1995 Caprice cough, sputters and idles fast

[NAAnderson]

Hello I have a 1995 Caprice that is running rough. It coughs, sputters and even does a small backfire occasionally and also idles too fast, it also cuts out occasionally but never dies. It does this when it is warm or cold. Any suggestions where to begin? Thanks.

[Blue Bowtie]

Is this the L99 or LT1 engine?

In either case, what is the mileage?

[NAAnderson]

I'm not sure which it is. I know that it is a 4.3 liter SFI V8 and that it has the distributor, wires and plugs that are on the lower part of the engine if that helps. It really does most of the coughing, sputtering, etc... upon excelleration however it does still run rough and won't keep the cruise control on for a long distance either. It has about 120,000 miles on it.

[Blue Bowtie]

That would be the L99 engine.

The distributor is the key part of the Opti-Spark system. The distributor caps on those are known to suffer internal insulation breakdown at anywhere from 90,000 to 150K miles. There is also a ventilation system connected to the distributor intended to purge any moisture and ozone, maximizing the distributor life.

It may be time to investigate the distributor, plug wires, and related components.

The description of symptoms may also indicate a problem with fuel pressure or delivery. Testing the standing and running fuel pressure may provide useful information.

[NAAnderson]

I noticed that every time I unscrew the gascap there seems to be an excessive amount of air that escapes. Is that normal on these cars? I've only had it for about a month but the previous owner kept up to date very well on the maintence as she had all the receipts for everything such as tranny filter and oil, oil changes etc...

[Blue Bowtie]

Tank pressure is normal. That means the tank is sealed. My '94 SS "breathes" for several seconds after loosening the cap - Always has.

[NAAnderson]

When I drove it yesterday I really tried to listen to exactly what happened when. It seems that when I am at a stop and then accelerate the car really struggles in 2nd and after that until I get to the speed I want to go. If I let up on the gas peddle it seems to even out a little and will still accelerate as I am pressing the accelerator down further than is necessary for it to go at that speed. When I get to a constant speed it levels out and only makes an occasional sputter so most of it seems to be upon acceleration. Does that change anything as far as what you think it might be? Also I checked at O'Reilly Auto Parts for a distributor cap and they run about $130.00 I then checked on Ebay and I can get one for less than half that amount and they say it is "new" and several other people have bought from h im and he has a high satisfaction rate. What is your opinion about ordering a part such as this off of Ebay? By the way he offers a 30 day return policy. One last question... there seems to be a red and a blue optispark any idea which is the right one or should/would I just look and be able to tell that way? Thank you for all your help I appreciated it SO very much!

[j cAT]

this summer I had a slight miss fire 96 chev impala SS LT1 5.7L engine. now that the temps and moisture has returned the intermittent misses are becoming more frequent. the distributor [opti ] is just three years old.

I disassembled the components air pump/water pump/distributor/crankshaft hub .

what I found was the distributor has a huge leak. the seals are shot. also the cap is distorted creating leaks. the venting system of the opti is 2 hoses. one hose goes to the air intake snorkel. the other hose goes to the intake manifold driver side . air enters the hose at the intake rubber hose then enters the opti at the top of it..then the other hose sucks out the ozone gases created at the bottom of the opti . this hose as it passes over the intake manifold has a screen filter orifice then a check valve so that only sucking is going to occur . by removing the hose at the snorkel that goes to the opti you place a vacuum gauge and check that you has some vacuum like good would be 7-10 inches .. bad would be 2 inches or less.

many think that the venting system is why this is not sucking but most of the time it is because the opti seals are shot. when this happens that sucking to remove gases causes the opti to suck in dirt and water which then wears out the internal parts.

In my case the $225 opti 3 yrs old not only had seal failures but also the rotor screws had loosened , the optical disk was hitting the optical sensor which is an LED and reader. the disk is a wheel with holes in it .as the wheel turns the sensor sees the slots passing telling the PCM where the cam shaft is. this controls the ignition and injectors. your vehicle uses the same optical sensor distributor as my 96.
so when the disk hits the sensor it causes it to not properly read then the miss fires. many have had then come apart internally .

you also have a high idle . that is most all the time a vacuum leak . check the vacuum lines esp. the PCV HOSES as they crack esp the 90 deg rubber 3/8 hoses.

the other issue you have is excessive fuel tank pressure this is not normal. the fuel system is designed not to have pressure but a slight amount of vacuum .. this is to prevent any air pollution. sucking when removing the gas cap is good but if you feel the cap is looking to blow out that is bad.

what has to be done is the canister hoses behind the front passenger side bumper and forward of the passenger side front wheel is where thes hoses must be replaced since they collapse and restrict the fuel tank vapors that is supposed to enter the charcoal canister .. then when the engine runs these gases are sucked out to enter the engine by a vacuum switch located on the pass side of intake manifold .. I replaced all these hoses.. make sure you wear gloves since the rubber will stain your hands do to 20 plus years of gasoline vapors eating at the rubber.

opti to buy is a skip white which is a GM rebuilt ... this appears to be the best available . you will not find a new GM distributor for this vehicle. many are selling [like my opti] chinese crap distributors which have a huge failure rate.

my 21 yr old opti which I replaced 3 yrs ago still worked but had a rotor wobble due to its bearing being worn after 18 plus years but had no seal leaks . so you best buy a rebuilt GM ac delco distributor with a good warranty . new in this case means very poor quality. a new gm distributor may be found .. the prices are about $700..

you test start the engine with the distributor only connected installed ... if it runs then complete the install. do not put on the water pump etc then test it . run test for 10 sec only ..
this is an expensive repair perhaps $1300 ..

[NAAnderson]

So here is what happened yesterday... I was driving the car and it was qcting uof p so I put the peddle to the metal and now the darn thing won't shift out of lowwon't! Is the tranny shot? My ex mentioned the throttle control sendor or something like that. I am at my wits end!!!;

[j cAT]

Originally Posted by NAAnderson

So here is what happened yesterday... I was driving the car and it was qcting uof p so I put the peddle to the metal and now the darn thing won't shift out of lowwon't! Is the tranny shot? My ex mentioned the throttle control sendor or something like that. I am at my wits end!!!;

looks like you bought a vehicle that was not properly maintained. no up shifting just 1st and reverse would be no/low tranny fluid pressures. the use of dexron III causes these issues .. could also be no tranny fluid. check fluid level engine at normal temp on perfectly level ground engine on should be in the operating range with NO air bubbles solid red color . tranny shop can test pressures so they can give an estimate .. these 4L60 trannies are well known for failures due to the dexron III fluid that is NO longer a GM fluid. the correct fluid now is the DEXRON VI FLUID.

GOOD LUCK .

[NAAnderson]

First thing I did was check the trsnny fluid and it was good I check my fluids often. The person who I bought it from even had the filter changed according to the maintenance chatt like she was suppose to she has teceipts for all the work done on it. I'm bringing it to the shop today to get a final answer. Thanks for your help.

[j cAT]

Originally Posted by NAAnderson

First thing I did was check the trsnny fluid and it was good I check my fluids often. The person who I bought it from even had the filter changed according to the maintenance chatt like she was suppose to she has teceipts for all the work done on it. I'm bringing it to the shop today to get a final answer. Thanks for your help.

unfortunately these vehicles are so old that the auto tech's fail to properly do what is required. is the transmission fluid type listed on the record ? the fluid to use is DEXRON VI NOT DEXRON III !!! ALSO you DO NOT FLUSH these transmissions ...... so if they did flush it with a machine then they killed it . also dexron III is a acid creating fluid that GM no longer approves of its use in any GM vehicle. now you may say or the shop may say it is the correct fluid . unfortunately GM did not send out a notice to owners , that own these that this fluid is destructive !!!! [year 2006]. GM went bankrupt because of this and other factors .. this fluid caused them a huge loss ... tranny shops use the III fluid because its good for their business ... why use the proper fluid that costs more $$$.. more profit at your expense , also more work !

[Tech II]

Question:

You said it was acting up, so you put the pedal to the metal and it wouldn't upshift.......what happens if you lightly accelerate? Does it shift ok then?

[NAAnderson]

Hello I ended up bringing it to NATCO a transmission shop. There are seversl things wrong with it but biggest so far is broken rings in drive. I know some about motors but when it comes ro transmissions I am totally clueless. He said it still does the sputtering thing so I will take everyones advice given to me on hete when I get it back. I know there's probably some people that think..just junk it, why waste the money, but it only has 130,000 on it, I like the way it rides and the power it has (when it's running right), insurance is a LOT LESS than a newer car as are tabs and I absolutely hate looking for a new car because I refuse to make payments. So there's a lot of reasons 😀 The tranny bill he quoted me is $950.

[Blue Bowtie]

$950 is only two car payments. It's worth the investment.

4L60s are easy to build into a very stout trans. If all the common upgrades are done as part of the rebuild you should be trouble-free for a LONG time.