have cover most of the basics.

[gbsean]

he said he checked compression... but..on a cold/dead cylinder I would be surprised that reading was within 5psi of the others.

[Recap]

I know you can ground the plug, but was warned by Red Armstrong about only firing one of the two paired cylinders as it can take out the module.  So picked up one those gadgets that connects between the plug and plug wire with the internal light to test it with this weekend, hopefully.  New 4 post lift arrived a week early while I was out of town so will be spending most of the weekend trying to put that together so I can get it off the drive.  Will let you know what I find out. 

I did check compression and all looked good.  All cylinders were cold when the test was done as I was changing the plugs out at the time and thought I might as well check compression while I was at it.  I am also planning to pull the valve cover and have a look at the valve train to see if there may be an issue there.  Having said that, I can't see how this could be an issue from sitting but at least it will rule it out.

Thanks for the interest and the suggestions.  Keep them coming!  I will post the results as soon as I get the checks done.

[Steve Wood]

I just plug the the sparkplug into the wire and lay it on the valve cover...that makes the ground.  It is very hard on the module to run the engine without all wires connected as he said altho many do it....I always wonder how much life they took from the module doing that, but?


Be sure you disconnect one injector connector at a time and "prove" #4 as the culprit.  I have been fooled before, cold pipe or not. 


Also be sure your egr valve plunger is not rusted partially open and that there is no leaks around its base.

[Recap]

Does checking the EGR involve removing it?  Have never had it off, so............ 

[Steve Wood]

crank the car up and let it idle.  before it gets too hot, stick your fingers under the can on top of the egr that contains the diaphragm. There are holes in the lower side that allow you to put your fingers on the actual diaphragm.  Lift up, the car should stumble badly...that means the plunger in the egr is at least moving...does not say for sure that it is completely closed, but...it's a start.

[Recap]

Well I think I have figured out what is going on.  Checked to see if all cylinders were firing with my new widget and to my surprise they all were.  So started to pull off the passenger side valve cover.  It's been 5 years so I forgot what a pain it is to remove.  Any way, got all the bolts removed and tried to get it off.  Forgot you need to remove the heater pipe running along the valve cover.  As I  was trying in to remove it with the heater pipe still installed I noticed a piece of blue anodized aluminum hiding in the from of the head!  Looks like I had a rocker arm give up the ghost.  Never would have guessed that one in a million years as the car has basically been siting for 5 years straight.   So hopefully once I get the valve cover off I don't have too much of a mess.  Thankfully I think T & D are just up the road from me about 15 miles.  Thanks everyone for all the input.  Will let you know the final out come once  I get the valve cover off.  My back had had enough for the night as I just got my 4 post lift assembled over the weekend and the GN was parked underneath it and the lift was just high enough to park the GN under it.  Oh my aching back! Bad planning on my part.

[Steve Wood]

I love my four poster....

sounds like you are making progress....I was pretty sure it was firing, but, I figured you had to prove it to yourself. 

I hope it is not too badly messed up.

[Recap]

Drained the rad and removed the heater pipe so I could get the valve cover off and inspect damage.  The rocker arm on cylinder 2 exhaust was the one that broke.  The pushrod on intake 2 was bent so bad I had to pull it out with a pair of vise grips!  As I am this far I think I will pull the intake off and make sure the lifters and cam are ok.  The intake has been leaking from the back for years so I can kill 2 birds with one stone.  I think cause of all of this is the splash shields on the valve springs.  It looks like there is a clearance issue with the roller rockers and the bigger cam.  I read in the GNTTYPE archives that .450 was as big as you can go without out having an issue.  Need to check my cam card, but am pretty sure the lift is more.  When the guy originally built the heads he did not put the splash shields on.  He also installed PC seals on the intake valve and no seals on the exhaust.  This made the car smoke like a fog machine at idle.  So I re-installed the splash shields, which only marginally helped and the installed seals on the exhaust valves which ultimately solved the issue.  So it looks like my fog fix caused the problem.  I can see some minor marks on the underside of the other rocker arms, but it was barely enough to remove the blue anodize.  Also better check all the other pushrods to make sure none of the others are bent.  Will try and post some pictures of the damage tomorrow if I get a chance.

[Steve Wood]

Roller rockers often cause problems, but, you know what you are looking for so...Hopefully the cam is okay. 

I am not so sure that the lift is the problem, but, I think it is more the rockers.

Strange that you had a smoking problem on the exhausts as they don't suck oil like the intakes that see vacuum.  The seals should have fixed that problem unless the guides are worn out.

At any rate, looks like you are on the road to getting it fixed.  Glad you figured it out.