Cadillac Owners Forum banner

1 - 17 of 17 Posts

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #1 (Edited)
I am chasing a chuggle, acceleration miss on my 93 sts. I decided to clean the plates/spacers. Does exhaust gas get circulated here? If so where is the entrance? By the water jacket below the TBody? How do I clean them out?

Second Q, the gaskets on the bottom side of the phenolic space have a clear "TOP" mark on them. They face the bottom. Will that matter? If so whoever worked on it installed them on the wrong sides. Is there any chance I can remove them and reuse in the proper orientation! I'm having coffee, so any quick posters appreciated before I go out and destroy it. I think you will recognize this pic, it has "TOP" clearly imprinted on it.
 

Attachments

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #2
Re: Phenolic plates, gasket?

Point me to a HowTo on this anyone? Thanks in advance.

----------

Looked it up on Nalley GMC and it is NLA. I guess I am going to keep it as is.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
Re: Phenolic plates, gasket?

The only thing I can tell you is those ARE exhaust gas passages for the EGR.
I believe they originate by the EGR valve and pass through the crossover manifold, but that was designed large enough so it should never need cleaning. The "mouse holes" you are dealing with are another story. I believe that is a '93/'94 design only.
 

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #4
Re: Phenolic plates, gasket?

I cleaned them up, reinstalled as is. The gaskets would have torn for sure if I tried to switch them. I still have a slight miss, but much better. Drove 30 miles tonight. Smoother, but still a slight miss on acceleration. Gas mileage guesstimator was 4-5 mpg higher, so something helped. I am about down to dropping in a new or re-flashed pcm. I did tug a bit on the wiring harness which is below the throttle body as there was some potential problems with them shorting out there. This engine was rebuilt by gm dealer at 70k, is now 135k. It seemed fine by appearance. Couldn't see the area that can sometimes touch the exhaust.

I swapped in a new ignition module, the one under the coils. I swapped a used set of coils in. New wires. Plugs are not new but look good, maybe a bit white. I suppose I could still have coil that gives up under heat.

Misses a bit on off idle revs, and moderate acceleration. Kick it down hard, and it sounds pretty good. Any other thoughts to check??
Thanks in advance.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,438 Posts
Re: Phenolic plates, gasket?

Make sure the ICM plate ground strap is installed and the terminals are clean and tight.

Ranger (???) posted pictures of the ground strap a week or so back ......... Engines; Northstar or Tech Tips
 

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #6
Re: Phenolic plates, gasket?

I was looking at that tonight as I was swapping in coils one at a time. I will search for that.
 

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #7
Re: Phenolic plates, gasket?

I have searched for over an hour and cannot find a pic of the ground strap. Is it a separate strap or part of the harness? I am heading out to look. I did switch the icm and may have easily buried a strap underneath as it was cold out that day. Stupid, but a potential easy fix. I think that's about when my issue showed up.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
Re: Phenolic plates, gasket?

I think this is the ground Sub is talking about



But I'm not sure that ground is for the ICM. I would expect the ICM to be grounded here at the mount. Unless that wire is connected to the ICM (and I don't remember that (but that's not saying much)), it can't be an ICM ground. Trace that wire back to it's source. THAT is what it is grounding.



I just replaced the ICM on my wife's 3800 '05 LeSabre last winter. Same set up and there was no ground wire.
 

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #9
Off idle lag and acceleration lag

93 n* just isn't right. New ckp's, new wires, new icm, no leaking from fuel regulator, no vacuum leaks found spraying carb spray around and under intake, erg cleaned, phenolic spacers and square ports cleaned. Spark plugs look good but maybe a bit white. I'm fishing for leads here. Anyone?

I have read about the " mouse holes" in the intakes. Should I have run a flexible brush or something through them?

I read there was a problem with crosstalk interference with 93-94 pcm's which would cause these symptoms? I guess that's probably next. It's getting to be expensive just throwing parts at it. The pcm tag looks original. Any way that can be looked up to see if Cadillac ever reflashed it?

Revving it from under the hood you can hear a big gulp of air rush before it kicks in. Makes me think of a vacuum leak.

As always thanks for any response.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
Re: Phenolic plates, gasket?

Please do not start multiple threads on the same problem. It just makes it hard to follow and hard to help you.

Threads merged.
 

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #11
Re: Phenolic plates, gasket?

No problem, I could change the title as it is narrowed down. I couldn't find any ground straps for mine. I have removed the icm and swapped one coil at a time in looking for a possible weak coil. When preparing to put the intake cover back on, I found this: this in a junction where all the injector wires run. It's very gooey and had electrician's tape separating the wires. Is that factory? There appears to be a crimp connector joining wire A from the two prong plug (hidden behind the wires) to wire C of the three prong plug visible to the right of the wires. Must be MAP sensor.
 

Attachments

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #14
Re: Phenolic plates, gasket?

Did all the idle learn and tps learns last night. I was optimistic because my iac was quite a bit off. It seems better, but still misses under load, unless I put it right to the floor. I went and ordered a new pcm as I have read that they needed to be replaced or reflashed for the 93-94 years. I keep making offerings to the mechanics idol. Getting sick of throwing money at it. I know I have to put my prom in, will I have to do the learn procedures again?
 

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #15
Re: Phenolic plates, gasket?

Reporting back for those who contributed, my bad. I decided to buy a couple plugs and start swapping them in one at a time. Cylinder one was carbon tracked. By the time I got to plug five it was wet with fuel. New plugs and it runs good. Haven't gone far yet, but hopefully it's another bad acdelco ??? 41-950?? I forgot already the numbers, but the recommended OEM.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,781 Posts
Re: Phenolic plates, gasket?

If the plug was carbon tracked, so was the plug boot. If you did not change the plug wire the carbon track will probably transfer back to he plug. Unless you change both at the same time you can chase this back and forth like watching a tennis match
 

·
Registered
1993 STS - Northstar
Joined
·
55 Posts
Discussion Starter #17
Re: Phenolic plates, gasket?

I did change the wires recently. No tracking on them yet, but something to watch. I realize the bad plug could be the result of another issue that may rear its ugly head again soon. The dreaded head gasket comes to mind, but the previous issue happened even after warmed up and my coolant levels remained even. I was looking again at the tracked plug and was able to chip the black off with my fingernail. There may be a hairline crack in the ceramic, it was hard to tell. I have put a few hundred miles on now with no issues. I am thinking I should do the idle and tps learn procedures again since I did it with the miss. Idle seems a little high now and letting off the throttle at speed is barely noticeable.
 
1 - 17 of 17 Posts
Top