Hello to all you experts. I'm a brand new Cadillac owner so I need some expert advice. Just purchased a '95 DeVille, with 4.9 Engine a few weeks ago. About 81kMiles. Clean car, well maintained and not known to have been abused by prior owner. From day 1, I noticed that when I start off from a traffic light (i.e., from a dead stop) and try to go for a slow, smooth, easy build up of city street speeds, there is a momentary "dip" or hesitation, then the engine sort of catches up with itself and speed increases. By the sound of it, engine RPM does not actually slow down, rather, it takes a bit to react to gas pedal position. It almost feels like the result of a small vacuum leak in a regular carbourated engine, but this engine is throttle body fuel injected not normally carbourated. The car has plenty of pep and can do a jack rabbit start if I press down briskly on the gas pedal, and drives smoothly otherwise at all speeds. Any thoughts please? BTW, an acquaintance of mine said he has driven Cadillacs all his life and they are "just that way."
Thanks for any response.

Has the air filter been checked?? It could also be a clogged injector, dirty TB, fuel filter, etc......

But, they will be that way, to a certain degree....... A big heavy car like this isnt going to have the throttle response of a little sport compact or whatever......

That is NOT the way they're supposed to be. You do have a problem causing it. There are MANY things that can cause your issue so it may take some looking. Mainly, it will take a good patient mechanic. A thorough tune-up and general inspection should reveal the problem. And yes, it could even be an intake leak.

Has the air filter been checked?? It could also be a clogged injector, dirty TB, fuel filter, etc......

But, they will be that way, to a certain degree....... A big heavy car like this isnt going to have the throttle response of a little sport compact or whatever......

Air filter is not new but pretty clean (will change it nevertheless). Have good acceleration and smooth highway speed changes so I don't think it looks like a clogged fuel filter. A mechanic used one of those "injector cleaner" liquid kits, some right in the throttle body and some in the tank. Seemed to help just a bit for a short while (maybe just wishful thinking). Any thoughts about using that kind of stuff? Any particular kind ?

That is NOT the way they're supposed to be. You do have a problem causing it. There are MANY things that can cause your issue so it may take some looking. Mainly, it will take a good patient mechanic. A thorough tune-up and general inspection should reveal the problem. And yes, it could even be an intake leak.


When mechanic looked at it (see my reply to "Elweso") he said that there were no codes indicating any problems and even said the plugs didn't have to be changed. (He is a rare breed - not recommending work that he feels doesn't have to be done.) I am more inclined to believe it is a vacuum (intake) leak although I might put another can of "injector cleaner" through the system. My experience (years ago on my old Chrisler Imperial 440 Cu in) leads me to think that with the high underhood temps, especially here in Florida, those rubber/neoprene hose ends can get hard and brittle over metal fittings and loose some vacuum over time. Would you agree that would be a good place to start? What should a normal idle vacuum reading be, 29" to 30" ? (I don't have any shop manuals on the car or the engine).

Dudes hes having the same problem I am! Low idle hesitation! Same motor too!

" those rubber/neoprene hose ends can get hard and brittle over metal fittings and loose some vacuum over time."

i dont have the problem myself , but i did notice that the vaccum line from the thottle plates thats about 4 inches long has been replaced on mine ....

i will see if i have a vaccum gauge out in the garage and take a reading of my vaccum and post it in this thread

i dont have the problem myself , but i did notice that the vaccum line from the thottle plates thats about 4 inches long has been replaced on mine ....

i will see if i have a vaccum gauge out in the garage and take a reading of my vaccum and post it in this thread[/QUOTE]

Thanks for the tip. I'll look for that line first and see what condition its in. Please post your vacuum reading (and where you tapped in to a vacuum source) so I have something to go by. BTW, something that makes me feel even more that its a vacuum leak is that at a cold engine start-up, for a few short minutes (until the engine reaches normal operating temp) the hesitation is not bad at all. I would think that the slightly higher rpm and/or richer mixture at cold idle tends to compensate for a small vacuum leak. Once warmed up though, the hesitation is back.

I had exactly the same symptoms and found a thread at caddyinfo.com (http://caddymb.netgetgoing.com/ use the searchable archives)on cleaning the EGR tubes and throttle body, and it was right on.Not only ran like new, but added gas mileage back to what it got years ago!

I had exactly the same symptoms and found a thread at caddyinfo.com (http://caddymb.netgetgoing.com/ use the searchable archives)on cleaning the EGR tubes and throttle body, and it was right on.Not only ran like new, but added gas mileage back to what it got years ago!


Thatr sounds like a winner! As soon as I can get the car back from my wife, I'll give it a try. But,....this may take a few days before I have access (she just loves the car).

Frank

I had exactly the same symptoms and found a thread at caddyinfo.com (http://caddymb.netgetgoing.com/ use the searchable archives)on cleaning the EGR tubes and throttle body, and it was right on.Not only ran like new, but added gas mileage back to what it got years ago!
Take off the TB, and reach inside the hole that the TB hooks to (plenum), and get some rags and TB cleaner....... It will make a world of difference!!!

Take off the TB, and reach inside the hole that the TB hooks to (plenum), and get some rags and TB cleaner....... It will make a world of difference!!!


That sounds like more than an hour's work, which is ok by me but not necessarily ok by the lady of the house. Its almost impossible to get posession long enough to for the engine to cool down so I can work on it. Will try the vacuum lines and egr valve options first, then the TB removal etc., if needed. Thanks for the tip.

Frank H

TB removal isnt really that hard...... Maybe 20 mins to get it off, and then however long it take you to clean/replace......

Might as well do it all and not have to worry about it!!!

TB removal isnt really that hard...... Maybe 20 mins to get it off, and then however long it take you to clean/replace......

Might as well do it all and not have to worry about it!!!


The only issue is getting the car alone to myself long enough. You know who, has claimed the car for herself. I'll have to wait a bit 'til she goes away for a weekend to visit the grandkids then I'l be able to muck around under the hood to my hearts content without getting "The Look".

Thanks

If you take off that TB, I promise you the car wont be going anywhere!!! :D

That could also cause other, non-TB related strife.....

Just make sure you clean out that plenum as best you can before you put the TB back on...... You may have to rig up a rag on a dowel of some sort, but it will be worth it...... it will make a difference of night and day!!!!

If you take off that TB, I promise you the car wont be going anywhere!!! :D

That could also cause other, non-TB related strife.....

Just make sure you clean out that plenum as best you can before you put the TB back on...... You may have to rig up a rag on a dowel of some sort, but it will be worth it...... it will make a difference of night and day!!!!

Years ago I rebuilt some carbourators (Carter 4160s as I recall) but I've never handled a TB. Is there a gasket between the TB and the Plenum that I need to replace just because I removed the TB? Are there gasket/seal kits I need to or should get ?

You will need a gasket from the TB to plenum...... They are paper, and if they rip your screwed.... Sometimes you may not need it, but better safe then sorry..... Thats about it for TB removal....

You will need a gasket from the TB to plenum...... They are paper, and if they rip your screwed.... Sometimes you may not need it, but better safe then sorry..... Thats about it for TB removal....

I decided to just take a look under the air cleaner inlet thing to get the lay of the land so to speak. I jiggled a few tubes a bit an lo and behold, there is a small diameter steel tube that feeds vacuum into the transmission (probably something to do with load sensing for shift points). This tube is about 1/8" dia. at most. The upper end fits into another steel tube comming out of the TB. The end of the 'goes into" tube is flared, BUT the only thing holding it in place and (theretically sealing the connection) is a piece of rubber tubing over both tubes, about 1" long! No clamps, spring locks, nothing, nada, nil... even though the diameter of the tubes are different (remember, one goes into the other). It was stiff but could be turned. So.... I am thinking this may be the source of the vacuum leak and possibly have something to do with a bit of the slight harshness of the 1 - 2 upshift. Its worth a try to at least replace this little piece of rubber hose before doing much else. It certainly can't hurt. When I'm ready to tackle the TB removal, I'll get the gasket (just in case). Is this a dealer only item or can I get it at an auto parts place? The Cadillac parts department closes at 5PM and they are not open on weekends, so getting parts from them is problematic. Look forward to any comments you may have.

Im not sure what you are saying...... so post a picture of this thing yo are talking about.......

Also... I think you could get the gasket at an autoparts store..... might as well check, and if not, cadillac dealer is the next best......

If you want to get it done and dont want to go to any dealer, you could get that gasket material and make your own make shift one until the dealer is open.......

im getting ready to take my TB off and do my EGR , got the gasket at NAPA for like 5 bucks and the EGR for 65 (gasket included) , found the vaccum gauge today but i wont be able to look at the car till tomorrow (damned deed restrictions)

fixed my oil leaks today too , seems there are two fittings for pipes that go into the oil filter got one full turn out of boath , might be something else to look at while your in there to keep you driveway clean , you know how ladys get when things start marking there territory around the house

im getting ready to take my TB off and do my EGR , got the gasket at NAPA for like 5 bucks and the EGR for 65 (gasket included) , found the vaccum gauge today but i wont be able to look at the car till tomorrow (damned deed restrictions)

fixed my oil leaks today too , seems there are two fittings for pipes that go into the oil filter got one full turn out of boath , might be something else to look at while your in there to keep you driveway clean , you know how ladys get when things start marking there territory around the house

I won't get a chance to get under the hood untill next weekend at best. Will try to get gasket in meantime. I think the earlier fix on the vacuum leak I mentioned seems to have helped considerably. My little digital camera (a freebie from Comcast) is not adequate to take a decent picture of the tube I'm talking about. I'll try again to describe it. There is a steel vacuum line coming from something attached to the transmission. It is no more than 1/8" OD and is flared at about 1/2" from its end. This flared end goes into a steel vacuum line coming out of the side of the TB just slightly (3/8") above the level of the gasket. This tube has an ID just a bit bigger than the OD of the other line that goes into in. The only thing holding these to tubes together is a short piece of thick walled rubber tubing whose ID is just about the same as the OD of the larger (receiving ) steel tube. The rubber tube is movable and so there is no good seal, hence vacuum leak. I repositioned it so that a tighter fit resulted and the hesitation seems to have improved greatly. Will first replace this little rubber tube, put some spring clips on each end and see if the improvement is permanent.

i fixed that tube today , that line broke on me. so i took a small bit of the vaccum line that fits the small tube to the tranny , slipped it on the tube , then on the big side i ran the larger vaccum line that fits the fitting on the throttle body out of it and over the section of small vaccum line , works good

i read 15 inches of vaccum after doing the EGR valve and various vaccum line that shatterd on me dureing the job

also , do you know where the EGR soleniod is ? if so im confused about it , on mine i have only one line that goes to the egr on the top outlet and nothing on the bottom outlet (ive plugged this one) i still have the supply line on the other side of the sloeinoid but i have 2 outlets and have no clue which of the 2 outlets the egr line is supposed to be on , top or bottom ... i took pic of this too if i seem to be rambeling and i have pics of the line your talkin about if you would like me to post them

i need a beer

my buddy had the same problem with his 93 seville 4.9, it turned out to be a transmission problem, it was actually launching in second, it needed about 2k RPM to get goin but it felt fine once it was out on the highway, it turned out to be a solenoid inside the tranny, i dont know if this is your problem but, have it checked out...

im getting ready to take my TB off and do my EGR , got the gasket at NAPA for like 5 bucks and the EGR for 65 (gasket included) , found the vaccum gauge today but i wont be able to look at the car till tomorrow (damned deed restrictions)

fixed my oil leaks today too , seems there are two fittings for pipes that go into the oil filter got one full turn out of boath , might be something else to look at while your in there to keep you driveway clean , you know how ladys get when things start marking there territory around the houseI turned one of those lines 1-2 turns at around 100,000 on mine when it was leaking oil. The other line was loose too. I'd say that could very well be a trouble spot. I'd agree with checking them for the heck of it.

I've posted about a similar issue on my 95 4.9. Finally took the time to clean the throttle body and it seemed to to the trick.

CLEAN THAT THROTTLE BODY, post back with your results, I've read about several other owners with a similar symptom. I'm sure we would all like to know.

I'm not so sure about that throttle body idea... Mine is clean as new and I have the same problem. Brand new injectors too. I'm leaning towards the trans, these weren't really meant to go behind a 300 ft/lb 8cyl. Let me know what you find man.

Peace,
D.