1995 Caprice cough, sputters and idles fast

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.

Is this the L99 or LT1 engine?

In either case, what is the mileage?

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.

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.

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...

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

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!

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 ..

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!!!:crying:;

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!!!:crying:;

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 .

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.

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 !

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?

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.

$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.

I just want to thank all of you who have responded to my posts you have all helped me to learn SO MUCH about my car! I am a 52 year old woman and I began doing "some" of my own repairs when I was 17 years old and owned a '74 Monte Carlo with a 454 and Rochester quadrajet which I eventually put on myself along with a lot more parts over the years I had it. I have to give credit to my older 2 brothers who when the fuel pump when out on it in the middle of a Minnesota winter at about -10 degrees when I asked them to help me, as I had never done anything mechanical in my life, gave me a Chiltons and some tools and that's all the help I got 😕 To this day I remember laying underneath that car trying to put that fuel pump in...it took me hours! LOL! My hands were freezing as we didn't have a garage and the gas was freezing my hands because I couldn't get the rod to go in the way it was suppose to and I was crying and they were freezing too. But because of that one moment my career was destined although I didn't figure it out until about 10 years later when I became a surgical technologist and surgeons first assistant. I don't work on cars but I assist "working" on people during total joint replacements along with general and all the other areas. You wouldn't believe it maybe but being a mechanic and working in surgery are two very closely related careers 😃😃So tomorrow I pick up my car from having the tranny worked on and I will give a summary of what was wrong and what they fixed

You've replaced one CV joint, you're replaced them all. ;) FWIW, the spherical joint in a tilt steering column is very mush like the "business" end of a replacement hip joint - right down to the preload design, except the steering column doesn't use titanium hi-lo screws to hold the parts to the bone.

Hopefully the shop provides a comprehensive list, and among the list is an upgraded sun shell.

😃!!!Yes. Like that!!!

with the idle sputtering this may be the ignition coil and ICM . when this old the coil will internally arc . I just did this work this week on this LT1 engine, in the dark I could see the flashing of the ignition coil and with my hand on the engine as it flashed the engine did a shake.
these parts are to be replaced as a set because a bad coil arcing damages the ICM.
if the coil is original then I would have/do this replacing. to remove the OEM original coil you will need to remove the 2 rivets that hold the coil on the bracket. I used a dremel tool with a cut off wheel then pushed the rivet out.

I think I mentioned it before the distributor can also do this idle issue but the parts I suggest are cheap and much less a PITA to replace. placing a timing light on the coil high voltage wire will reveal the poor spark also. should be steady flashes with no misses .

on knee replacing cobalt is a great metal to use. LOL..

Ok I got my car back from the tranny shop and this is what was wrong with it and what they did...
Has a broken 2-4 brake band. Need to remove transmission from vehicle, replace brake band 3-4 clutch frictions and 1-2/2-3 shift selenoids and filter. It also had a cracked torque converter so they put a new one of those on. I really don't know anything at all about transmissions but everyone from the area bring their cars to this shop (but then he's the only shop in the area) but seriously I've only heard good things.
Blue Bowtie I'll look for that spark as now I'll be concentrating all effort and $,$$$. to getting the engine fixed. Love the power I beginning to get a glimpse of 🔥👸🚀🚓

If you want to get an idea what they did, read this in your spare time:

http://www.wwdsltd.com/4L60/4L60ERepairs.html

Keep us posted on the misfire diagnosis.

I should maybe put a run down of the expenc3s on the tranny just in case anyone is interested
1 Torque Converter $195.00, 1Trans Filter $25.16, Trans Pan Gasket $10.41, 10 Trans Fluid @ the 5.12 each $51.20 =
Parts $281.77
Labor $612.00
Supplies $4.47
Disposal $5.00
Tax $19.68
TOTAL = $922.92

I should maybe put a run down of the expenc3s on the tranny just in case anyone is interested
1 Torque Converter $195.00, 1Trans Filter $25.16, Trans Pan Gasket $10.41, 10 Trans Fluid @ the 5.12 each $51.20 =
Parts $281.77
Labor $612.00
Supplies $4.47
Disposal $5.00
Tax $19.68
TOTAL = $922.92

looks like they installed the wrong tranny fluid dexron VI costs about $9 USD a QT.

as I stated before DEXRON III IS NO LONGER AN APPROVED GM FLUID YEAR [2006] .. DO NOT USE IT IT CAUSES ALL THE DAMAGE YOUR TRANSMISSION HAS NOW. this fluid is one reason GM went bankrupt....!
SERVICE BULLETIN 04-07-30-037D
DEXRON®-VI Automatic Transmission Fluid (ATF) is the ONLY approved fluid for warranty repairs for General Motors transmissions/trans axles requiring DEXRON®-III and/or prior DEXRON® transmission fluids.

since the torque converter blew up the tranny fluid cooling system requires a good flushing to prevent particles from damaging the components.

the work should include a 1 year warranty.
the transmission should also be re-inspected after a couple of K miles to ensure no leaks/fluid issues/pressures are correct.

good luck.

Thank you j cAT. I told him about the tranny fluid and I could tell I wasn't going to win so I decided I'll just have to bring it some other place that will put in what I want. And thank you for the advice on the timing too I'll have that checked.

j cAT is correct that Dex 6 is the superior and preferred fluid. I doubt that Dex 3 had anything to do with the failure of the band or band anchor, but it may have contributed to wear and glazing of the direct clutch.

It would be good to run the trans for a few miles/days/weeks and then drop the pan/filter to change the fluid and check for excessive material. There will undoubtedly be a bit of metal from the band and rebuilt direct clutch stack wearing into the steels and input drum. Clean the pan and magnet and refill with about 6-7 quarts (usually on a 4L60) so that over half the oil is clean Dex 6.

Did the shop install a drain plug? They should have (my opinion) because you will want to change the fluid soon and again after about 20-25K and don't lose any more sleep. Return to the regular service schedule after that, or about 50K between changes.

Thank you j cAT. I told him about the tranny fluid and I could tell I wasn't going to win so I decided I'll just have to bring it some other place that will put in what I want. And thank you for the advice on the timing too I'll have that checked.

good change. they use the old damaging fluid because it creates more $$$$/repair work for them. DEX VI is the proper fluid not III...

my 1996 Impala has had synthetic fluid in it since 1998.. took out all the dexron III . still no transmission problems shifts better than new when the DEX III was in it..

you will see this when the air temp drops to zero deg F. DEX III turns to acid also after it is exposed to the hot typical temps..

I agree also to have the pan drop filter change after a few K miles.. I would also have the better repair shop inspect the pressures at this time to be sure all is good..
MAKE SURE YOU GET THAT 1 YEAR WARRANTY ...I would expect $1500 for this repair work ... tranny shops have lots of experience doing these due to the defective GM fluid used lots of parts available.