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Surging\rough acceleration


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It could be your throttle body plate and throat needing to be cleaned. Get some O2 sensor safe carb cleaner or GM upper engine cleaner and a tooth brush and clean the TB and TB plate, especially the rear of it and where the plate meets the throat... When I do this my acceleration is silky smooth...

The rear of the plate is usually really really dirty, its w good practice to clean the TB/Plate at oil change that way it will stay clean...

DO NOT get a LOT of solvent down the TB, by pouring it or spraying it, we have seen a few engines hydrolock. One that comes to mind was a NS that was at the dealer and the tech used too much upper engine cleaner and when they test drove it, as soon as he pushed the accelerator to take off, the solvent that pooled in the intake was sucked into a cylinder and blew a rod out of the side of the engine, so be careful! Here is the link but the pictures are no longer valid:

http://caddyinfo.ipbhost.com/index.php?sho...98&hl=hydrolock

A stiff tooth brush or nylon detail brush does the trick, don't use a brass detail brush that might create scratches.

Also, does your engine have the phenolic plates or did that start in 1994? If it does see this thread and look for my post with a bbobynski clip in it. Something tells me you don't have phenolic plates however:

http://caddyinfo.ipbhost.com/index.php?sho...&hl=mouse+holes

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Let me tell you hydrolock is NOT fun...

Sounds like you are having the same problem I did a few short days ago.

I cleaned everything, and also set my timing to 3 degrees. I have not had a problem since.

Big Jay

Life is too short to grow up!

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The TB (throtle body) you must know where that is? It is where the gas goes into your intake.

Life is too short to grow up!

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Follow the air intake duct from the ait filter where is connects to the engine. Remove the clamp and pull off the duct. You will be looking at the throttle body.

How many miles are on the car? The phenolic spacer plates may be crudded up - you will need to remove the intake to clean the passages and EGR delivery ports to the cylinders.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Well I cleaned out the plate in the TB and the bit of sticky carbon that had built up around the rim but the back of the plate was pretty spotless. Not black or covered with carbon as i would have thought. Maybe my spirited driving habits? Either way the car does seem to be much better. Maybe its just having a good day but its much smoother and the rough shifting went away. Hm...hope it stays this way. Thanks.

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About 50% of the time I have a surge in my acceleration. It is usually more noticeable going up a hill. If you keep a steady pressure on the pedal while accelerating it will surge up by maybe 100 rpms (very rough estimate) and it seems to also be related to my hard shifting. It does seem to have gotten better since i cleaded the plate on the tb. EGR is still dirty no doubt but would it cause problems like that during acceleration or just during idle?

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Could the fuel filter cause the same sort of problem? Im not sure when the last time it was replaced was. Def not within the last 3 years.

3 years???? you definately should start with that! You should not wait that long for a fuel filter change. Your filter is so full of debris, I guarantee that! Did you get the carbon out, I really didn't catch if you did or not?

Big Jay

Life is too short to grow up!

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I would not worry about the fuel filter its not even shown on the list of items to replace on the maintenance schedule.. Change it if you want but I doubt its your problem.

Have you looked at your FPR to see if you have fuel present?

If you can hook up a fuel pressure guage tape it to the windshield and watch it for fluctuation do it at idle racing the engine also.

Have you disconnected the battery to "reboot" the system?

It also sounds like you could be getting an intermittant on a plug, plug wire or a ground out.. Take a close look at your ignition wires, if you have an ohm meter check each one and write down the results... Check the each wire is making a positive connection at both the plug and coil. Look at the engine in pitch dark while revving the engine for arching with the cover off if yours comes off. Pull the plugs and look at them for fouling, missing pads and cracks in the porcelin and near the electrode. IF you used dilectric grease on your wires clean it off both ends good, dilectric grease can cause arching on these wires and its NOT recommended. Are you setting any codes? If you had an EGR problem it would set a code

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Well Ill check the fuel pressure as soon as I get a chance at school. I am having an intermittent EGR problem. I think the code is PO39 or PO36. Yes I did get the throttle body cleaned. It wasnt really that dirty at all. Although it did seem to help. I have disconnected the neg cable to do a re learn. Ive even tried rubbing the steering wheel and asking it nicely to stop it. Ill look at the wires when it gets dark tonight. Ill wet them down and look for arcing. And when I get my hands on a fluke 88 ill check the resistance. Thanks.

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Scotty, Ranger.

Hey are you saying I should not be changing my fuel filter every 50k Kilometers?

When I do, and I always have there is some nasty black debris in there.

The Deville I just baught 97 D'Elegance had the original fuel filter on it. When I changed it, it must of weighed 3 pounds. Ya i didn't notice a difference, but don't you think it is in good practice to change them, especially since they are a dime a dozen?

Big Jay :huh:

Life is too short to grow up!

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Big Jay,

"Hey are you saying I should not be changing my fuel filter every 50k Kilometers?

When I do, and I always have there is some nasty black debris in there."

You might want to consider not siphoning fuel residues from closed up oil wells, tar pits, etc across the frozen northlands... :D;)

What the heck is all the residue? Do you have an upset neighbor that has been trying to poison your Caddy over time (ie: does the Caddy bark and howl at night) ? :(

My 94 Deville Concours with a 4.6 has had the same fuel filter for about 100,000 miles at least, maybe for all of its almost 180,000-miles. :unsure:

Maybe it has something to do with the velocity of fuel passing through the filter and how often the fuel tank is replenished. <_<

I'd say more WOT's can't hurt. If your'e not into that knid of driving, insure it well and lend the car overnight to a kid delivering pizzas. :P

F.G.B.,

I would certainly replace the EGR at this point, since you suspect it has a problem anyway.

Good luck and let us know what the problem was at some point.

Add power to leave problems behind. Most braking is just - poor planning.
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