Hello all i am in a bit of a mess here at the moment and my poor monte is sitting in the driveway sick.Here is basically what happened to this point.
I have a 1995 monte carlo with a 3.1 that was running tip top shape until the intake manifold gaskets started leaking and mixing with the oil,so the car was parked and was running fine at this time.I have someone who replaces the gaskets and has the heads checked by a shop to make sure they was fine,which they was.

They reinstall the head gaskets and all gaskets and after getting it all assembled it has a slight miss,i dont know how to explain it but it miss's.It idles fine but you can here a slight miss pop as it idles,and as you drive it you can feel it ,faster you accelerate the more it miss's like popcorn popping lol! I checked the spark plug wires and on the coils and according to what i have read online they are correct.I was wondering if its possible they installed one of the pushrods in the wrong position since the intake is diffrent size as the exaust? I am at lose here and not sure what to do since they did the repairs and now are out of town for a month and curious if someone has had this issue also.Any insight would be greatly helpful as i live in rural kentucky and most shops are a month booked.

 

did you replace the old plugs and wires?

 

When I did the heads on my 95 grand am 3100 they actually had to machine off .045" off one head and .048" off the other. And I noticed something similar, for me running 91 octane fixed it because they took so much off the heads that the compression ratio changed enough that it pinged afterwards. A good machinist told me later that those heads must have been machined prior to that time and possibly had closer to .060" off each head. Ask your guy if the intake was a little hard to line up the bolts with the engine. And try higher octane gas and see if it's better. My car was stupid fast after that, it was probably the best accident I ever made for performance reasons. I just wish it was something I tested for compression with my tester to see where it was at before the engine blowed up. It had 303,000kms on it when that happened.

 

Oh yeah the push rods would keep a valve open and a valve closed almost completely so I doubt that is the case. Keep your fingers crossed for higher octane fuel fixing it and then it's faster too

 

i am going to check the plugs and wires tomorrow they was replaced a few months ago but someone said that one may be bad? Also me define this miss as when you are doing 40mph or so you will feel it popping in the steering wheel like mad from the engine.The shop said the heads did not need shaved i am not sure what that could be.I will also check grounds and such to see.I ran a can of seafoam thru it also to no change and the wife said she drove it a short distance and it had a noticeable jerk as it misfired.

Also the guy said he replaced the valve seals in each head if that may help.I have called every mechanic in our area and no one can get it in for the next 2 weeks :-/

 

Have CHECK YOUR PLUGS!!!! If they cracked 1 reinstalling them that would be your popping. Or Ger a spray bottle, fill with water, have someone in your car power brakeing it "putting load on motor", and spray water on plug wires by the block and on. Coil packs. It has to be darker to. Do this but if you have bad wires or plugs you will see the electrical arc. Just ne carefully not to get ran over

 

I've done a lot of work in the '94-'95 3100s. A couple of things to know/check:
1. - Did anyone change the injector O rings? Given how old they are (plus how CHEAP replacements are), it would be wise to change the ones that were exposes (should be just the O-rings on the intake side, as there should nto be any reason to remove them from the fuel rail side).
2. - Can you smell gas around the injectors? If so, my guess would be they are not making a good seal (when they were put back in, it's possible they were not properly seated). Even if you don't smell gas, does not rule out bad injector seating (or bad O-rings), it's just the obvious sign.
3. - I know the 3100's I've worked on had a torque spec for the tightening the rockers down. Was that spec looked up and followed? A loose rocker should also give you some extra "chatter" (so I'm not suspecting that since you mentioned a popping).
4. - As stated by others, pop the spark plugs out and inspect. Make sure in this process, none of them were damaged. When I've done head gaskets, the car is close enough due for plugs (and they are cheap enough), I just put new ones in from the start (still, you could have a bum plug even with new ones). Another thing that could be, perhaps not a damaged plug, but one that's not snugg in it's cylinder.
5. - Inspect the plug wires. Make sure the sheathing is not damaged.
6. - Inspect the soil towers. If the metallic points look dirt or corroded, get a Scotch Brite pad and clean them up.

And a handy tip, if the boots of the plug wires were nto recently greased, re-grease them. Helps prevent corrosion and makes them easier to pop off in the future.

Best of luck! Keep us updated!!

 

They never had to machine the heads?!?!? Those must be the only ones ever that didn't warp in '95. Or they didn't check

 

Yea they said they was fine and cleaned them,all i know is i picked them up and they was covered in this red power dye stuff and took forever to clean it off the guy said.Its been raining here but this weekend i got a new set of plugs,and wires going to try that first.a guy at work who "shade tree" mechanics but does alot of racing locally said that he was betting money the guy tightened one of the rocker arms too tight and it is keeping one of the valves slightly open and that explains the popping,so i am going to google the torque value of the rocker arms and get a torque ratchet from autozone this weekend if weather allows.

 

When I did the head gaskets on my '94 Grand Am with a 3100 back in '09 at 180,000ish miles, I did not even send them to be inspected. I visually inspected them AND I used a straight edge to inspect the desk surface to see if it was still flat. Everything checked out.... I put the car back together. It has been running awesome ever since (has about 207,000 miles on it now and I drive it everyday right now).

I'm not saying everyone should or should not do as I did. But what I am saying is what I did worked fine.