Ignition Module Failure....???"

[LannyL81]

Driving down the highway on Friday....all of a sudden I hear and feel a vibration / engine knocking....rough running...whatever you want to call it. Get off highway and having trouble keeping it running....sounds like I have lost a cylinder or something.

Will not idle....runs really rough. Oil pressure is fine.

Long story short....I removed valve covers, everything appears fine and all are moving normally.
Pulled #7 plug out...it is wet with fuel.
Run engine for about 20 seconds and then using my hand check the temp of each header tube.....find that cylinders 4, 6 7 are much cooler than the others....okay burned hand on the others.....

I originally thought I had spun a rod bearing from the noise....but now I am thinking the ignition module has failed. Any thoughts????

UPDATE: 4/9....see my latest posting.

 

[Hib Halverson]

If the ign. module fails the engine won't run.

Your engine is running...not well, but running...so it's unlikely the module has gone bad.

 

[bill81vette]

Check plug wires..see if they melted some where...
or distributor going bad..rotor???
something is stopping it from firing in those cyl's

Good Luck!!!!

 

[6880 Mike]

It may have jumped timing. How old is the timing set?

 

[LannyL81]

All the plug wires look good...nothing burned or melted.

The timing set is a double roller I put in when I did the rebuild about 8k miles ago. I will check the timing by aligning the balancer mark with the distributor rotor.

Distributor is about 9k miles old.

The ignition module is one that came with the car when I got it in 2000. It is a Wells brand....which is far from the best.

The distributor came from Performance Distributor.

I guess it is possible the coil has weaken and not able to supply all cylinders...but I would think that would be on a radom basis.

I am stuck for now.

 

[Hib Halverson]

If this is is a case of some but not all plugs firing, it's unlikely that the ign. module is the cause. Also, Wells brand ignition parts is actually one of the better brands of replacement ignition parts on the market. Better by a long shot than the low cost stuff you might find on eBay or at a mass marketer.

Based on the OP discussing #7 wet with gas, have you checked to make sure the carburetor ok? Internal leaks? Floats stuck and so forth?

 

[tmkassin]

Ouch! Sure sounds like it jumped the timing. Have you checked it with a timing light?

 

[LannyL81]

Just check timing....rotor is way past #1 at TDC.....looks like it jumped a tooth.

So....as I have never experienced this before...still puzzled as to how a double roller could jump a tooth and the chain is not all that old / miles....anyways....where do I go from here??

Is there enough tolerance in the engine timing for one tooth so that I do not have a bunch of junk valves and pistons??....or am I looking at another engine rebuild/replacement???

 

[tmkassin]

It could be just the distributor. Pull it out and inspect the gear that engages the cam. If that is ok then the next step is to remove the timing chain cover and inspect the chain and gears.

 

[GerryLP]

It could be just the distributor. Pull it out and inspect the gear that engages the cam. If that is ok then the next step is to remove the timing chain cover and inspect the chain and gears.

Concur on the course of action, unless perhaps the distributor hold down clamp was not cinched-down or even not holding the distributor body at all?!?!?!

I was originally thinking on the problem while reading the posts that perhaps the coil could be shot, for If you found 4,6,7 cold, then those are the cylinders next to 3, 5, and 2 respectively in the firing order...but you found it skipped a tooth (hopefully on the distributor), so never mind...

Good luck!

 

[LannyL81]

I was hopefull.....but pulled the distributor out and the gear is fine. Looked at the cam drive gear as well....looked fine.

So timing jumped. I am going to remove the valve covers again and watch #1 valves while I rotate the engine to double check that the balancer has not slipped.

After that all I can think to do is to drain coolant and remove front cover to verify if timing has jumped. If so, then pull heads off and check valves and pistons. Well, have to drop the oil pan first before removing front cover.

Time to get another engine stand and hoist...........

 

[Tim81]

I hate to say it but I agree that the timing has jumped, Here is a thought before you pull the heads check the compression on the dead cylinders, if the compression is good then I would expect the valve train to also be fine. Hopefully its just a timing set. Good Luck Tim

Just had another idea, when the computer went bad on my car it ran like you have described, pull the 4 pin connector that runs to your dizzy and see if the problem goes away...

 

[TimAT]

Better than 99% of the time, if the CAM timing/chain jumps a tooth, you get to walk home.

I'd suspect the ignition- cap/rotor/coil before anything else. As Hib noted- ignition module is really not a likely suspect. As a solid state electronic device, it works or it doesn't. I would check the wires from the pickup coil- it's possible one or both of those is getting bad.

Unless you already have the rocker cover off, just pull the spark plug and stick your finger in the hole (or a compression tester) and bump the starter- when #1 comes up it'll register on the gauge or blow your finger off the hole. Also an easy way to get close to #1 on the balancer..

 

[LannyL81]

The engine will still "run"....not very well....but it will still move the car.

Unless the balancer has shifted such that I no longer have a #1 TDC reference, then timing has indeed jumped....no doubt about it. Confirmed by seeing distributor rotor between #1 and #8 when balancer indicated #1 @ TDC.

Oh well...I had low compression on the engine anyways....speculate that the moly rings never bedded-in...even though I had the block honed for moly rings. Anyways there is some reason why I had such lousy compression....and now I get to find out why.

Not going to be anytime real soon though. Do not even have an engine hoist or engine stand anymore.....sold them. Have lots of house projects to be done before the engine comes out. I will drain the coolant and pull the water pump and front cover off....gotta see what the timing set looks like. If anything "good" I will take a picture and post it.

 

[TimAT]

Before you rip the front off the engine, pull the left rocker cover and #1 plug. Watch the valves on #1- Intake will open and close, then the piston comes up- you can use a small screwdriver or wood dowel to GENTLY probe into the cylinder and feel when the piston is at TDC- that will prove your balancer marks.

Easier to do that to prove the balancer than rip that front cover off. Won't prove the timing chain but it can be a bear getting the front cover back on.

I've never had any problems with moly rings seating- do a leak down test before anything. Cast iron rings seat nearly the first trip up and down, moly may take 50-100 miles, and chrome rings should be in there by 500. Unless your builder stacked the oil rings or didn't stagger the end gaps correctly.

 

[GerryLP]

Lanny,

Have you tried running the engine since the problem appeared? Often is good to re-visit square one to let one know that one has not been chasing one's tail.

It has to be something more simple than piston rings not bedding down.

Also, please remember that almost no one runs their engine at top dead center. The disparity you may be noticing is simply the initial timing you may have had set in the distributor. Go to your local speed shop, and get an MSD or other brand timing strip sticker set. It comes with the correct length for differently sized vibration dampeners. Normally, you'll only need the one for the diameter of dampener you have installed. These strips will show you up to 45 degrees. Then, match the zero on the strip with the dampener's groove. Next, mark the #1 lead position on the rotor cap, and transfer it to the distributor's cap base. Move the rotor cap out of the way. Once you determine that the piston is on it's way up on the compression stroke, align the distributor's rotor with the mark you transferred. Now look at the timing strip on the dampener, and read off the degrees advanced or retarded.

If the engine fired off normal as suggested in the first paragraph of my reply, then you likely have a coil going bad (when it heats up, the windings are separating or something), or it is q different problem altogether.

If the engine does not fire off, or if it is as bad as it was, then try my reply's 3rd paragraph.

I have some more suggestions available, but you must try these ones first.

 

[LannyL81]

I do not have a stock style balancer....have one that has the tape on it already. I think it goes to 60 degrees or so.

And yes I am going to put the distributor back in at the correct position and restart engine before I tear anything more apart. Well since I have the spark plugs out and headers hanging I will do a compression check on a few of the cylinders first and then go for a start and see what happens.

Going to take some time to get all of this done.

 

[LannyL81]

The balancer has not slipped, it is fine.
Put the distributor back in and set with #1 at TDC. Did notice that the oil pump shaft sure wiggles around alot.....the sleeve must have slide down or something.

Anyways put the compression gauge on #7...got 130....same as I did last summer...low, but the same.

Blocked-open the carb and redid.....got 132.
Squirted oil into cylinder....got 135....so the low compression is not due to rings...must be something going on with the 882 heads I have.

Anyways, going to pull all the spark plugs back in and see if engine runs normally or with problem.

Will probably pull the heads off and get a set of alumimun one of these days soon. Just need to find a spare $1000 sitting around.

I will update with how the engine does later.

 

[LannyL81]

Got engine to run....did not have time to get a timing light on it....but something is still not right, timing seems to be way off and I hear a knock...sounds like a hammer hitting inside the block...got to get a timing light on it tomorrow....I still might have a spun rod bearing(s).

Have to figure this out.

 

[GerryLP]

Lanny,

On your first post you said that you had to get off the freeway, and that it was running rough, but that the oil pressure was fine.

But before I can tell you what I am thinking, a quick trick is that while rotating the engine (by hand) on the power stroke, Set the dampener zero mark to 12 or 14 degrees on the degree plate, and then you can cinch down the distributor hold down fingers with the rotor aligned with the #1 cylinder wire electrode at the rotor cap. This essentially will give you an initial timing of 12 or 14 degrees. No light needed.

In 2007's Cruise Fest, I was heading down from Colorado Springs to Rio Rancho, NM, and my Vette ran perfectly most of the way. Once I left behind the New Mexico's northern mountains, I left behind the cool dense air, and entered nearly 40 degrees warmer of day temperatures. It was hot and muggy. It was approximately 95 degrees and 70% humidity. It was hot indeed. Well, just a half hour north of Santa Fe, the Vette started surging and knocking and studdering, and I took the next freeway exit, the exit was about 10 miles to the town of Glorietta. I barely made it to the local gas station, and luckily, it had some protection from the downpour and lightening from the Monsoonal thunderstorm.

The engine smelled like it had a lot of fuel dump into it, and it would not start. I waited about 20 minutes for it to clear, and I was able to start it. Again, it was hard to keep running, and I had already removed the air cleaner to look into the carb, when I saw it happen...gushes of fuel was entering the carburetor through the rubber hose that connects to the charcoal canister.

Well, I thought I would have to tow her to the house, but when Investigating possible causes, I loosened the gas tank cap, and a very audible pressure release let go of the pressure in the tank, and I saw the fuel gushes stop and the engine began to run better and better as it was burning off all the excess fuel.

When I hit the road again, I left the gas tank cap loose, and she ran fine all the way home in 100 degrees weather.

Since then, I thought that the stock gas cap on car had gone bad, but when I replaced it, it was still doing the same. The only constant or common condition is heat from any particularly hot day.

My theory is that the liner in the fuel tank (I believe that there is one), separates from the fuel tank walls, and this pushes the fuel towards the charcoal canister, or the pressure buildup siphoens the fuel towards the charcoal canister.

That's why your story was sounding very similar to me.