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Hi,

   I lurk a lot but seldom post.  Hoping you guys can point me in a good direction.

   1995 Fleetwood Brougham, with the 5.7 Lt1.  The car has 135 k miles on it.  I have had it for 7 years and since 105 k miles.  It has always run perfect.  It is 100% complete and un-butchered.  lol.  Everything works as it should except the trip meter acts like a Vegas slot machine and the radio is fuzzy.  Probably antenna.  Point is, clean and un-molested.

   I run only ethanol free gas.

   It has a low throttle stumble that is slowly getting worse.  It happens just off idle.  So you feel it under very light acceleration or when holding a steady speed when you have to just touch the gas.

   I don't know when it was tuned up last.  I have not done it. (not broke, don't fix it)

   My question is, should I start with a tuneup or does this sound like a fuel problem (injectors or something).  Throttle body in need of cleaning?

   I figured I would ask before diving in.  My first step is going to be to clean electrical connections wherever I find them with electrical cleaner.  I have eliminated several problems over the years (on many vehicles) just by doing that.  But, assuming that does me no good, what do you all suggest.

Thanks!

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Usually a tip in hesitation is caused by a throttle position sensor. Not uncommon and relatively inexpensive to repair.

Personally, I would clean the throttle plates and bore and see if that improves the condition.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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I would be looking at that as well. Especially on that era. 

When it starts to go it does not always get a accurate throttle position and the actual throttle position does not match what it should be

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Perfect.  Thanks Guys. 

I guess I was on track with my thinking.  I have had 2 vehicles in the past that a simple connection cleaning did the trick when the TPS was suspect.  That thing can really mess up a vehicle.

I will report back and let you all know if I wind up actually having to replace the TPS.

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If you do I recommend using a Delco one. 

I have had rotten luck with aftermarket ones, Sometimes cause more issues than they fix

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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OK Folks - For the benefit of anybody looking...

I took things apart and cleaned the throttle body until it and the butterflies were shiny beautiful.  Got as much inside as possible.  I used throttle body cleaner.  If I had bought 2 cans I probably would have had a party and used it all.  Maybe it was just the fumes.  LOL.

Then I disconnected every electrical connection I could find, including the TPS connector.  Cleaned both halves of each with Electrical contact cleaner.  (good old Tri-chlor)  Good stuff.  Nothing organic remains after a bath in that.

Put it together and test drove.  Nice.  Stumble gone.

Thanks to those that pointed me in the direction of the TPS.  It woke up old memories.  I don't work on my cars as much as I used to.  Case of use it or lose it. 

Mission accomplished.  Thanks all.

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Ok Folks - I was a bit premature on that "all good" announcement.

Worked on it Sunday, Drove it about 10 or 15 miles and filled the tank.  It seemed OK.  Definitely smoother leaving idle but that was due to cleaning the TB.  

Drove it about 100 miles on Tuesday and about 20 miles in it was apparent the problem persisted.  By the time I got home that night it had devolved from a stumble to a full blown crumble.  LOL.

I pulled codes.  There were no new ones.  There were several old ones in the CCM (prefix of "1") and I cleared them.  Ran the car and checked them again.  One returned, as historical,  128, VES Open or short.  Did it again, 128 came back.  That isn't my issue but it does explain why it feels like flying a plane when it drives which always struck me s odd.  Caddy's don't don't feel like that.  Maybe an old Mopar but...

So to rule out water in the gas, last night I threw two bottles of Tekron in and a bottle of Heet to eliminate any water.  Last time I put dry gas in it 7 years ago, the gas gauge went crazy.  Took 5 Tekron tanks to fix that.  Figured I would do it all at once this time.

I just drove it for 20 miles and no change.  I ordered the TPS today and will just finish off that line of thought.

But I think I am headed for a tune up.  That is why I am writing now.  What are your recommendations regarding the distributor?  (OptiSpark)  Cap and rotor or just replace the whole thing?  I have never touched one.

Coil?  Replace?

I will replace the water pump while there because I know it will hemorrhage all over the new distributor after I put it together.

I need to look around at parts options but I always look for ways to pick a HP or few so if you have any suggestions let me know.  Otherwise, I will play it safe and buy good OEM stuff.

Thanks guys.

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I forget that is the last era with the distributor. That will cause issues in itself.

I stick with Delco caps, rotors, and wires. 

I do not care for autolite wires.

Napa ones are good. 

 

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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BTW............Have you checked the timing?  If hi-miles the timing chain is stretched a bit and

could effect timing thus the lag at accel. tip- in.

Timing retarded could cause the tip-in stumble/lag.

Cheap and FREE look see!

 

Edited by sonjaab

93 DeVille-13 Chevy Impala

72 GTO - 77 Triumph Bonneville

84 Z-28

Syracuse NY

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My TPS won't be in til Tuesday and I probably won't get to putting it in until next weekend.  That is my next step.

Meanwhile I have been looking into the OptiSpark distributor.  It has a few inherent problems.  I will probably opt for straight up replacement vs fixing.  Comparing aftermarket units like MSD etc.  Lot's out there.

I don't suspect the timing chain because symptoms came on so suddenly but, you never know where this could go.  I can be crazy at times and keep looking for and fixing problems (or making improvements) far beyond the problem at hand. Years ago I had a Chevy where the chain was so stretched it slapped the side of the timing cover at idle.  LOL.  At idle it sounded like it it had a crazy cam.  My Caddy runs far worse than that did.

Ignition timing?  I don't believe the OptiSpark gives you that option.  Please correct me if I am wrong.

Gonna drive it today to see if any possible water in fuel problems have healed after soaking in tekron and dry gas for a few days.  Not expecting any miracles there.  Just eliminating a cause.  TPS this week and then start looking seriously at the ignition.  I see my garage being very full of a large white Cadillac for a while, in the near future. Once I get started... I have a lot of "good" ideas rattling around in my head.  Great engine and it can be greater... I am my own worst enemy.  LOL.

Stay tuned and feel free to advise!

RC

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OK.  Problem wasn't water in the gas.  The TPS came in today and I put it in tonight.  No difference.  Now I have a spare TPS 🙂

Tune up it is.  Anyone have experience with aftermarket distributors vs OEM.  I figure to replace the entire thing as well as put on a new water pump when done.  I have seen suggestions out there to replace the the intake manifold gasket while there.  That seems odd to me.  Is there any substance to that? 

That's where all my "good ideas" come into play.  I mean, if the intake comes off then why not go a bit further and put LS4 heads, intake and throttle body on.  Pick up a few HP.  And while I'm there the cam would be taunting me.  And I could eliminate any current or future timing chain doubts with a sturdy double row chain.  See what happens...

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I guess the first question I have is - has the vehicle ever had a tuneup ? The mileage would indicate a tuneup is past due. Plugs, Cap, Rotor, wires. Coil if it is burnt or the button is bad.

Replacing the distributor seems a little extreme.

You say you went from a tip-in hesitation to a "crumble", does that mean miss?

There is a base timing, and the computer "controls" the timing from there. I doubt very much that the timing is off if it has been unmolested.

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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Hi - I don't know when it was last tuned up.  I am the 3rd owner and have owned it for 7 years and put 30k miles on it.

Sorry for my sarcasm/slang.  When I say crumble I mean and all over the place roughness in which I am beginning to discern a skip or two. Severe enough the hood vibrates. (I am a fanatic.  If it isn't purring, it's broke)

You think replacing the entire distributor is extreme?  I have not worked on these ever so my thought is to eliminate as many issues or potential issues as possible along the way.  Considering the water pump involvement, I would just as soon not have to go back in to fix something else in a couple months.

And correct me if I am wrong but that base timing is simply established when the distributor is bolted on the engine, correct?  There is no rotation of the distributor or tab with timing marks on the harmonic balancer as there is on a typical small block Chevy.

The guy that had it before me was an old guy in bad health who owned it about 5 years and 15k miles.  I bought it off his wife a year after he passed away.  I kind of doubt he had it tuned up.  He didn't do a lot with it.  The original owner had it 12 or 13 years and 90k miles.  I assume he would have had it tuned somewhere along the way.  To be honest, I have never looked up the maintenance schedule so do not know when the first tune up would have been done, assuming maintenance schedules were followed.

I have done a fair amount of work on it beyond the initial INTENSE cleaning it needed but not on the engine except for an idler pulley when I first bought it.  Like I said earlier... not broke? Don't fix it.  Besides, every time I approach it with a wrench, 500 bucks flies out of my wallet.  lol.  Seems to be a "thing" with this car.

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Don't read me wrong there OldCadTech.  It may be extreme to just replace the distributor but I am just being cautious.  Maybe it isn't necessary?  I don't know.  Tell me where I'm wrong.  I don't mind saving a bit of work and a few bucks if I'm comfortable with it.

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The only way I would replace the distributor itself is if the shaft is worn. 

But if it is not the worm gear type then I doubt it will be bad.

I would lean toward a tuneup. Especially being you dont know that history.

That is one of the first things I do on every vehicle I buy is a tuneup and coolant change.

If the intake gaskets are original that may not be a bad idea. I am not sure but I think yours are wet and may be the concrete ones if original

GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Thanks Rockfangd - I will be doing some homework before parts shopping.  I will look into the intake gasket situation too.  

The distributor mounts on the front of the block and is driven directly by the front face of the camshaft (a pin on the cam is received into the distributor).  I haven't had one in my hands but it looks like the shaft might be all of 2 inches long, if that.  From what I read, it is the optic sensor that ages out.  Ozone kills it given enough time, they say. The shaft or bearing almost never goes unless the front cam bearing is bad putting excessive load on the bearing in the distributor.  

I did learn something today... a misfire condition can be caused by a blocked distributor vent tube.  The distributor has manifold vacuum applied and the vent tube permits a constant flow of air through the distributor, flushing the ozone.  It is possible that if the vent side is plugged, that the front surface of the distributor cap can be sucked in enough that it actually interferes with the rotor.  It can also cause crossfire between the ink traces. 

Easy test - Pull the vent tube from the intake tube up by the MAF sensor and see if there is vacuum present.  I will look at that tomorrow night.  Odds are it isn't the problem but I like to find out all these details.  Interesting stuff.

Glad it's not my daily driver though.  LOL.  I would be stressing.

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Okay, now that you straightend me out on the optispark system, I was still thinking distributor at the rear of the engine, sorry.

The optispark was not as reliable as the regular shaft driven distributor and earned several infamous names. SO, in short, replace the optispark and do the tune up. I think you'll get the smile back!!

I'd go reputable, quality aftermarket for the optijunk (oops) Opti-spark......

Edited by OldCadTech

THERE IS ALWAYS ENOUGH TIME TO DO THE JOB RIGHT - THERE IS NEVER ENOUGH TIME TO DO THE JOB AGAIN !!!

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