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Discussion Starter #1
Hello, I am a newcomer here. Seems like people here know
a lot about Cadillac, how nice!

Anyway, I bought a 95 DeVille (4.9 liter) about a month ago.
She is a wonderful car (I owned a 83 Eldorado before this
DeVille). And until a few days ago, she was running just fine.

Recently, she started to hesitate accelerating while driving.
It doesn't happen all the time. It feels like the engine misses
firing correctly or fuel is not delivered smoothly (that's what
I FEEL like). When she is at the red signal, her idling fluctuates
and sometimes stalls. After she stalls, when I try to start her
again, she starts right away. These problems go away after
a while, if I keep driving. Most of the time, she is running
fine, though.

Any suggestions on what is wrong on this car?
Does it just require computer reset? If so, how? (pressing OFF
and HOT for a while or something like that?) Please help me.

Thank you very much!
 

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Welcome aboard. Curious, how many miles on it? At what speed does it hesitate, is it at high speed? What are you getting for gas mileage?

According to my Chilton's book:

1. Check the engine ignition system operation.
2. Check for restricted fuel injectors.
3. Check the fuel pump output and delivery. Inspect fuel lines for restrictions. If the fuel pump pressure is below specification, replace the fuel pump.
4. Check the operation of the engine management system and repair as necessary.

That is what the book says for hesitation, however I would probably recommend a complete tune-up. I might be suspicious of clogged fuel injectors, fouled or worn plugs, clogged air filter? You need to talk to Katshot, he knows the guts of these cars.
 

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Discussion Starter #3
Hello Ralph, thank you for a quick reply.

It is getting worse fairly quickly day by day. Her engine
doesn't run smoothly almost all the time.

Answering your questions:
she has 84K miles and the engine hesitates at any speed.
It started just a few days ago, so I don't know what is the
milage right now, but it was 15 - 18 in town and 20+ on
highway. Seems like nothing was wrong. I checked the air
filter, but it was clean.

By the way, I checked the computer readings and it said
that there was no error.

I think I should check the fuel pressure and at the same
time, I should clean the fuel injectors. Is cleaning a fuel
injector something a home mechanic can do? I used to
work on TBI and it was a easy thing to work on! I have
never worked on real high pressure injector systems.

Again, thank you very much.

More suggestions are welcome, since I would like to have
a statistical feeling of possible problems on this car...

Ralph said:
Welcome aboard. Curious, how many miles on it? At what speed does it hesitate, is it at high speed? What are you getting for gas mileage?

According to my Chilton's book:

1. Check the engine ignition system operation.
2. Check for restricted fuel injectors.
3. Check the fuel pump output and delivery. Inspect fuel lines for restrictions. If the fuel pump pressure is below specification, replace the fuel pump.
4. Check the operation of the engine management system and repair as necessary.

That is what the book says for hesitation, however I would probably recommend a complete tune-up. I might be suspicious of clogged fuel injectors, fouled or worn plugs, clogged air filter? You need to talk to Katshot, he knows the guts of these cars.
 

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100 said:
Hello Ralph, thank you for a quick reply.

It is getting worse fairly quickly day by day. Her engine
doesn't run smoothly almost all the time.

Answering your questions:
she has 84K miles and the engine hesitates at any speed.
It started just a few days ago, so I don't know what is the
milage right now, but it was 15 - 18 in town and 20+ on
highway. Seems like nothing was wrong. I checked the air
filter, but it was clean.

By the way, I checked the computer readings and it said
that there was no error.

I think I should check the fuel pressure and at the same
time, I should clean the fuel injectors. Is cleaning a fuel
injector something a home mechanic can do? I used to
work on TBI and it was a easy thing to work on! I have
never worked on real high pressure injector systems.

Again, thank you very much.

More suggestions are welcome, since I would like to have
a statistical feeling of possible problems on this car...
I say change your plugs immedietly. Change the wires too. It is easy and cheap to do and it needs to be done anyways. I am not sure how effective those fuel additives are at cleaning out injectors but try buying the best one on the shelf (apprx, $10-$12) and mixing it in 1/2 a tank of gas (to keep it concentrated). Post more symptoms.
 

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Use BG44k....... Best stuff on the market (fuel injector cleaner)......

In reality, none of the OTC products will clean dirty injectors...... Their not meant to (sorta)..... They would have to use something VERY strong, and if you messed up the concentration, it would be deadly..... And they dont even wanna mess with that...... BG44k is the most concentrated fuel injector cleaner available to the general public (to my knowledge)......

IF you want to get the injectors really clean, do a pressurized fuel rail flush....... You'll have to take it to a dealer or independent shop to get it done..... Youll probably fork over about $100, but it will restore the injectors to as new working order (assuming their in decent condition).......

The OTC fuel injector cleaners are more/less made for keeping clean injectors clean, not cleaning dirty injectors.......
 

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Discussion Starter #6
code P041

Update:

The fuel filter was somewhat clogged, so it has been changed.
For first 5 miles or so, the problem seemed to be gone.
But after I left the car for a couple of hours, the problem
came back. Since changing the fuel filter somewhat fixed
the problem momentarily, I have decided to change the
fuel pressure regulator before I took the car to the shop to
check the fuel pressure. At the same time, I was able to
visually check the condition of the fuel injectors. It turned
out that they seem to be all right.

And now, I am trying to change spark plugs. How come it is
so difficult to change the spark plugs? The boots don't
come off. I was able to change only one (No 7) for now.
Seems like this particular plug is a bit too worn out, so I am
sure changing plugs will somewhat fix the problem (hopefully
entire problem).

Well, by the way, the car finally decided to give me a code.
"service engine soon" light came on for a while. The code
was P041. Chilton says 4.9 liter is supposed to give me E041.
According to Chilton, all codes from 4.9 liter start from "E",
codes starting from "P" are for Northstar... Well, it is not
essential. Question is why P041 (Cam sensor circuit problem).
Does this mean I have a problem in the distributer??
Maybe the hall effect switch or the pick up coil??

When the car hesitates, to me it is like she loses all power
at once, not missing only some cylinders (English is not my
first language, sorry that my expression is not good).
More like the entire ignition system or the fuel delivery system
stop working for a moment, so if the problem is related to
the ignition system, it makes sense, but what I don't understand
is that it doesn't appear all the time. When the car runs good,
I just don't notice anything! But when she doesn't feel like
she wants to run, she starts to hesitates all the time...

Anyway, please give me some advises.

Thank you!
 

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I thought the fuel filter might have gotten it fixed after you mentioned it. I cannot believe you are able to change those plugs, I have the same engine and I am not even able to get my hands in there along the firewall side of them! What about the ignition coil? Maybe it is played out or faulty.
 

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Discussion Starter #8
update

I should have bought the fuel pressure gauge long before.
Well, I bought one and measured the fuel pressure.
When I turned on the ignition without running the engine,
the gauge said 40 psi at the end of the fuel rail. When I
started the engine, it dropped to 35 psi at idle. Seems not
too bad. Does anybody have opinions about these numbers?

Also, I checked the distributor. The coil, cap, and rotor
seem to be OK. All connections are tight. So I don't quite
understand why I sometimes get the code P041.

Well, but all plastic parts in the distributor are quite detariorated.
So, maybe the hall effect switch or the pick up coil is getting
bad from heat. I will work on the distributor and see if it
would help. After I put the distributor parts back, for some
reason, the car has been running quite well. Maybe
disconnecting and reconnecting terminals fixed the problem...???
(although they didn't look bad when I first opened the cap)
 

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Discussion Starter #10
Still...

Thanks Ralph, but apparently I didn't fix her.

The car was doing fine only for a several miles last night.
This morning on the way to my work, she stopped a few
times while she was running. I thought it was not going
to start!

Then, I got all kinds of error codes (now, all of them are
"history", though):

P031, P041, I022, T072, and T077.

What is going on!?? Could someone tell me what they
mean? (My Chilton doesn't say anything about them...)

I took her to a mechanic. Flustrating thing is that she
was just doing fine while he tried to figure out what was
wrong!! He ran his electronic diagnose device and it
indicated that EVERYTHING WAS FINE. Yeah, she was
doing great while he was in...

I badly need some help.

Thanks in advance for any kind of opinions.
 

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OK, that's it! It's time to buy a Lincoln! :D Naw, it can't be that bad. That's typical, that it would run good when it is at the mechanic! That happened to me all the time with other cars I've owned. Did you take it to the Cadillac dealership? I've learned these cars are difficult to diagnose. I would leave it at the Caddy dealer for a couple of days maybe, and let them sort it out properly. I would be stressed if I were you, and I am sure you are! I would be interested to find out what those codes mean, Katshot, where are you!!?? I am unfortunately starting to wonder if you need a whole new computer? (engine management) OUCH.
 

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Idle Control?

Your problem might be related to your automatic idle control motor. If you remove plastic the air intake cover from the throtle body you'll be able to see it clearer. It's a small black actuator with an adjustable screw in the end that pushes the throtle cable pulleys. It's job is through a series of mesurements best guess where to have the engine idle. If it malfunctions it will kill (or floor, depending on source of malfunction) the engine. There is a standard idler screw on the front side of the throtle body close to the manifold. Although it is not used when the auto idle controler is functioning, it can be used to temporarly bypass the system. Remove the auto idle actuator: disconnect the gray wiring harness from the rear of it and carefully remove the three screws that hold it to its mount. Then, using creative wiggling, slide it away and out of the engine. Figure out what size socket the standard idle screw takes and adjust it to push the throtle cable pulley into a clean idle (may take some tinkerin'). Sometimes it works best to slide the socket alone along the grove in the throtle body onto the idle screw and then attatch an extention to it by comming in through the provided hole in the auto idle acuators' mounting bracket. Once the car has a clean idle provided by the standard idle screw re-assemble the intake housing and drive the car. If your problem is gone and doesn't resurface you can leave it alone or get a new idle motor (re-assembly is reverse of above and be shure to retract andjustments you made). Still got a problem? Then I just wasted alot of time- lol.
 

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Discussion Starter #13
Update

Thank you for all your advises. I really appreciate them.

Anyway, update:

By the way, I have replaced the distributor. I had a
doubt on the distributor and the computer. The computer
is more expensive and I will not be able to get it until
next week. So, I have decided to work on the distributor.

I was told that I need a special tool to remove 15 mm nut
holding the distributor, but I was able to remove it with
a 12 points closed 15 mm wrench (6 pt wrench won't
work). I needed to grind it to make it thinner though.

Anyway, the old distributor seemed fine, so I was rather
disappointted, but anyway, I changed it. Only difference
I noticed was that the previous distributor had a little bit
(really a little bit) more play than the rebuild one. And I
know the rebuild one has a new hall effect switch and
pick up coil.

Well, I have driven more than 10 miles so far, the problem
seems to be GONE! Since the problem was intermittent,
I will have to observe the car for a while if the problem has
been really solved.

I will post later if the problem has really been solved.
 
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