I'm new to this place, but came across it many times while looking up info about issues I've had with my 1996 Monte Carlo LS 3.1L, so what better place to ask than a forum full of enthusiasts, right?

Anyway, some back story... about a month ago, my fuel pump died while I was at the post office... $450 to get it fixed was not my thing, so I bought a fuel pump and did it myself for about $72... that tank was one hell of a pain in the *** to get off due to not having anything but a 3" extension, but it was still worth doing.

Taking care of that has spurred me into taking care of all the other issues I've had over the last 6 years I've had the car, but since I've never actually gotten into fixing up cars, despite having plenty of know-how, there's a lot I'm still learning as I go, and I need some help figuring out some issues I'm having.

Anyway, there's a few things I'd like to point out so you have the info...

When I got the car, I did do a lot of gravel road travel for about 2 years, so there's plenty of dust around... I'm cleaning it off as I go, including having cleaned the MAF sensor, and cleaning whatever else off that I'm working on.

I ended up running this car with 5 1/2 quarts... I think... I may be wrong, though, but I think I did once at least, believing this car did take 5 1/2 with filter change, and it had to have ran for a good many months like this... though I never drove it around more than a few miles a week, so I don't think it really did anything. I never noticed my engine running any differently after any of my oil changes if I did do this.

I'm still not sure if I actually did run it like that, since there's no way to tell... all I know is, when I changed the oil, I was paying a lot more attention and checking the level as I added and was making sure to get it perfect, since I was fixing all my issues, and I did think it was 5 1/2 till I had 5 in and saw it well over the full mark, and realized that it was in fact 4 1/2. But anyway...

3rd is, when my fuel pump died, I think it was killed due to a frayed throttle cable which was stuck holding the throttle open. When my car failed to start at the post office, I thought it was flooded, and kept trying and waiting... eventually, with the help of another person and some jumper cables, my car finally kicked to life, but the engine first ran like it was flooded for a few seconds, then revved clear up to like 4000RPM, made a VERY loud couple of bangs, and revved more and sat there running at full throttle for about 10 seconds till I jumped around and pulled the throttle back shut, noticing the cable had gotten stuck holding it open.

I mention this in case that caused anything to happen to my engine, though I don't hear or feel it running any differently than before the pump went out.


Ok... sorry for rambling there... on to the things I'm trying to figure out. The net hasn't been very friendly on results to what I'm searching for.


First up, for quite a long time now, many years, I've noticed this knocking kind of sound coming from my engine... for the longest time, someone had me believe it could be a bent cam shaft, but I'm wondering if it's a lifter that's not closing all the way... it happens every rotation, once per rotation of the engine as far as I figure, about 4 times a second at 800RPM idle.


Second, my idle is a bit rough... like it feels like it's missing randomly once every 2 to 10 seconds, and when it happens, my RPMs will be at about 700-800 sitting steady, and drop to about 600-700 while I feel the car shake... it's just for a split second randomly every few seconds, and sometimes can last a few seconds as well.

One thing to note... I was having this, and my idle does feel slightly better after running awhile.. or it did. I has cleaned the MAF sensor, as it was covered in black stuff, like exhaust backflow or something, and after I did that, the idle definitely held steady a lot better. But the other day, I decided to clean out the throttle body with some carb and choke cleaner, and while I was at it, was cleaning the IAC valve off, too, since it was also completely covered in black greasy crap. Well, some cleaner ended up inside the thing, and it didn't feel quite right to me, though I'm sure I got it all out. But after I got it back on, my idle has gone back to being rough again, maybe even moreso than before. However, the valve seems to be working, as when I pull off the wire, the engine just revs clear up, so I know the thing is still working.

But yeah... I had already changed 3 of 6 spark plugs, and still have to finish the other 3, and have had a can of sea foam running through... but I am wondering what other things could cause a rough idle that I should take a look at. I plan to check out and clean the EGR valve already, and install the back side 3 plugs behind the engine, and I'd also like to check out my fuel injectors, too.


Third thing I want to take care of right now is that I have a strange electrical issue that just makes no sense to me.

For a long time, I noticed this on my courtesy lamps on my mirror, and thought the bulb was going out or something. I was only using these due to my dash lights going out when the headlights were turned on, and I needed to see my speedometer at night (I just fixed that issue with a replacement dimmer switch / headlight module).

Anyway, I noticed that it wasn't just the bulb going out the other night after putting my air cleaner parts back on to test my engine after cleaning the throttle.... all my lights, inside and out, have this issue, but it gets better.

The issue is specifically, at exactly 1500 RPMs (and I think other specific RPMs as well, since I had this going on while driving on the interstate, which was above 1500), all of my lights have a slight flickering going on, and I notice that the engine also sounds like it's revving up and down, just slightly, like all the electrical system is losing voltage at some specific RPMs for some reason, causing my lights to flicker a bit and probably makes the fuel pump slow a bit which would explain the engine doing that.

Any idea at all why this only happens at some specific RPM and not all the time? Any other RPMs, holding steady, everything is perfectly fine, but trying to hold steady at 1500 for sure makes the lights start flickering and the engine start to rev slightly up and down.


Last thing I hear that I don't think sounds right is that my engine makes a high pitch whining sound while running, like air rushing through a small space, possibly a vacuum leak... I do notice the plastic tube attached right after the throttle that has a line running up to the valve cover that you put oil into is kinda loose, but the sound doesn't change pitch at all when I push that down to try to seal it, so I'm pretty sure it's not coming from that.


Sorry for the super long post, but I figured I'd ask what I'd like to know and explain what I can for convenience.

Thanks to you all in advance for any help you might provide on those 3 issues. If you need more info, feel free to ask and I'll let you know what I've got, or go check out what you'd like me to.

Take note, though... I live in an apartment and don't have any high grade professional tools or stuff (such as sensing equipment or computer code readers), just enough to work on and fix the car. I have to do this in the parking lot, so if you got anything you want to know, keep that in mind, please.

 

Check for a vacuum leak

Clean the EGR, that could cause idle issues

FYI: to change the back three plugs, you have to unbolt the dogbones and tilt the engine forward

 

I'll take care of the EGR and spark plugs this week or weekend and see how the idle is.

Not sure where the prime suspects for a vacuum leak would be at, or how I could check without pro tools, though.

As for the plugs, thanks for confirming for me what I was gonna try to get to those. :P I was gonna unbolt the front engine supports and tilt it forward with a 2x4 to help keep it tipped, but wasn't sure if I could till now. Thanks!

They sure make those a real pain to get to.

 

Vacuum leaks can occur lotsa places. Look at your brake booster (the big round thing on your firewall, near the brake fluid reservoir and the master cylinder) there's a big hose coming from it. Follow it, check for leaks with the car running. Spray some water/soapy water around the vacuum lines (just follow the big hose and follow everything it attaches to. Some of the T's might be split.

And yes, 3100 plugs suck lol, haven't had a problem with my 3800 though

Oh, and don't forget to change your fuel filter & PCV. They're cheap and easy, and could be causing your issue

 

I changed the PCV way back when I got the car, I think... and maybe 2 times. The L shaped rubber part connecting to the PCV is pretty loose fitting for some reason, but when the engine's running, it sucks down tight anyway... how does that PCV valve work, anyway? Is it just a little spring loaded weight that's sucked up under certain vaccuum pressure? Also, what's it do?

As for the fuel filter, I've already got that one coming along, but I have a weird issue. When I got a replacement, it ended up feeling loose, and I could hear an air sucking noise when wiggling it... doubtful it would hold the 50 PSI line pressure from the new fuel pump without leaking.

The weird thing is, it's only .003" smaller than the original filter that's still on there. I'm guessing the deal is, that it's been on there so long and the rubber being this old, it's learned the fit of the original filter and not contracting back down much more than that.

I've got another filter that I've measured at being only .002" smaller, but if I have to, I came across one that's .001 larger than the original... it just costs $10 more because it's from a garage instead of a retail store.

I was going to take my line off this weekend for the whole weekend and see if the rubber will contract. I haven't done so for an extended time due to wind and not wanting dirt in the lines.

Oh, another question, about cleaning the EGR and stuff... not sure where at I clean and what I'll need other than a file and choke cleaner. I was just going to wing it if I didn't find out.

 

The PCV allows the crankcase to breathe (PCV stands for positive crankcase ventilation). It also picks up oil - if your PCV isn't functioning correctly, oil will seep out of various gaskets. To check a PCV to see if it's good, just shake it. If it clicks around and moves freely, it's fine.

Why are you messing with rubber around the fuel filter? It's in line with the hard metal fuel line under the car, no hoses need be there

To clean the egr, get some carb cleaner. Remove the EGR and spray away. You could do the same with the throttle body. Just make sure you remove the MAF before you hose down the throttle body with anything.

 

The fuel filter is connected in line in front of the fuel tank.. a rubber fuel hose runs from the top of the tank where it goes in to the pump, over the top of the tank with 2 other lines (I know 1 is the return line, but the 3rd, I have no idea... was too busy to look, but it didn't go to the tank).

The rubber fuel line comes over to the front of the fuel tank and has a hard plastic connector attached that the fuel filter clips into on one side. The unthreaded end of the fuel filter slides into the rubber hose part and then the clip attaches to the meshed in plastic part on the fuel line.

The rubber hose is what I'm talking about, and at the moment, I REALLY do not want to pull the fuel tank off again after working on it for an entire day without my socket extensions and all... The hose is as old as the car, and rubber, over time, does learn the stretch of whatever it's being stretched by... I have no idea how it's that intolerant of contracting for only a few microns, but it just doesn't seal, even if the unthreaded end of the fuel filter is only smaller by .003"... Like I said, it's unusual, and I'm sure I'd have to just replace the hose... someday I will... maybe.

I just checked my ECM's error codes awhile ago, didn't erase anything... I got a P0102 and P0133.

OBD-II Trouble Code: P0102 Mass Air Flow (MAF) Circuit Low Input

I cleaned off the MAF sensor last weekend with electronics cleaner, it was coated in black crap... the car ran a bit better after that, actually, but not too much better.

OBD-II Trouble Code: P0133 Oxygen Sensor Circuit Slow Response (Bank1, Sensor1)

The other code says the MAF sensor might cause the O2 sensor to not respond as fast as it should to adjust the airflow into the engine, which does sound like what may cause the rough idle, but it also says it could be an inlet vacuum leak or an exhaust leak (that whistling sound I hear).

At the same time, the MAF sensor low voltage code... I also think about that strange electrical issue that I see at about 1500 RPMs, where all my lights and all electronics start flickering.

Anyway....

My PVC seemed ok, it isn't clogged, but it has a bit of rust looking crap on it. I still do have oil that has leaked from my engine, but I ahve no idea how long ago that's been... I remember it being there 3 or 4 years ago, though... but I never see a drop in my oil level.

The coolant level doesn't go down either, but I have and do smell a bit of gas smell in the oil. I assume that's just because I normally only drive my car only a few miles a week... so it doesn't have enough time to burn off or evaporate any gas that may have run down the piston shaft into the oil pan.

My coolant low light is constantly on, and has been ever since I, uh.. accidentally left the car idling for 3 hours. Hey, I went to work so tired, I just forgot all about it. o_o;

I'm sure the sensor just needs replaced... might've gotten hot and damaged it. But the coolant is clear full in the radiator, the overflow tank, and when opening the relief bolt at the top of the line from the coolant pump.

That is, unless it's not that radiator coolant it's on for, because my AC coolant is gone, I think... the AC doesn't work at all, and died during a winter. But I don't know why it would have a single light for both the radiator coolant AND the AC coolant.

 

The low coolant light is a sensor that's gunked up, common failure in 5th gens

Check all your wires from your MAF, MAP, TPS, O2

Seafoaming the engine couldn't hurt either

Hopefully you only need a MAF or an O2 sensor

And don't feel bad, my engine oil smells like gas too lol