Jump to content
CaddyInfo Cadillac Forum

Engine cut out at high rpm -93 Northstar


jlinde

Recommended Posts

My 63000 mile Eldorado TC has started since around a year to cut out(I do not know if that is the right

vocabulary for rpm decreasing) for tens of a second. It happens at full throttle: cuts out -accelerates cuts out etc until I release

the gas pedal so the engine goes back to around 4500rpm. The fluctuation up and down in rpms is very fast - feels like part of seconds.

In fact I do not know if it is the rpms in engine only or if it shifts up and down. I do not like to test the situation for the moment

as I am out for a tour and the Eldo works beautiful except for this and no codes at all. I have some extra parts with me on the tour

like ignition module and PCM. If it is problem with fuel pressure the engine would be dead a little bit longer than just tens of seconds

in my opinion. /Jan L.

Link to comment
Share on other sites


With no codes, including a code for a miss or a near-stall, I'm a bit mystified. It could be the rev limiter, which cuts off the gas and suppresses the miss and stall codes, but that shouldn't kick in unless you hold the transmission in a lower gear and deliberately over-rev the engine. In fact, I think that the PCM will shift the transmission anyway if you try that, although I haven't tried it.

One possibility that might cause this and would not set the miss codes would be the crank or cam sensors. But, those rarely give problems on the 1993-1999 Northstar. You might check the wiring and connectors to them, though. But, on OBD II systems, an intermittent crank or cam sensor will set a code.

I would try a tank of premium gas. You are already on a tour, and that kind of driving is great for cleaning out the combustion chambers of a Northstar, and putting a few tanks of gas through a car tends to flush out traces of water condensation and good quality gas will clean the injectors a bit. If that doesn't help, then you really should look at things like the fuel filter, plug wires, and loose connectors on the crank and cam sensors and the ignition module and such.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Link to comment
Share on other sites

I think that what you say about good gas -there is a special high priced Shell available here in Europe-

is the best I could try for the moment. The miss feels in fact like rev limiters that I have experienced on

some of our older 94 V6 Pontiacs when trying to rev the engine up in Neutral. Maybe I can later on check the

instrument panel display for the parameter for engine rpms.Also maybe use the possibility to shut off the traction control

for a couple of ignition cycles. Just to exclude the ABS-Traction part though that would normally display 'Traction active' .

/Jan L.

Link to comment
Share on other sites

The rev limiter only operates in neutral. How's your fuel pressure and fuel filter? If it only happens at WOT, maybe it is fuel starvation, though your description does sound more like ignition.

Link to comment
Share on other sites

I cannot say I have ever heard of that happening in gear. The rev limiter kicks in in park and neutral at 4500 rpm.

GM FAN FOREVER

Nice, clean, luxury= fine automobile

Link to comment
Share on other sites

I've just learned a lot about the rev limiter. I'm not surprised that it isn't needed when the transmission is in gear because the PCM can always upshift, no matter what the PRNDL switch says, and I've heard it mentioned here in the past that this does indeed happen. Also, I hear that it is set at 4500 RPM and operates in Park and Neutral, which is good news because high RPMs for unloaded engines is bad news, so I understand.

Could it be the PRNDL switch? I don't see how the PCM could both think that the selector is in Neutral or Park and still put the transmission in gear, but if the cut-out is happening at about 4500 RPM that might be something to look at.

I've had high-speed cutouts in cars a few times over recorded history, and most times it was coil breakdown. With the four coils of the Northstar, all of the coils breaking down at the same time and to the same amount seems improbable. But, the last time this happened to me was with a Quad 4 HO, which had two coils and an ignition system very similar to that of the 1993-1999 Northstar. Could the cut-out be due to losing two cylinders, or four cylinders? If so, you might look at the coils.

Why did you replace the PCM and ignition module? Were you trying to fix this problem? Did you see any change at all?

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Link to comment
Share on other sites

I have not changed the PCM or Ignition module -I have them with me just in case-the 93 runs excellent so far

except for the mentioned problem -I am down in Europa and the average is 23 miles per gallon.

Although around 5 years ago I changed the PROM because of some 'chuggle' with the original one. I also had a

kind of hesitation at startup -some code like '24x ref signal' and then I found a new Ign Module on ebay and

replaced the original and have never seen the code since. I will do testing with different things later on

just wanted to get some hints - I have another 2000 miles to drive. Before this ongoing trip I only got

this cutout once and that was last summer and I thought the fault was just intermittent so I did no testing.

As said fuel starvation probably feels different but I have no experience with injected engines - I have a

35 Auburn and the mechanical pump on that one doesn't deliver enough so I added an electrical one but that was

an easy problem to solve.

/Jan L.

Link to comment
Share on other sites

The 24X reference signal was one of the crank sensors or a line from the PCM to the spark control module, and was probably a connector. Modules very rarely fail without cause, such as hooking up jumper cables backward or a lot of salt on the electronics.

Plug wires are another matter. As are spark plugs. At 60,000 miles you could be ready for your first plug change, too.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Link to comment
Share on other sites

I've just learned a lot about the rev limiter. I'm not surprised that it isn't needed when the transmission is in gear because the PCM can always upshift, no matter what the PRNDL switch says, and I've heard it mentioned here in the past that this does indeed happen. Also, I hear that it is set at 4500 RPM and operates in Park and Neutral, which is good news because high RPMs for unloaded engines is bad news, so I understand.

Could it be the PRNDL switch? I don't see how the PCM could both think that the selector is in Neutral or Park and still put the transmission in gear, but if the cut-out is happening at about 4500 RPM that might be something to look at.

I've had high-speed cutouts in cars a few times over recorded history, and most times it was coil breakdown. With the four coils of the Northstar, all of the coils breaking down at the same time and to the same amount seems improbable. But, the last time this happened to me was with a Quad 4 HO, which had two coils and an ignition system very similar to that of the 1993-1999 Northstar. Could the cut-out be due to losing two cylinders, or four cylinders? If so, you might look at the coils.

Why did you replace the PCM and ignition module? Were you trying to fix this problem? Did you see any change at all?

Well the quad 4 is actually pretty differnet than the northstar because the quad 4 has the coil over plug setup that is sealed and does not use wires, and the northstar has 4 coils at the firewall and plug wires that run to each cylinder.

Maybe it has to do with your NSS not knowing it is in gear but it seems that it would throw some kind of a code

GM FAN FOREVER

Nice, clean, luxury= fine automobile

Link to comment
Share on other sites

Actually the Quad 4 HO that I had in my 1990 Grand Am GT did have two coils. The plug boots were mounted directly on the coils, so they might be considered a coil-on-plug design but they used two coils, not four.

Over the seven years and 90,000 miles that I had that car, I got to know it pretty well. The only problems it gave were a coil breaking down in the first year, a PCM (so the dealer said) in the second year, a cracked head in the third year (so they said; when I got home the head hadn't been changed; the tech build engines in his garage including a Quad 4, and he wasn't there anymore when I came back for service a few months later).

I kept LokTite for the ignition cover bolts, anti-size for the plug threads, and dielectric silicon grease for the plug boots, plus three torque wrenches just to change the plugs. I was (am) picky about perfect engine tune, so I did that several times. I was all too familiar with the plug and coil arrangement, and the issues of putting the coils back on over the plugs properly. I quickly found that most techs did not have the patience to do that properly and always did it myself after that. Only once, after the coils were changed, did I find out that the plugs had anti-seize and were properly torqued, and the plug boots had all been seated properly when I got home.

I ended up trading that car for my 1997 ETC; I had been watching the Northstar for years and picked the ETC over the STS because it was 250 pounds lighter and 0.2 seconds quicker 0-60 mph than the STS, according to Car & Driver, with a best published 0-60 mph time of 6.3 seconds. The Northstar project began with something they called a Quad 8, and lots of things are similar. I consider the Quad 4 a direct ancestor of the 1993-1999 Northstar, although the auto journalism community refers to the Northstar as a descendant of the Lotus-designed LT5 used in the Corvette ZR-1 from 1990 through 1995 and don't mention the Quad 4 in that connection anymore.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Link to comment
Share on other sites

Is this problem solved yet?

I would hook up a fuel pressure gage and tape it to the window to see if the engine is being starved. Check for collapsing fuel line

Also check the power feed to the coils, its possible that vibration or torquing of the power train that occurs at a specific rpm is interfering with that connection. Just a long shot with that thought, but this sounds like fuel problems

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Hi again, now I am home in Sweden again after the 3rd trip (4000 miles) down to southern Europe.

The old Eldo TC has been behaving very well average 22.3 miles per gallon driving in the Alpes

Italy, Austria, Germany, Slovenia and Croatia -up to around 80 mph on the autobahn being passed by

Mercedes's, Audis and BMW's driving up to 150-160. I had no idea of competing with those guys though.

Anyhow the rpm is still being limited now and then to these 4500 especially when I step on the gaspedal

for kick-down and accelerating.The engine simply cuts off and comes back in tens of seconds just like

in Neutral or Park. I will take it out for testing in a couple of days to watch more thoroughly if I lock

the trans in different gears./Jan L.

Link to comment
Share on other sites

It seems like the engine is being starved, as if the fuel pump can not keep up with the engines demand, or the fuel filter is clogged not allowing sufficient flow.

I would tape a fuel gage to the windshield and watch it when this happens.

What speed are you at when you hit 4500 rpm? Could your speed be limited to 90 mph or 144 kph?, because of suspension issues?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

If the tires, brakes, suspension, and drivetrain are in good shape, the ETC/STS is intended to hold 120 mph (195 kph) on the Autobahn all day long, or for at least a full tank of gas, without straining. You need Z-rated tires to get the 125 mph governor taken off, after which the car was expected to top out at 150 mph (240 kph).

But it does sound like the drive train is just fine, if you average almost 23 mpg on a 4,000 mile trip that includes a drive through the Alps. I'm sure that this is a fuel starving issue, as BodybyFisher says, because the long drive would have brought out any other issues.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Link to comment
Share on other sites

I am not sure if the 93 would flash a code for a suspension problem like an inoperative strut, I know the 91 had a special method to extract the suspension codes. But on later year Northstars, if there were an ABS or Strut issue the speed is limited to 90 mph, but a message is flashed on the dash. I am not sure how speed is limited does anyone know?, I would think stopping the fuel flow could be potentially dangerous, anyone know how speed is limited?

Does this happen for the 93?, will it limit speed and than flash a message on the dash that speed is limited? I was just sitting here thinking.

The guru was big on taping fuel pressure gages to the windshield, my hose is not long enough, to do that, but I guess, I could lengthen it with high pressure hose if I needed to..

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

  • 3 months later...

Just wanted to tell that the problem got solved by putting in a new ignition module (but with

the old ignition coils) so the ETC is back to its normal bahavior at high rpms (OK up to 6300-6500)

I put in a new gas filter and checked the fuel pressure which seemed OK between 40-50 psi

depending on throttle opening so I decided to buy a new Delphi ign. module on Ebay. I wonder if those

modules can be taken apart and checked for faulty components....

/Jan L.

Link to comment
Share on other sites

  • 1 year later...

Hi, this type of fault is still showing up but more often consisting of a miss or hesitation at around 4500 rpm and up

and it means that I can never thrust the engine to give full power at kick down. I have recently done a couple of trips

totally 3000 miles and the Eldo TC behaves just beautiful =23.3 miles per gallon on the Autobahn at 75 mph

AC working and so on. I have checked the fuel pressure and despite showing OK I changed fuel pressure regulator

fuel pump and filter. I have also changed the PCM to my newly remanufactured spare one and the TPS to another

used one. I cleaned all the reachable electric contacts around the relay center under hood. The things that I have not

touched is the A and B sensors and cam sensor and some electric grounds. During the last 2 years the only PCM code

I got is ONE P083 (pointing to A or B sensor and ICM). As it feels that all the cylinders are missing at the occasions

and as there are (after what I hear) no exhaust explosions I am thinking of that the injectors just cut off for tens of seconds

-but why??? I have been trying to solve this problem for a long time now and just hoping for some other approach.

I can still change the ICM and the cables again and the crank- and cam sensors and maybe some relay that gives 12 volts

to the injectors. As I have never seen 'TRACTION ACTIVE' during the hesitation I do not think the ABS computer

is involved.

/Jan L

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...