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Fleetwoods
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Discussion Starter #1
I have a 1985 Cadillac FB coupe with the ht4100 engine and my problem is that it starts to vibrate pretty bad when I put it in drive. I did a tune up on the car not too long ago and the problem still continued. The "service soon" light comes on when the car warms up and I pulled these codes from the car 30 and 52 but not sure what they mean.
Any help would be greatly appreciated
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Did you do the tune up to hopefully cure the rough idle in gear or did this start after the tuneup?
 

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1989 Brougham d'Elegance, 1985 Fleetwood Brougham *Coupe*
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30 is idle speed control circuit error and 52 is ECM memory reset indicator. 52 means that power was lost to the computer (the battery was disconnected) and the stored memory was erased and it would not turn on the light.

A vibration that only occurs in a froward gear could indicate that the torque converter or driveshaft may be out of balance. If the vibration happens only after the car starts to move, then have the driveshaft balance checked.

If it happens as soon as the gear is changed, then have the idle control circuit checked. Also change any old vacuum hoses and have the routing checked because vacuum leaks can cause vibrations in certain gears.
 

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Fleetwoods
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Discussion Starter #4
I did the tune up hoping that the vibration would go away but it didn't cure anything.
It starts to vibrate as soon as I put it into gear and when in park the car idles up and down but not too bad, so I'm going to check the
idle control circuit and hopefully this cures my problem.
Thanks for the help
 

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1989 Brougham d'Elegance, 1985 Fleetwood Brougham *Coupe*
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^Yeah, engine surge when idling is usually the primary concern with an Idle Control Circuit error.
 

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Fleetwoods
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Discussion Starter #6
^Yeah, engine surge when idling is usually the primary concern with an Idle Control Circuit error.
I changed the idle control thing and still no luck. I also tried to drive the car up on some ramps today to change the oxygen sensor but the car didn't have enough power or something cause it just wouldn't go up.
Any idea what that could be?
 

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90 Brougham 5.7, 05 Deville DTS
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Make sure you have correctly adjusted the Idle control motor. If that is not the problem have your catylitic converter checked.
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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The idle control motor will not affect smoothness or roughness of idle only speed of idle, either too high or too low. I agree, the cat converter can plug up and restrict power. You need to do the basics, compression test first then plug wires second.
 

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Fleetwoods
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Discussion Starter #9
The previous owner had a new exhaust system installed back in 2005 and pretty much sat ever since until I bought the car a couple of months ago. The car has 44,xxx original documented miles. Is this a common problem for the ht4100 engines?
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Most common issue is not changing the coolant every 2 years without fail and adding the sealant mentioned on the decal by the radiator. Failure to do this will cause intake gaskets to fail and coolant wiping out the cam. This car can break the rocker arm supports and cause engine roughness. Do a compression test. Pull each plug wire one at a time with insulated pliers ( engine running) from the cap to isolate which cylinder is not firing and report back. How old is the fuel filter?? wont cause rough running but will affect power.
 

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1989 Brougham d'Elegance, 1985 Fleetwood Brougham *Coupe*
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After being covered with a tarp since 2005 :(
:worship: Behold, the coveted Fleetwood Brougham Coupe. Only 28,480 ever produced (just 3,000 from 1985).

I've had my eye on one for a while. Got an evil plan to loose the 4100 and drop in a race tuned 364 small block with a Powerglide; make it into a sleeper. My Uncle used to have a 65 Bel Air, which he build to stockcar racing specifications. When the car died in the Ohio salt, he pulled the engine and transmission; I just need to find time to rebuild them.

Back to your problem.

A clogged, new, exhaust pipe is not that uncommon, especially with cars that have sat for a while. Rodents build nests or hoard things in tail pipes or neighborhood kids try to steal the Cat and end up just smashing the catalyst. Even the slightest restriction can cause major problems.

One way to tell for yourself, with out any special tools, is to wrap your hand in a rag and hold it by the tailtip. You should feel a smooth flow of warm air. You could also hold a piece of paper near the tailtip and see if there is any flow (if the paper occasionally gets sucked to the pipe then one of your exhaust valves is not seating properly). If you want to spend some money, then get a vacuum gauge, hook it to manifold vacuum and increase the engine speed slightly. If the needle slowly drops to zero, then the exhaust is restricted.

Other problems that could be linked to engine roughness are plugged injectors and fouled sparkplugs. Running Gumout with Regane will clean the fuel system and make the engine run better.

 

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Fleetwoods
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Discussion Starter #14
Most common issue is not changing the coolant every 2 years without fail and adding the sealant mentioned on the decal by the radiator. Failure to do this will cause intake gaskets to fail and coolant wiping out the cam. This car can break the rocker arm supports and cause engine roughness. Do a compression test. Pull each plug wire one at a time with insulated pliers ( engine running) from the cap to isolate which cylinder is not firing and report back. How old is the fuel filter?? wont cause rough running but will affect power.
The fuel filter was replaced when I did a tune up,
Im gonna have to try that compression test and Hopefully all the cylinders are good.
Thanks
 

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Fleetwoods
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Discussion Starter #15
:worship: Behold, the coveted Fleetwood Brougham Coupe. Only 28,480 ever produced (just 3,000 from 1985).

I've had my eye on one for a while. Got an evil plan to loose the 4100 and drop in a race tuned 364 small block with a Power-glide; make it into a sleeper. My Uncle used to have a 65 Bel Air, which he build to stock car racing specifications. When the car died in the Ohio salt, he pulled the engine and transmission; I just need to find time to rebuild them.

Back to your problem.

A clogged, new, exhaust pipe is not that uncommon, especially with cars that have sat for a while. Rodents build nests or hoard things in tail pipes or neighborhood kids try to steal the Cat and end up just smashing the catalyst. Even the slightest restriction can cause major problems.

One way to tell for yourself, with out any special tools, is to wrap your hand in a rag and hold it by the tailtip. You should feel a smooth flow of warm air. You could also hold a piece of paper near the tailtip and see if there is any flow (if the paper occasionally gets sucked to the pipe then one of your exhaust valves is not seating properly). If you want to spend some money, then get a vacuum gauge, hook it to manifold vacuum and increase the engine speed slightly. If the needle slowly drops to zero, then the exhaust is restricted.

Other problems that could be linked to engine roughness are plugged injectors and fouled sparkplugs. Running Gumout with Regane will clean the fuel system and make the engine run better.

I replaced all the spark plugs,dist. cap/rotor but one thing I didn't do was the wires but tomorrow after work I'm gonna swap them out and well see if that helps. Also I did try that fuel cleaner on my 95 Cadillac FB and did notice that the engine idles a lot better now.
Thanks for looking out fellas
 

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Fleetwoods
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Discussion Starter #16
I had a chance to change the spark plug wires but didn't notice a change.
It now throws codes 27,30,52 when I do diagnostic test. :(
 

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1989 Brougham d'Elegance, 1985 Fleetwood Brougham *Coupe*
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27= Open Throttle Switch Circuit
30= Idle Seed Control Circuit
52= ECM Memory Reset indicator

An open throttle switch error was set because when you throttled up the engine, the nose switch on the IDLE SPEED CONTROL MOTOR, that keeps the engine idling, did not detect the throttle linkage touching the nose switch on the ISC motor.
 

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Fleetwoods
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Discussion Starter #18
27= Open Throttle Switch Circuit
30= Idle Seed Control Circuit
52= ECM Memory Reset indicator

An open throttle switch error was set because when you throttled up the engine, the nose switch on the IDLE SPEED CONTROL MOTOR, that keeps the engine idling, did not detect the throttle linkage touching the nose switch on the ISC motor.
I cleared the codes today and now I only get code 30,52
What about if the gas tank is diryt? would it have anything to do with the idle and vibration problem?
 

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1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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Very frustrating to try to help when someone's bound and determined to throw parts at a car. Did you run the compression test? what were the readings? The ISC will not cause a rough idle. An open throttle switch circuit could possibly because the TPS tells the ECM what amount of fuel to deliver. I would hope that all these tune up parts are not on an engine with an internal problem??
 

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Fleetwoods
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Discussion Starter #20
I think your right, it might just be an internal problem the reason I say that is cause when I accelerate the car there's some loud poping noices coming from the trottle body.
 
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