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H4100 1983 Seville stutters 0-5~10, then goes. Climate control won't hold 70

Started by ImJustSayn, February 12, 2017, 11:15:54 PM

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ImJustSayn

Hello Forum Friends:

My 1983 Seville with 101,200 miles, the HT4100 sputters a bit when going from a complete stop to accelerating. I have had new spark plugs and wires installed, engine tuned up, fuel filter replaced. Once I am traveling about 10-15 miles per hour, stepping on the accelerator the engine will accelerate normally. Its only when going from a complete stop to accelerate to 10-15 mph. I have to pump the accelerator and it will then seem to get over this hesitation hurdle. I have had two Cadillac Repair shops go inspect and review this but to no avail, it still happens.

There are no service lights or codes thrown.

One thing to note, too, the climate control, will blow full cold at 60, and full hot at 90. However, if I set the climate control to 70 or 72, the temperature will not maintain. It will wander especially after putting the accelerator completely to the floor, then letting up on it. I have not figured out how to take out the glove box yet to check the mixing door to ensure its not rusted, but it doesn't seem that could be it. Since the engine stutter and temperate wandering seem to be related. Any advice of where to start would be really appreciated.

I did review this post: Unhappy1983 Cadillac Seville HT-4100 Vacuum Leak? I saw that article. Not sure though if my problem is different from his.
Allen G., CLC #30300
1985 Seville Elegante
1983 Seville

The Tassie Devil(le)

G'day Allen,

You have an email from me that requires your attention.

Thanks,

Bruce Reynolds,
Forum Administrator.
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

ImJustSayn

Hi Bruce,
I looked in my email and I don't see anything from you. I added my CLC# to my profile. Is there something else I need to do?
Thank you,
Allen Goetsch
Allen G., CLC #30300
1985 Seville Elegante
1983 Seville

Scot Minesinger

Allen,

If you have not already, please buy the shop manual, it should really help on the climate control.  There are two electronic controls under hood that from my experience are more likely to be the problem than under dash.  I would start there.  It is difficult to find good used replacement because NOS are not available.  Often you buy a used and it is no good.  The process of finding good ones can be time consuming.  The good news is these are easy to get at and replace.

I'm answering this presuming your heater core and valve are good and your refrigeration circuit is good too.  Since you write it cannot maintain either a heating or cooling setting it seems it would be a control issue, not refrigeration or heater problem.

On the 4.1, reliability aside not a fan of that engine.  It may good to research this as you have started.  If it turns out major engine work is required it may be better to replace it with a stronger more reliable engine, as many already have.  Hope you get it fixed for low cost and enjoy.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

Most common issues I saw with the TBI systems which includes the 4100 is the base settings were done incorrectly or are wrong.    The critical ones are the throttle stop and timing.   To set both of those there is a very specific sequence that must be followed.   Part of the sequence is to put the computer into the proper mode and then to set it to the factory spec.   One setting effects the other and if they are done in the wrong order or to the wrong specs or without the computer in the proper modes you get all sorts of odd things going on because the computer is trying to compensate from not knowing where its starting from. 

For some reason the distributors seem to come loose in the 4100's so make sure its tight.   4100's were also hard on the distributor drive gears so if timing is suspect may be worth pulling it for a look.   

Check the vacuum lines running to the MAP sensor which I think in that car is mounted behind the glove box.   The C car is there in that era so I am assuming the Seville is there too but I could be wrong.   A crack in that vacuum line will be feeding the computer more bad info.

You could try disconnecting and plugging the egr valve to see if that changes things.   Maybe its sticking then suddenly popping open.

Seen it a few times and read about it more recently where you get a split in the short piece of fuel hose that the pump hangs from inside the tank.   It didn't used to happen back in the day but now that this stuff is this old it seems to be more common.   High demand it doesn't leak because the pressure drops and idle is fine because demand is low, its just those transition periods where it drops the pressure enough to cause a problem. 

Have you had a good look at the spray pattern out of the injectors?   It should be a mist, no dribbles or streams till it hits the walls.    Have you done a refresh kit to the throttle body?   The fuel pressure regulator is part of the throttle body and at this age has likely failed.   The refresh kits have the o rings for the injectors, a regulator, and gaskets.   When changing those you get a look at the screens around the injectors and will get an idea how clean the fuel system has been over its life.     The TBI systems were very simple and reliable but are now at least 20 years old, or like this over 30 and rubber just doesn't last that long especially around modern gas. 
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

ImJustSayn

Morning TJ and Scot, thank you both for the in-depth posts. I will troubleshoot based on your suggestions and give my mechanic the guide to ensure base settings where done in correct order.

As for the HVAC system, the heater core is stellar, new radiator and hoses, new AC compressor. I can check the heater control valve, I see that is a low cost item to replace.  My mechanic had done a complete check of the hoses on the engine and climate control hoses in the engine compartment. He didn't find any leaks. And the vacuum pump pulls at normal pressure.

Seeing that the temperature mixing will vary about 7-12 seconds 'after' a full throttle acceleration and then easing up off the gas to return back to the any of the legal speed limits, my hunch its a vacuum leak causing the mixing door to move around. We did check the ambient temperature sensor inside the car and it reads normal on the tests (per my mechanic).

I had read in another post that I can't seem to find (lesson learned -bookmark it) about removing the glove box and checkin the mixing door lever and actuator. Some said it can get rusted and stick. 

To buy replacement vacuum hoses I welcome suggestions on which vendors/brands to buy from and the hose sizes.

------ regarding the stuttering of the engine ----

My mechanic did check the distributor assembly and replaced it, as it was a bit sloppy.

I will check those vacuum lines behind that glove box door to the MAPs sensor. Are there two sensors? MAPS and Barometric Sensor?
Given I'll have the this all open, would it be advised to just replace the sensors?
Is it advised to always buy premium for ACDelco brand or after market one made to the specs?

Inside the engine compartment, is this the piece that can fail under load, accelerating and causing stuttering?
http://www.ebay.com/itm/ACDelco-17078259-Throttle-Position-Sensor-1983-Cadillac-4-1L-Deville-Seville-/371761213997?hash=item568eb1f22d:g:9gcAAOSwzaJX~nmH&vxp=mtr

Thanks again for the help.

Allen G., CLC #30300
1985 Seville Elegante
1983 Seville

TJ Hopland

I don't have a manual handy or the greatest memory,  didn't these have a belt driven vacuum pump that ran things like the HVAC and cruise control?
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

ImJustSayn

Hi Friends,
Just picking up this thread where I was investigating stuttering under load when accelerating from zero to about 15-20.

Is this the correct part to replace or check out for the throttle position that can cause stuttering? The Distributor and rotor was replaced and tightened up.

Inside the engine compartment, is this the piece that can fail under load, accelerating and causing stuttering?
http://www.ebay.com/itm/ACDelco-17078259-Throttle-Position-Sensor-1983-Cadillac-4-1L-Deville-Seville-/371761213997?hash=item568eb1f22d:g:9gcAAOSwzaJX~nmH&vxp=mtr

Thanks again for the help.
Allen G., CLC #30300
1985 Seville Elegante
1983 Seville

TJ Hopland

Throttle position sensors are easy to test with an ohm meter, ideally an analog one.    Think of them as a volume control or light dimmer.    Say cruise is 30% what can happen is at that setting they can wear so the signal to the computer is kinda intermittent or scratchy.   As soon as you go to 25 or 35 you are fine.   With the meter you would be looking for places where the needle wiggles vs moves smooth.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

smokuspollutus

As TJ said, it is very easy to test a TPS with an ohm meter using the test plug, or can be accomplished via OBD if you have the manual. I personally don't see the TPS being the problem if it doesn't waver at idle.

Check the heat stove pipe for proper connection and operation. If that checks out, disconnect the pcv supply hose from the passenger side of the air cleaner and drive the car (will not harm anything). Does the stumble go away?

Is the stumble present with the engine cold?

The HT4100 likes running with timing a bit advanced, 12 BTDC is where most are happy. You might be able to get to 14 or so and still stay on 87. I don't recommend changing settings before the problem is solved but if all else checks out its worth a shot.

The mix door is 100% divorced from any vacuum system on this car.