: acceleration troubles...



samm
12-08-05, 04:10 PM
my car has been somewhat jerky during very gradual acceleration or very hard acceleration.
it is most noticeable during climbing hills (not accelerating, it even does it holding speed, and does it in cruise control while climbing hills, too). the jerking feels sorta like a fuel problem or maybe an engine problem, but a code came up that said something about transmission range to pressure switch correlation... however, the MAF sensor performance code also came up. any suggestions to fixing this annoying bucking bronco?

samm
12-09-05, 12:27 PM
is this forum really that untraveled or are people ignoring my posts cuz i am annoying?

mcowden
12-09-05, 01:01 PM
is this forum really that untraveled or are people ignoring my posts cuz i am annoying?

Please post the codes you received, then we can help. Nobody is ignoring you, but when there is not enough information in the post, it's hard to help so most people pass.

Ranger
12-09-05, 10:22 PM
How many miles on it? Start by pulling codes. Then maybe the basics, plugs and wires.

samm
12-10-05, 12:17 PM
121k. i didn't know you wanted the numeric code... i just figured i would interpret the codes for you to save you time... now, there are no powertrain related codes- or anything that would pertain to this problem. perhaps the fuel pump? it does show the same symptoms as a failing fuel pump, just from my experience with other vehicles. but this would probably throw up a code wouldn't it?

Ranger
12-10-05, 12:39 PM
Not sure if a fuel pump will throw a code. Best way to check it is to put a fuel guage on it. If possible, use one with a long hose and tape it to the windshield and observe it while driving when the problem exists.

Eldyfig
12-10-05, 01:56 PM
I would start by checking for spark to each cylinder. How does it do starting up and how about idling?

Do you still get the MAF sensor code?

powerglide
12-10-05, 06:16 PM
Yeah its hard to say. Did it throw a p0300 DTC?

It could be fuel it could be ignition.

How old are the plugs and wires? Are they AC DELCO?

Usually a plug and wire change cures these things. Could be the coils also, they are easy to check and replace. Measure resistance across the terminals. All 4 of them should read about the same. The one thats way out of range is your culprit. Easy fix.

samm
12-12-05, 12:10 AM
starting is usually alright, as is idling. and no, the MAF code is not there anymore. Plugs and wires i imagine are original. I'm not entirely sure, they havent been changed for the last 60K for sure. No, no p0300 code either.
checking spark for the plugs... how would i do that? i don't imagine i can just take them out one at a time and then plug the wires back into them, then turn the car on and look for spark can i? lol, i'm hoping its not that easy, that would be no different than checking for spark on a 2 cycle...
where are the coils/terminals located?

powerglide
12-12-05, 12:34 AM
The coils in my deville are on top by the firewall, right next to the strut tower bars.

they look like this:

http://www.cadillacforums.com/forums/attachment.php?attachmentid=8611&d=1112649489

heres an old thread about diagnosing coil packs.

http://www.cadillacforums.com/forums/showthread.php?t=36384&highlight=coil

Good luck

Eldyfig
12-12-05, 12:38 AM
There are a few ways to check for voltage to the plugs:

An in-line spark plug tester ($2 @ harbor freight) put between the plug and the plug wire. Start the car and look for the light to blink.

Using a timing light, put the inductive clamp on a wire. Pull the trigger on the timing light and see if it illuminates.

Do an injector disable test in the OBD system to check for fall off between cylinders when each injector is disabled.

I have also pulled the wire off of one plug at a time while the engine is running to check for fall off. If you hold the plug wire off the plug, but don't take it out of the plug well, you will hear the spark arcing. Don't lean on the engine when doing this.

samm
12-12-05, 10:33 PM
alright. could it also be the fuel pump if it isnt the coil, plugs, or wires?

eldorado1
12-12-05, 10:52 PM
Yesterday I posted a writeup, and then the forum got all slow and didn't take my post. So I lost it. Anyways, there could be any NUMBER of things wrong with your car. Here's a list to get you started.

+Clogged fuel filter(25% chance)
+bad fuel pump (10% chance)
+faulty fuel pressure regulator (1% chance)
+bad coil (10% chance)
+bad plug wires (20% chance)
bad TPS (25% chance)
bad MAP (5% chance)
bad MAF (25% chance)
bad spark plug(s) (depends on when they were last changed, they "should" last 80-100k)
bad connector/connection (5% chance)
vacuum leak (8% chance)

Is that enough yet? Start with the simple, cheap and free things.

Spray the engine in the dark with water, look for arcing. That takes care of plug wires and coils (sortof). Change the fuel filter ($10) or rent a fuel pressure gauge from autozone ($20 deposit or something... free if you return it).

If you've tested to this point, you've checked all the problems with plusses. Let me know when you get to that point.

Eldyfig
12-13-05, 01:49 PM
Please do let us know when you get this thing nipped. Very curious to know what it ends up being.

samm
12-13-05, 04:16 PM
yeah ill let ya know. sorry, i just wanted to narrow it down as much as possible before i dug into my car. but now i will try to diagnose it.