quote:


it was a coil
thanks

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by Allantesource

the ignition coils if original are the most cause of a miss.

Spark plug wires are the second most common cause. The plugs are platinum and probably are fine.  GM recommends a 100,000 mile change interval, but a Northstar powertrain engineer who used to post here said that change interval was arbitrary. They just didn't want to say anything would be good forever, for the life of the car. But the platinum plugs probably would be. I just replaced 4 originals on my '91, and they had about 180k miles on them.  I had replaced the front 4 at about 100k miles and just had never gotten to the rear bank. The only reason I changed them was that I decided to replace the original spark plug wires. The rear plugs were still fine.

I really doubt that replacing your spark plugs will have any impact on your problem. You can isolate the problem cylinder through the on-board diagnostics, and then replace the coil. Or you can buy a coil and swap it through all 4 positions until you eliminate the problem one.

quote:

By Allantesource

In addition to the coils, '93 PCM's are also a real weak spot.

I have not seen an original still in place in years. Apparently most have needed replacement over the years.

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ORIGINAL: Stealth

'93 unique topics

- plenum failure
- flying soft tops
- flying boot covers
- headbolts
- struts
- transmission
- overheating
- oil leaks
- ???

.. to come ...

quote:

by Allantesource

There is a definite reliability gap between the early Northstars and the 4.5's. Now that GM is not replacing '93 Northstars under warranty, that alone is a real good reason to opt for a Phase 2. The head bolt problem is expensive to fix, not to mention the oil leaks and the plenum issues.

quote:

by unk

on the cover for a 93, GM offered two designs intake mainifold cover...
- ORIGINAL design used bolts without grommets,
- second design is with grommets
 
newer design pn 17090937 costing around $210 if avail, shared with other models such as EldO '94
 
what do the grommets do?

quote:

by Allantesource


With grommets means that there are rubber grommets under the cover retaining bolts that will give if there is an explosion inside the plenum. Without the give of the rubber grommets, in the event of an internal explosion (such as from a leaky fuel pressure regulator) the plenum blows up and has to be replaced. I have no idea if the plenums will accept both covers or not. The only plenum I replaced personally was a later style, and it had been hit and cracked by a piston that went up through the valley. I sold an early plenum to someone who had the explosion in a very early '93 Allante'. But he would have used the cover that came with the one I sold him. You could always pick up a plenum off a '94 Concours, Seville, or Eldorado Northstar. Those are all the grommet style.

quote:

by jefft

Wait a minute, EXPLOSION?  WHAT EXPLOSION.  Every day is a new learning experience.
 
Just when you thought buying a 93 was a "safe" proposition ol Dick tells us all about the EXPLOSION in the valley!  Jeezsch!

quote:

by Allantesource
The plenum issue is explosions in the plenum when the fuel pressure regulator malfunctions and leaks gas which can get ignited. The "fix" was to place rubber grommets under the cover bolts, so if/when there is an explosion, the cover lifts to vent the force generated and the plenum doesn't blow apart. That whole plenum system was redesigned for 1995. Early 1993 Allante's did not have the cover grommets. All were supposed to be modified, but as with every recall, some were missed.

quote:

by unk

An explosion can be caused by a faulty FPR

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ORIGINAL: foxpaws

When the ASA (Auto Inc) website has an article on rebuilding engines and the single Cadillac engine they quote.... "Cadillac's 4100 engine has suffered from a series of glitches including overheating, cracks and bottom-end knocking, most stemming from its somewhat unusual design and cooling system requirements." along with only 2 other brand name engines - Chrysler's 2.2-2.5 and Mitsu's 2.6 you know there has to be more then "legend" to the moniker "Hook and Tow"

Article quoted (the bad engines are listed about 1/2 down in the article...)

http://www.asashop.org/autoinc/june99/mech.htm

No Northstar on that list - and I have the late series Northstar - I hopefully won't burst into flames anytime soon...

quote:

by the Engine Rebuilders Association (AERA)

In researching this engine, we discovered that few rebuilders are overhauling Northstar V8s - not because these engines are lasting forever (they're not) but because the Northstar V8s are such expensive and complex engines.

Cadillac has no reman program for Northstar V8s (if one fails, replace it with a new one).

None of the major production engine rebuilders are doing Northstar V8s, and some rebuilders told us certain critical internal parts are unavailable (such as oversize crankshaft bearings).

Add to this the fact that the cylinder liners can't be replaced or overbored and it doesn't leave much to rebuild.

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ORIGINAL: hyperion

"B--U--T????? My neighbor in Texas bought a 93 Cad sedan for his wife for "economies" sake.  He was impressed with the first car engine that you went 100,000 miles before even replacing the sparkplugs!!
Couldn't answer my question about how difficult it might be removing some spark plugs from an aluminum block engine after it had gone those 100,000 miles!