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Discussion Starter #1
Hello:

My 81 Eldorado engine has started to run roughly in 4 cyl mode.
Sometimes in that mode I get a 44 error code and a check engine light.

The manul details a pretty lengthy diagnostic process, which I
am not qualified to execute.

I'm hoping that a shortcut might be in order: Can anyone recommend a very likely cuprit for this (some sensor, perhaps) that I can likely just replace and make it all better?

THANKS!
 

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Welcome aboard,
All my tech literature is at work but as I recall, the code 44 is a lean mixture code. Since you have a carburetor, there's a lot of things that can cause the code. I'd start by looking for a vacuum leak, clogged fuel filter, weak fuel pump, improperly adjusted carb (and I DON'T mean the idle mixture screws), and maybe even a bad O2 sensor.
 

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Discussion Starter #3
Thanks for the heads up. There a few things there
I can just try replacing.
Are there any of these that would react specifically in
the 4 cyl mode? Or do you suspect that the fact I
have only observed this in 4 cyl mode to be a
"red herring", since on the highway, the car spends
most of its time in 4cyl mode precludes me from
seeing the effect in 6 or 8 cyl mode...

Thanks!
DC
 

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Welcome to the forums, Memphis!

You're one of only a few I've seen with the 8-6-4 who kept it that way. I lot of people disable it and stick with straight V-8 mode all the time. It's a good engine, but the computers didn't always handle the transitions properly. You must've gotten a "Wednesday car."

Good luck with your problem.
 

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Discussion Starter #5
Elvis said:
Welcome to the forums, Memphis!

You're one of only a few I've seen with the 8-6-4 who kept it that way. I lot of people disable it and stick with straight V-8 mode all the time. It's a good engine, but the computers didn't always handle the transitions properly. You must've gotten a "Wednesday car."

Good luck with your problem.

---------------------
Agreed. Wednesday car for sure.
I think its pretty cool when it works. I show people
the active cylinder display and get oohs and aahs.
I read on the other thread about putting a switch in for that
wire on the tranny. That makes good sense, I think I'll do that.
 

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damn, this makes me want to get a car with the V8-6-4.....

when the 368 is running in V8 mode, how is the power? can it get out of it's own way? or is it as slow as my mothers '89 Brougham with the 307?

368 IS a Caddy engine, smaller brother to the 425, right? still, does it have pep?
 

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Discussion Starter #7
Night Wolf said:
damn, this makes me want to get a car with the V8-6-4.....

when the 368 is running in V8 mode, how is the power? can it get out of it's own way? or is it as slow as my mothers '89 Brougham with the 307?

368 IS a Caddy engine, smaller brother to the 425, right? still, does it have pep?
--------------

Caddy engine it is, as you described.
Pep? Sort of.
Definitely better than the 4100, but the car and
motor are both very heavy. The HP is low, but the torque is
good. It pulls itself up on ramps and passes with gittyup.
I'm not a performance guy really, so its adequate for me.
I like the confort and feel of the car (except going around turns)

I drove a 307 brougham, this is better, but not by a huge margin.
 

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Memphis,
Maybe it was an oversight, buy Katshot totally missed that you have the "V8-6-4 DFI (digital fuel injection)" engine. I have two '81 V8-6-4 Coupes. All V8-6-4's were fuel injected. Consequently, they have a computer, sensors and a ;throttle body. Also, the '81 V8-6-4 (also called "Modulated Displacement"; the new GM trucks are using a similar in principal design called "Displacement On Demand") was the first computer in a car with on board diagnostics (trouble codes). And, Cadillac was the only car for the longest while to offer the ability to get the codes from the ECC (Electronic Climate Control) Head.
He is right about a code 44 being a "low O2 sensor reading". The O2 sensor in the V8-6-4 is a non-heated type that sends a low voltage signal varying from 0 to 1 volt depending on the oxygen content in the exhaust. The computer adjusts fuel so that the resulting oxygen content causes the O2 sensor to "go back and forth" over .5 volt. If the computer does not see the O2 sensor's output voltage going back and forth over .5 volt, it sets a code and you get a check engine light (the voltage only has to go slightly over and under, but in actuality, it runs from about .4 to .6 even at idle; a much bigger difference under varying throttle).
As the sensor gets older, it's response time lags. Furthermore, as the sensor is about to go bad, it's voltage drops or goes completely. Since a "lazy" O2 sensor cause a reduction in performance (it reacts too slowly), it is a good idea to change it at least every 60,000 miles (Bosch recommends every 30,000 miles).
If your O2 sensor has been in for quite a while, I would recommend replacing it and resetting the code. In the very least, performance will increase.
Finally, it is good to see there are others with working modulated displacment engines. I swear by them and am even building one up for increased performance. Certainly, the engine is many times better than any 4100 (the POS that replaced it).
 

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Night Wolf. The 368, 425, 472 and 500 are in the same engine family, however, the 368 only shares it's oil pump and drive, oil pan and pickup, timing cover, pointer and chain and cam. All other parts are different. Many more parts can be swapped amoung the 425, 472 and 500. For example, the only difference between a 472 and 500 is the crank and pistons (except that the later '75-76
open-chamber heads use the same size valves but shorter because they don't have to reach as far into their "open" chamber heads). 425 heads can be used on 472/500's to increase compression to about 10:1, but they have smaller valves and ports. The increased compression gives about a 35 hp increase, and works very well for a low rpm toque motor.
For a quick lesson, in '68 Cadillac released the 472 with a 4.300" bore and 4.060" stroke. Beginning in '70 the stroke was increased to 4.304" to make the 500 that was used in Eldo's only through '74. In '75 and '76, all Cads got 500's. In '77, the bore was reduced to 4.08" and the stroke reduced back to the original 4.060" used in 472's to create the 425. Furthermore, in '80 the bore was reduced to 3.800" to create the 368 (same 4.060" stroke).

Pat

memphis said:
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Agreed. Wednesday car for sure.
I think its pretty cool when it works. I show people
the active cylinder display and get oohs and aahs.
I read on the other thread about putting a switch in for that
wire on the tranny. That makes good sense, I think I'll do that.
 

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Night Wolf,
The 368 is light years better than the "High Technology" 4100. After buying my first V8-6-4 car (my mother had had one for three years previous and I loved the power/mileage, especially compared to a 4100), I realized mine had a high idle problem that I believed was caused by the computer telling the ISC (Idle Speed Control) motor to make the engine idle too fast. However, the engine had no trouble codes stored. Upon checking with a Cadillac dealer in the Detroit area, I found a common problem was with a leaking intake manifold gasket (aluminum intake with cast iron heads were very common on GM and Chysler engines with the aluminum/cast iron combination). Also, I noticed about a half dozen V8-6-4 cars in the lot. Based on what I had heard about the V8-6-4, I thought they were used cars for sale. Upon further conversation with the service manager, I found they were employee cars! It seems even the dealer and employees perferred the V8-6-4 over the 4100 cars.
While the 4100 is ONLY rated at 5 hp less than the V8-6-4 ([email protected] vs. [email protected]), the 368 makes 65 ft.lbs. MORE torque and at a lower rpm (265 ft.lbs. @ 1600 rpm vs. 200 ft.lbs. @ 2000 rpm). The 307 Olds motor is rated at 140 hp @ 3200 rpm and 255 ft.lbs. at 2000 rpm. Even compared to the Olds engine, the 368 makes 10 ft.lbs. more torque and at 400 rpm less.
I have a '81 Coupe that had the Buick 4.1 V-6 (about 140 hp, but I can't remember the torque; however, it is much less than a 368) replaced with a '72 500 rated at 375 hp @ 4400 rpm and 525 ft.lbs. @ 3000 rpm (and yes, it really runs great!).
I am further looking into building up my '81 368 (V8-6-4) by installing the bigger valves out of a 472/500 (2.004"/1.625" vs. 1.700"/1.500") along with more cam timing (RV cam) and the throttle body out of a Chevy 454 (670 cfm and replacing the 65 lb/hr with 85 lb/hr injectors). I have already constructed a full 2 1/4" dual exhaust. My current problem is not enough fuel flow off idle/very low speed. However, once this speed is overcome, performance is greaty increased over the stock single exhaust with a catalytic converter.
Additionally, I have two other '84 Coupes which I removed the 4100's from. I have acquired two 472's. I am looking for more 500's. One of the '84's will get a 478 (.040" over 472); the other will get a 512 (.050" over 500). These cars are for me and my wife. The '81 with a 500 will be a winter car (it is rust-free, but I will keep it undercoated and washed frequently) and get the 500 replaced with, you guessed it, a V8-6-4 and computer/wiring).

Pat

Night Wolf said:
damn, this makes me want to get a car with the V8-6-4.....

when the 368 is running in V8 mode, how is the power? can it get out of it's own way? or is it as slow as my mothers '89 Brougham with the 307?

368 IS a Caddy engine, smaller brother to the 425, right? still, does it have pep?
 

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memphis,
Since most Cads develope bad springs, what I have done in my cars so far is to replace the stock rear springs with Moog "Cargo Coils". They are inexpensive (about $80 with tax) and easy to replace. If your shocks also need replacing, you can do both at once since you have to unbolt the shocks from the lower mounts to remove and replace the springs. While the car will handle better, and easily accept a full trunk/back seat passengers, the car will ride a little harder, but certainly not too hard. Also, IF you have bad shocks, and especially if you have the "Level Ride" system which isn't keeping the car up to the correct height, the new springs will quickly show bad shocks as the car will "bounce" pretty much.

Pat

memphis said:
--------------

Caddy engine it is, as you described.
Pep? Sort of.
Definitely better than the 4100, but the car and
motor are both very heavy. The HP is low, but the torque is
good. It pulls itself up on ramps and passes with gittyup.
I'm not a performance guy really, so its adequate for me.
I like the confort and feel of the car (except going around turns)

I drove a 307 brougham, this is better, but not by a huge margin.
 

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memphis,
If at all possible, keep the system operating. You will definately notice the increased fuel mileage and miss it if you disconnect the system. Even if you have to put some money into it, it will still be worth it.

Pat

memphis said:
---------------------
Agreed. Wednesday car for sure.
I think its pretty cool when it works. I show people
the active cylinder display and get oohs and aahs.
I read on the other thread about putting a switch in for that
wire on the tranny. That makes good sense, I think I'll do that.
 

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Discussion Starter #13
Pat:

Thanks for the prolific information.

I really con't get much use out the 81 factory manual I have.
That manual is definitely for highly trained technicians.
02 Sensor is not listed in the index.
Can you tell me where the 02 sensor is? I'd love to replace it.
However, the car seems to behave bettern now that I
reseated those solenoid wires on top of the valve covers.
I think they were fouled by oil that pushes up through those
holes.

My Eldo is level I replaced the shocks and the leveler still works.
The springs are holding up fortunately. That's one of the few things
I HAVEN'T replaced. Everyone bashes the engine, but the engine
generally runs great, its all the stuff around it that has gone bad!
But hey, its all new now.

My fuel consumption runs around 15 average and 19 on the highway.
SHould it be better? Could you give me a run down of other
sensors that should be routinely replaced that I can do myself?
Page numbers in the manual might be enough of a reference so
you don't have to describe too much in detail.

In another post, I mention that my heater core is out of commission.
I'm looking for a way to replace it or re-engineer it without taking the dash out. As I said there, I'm willing to cut a hole thru the fire wall to
avoid that.

Thanks so much- with your kind help hopefully I'll get lots of miles out of this car as I should.

Wanna see it? go to http://www.crawfordltd.com/eldo

In o
 

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My V8-6-4 was disconnected when I bought it. I wounder if it would work if I hooked it back up?

only the two wires have been cut from the tranny!

All I'd have to do is hook them back up, and keep my fingers crossed. :eyebrow:
 

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I would recommend replacing an O2 sensor first ,it seems to be the most probable cause. If the code remains I'd go further, besides it is a good idea to have a "fresh" O2 sensor anyway.
 
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