Northstar rebuild: Will style (Page 66/119)
IXSLR8 JUN 21, 01:15 AM
Well, hats off to your build, Will! That's great results.
Will JUN 21, 06:26 AM

quote
Originally posted by 1fatcat:

I know this is an old quote, but I've done head gaskets in 6 of these engines to date. Used timeserts in every headbolt hole of every engine (120 timeserts) never had an issue with a single one.



My engine's built in a '93 block (has block drains) and I had zero problems with timeserts.
Will OCT 08, 10:40 PM
In addition to getting started on the 2.5" stainless X-pipe exhaust that I realized I could fit, I swapped out a couple of coil packs.

The "ignition drops" I've mentioned before were getting pretty bad. The car was difficult to drive in higher gears below 2000 RPM under load and pretty much wouldn't pull cleanly from 1000 RPM in 4th or 5th.

I swapped out one of the two coil packs I had out in the shed. It was worse. In addition to ignition drops being at least as bad as the original coil pack, it also had a bad coil and dead miss. Bleh.

The second swapped pack was much better than either original or the first swapped pack in terms of ignition drops and did NOT have a miss. I left it installed. It seems to have ignition drops based more on time than anything. When I was out for the test drive, sometimes it would pull cleanly from 1000 RPM in 5th uphill and not have any problems until it had a cluster of 3 or 4 drops at 1800, then keep pulling. Sometimes it would have 2 or 3 drops at 1200, then keep going. Sometimes it would be clean all the way from 1000 to more than 2000.
The original coil pack wouldn't allow the engine to idle for more than a few seconds before an ignition drop stalled it. The current coil pack allowed the engine to idle for more than a minute when I got back from my test drive. During that period, it experienced a couple of ignition drops, but none of them stalled the engine.

I've never seen the ignition drops happen above 2000 RPM. An ignition drop, if you remember from earlier in this thread, is a momentary loss of ignition. I can be seen by a flicking of the tach, heard in the exhaust note and felt via a split-second power interruption. Since the power delivery is actually interrupted and the tach flickers, the problem must be either in the trigger signal path or power. The trigger signal starts at the crank sensors then goes to the coil pack (ICM) to be translated into something the ECM can understand as well as driving the ICM's tach output, which goes to the tach. Somewhere in that path is the problem.

I guess it *could* be something esoteric with the ECM, causing it to drop the coil trigger signal while keeping the bypass line active. Not sure how the ICM would react to that. I suspect that's a long shot because the tach is showing signs and it is driven by the ICM using crank sensor signals, not by the ECM.

Ideas?
Will OCT 30, 11:30 AM
I scoped the crank sensor and ICM signals. The crank sensors are constant through the drops, but the ICM 4x and 24x appear to drop out during the ignition drops.

I was told on RFT that this is a known failure mode of the ICM's.

I'll do some more scope work today to try to confirm.
joshua riedl OCT 30, 05:40 PM
Are you sure this can't be a tuning issue? I had a similar problem after a cam swap and tuned it out in the AE vs AE pulse table. It seems plausible to me that if the car is going lean and the engine struggles, rpm's drop along with voltage until it recovers with an increase in blm's. I can't see your car so you obviously know more than me but reading your posts really seems like what I had going on.
Will OCT 30, 09:23 PM
Nothing's changed that would affect the idle tune.
It's ALWAYS had an idle surge.

This is not an idle surge.

Like I said... preliminarily confirmed with the o'scope.

[This message has been edited by Will (edited 10-31-2011).]

IXSLR8 NOV 12, 11:49 PM
How's it going on figuring out the ignition drops?
Will NOV 14, 08:44 PM
Slowly... didn't get to do any more scoping this past weekend. Working on getting the new exhaust welded up.
cptsnoopy NOV 15, 01:49 AM
My engine occasionally stops firing for 1 to 2 seconds and then runs normally again. Since I mostly idle the engine that is when I notice it the most. It happens rarely but when it does it lasts just long enough for me to think it will stall but it has not done that yet. Is this similar to what you are experiencing Will? My engine has new ignition components but it is using the 950 for fuel and spark management.

Charlie
Will DEC 12, 03:33 PM
Stops firing for 1-2 seconds and doesn't stall?
Your flywheel is too heavy

I've had the car up on ramps while I work on a Gucci new full exhaust for it... haven't done any additional work on the ignition drop problem.

Will probably also build my oil cooler setup before putting the car back on the ground.

These two products in parallel:
http://marineengineparts.co...html/product106.html



http://marineengineparts.co...html/product110.html



Should handle engine oil flow. The second also has a secondary cooler which can be used for the Getrag (or F40) transmission fluid.

The line drawings are a little deceptive, as the oil section of the dual cooler is essentially the same as the entire single cooler.

I have a horizontal tubing run across the forward cradle crossmember from the right coolant pipe to the thermostat connection into which the dual cooler can be substituted, as well as the vertical run from the left coolant pipe to the upper coolant connection on the waterpump into which the shorter cooler can be added.

I need two of these because the largest connection I can get is 1/2" NPT. 1/2" NPT hose barb fittings tend to have about 5/8" ID. Alan Johnson has said that no restriction in the external oil system should be smaller than the ports on the side of the block... which are 3/4" ID ( ! ). Two 0.625 ID orifi have greater area than one 0.750 orifice, so the pair of coolers will work just fine.

Also, the ben radii available for 3/4" hoses and fittings is significantly larger than that available for 5/8" hoses and fittings, making the whole setup easier to package under the car.

And I'll have to figure out where to put my Accusump...

[This message has been edited by Will (edited 12-12-2011).]