: sticky gas pedal/rough idling/accelerating



hankk17
03-02-04, 10:25 AM
Hi Everyone. I have a 99 Eldorado (non ETC) that I've owned since it was brand new with 6 miles on it. It's had its share of little issues here and there including a strange alarm problem I'll post a question about in the appropriate forum, however for this go-around my issue is north* related.

I've recently gotten a job that's 50 miles away from home, so I'm doing a lot more highway driving than previously. Recently I noticed that my gas pedal was getting sticky, and when I'd accelerate to get into traffic on the highway I'd have some really weird hesitation as it went through the gears.

Then the problem got worse and extended itself to EXTREMELY rough idling at stop signs or even when the car was in park.

I read the forum here a few days ago and found that it was most likely a carbon-fouled throttle that was the issue, so last night I carefully took the air-intake apart and sure enough it was BLACK with carbon. I cleaned it with a toothbrush and some carb cleaner and the problem has gotten better but is still there. I looked inside the intake and the entire intake seemed to be black with carbon as well... What's my next step? Top Engine Cleaner?

I've also read here that this year north* has had issues with the crankshaft sensor. Could it be a culprit as well?

The engine has 81K on it and up til now has treated me very well.

Any thoughts are definitely welcome, and thanks to all for the tip on the carbon - I think it's set me on the right path to fixing the issue.

-Hankk17

BeelzeBob
03-02-04, 11:40 AM
Did you hold the throttle wide open and clean the throttle bore all the way around the perimeter of the bore where the blade contacts it? Also, clean the backside of the throttle blade. Not looking for squeeky clean here, just get the worst of the deposits off.

The deposits in the manifold are perfectly normal. Dry intake manifolds on PFI engines do not have gasoline sluicing thru them like on carbed or TBI engines so the intakes will tend to get sooty and oily from the EGR introduction and the PCV oil mist.

Crank sensors were not typically a problem with the 99.... The crank sensors changed design for 2000 and later and there were some quality issues off and on with those...but that doesn't apply to the 99.

Your onboard diagnostics has an engine misfire detection code logic that is very robust. If the engine were missing it should turn on the SES.

Have you checked for any codes to see if there is anything in the diagnostics?

BeelzeBob
03-02-04, 11:41 AM
Also, read the following and take heed..... http://www.cadillacforums.com/forums/showthread.php?t=226

BeelzeBob
03-02-04, 11:44 AM
The other thing that you should check is the fuel pressure regulator. Take the silver top cover off and you will see the small canister shaped device on the fuel rail that has the fuel return line coming out of it and a vacuum line hooked to it. Take the vacuum line off while the engine is idling and watch the vacuum nipple for any signs of fuel...there should be none. If there is any fuel present at the vacuum nipple after idling for several minutes with the hose off then replace the FPR.

hankk17
03-02-04, 11:58 AM
wow - a bobbynski trifecta! :)

Thanks for the quick replies.

OK - I checked the computer - no codes.

I did indeed clean around the entire throttle opening and made sure that the valve opens and closes smoothly. I also did clean the back of the valve as well.

I will take your suggestion about the FPR and will investigate.

While I have your attention - I have a slight oil leak coming from my front valve cover. is this a relatively straightforward job to do?

Thanks!!

-Hankk17

(also an nski..)

hankk17
03-02-04, 12:09 PM
Also, read the following and take heed..... http://www.cadillacforums.com/forums/showthread.php?t=226
Oh, and I live in MA. subsequently I have certain bad driving habits.. one of them being that I go 80-85 when I hit the highway. This morning, after I had cleaned the throttle body last night, I opened it up and did about 90 all the way to work, and hit it hard on the hills to help blast out the crud.

I'll know if I did anything tonight on my way home.

Thanks again!

-Hankk17

BeelzeBob
03-02-04, 12:44 PM
Oh, and I live in MA. subsequently I have certain bad driving habits.. one of them being that I go 80-85 when I hit the highway. This morning, after I had cleaned the throttle body last night, I opened it up and did about 90 all the way to work, and hit it hard on the hills to help blast out the crud.

I'll know if I did anything tonight on my way home.

Thanks again!

-Hankk17
Keep hammering it. Do some of the manual second gear, WOT from 55 to 80 and then allow the vehicle to slow down with the heavy engine overrun/engine braking of manual 2...then do the WOT to 80 again and repeat ... as often as you can until the exhaust is clean and doesn't give you a cloud when you nail it. Driving 80 is great but it is not really stressfull on the engine at all. You need the WOT and high RPM of the upshifts. Always merge from 55 to 80 at WOT and you'll start to clean it out....

The cam cover is pretty simple to remove and touch up the seal. I would just pull it off and see what is causing the leak. It may be a cut seal or a surface defect (scratch) in the mating suface on the head....just clean the area and patch locally with some good high temp RTV....just a dab will do it. No need to replace the seal generally.

hankk17
03-02-04, 12:51 PM
Keep hammering it. Do some of the manual second gear, WOT from 55 to 80 and then allow the vehicle to slow down with the heavy engine overrun/engine braking of manual 2...then do the WOT to 80 again and repeat ... as often as you can until the exhaust is clean and doesn't give you a cloud when you nail it. Driving 80 is great but it is not really stressfull on the engine at all. You need the WOT and high RPM of the upshifts. Always merge from 55 to 80 at WOT and you'll start to clean it out....

The cam cover is pretty simple to remove and touch up the seal. I would just pull it off and see what is causing the leak. It may be a cut seal or a surface defect (scratch) in the mating suface on the head....just clean the area and patch locally with some good high temp RTV....just a dab will do it. No need to replace the seal generally.
OK will do. Thanks!

Incidentally - I'm still a noob to these forums.. what the heck is WOT?

hankk17
03-02-04, 06:24 PM
just an update - after a long HARD drive home on Rt 495, the problem persists and is just about the same as before I cleaned the throttle body. Guess I'll try looking at the FPR next.

I've also picked up some top engine cleaner as well and will use that just for kicks..

BeelzeBob
03-02-04, 11:19 PM
OK will do. Thanks!

Incidentally - I'm still a noob to these forums.. what the heck is WOT?

Wide Open Throttle...also known as WFO...LOL

Eldobroken
03-03-04, 12:16 AM
Hi Everyone. I have a 99 Eldorado (non ETC) that I've owned since it was brand new with 6 miles on it. It's had its share of little issues here and there including a strange alarm problem I'll post a question about in the appropriate forum, however for this go-around my issue is north* related.

I've recently gotten a job that's 50 miles away from home, so I'm doing a lot more highway driving than previously. Recently I noticed that my gas pedal was getting sticky, and when I'd accelerate to get into traffic on the highway I'd have some really weird hesitation as it went through the gears.

Then the problem got worse and extended itself to EXTREMELY rough idling at stop signs or even when the car was in park.

I read the forum here a few days ago and found that it was most likely a carbon-fouled throttle that was the issue, so last night I carefully took the air-intake apart and sure enough it was BLACK with carbon. I cleaned it with a toothbrush and some carb cleaner and the problem has gotten better but is still there. I looked inside the intake and the entire intake seemed to be black with carbon as well... What's my next step? Top Engine Cleaner?

I've also read here that this year north* has had issues with the crankshaft sensor. Could it be a culprit as well?

The engine has 81K on it and up til now has treated me very well.

Any thoughts are definitely welcome, and thanks to all for the tip on the carbon - I think it's set me on the right path to fixing the issue.

-Hankk17
Hi Hank I am not totally sure if this will solve your problem but a similar problem i had. When i was replacing the injector fuel rail before i found these forums, I happened to remove the plastic intake plates to replace gaskets. They were so full of carbon and crap it took me 4 hours to completly clean them. Just a thought as you are going to have to remove beauty cover to check fuel pressure reg anyways. Not sure if mine was a one of a kind problem but i have 167k miles and drive my car real hard i dont beat it to death but WOT is an everyday thing for my eldo. Hope this info is helpfull.

hankk17
03-03-04, 10:30 AM
Wide Open Throttle...also known as WFO...LOL
duh.. I should've guessed that. :)

Thanks for all the advice Mr. nski!

-Hank

hankk17
03-03-04, 10:36 AM
Hi Hank I am not totally sure if this will solve your problem but a similar problem i had. When i was replacing the injector fuel rail before i found these forums, I happened to remove the plastic intake plates to replace gaskets. They were so full of carbon and crap it took me 4 hours to completly clean them. Just a thought as you are going to have to remove beauty cover to check fuel pressure reg anyways. Not sure if mine was a one of a kind problem but i have 167k miles and drive my car real hard i dont beat it to death but WOT is an everyday thing for my eldo. Hope this info is helpfull.
I think I'm going to hit it with some top engine cleaner first to see if that will un-gum whatever it is that's causing the problem.

I sent my dad off to get the chemicals from our local GM dealer and he came back with 4 cans - two liquid and two aerosol.. I didn't know they made it in aerosol.. anyone had any experience with them? I've done the liquid Top Engine Clean before.. you pour some in the carb and keep the car running for 30 seconds or so.. then let it stall and pour the rest in the engine. Then let it sit for 5 minutes or so and then turn it over and revv it to burn off the stuff. I'm assuming that with EFI I just disconnect the fuel lead on the top of the engine somewhere and use a funnel or something to pour it in the injectors.. yes?

I've recently gotten the manuals from Helm (www.helminc.com (http://www.helminc.com)) for my car as well. I'll be studying them up.. hopefully the procedure will be in there somewhere.

BeelzeBob
03-03-04, 10:38 AM
Hi Hank I am not totally sure if this will solve your problem but a similar problem i had. When i was replacing the injector fuel rail before i found these forums, I happened to remove the plastic intake plates to replace gaskets. They were so full of carbon and crap it took me 4 hours to completly clean them. Just a thought as you are going to have to remove beauty cover to check fuel pressure reg anyways. Not sure if mine was a one of a kind problem but i have 167k miles and drive my car real hard i dont beat it to death but WOT is an everyday thing for my eldo. Hope this info is helpfull.

Eldo, your engine must be a 93/94. ONLY the 93/94 Northstars have the phenolic spacer plates between the intake manifold and the cylinder heads. Beginning with the 95 model year Northstar the engine has a completely different design intake manifold. It is a one piece plastic intake manifold and the silver top cover is just a beauty cover/noise shield...not an integral part of the intake like on the 93/94. Your comments apply to 93/94 engines only....hank's 99 Northstar does NOT have the phenolic plates to clean out...just the EGR valve itself.

hankk17
03-03-04, 04:29 PM
I went and picked up a FPR today on my lunch. Such a teeny little thing. It looks pretty straightforward to replace based on the clips they gave me. Gonna give it a whirl tonight.

I'll post my findings tomorrow!

hankk17
03-03-04, 10:14 PM
OK here's the update:


I replaced the FPR - no difference.

I ran 2 bottles of top engine cleaner through the car without the throttle body cover on - I just sprayed it directly at the throttle while the car was running and the vacuum sucked it in naturally. I did get a fair amount of white smoke out the tailpipe so that did something I think. However, the rough idle persists.

Also - I'm finally beginning to understand how to read the computer I think. I always thought the "history" messages were just top of the menus, not the actual codes themself. I finally figured out that they were indeed the codes, so I wrote them all down and have come up with some possible solutions for my RADIO problem, which is totally unrelated to my idle problem I think. One code that is persistent is 1522 - which indicates a problem with the body control module. I suspect that the morons who installed my stereo blew the EPROM and I've been dealing with that ever since because that code is constant.

At any rate, the other codes that I saw were a result of me disconnecting the battery and running the car without the throttle sensors hooked up. I've cleared all those and will take note of new codes tomorrow when I arrive at work.

Until next time..

Eldobroken
03-04-04, 12:01 AM
Eldo, your engine must be a 93/94. ONLY the 93/94 Northstars have the phenolic spacer plates between the intake manifold and the cylinder heads. Beginning with the 95 model year Northstar the engine has a completely different design intake manifold. It is a one piece plastic intake manifold and the silver top cover is just a beauty cover/noise shield...not an integral part of the intake like on the 93/94. Your comments apply to 93/94 engines only....hank's 99 Northstar does NOT have the phenolic plates to clean out...just the EGR valve itself.Thanks Bob. Ok im going to go a little off topic then. Cause i was reading on here that it was called a beauty cover. So on my engine it is not called that? Thats cool beacuse i was wondering the 10 times i retorqued it while dignosing what seemed like a intake backfire "leaking fuel rail" if it was a beauty cover I was wondering why i had to retorque in sequence. Anyway could you explain the theory behind this and my 2000 seville that i have not had to take apart yet Knock on wood, I do not have to check in there or clean? Thanks in advance.

hankk17
03-04-04, 10:08 AM
Here are the codes generated from this morning's drive to work:


TCS - C1255

PZM - B1552, B1558

My shop manual is at home so I'll have to check them later, but I wanted to see if anyone could post what they mean before then..

It's still idling really rough after it warms up and if I let it go long enough it'll want to stall and will throw the code for the "near stall condition" I'm pretty sure.


To recap - at this point I've:
Cleaned the throttle body twice with a toothbrush and carb cleaner. it positively gleams now and no longer sticks

Run two bottles of aerosol Top Engine Cleaner through the car which did produce a fair amount of white smoke. The engine DOES seem to be running smoother at 80 now.

Replaced the Fuel Pressure Regulator. The old one seemed OK, but I figured a new one couldn't hurt.

After each successive treatment of cleaning the throttle body and the Top Engine Cleaner, I've disconnected the negative battery cable for 30 seconds to reset the throttle sensor.

My rough idle persists.. anyone have any other suggestions?

Thanks all!

-hankk17

hankk17
03-04-04, 11:16 AM
Could a failing/messed up Body Control Module potentially cause this problem?? The more I research this over the web, the more it seems to indicate that it could be the problem, or at least a contributing factor....

Eldobroken
03-04-04, 12:27 PM
Could a failing/messed up Body Control Module potentially cause this problem?? The more I research this over the web, the more it seems to indicate that it could be the problem, or at least a contributing factor....Mabye Crankshaft position sensor. It would cause rough Idling. Had to have it replaced in my 2000 seville twice. Under warranty :) they replaced a bunch of stuff even the catillaic converter when it was just a dirty air filter and Crankshaft sensor.

hankk17
03-04-04, 12:49 PM
Mabye Crankshaft position sensor. It would cause rough Idling. Had to have it replaced in my 2000 seville twice. Under warranty :) they replaced a bunch of stuff even the catillaic converter when it was just a dirty air filter and Crankshaft sensor.
Bobbynski had mentioned earlier in the thread that this year North* wasn't succeptible to that problem.. but at this point, I'm willing to try anything.

I got a price for a new BCM today - $442.00 from the dealer. ouch.

Also I'm figuring out that I may not be able to get a used one from a junked car to work either.. If I'm correct, the BCM contains the system that checks the resistor in the key.. if you change the BCM, then the code it checks against will be wrong and you won't be able to start the car..

just all around.. yuck.

Eldobroken
03-04-04, 11:20 PM
Bobbynski had mentioned earlier in the thread that this year North* wasn't succeptible to that problem.. but at this point, I'm willing to try anything.

I got a price for a new BCM today - $442.00 from the dealer. ouch.

Also I'm figuring out that I may not be able to get a used one from a junked car to work either.. If I'm correct, the BCM contains the system that checks the resistor in the key.. if you change the BCM, then the code it checks against will be wrong and you won't be able to start the car..

just all around.. yuck.
I know there is a way to OHM it out with an ohmmeter but i am not sure what the resistance is supposed to be and what range. A friend of mine diagnosed his seville this way i think its a 99 also. Try running a search on checking crank sensor. I think he was saying not common for it to go bad but who knows fixed my friends car. Goodluck let us know how you make out.

BeelzeBob
03-05-04, 12:26 PM
Thanks Bob. Ok im going to go a little off topic then. Cause i was reading on here that it was called a beauty cover. So on my engine it is not called that? Thats cool beacuse i was wondering the 10 times i retorqued it while dignosing what seemed like a intake backfire "leaking fuel rail" if it was a beauty cover I was wondering why i had to retorque in sequence. Anyway could you explain the theory behind this and my 2000 seville that i have not had to take apart yet Knock on wood, I do not have to check in there or clean? Thanks in advance.

The "theory behind this....???"

The intake manifold assembly on the 93/94 Northstars was a large magnesium die-cast enclosure with the plastic tuning tubes, injectors, fuel rail, fuel pressure regulator, wiring harness,etc. inside the box. The silver top cover was an integral part of the intake manifold as it formed the top of the box and that is why it is bolted to the lower part of the box with the perimeter row of screws. The silver top cover is "styled" on the 93/94 engines so as to look pretty but it is more a funcitonal part since it actually forms part of the intake manifold itself. I don't think that I have ever referred to the silver top cover on a 93/94 as a beauty cover.....

The 95-99 Northstars have a single piece plastic intake manifold that forms the plenum, tuning tubes, etc.... The fuel rail and injectors are external to the manifold. On the 95/99 engines the siver top cover is styled to look just like the 93/94 engines....but it is not "functional" in the sense that it is just a beauty cover (or modesty shield....LOL) to cover the intake/fuel rail/plumbing/wiring/etc. below.....and....it acts as a noise barrier to minimize the injector "clicking" that can clearly be heard. The 95/99 engines will run fine with the silver top cover removed so it is typically called a "beauty cover" as it is not functionally needed to run the engine. That is also why there is no perimeter row of screws holding the cover on with the 95/99's.

The 93/94 engines have the phenolic spacer plates that form the EGR passages and need cleaning. The 95/99 engines do NOT have the phenolic spacer plates. Neither do the 2000/current engines.


The 2000/current Northstars are heavily redesigned/revised but they still use the one piece plastic intake manifold and the silver beauty cover. The silver beauty cover is mounted and retained differently but you will not see any perimter row of screws holding it down and the engine will run fine without the silver top cover so it is just a noise/beauty shield. There is nothing to clean under it really.