[AElayyat]

My car is a 85 Cad. Fleetwood Brougham w/ 4100 RWD.

I need any advice fellas. First off I have replaced the following parts within the last 2 weeks:

1) Fuel pump
2) Fuel Sending Unit
3) Fuel Filter
1-3 done by Cadillac dealer due to bad parts.
4) Vaccum pump (went bad, I replaced it last Tuesday with the part from Cadillac)
5) Distributer cap
6) Distributer rotor
5-6 done by me using Cadillac parts.
7) Muffler, resinator, a exhaust flange, and driver's side header gasket (done at Midas).

All of the above were things that went bad and ended up hitting me at the same time.

And after all of this shit, my car is hesitating when accelerating, mainly when I come to a stop and attempt to take off.

Any advice, my dad is guessing that the car needs a tune up (replace spark plugs, and wires) or valve adjustment.

 

[illumina]

My car is a 85 Cad. Fleetwood Brougham w/ 4100 RWD.

I need any advice fellas. First off I have replaced the following parts within the last 2 weeks:

1) Fuel pump
2) Fuel Sending Unit
3) Fuel Filter
1-3 done by Cadillac dealer due to bad parts.
4) Vaccum pump (went bad, I replaced it last Tuesday with the part from Cadillac)
5) Distributer cap
6) Distributer rotor
5-6 done by me using Cadillac parts.
7) Muffler, resinator, a exhaust flange, and driver's side header gasket (done at Midas).

All of the above were things that went bad and ended up hitting me at the same time.

And after all of this shit, my car is hesitating when accelerating, mainly when I come to a stop and attempt to take off.

Any advice, my dad is guessing that the car needs a tune up (replace spark plugs, and wires) or valve adjustment.

Try the tune-up. It might be that simple.

I don't think that the 4.1 liter needed the valve lash adjustment. At least mine didn't anyways...

Try a compression check and see where your engine is at. It should be pretty even across the board and ideal readings should be around 110-120 psi for an engine that old. If there are uneven readings, then you have some problems...

 

[guidematic]

At what stage did this problem first appear? Maybe it was something that was done that caused it.

Retrace your steps. You may find the problem by rechecking the work.

Mike

 

[AElayyat]

Try the tune-up. It might be that simple.

I don't think that the 4.1 liter needed the valve lash adjustment. At least mine didn't anyways...

Try a compression check and see where your engine is at. It should be pretty even across the board and ideal readings should be around 110-120 psi for an engine that old. If there are uneven readings, then you have some problems...

The engine was rebuilt about 10 years ago using Cadillac parts and it now has around 80k. I did pick up a set of spark plug wires from the Cadillac dealer today, I still need to get the plugs and I'll try that out.

 

[AElayyat]

At what stage did this problem first appear? Maybe it was something that was done that caused it.

Retrace your steps. You may find the problem by rechecking the work.

Mike

This problem started out when I ran out of gas and I thought the problem was the ignission module inside the distributer, after that is when the hesitation problem showed up. The module tested good at 2 different Auto Zone's.

 

[AElayyat]

I changed the spark plugs (I got Bosch plugs from Kragen), and I did gap them (.060), and I changed the spark plug wires (picked them up from Cadillac). I also changed the PCV valve, and Crank Vent Filter, the air filter was still good.

After this the roughness is gone, but the car still has the hesitation. Could the problem be a transmission issue?? (I remember the tourque converter and front pump went out in my trans about 3 years ago and if I remember correctly I was getting somewhat simillar symptoms).

Any more suggestions guys??? I've dumped A LOT of $$$ and time into my baby and she is not being very nice to me.

 

[peteski]

It could be the transmission or it might possibly be the EGR valve. It might also be low fuel pressure. Maybe running out of gas messed up the gas pump.

Peteski

 

[illumina]

yes it bogs and hesitates when you give it too much gas, but that is normal.

Normal for your car, or normal for every Cadillac with the HT 4100?

Quite frankly, bogging and hesitation is never normal and Cadillac (or any other car maker for that matter) didn't sell their cars with the stipulation that bogging and hesitation is normal. If so, then they never would have sold millions of cars with those engines. If your car is showing the aforementioned symptoms, then there is a failiure in the mechanical/electrical/fuel areas that needs to be addressed.

And as far as not checking the gap on a new set of plugs, then you're asking for trouble there. Yes, they may come 'pre-gapped,' but that doesn't mean that a good home mechanice shouldn't check to make sure that their plugs are gapped properly anyways. I've seen several cases where plugs are often not gapped to factory specs, thus causing issues later on down the road. Take my advice: check gap anyways. It only takes five minutes if that.

 

[AElayyat]

It could be the transmission or it might possibly be the EGR valve. It might also be low fuel pressure. Maybe running out of gas messed up the gas pump.

Peteski

peteski, the fuel pump was replaced by the Cadillac dealer.

Earlier this afternoon I found a disconnected vacume line (the one that goes into the EFE? unit; it's the device on the passanger side header) and I re-connected with little chage.

I also checked the EGR valve (press the dighrapham up and the engine RPM decreased), which according to this forum and my FSM tests as good.

I am now thinking the problem might be an issue with the transmission, but I have to completely elimanate any problems with the engine.

 

[AElayyat]

Normal for your car, or normal for every Cadillac with the HT 4100?

Quite frankly, bogging and hesitation is never normal and Cadillac (or any other car maker for that matter) didn't sell their cars with the stipulation that bogging and hesitation is normal. If so, then they never would have sold millions of cars with those engines. If your car is showing the aforementioned symptoms, then there is a failiure in the mechanical/electrical/fuel areas that needs to be addressed.

And as far as not checking the gap on a new set of plugs, then you're asking for trouble there. Yes, they may come 'pre-gapped,' but that doesn't mean that a good home mechanice shouldn't check to make sure that their plugs are gapped properly anyways. I've seen several cases where plugs are often not gapped to factory specs, thus causing issues later on down the road. Take my advice: check gap anyways. It only takes five minutes if that.

That is good advice, to check the gap, which is what I did. And guess what, all of the spark plugs (6) but 2 were gapped at .060. One was less than .060 and the other was more than .060.

 

[DrDave]

Ummm... Did anyone say O2 sensor?

$20-35.. needs changing if it's never been changed. Can cause severe hesitation, bogging down, and your other symptoms if it's really bad. Worth the try if you haven't replaced it in a while.

Hesitation isn't normal for these engines--the cat converter however can make them hesitate like none other if it's going out. Also causes rough idle. When they really get clogged, they can make the engine shake so violently you'll swear it's going to explode.

 

[AElayyat]

Ummm... Did anyone say O2 sensor?

$20-35.. needs changing if it's never been changed. Can cause severe hesitation, bogging down, and your other symptoms if it's really bad. Worth the try if you haven't replaced it in a while.

Hesitation isn't normal for these engines--the cat converter however can make them hesitate like none other if it's going out. Also causes rough idle. When they really get clogged, they can make the engine shake so violently you'll swear it's going to explode.

Should I wait for the 02 sensor code, or just go ahead and replace it?? I don't know when the last time it was replaced so...

 

[DrDave]

Mine needed replacing before the 'check engine' light ever came on if that's what you mean. You can enter diagnostics and check parameter 0.7 (I think?)--one of them shows the output of the O2 sensor and it ranges from .00 to 1.00 (you'll typically see it rapidly jump around every <~1sec from .15 to .85, +- 10 pts. Also, the "econ" light in diagnostics will flash on and off, indicating a rich or lean condition. If it's always on, or always off, that's another indication that it's sending the wrong signal to the computer. However, just make sure the O2 sensor is "warmed up", by having the engine at FULL operating temperature (around 88-90 degrees C, as per 0.4 parameter) so that the O2 is functioning as it should. If it's not warmed up and in closed loop mode ("off" lit in diagnostics), the O2 sensor won't read the right signal yet.

You can probably get more info on diagnostics in other forums. But in a nutshell, hold "off" and "warmer" until it enters diagnostics. It'll flash trouble codes if any, and then default to "7.0". From there, press "reset" once on the fuel data center, then "Inst/Avg", and keep incrementing with "inst/avg" until you get to the right readout for the O2 sensor. You can check the 'off', 'econ' lights at any time in diagnostics.

 

[peteski]

Even if the fuel pump was replaced recently, it still woudln't hurt to check the fuel pressure (with a gauge). Maybe the press. regulator is going bad.

Also, try totally disconnecting the vacuum hose from the EGR valve and see if that makes any difference (while driving).

Also, was the ignition timing checked? I see that you hade stuff done around the distributor. Maybe it got disturbed...

Peteski

 

[DrDave]

Fix the cat... hesitation disappears.

Perhaps on later models they fixed it, but on my '82 it didn't show the 'check engine' light when the O2 sensor was going out, and was causing severe bogging on acceleration.

 

[AElayyat]

These are all very good suggestions fellas, I think I'll change out the 02 sensor and I'll go from there, I'll keep you guys updated, and by the way you guys kick ass!

 

[AElayyat]

Ummm... Did anyone say O2 sensor?

$20-35.. needs changing if it's never been changed. Can cause severe hesitation, bogging down, and your other symptoms if it's really bad. Worth the try if you haven't replaced it in a while.

Hesitation isn't normal for these engines--the cat converter however can make them hesitate like none other if it's going out. Also causes rough idle. When they really get clogged, they can make the engine shake so violently you'll swear it's going to explode.

On the RWD 4100 in my Fleetwood Brougham, I could only find 1 o2 sensor. It was located on the rear of the driver's side header. Is there a second one on these engines of is it just the one? (I know my 89 DeVille w/ 4.5 has 1 o2).

 

[guidematic]

I find that replacing the O2 sensor can make a world of differance. They do wear in time and should be replaced periodocally. Replace it with a Delco unit only. Also, I would have recommended that you have replaced the plugs with Delco plugs. They are the only plugs that really work well in these GM engines.

Have the fuel pressure checked. It should be in the vicinity of 14-17 lbs. If not, the pump or the regulator is weak.

All these things can cause hesitation.

Mike

 

[AElayyat]

*UPDATE*

PROBLEM SOLVED!!!

Thanks for all of the wonderful suggestions fellas. This past weekend I changed the engine oil and trans. fluid, filter and pan gasket, and that was the end of this little drama. No more hesitation and tranny shifts smooth once again.

 

[peteski]

That is good, but what do you thing fixed the problem?
Only thing remotely related would be the transmission fluid. Still, it is strange that it woudl make that much difference.

I don't think that fresh engine oil or pan gasket have anything to do with the problem.

Enjoy cruising around in your Caddy!

Peteski