OMG need help fast

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Change the #2 spark plug, then report back!! Reason is, we had a 340 Challenger years ago, it was popping through the exhaust. Changed everything, timing chain, carb, ignition, everything... that is except the spark plugs, which were "new". Well, one had a cracked insulator, never saw it and the plug looked fine. Several $$$ later and more time than it should've took, one plug and problem solved!!! At least it's isolated to one cylinder, it should be easy to find!!! Good luck with the diagnosis, Geof
 
Switch your #2 wire and spark plug to the nearest one and re check if problem still on cyl 2 then u have other issues. if it changes to other cylinder you can go get some new wires,plugs
 
mike340duster said:
Switch your #2 wire and spark plug to the nearest one and re check if problem still on cyl 2 then u have other issues. if it changes to other cylinder you can go get some new wires,plugs
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First thing I would do is turn the crank over by hand to top dead center, then move the crank back and forth to see how much the distributor moves if any-that will tell you if you have any chain stretch, and also while it is set on top dead center make sure the distributor is set at #1 cylinder,if not then the chain has jumped. If all that is ok then move to the wires and plugs,at least try changing the #2 wire and plug if that seems to be the only cylinder that changes when you pull the wire. You indicated that all looked good with the rockers and pushrods-do they all look like they are lifting the same height while running? Try spinning the pushrods by hand to see if any look bent. Most likely if the timing has jumped it wont be running at all. I had an old Chrysler 300 many years back that I bought and drove home, but that was the last time it ran as it had jumped timing and wouldnt restart, even with 3 people trying at the same time:toothy10: 1 cranking,1 moving the distributor and 1 working the carb. Keep us informed as to your progress as it is very hard to help/diagnos problems without physically being there to help.
 
i know when i have problems that post on here i try to get a vid or pics to show what i am looking at. could help the diag.

but im thinkin timing chain cuz i set my stock slant off a tooth once and it runs really rough and wouldn't rev past 2K if u were lucky.

timing chain
 
tomarrow i am first putting an alternator on a dodge intrepid then i am starting the ole girl and checking the lift of the rockers since i already pulled the valve cover lol hopefully they both open and close the same as the number 4 cyl. if thats the case then were on too the timing chain set ..... but i'm fearful the cam might have wore on them lobes ..... it just keeps jumpin thru my mind.... ok i'ma go vomit now lol
 
backfires are caused by a timing issues or burnt valves. you have a bad chain or burnt valve as already mentioned. you could have put a chain in it already.....
 
Like mentioned before, check the exhaust rocker on number #2 cylinder to see if going up and down. I'm betting you have a flat exhaust cam lobe on #2 cylinder. If the exhaust lobe is flat the combustion from the cylinder has know were to go but up into the intake because the intake valve opens while the exhaust valve is supposed to be closing.

When you pull the wire you take away the fire part but the cylinder pressure is still making it's way into the intake but you don't notice it because the lack of combustion from the plug.

Chuck
 
Popping through the carb can also be indicative of a lean condition. Spray some brake cleaner around the manifold and carb base. If the car evens out or runs better - there's your sign.
Also -- if it's pre '73 the seats probably aren't hardened so you could very well have a burnt valve or seat.
Think I'd look at the easy stuff 1st.
 
I've had rockers to crack but not come all the way through but still cause problems, it sounds kind of like mine did when I broke a spring too
 
One time I saw anything like this was due to bad ignition wires. In a dark garage, I could see a blue arc between the wires.

Ditto the other time. Couldn't get the car to hold a tune for nothing. Went back and forth on valve adjustment. Started car in dark garage and saw blue arc through a crack in the distributor cap.

Both times I had problems, it was electrical and easily fixed. If valve gear is OK, I'm hoping that it's that easy for you.
 
cosgig said:
Change the #2 spark plug, then report back!! Reason is, we had a 340 Challenger years ago, it was popping through the exhaust. Changed everything, timing chain, carb, ignition, everything... that is except the spark plugs, which were "new". Well, one had a cracked insulator, never saw it and the plug looked fine. Several $$$ later and more time than it should've took, one plug and problem solved!!! At least it's isolated to one cylinder, it should be easy to find!!! Good luck with the diagnosis, Geof
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I've had that happen too. About 20 yrs. ago I worked on a 72 chevy 350 that was popping bad through the exhaust and carb and one mechanic told the owner it was bad valves. I pulled the plugs and they were toast. Put in a new set of plugs and it ran great.

mike340duster said:
Switch your #2 wire and spark plug to the nearest one and re check if problem still on cyl 2 then u have other issues. if it changes to other cylinder you can go get some new wires,plugs
Click to expand...

This is a good easy cost effective way of eliminating that possibility.

Since it's just one cylinder I'm inclined to think it's ignition or cam/valve/rocker gear related that's just affecting one cylinder rather than timing chain related which would affect all cylinders but at 90,000 miles it's do for a timing chain so I'd plan on doing that soon just to be safe.
 
So, when you pull the #2 wire the popping stops. Does the engine sound better (ie, not as rough)? Obviously it will be down a cylinder, but if the "problem" goes away, you can pretty much rule out a timing chain. It may be shot at 91,000 miles, but you'd be missing on all the cylinders (or more of them), not just #2, if it skipped time.

Check the compression across the board, see if #2 is different. If it isn't, go back to the ignition. If it really is isolated to #2, you're looking at a wire, a plug, or maybe an issue at #2 at the cap.

If the compression on #2 is down, based on what you're describing, I'd go with a stuck/burnt valve, or maybe a rocker problem. It might be a cam/lifter problem, but I'd put money on a valve at this point. Squirt a little oil into #2 and see what the compression does just in case, it should come up a little (10 psi or so), but not all the way back to normal. If it does come back to normal, its rings. If it doesn't you're back at the valves. The good news is, even a small piece of carbon deposit can hang a valve open, and it doesn't take much. Bad news is with 91,000 miles and unleaded fuel, that's probably not what it is.
 
I like 72blu's method. If you get to where you think it's a valve or a cam lobe, you could just remove your rocker arms on that cylinder and do a leakdown test. If air blows out your carb or exhaust you know which valve is the problem. If it blows out through the crankcase you have bad rings. I don't know how to check the cam lobe other than watching the rocker arm move as somebody turns the motor over. Good luck.
 
moper said:
Burnt valve.
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Usually it's the exhaust valve that gets a chunk burnt away in which case you'll get a popping out the exhaust from unburnt fuel igniting in the piping instead where it should. Popping out carb and finding problems with one cylinder only would lean me towards the intake valve being stuck open or spring broke.
 
Do a compression test and a leak down test (If you have the tester). Most likely you have a burnt valve or if the engine is pre unleaded you have a sunken seat. During a leak down test you can hear where the air is escaping and will be able to tell where the problem is. Swap the plug for that hole. If the miss follows the plug then the plug is bad. Swap the wire with another spark plug wire. If the miss follows, then the plug wire is NG. If you have a bad timing chain sometimes you will have low compression accross the board but being the miss has been isolated to 1 cylinder, it's most likely not a timing chain. (but with that many miles on a silent chain, it probably needs to be replaced.) You have already checked the rockers and make sure you check the valve springs and retainer. If you do the leak down test and the cyl is showing that it is holding compression and you can't find any other problems, you might have a bad cam.
 
update .... the sleet and freezing rain has stopped work on the intrepid but i did turn over the 318, and no rocker arm movement at all on the exhaust valve and the push rod spins freely..... how much up and down movement should a push rod have when the valve is shut ?????? and the rocker arm is touching it
 
You gave the engine a few good revolutions in your check right? You'd have to do 2 full crank revolutions for a complete cycle. If your valve isn't opening it sounds like your exhaust lobe is worn down to nothing. You could pull the intake and visually see the cam lobe. If the lifter is not raising when the engine is turned that would indicate a lobe is gone. Maybe somebody else has seen that before can chime in.

Edit - Maybe you have a collapsed hydraulic lifter. If the lifter raises in the bore but your pushrod just keeps collapsing into the plunger in the lifter that would be good news compared to a worn out cam. But I've never seen this issue in person, I don't know if a lifter can collapse enought to not even open the valve.
 
really none, the hyd. lifter should take up the slack. If you push the rocker against the pushrod and it doesn't move, then the cam is not lifting the lifter. If it moves up and down same amount as others then maybe the lifter is collapsed.
 
ok more updates ok lets see lack of camera.... ok the top of the valve spring is a plate on all valves the plate is flat ..... on the non moving valve that plate is sucked down into the top of the spring making it concave towards the valve what would cause this ???????
 
That is the valve spring retainer. In the center of it is a cone shaped piece (actually 2 halves) called the keeper which has ridges on the inside that lock into grooves on the stem of the valve.

1st - is the pushrod moving up and down as it should?

2nd - is the spring broken?
 
where the valve stem sticks thru the top of the valve spring there is a flat plate holding the spring down that plate looks as if it was sucked in around the area of the valve stem making it concave in the center
 
spring does not appear to be broken as for it looks just like the intake spring and yes it is all moving up and down just not moving the rocker arm ?????
 
bama-a-body said:
spring does not appear to be broken as for it looks just like the intake spring and yes it is all moving up and down just not moving the rocker arm ?????
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OK, The pushrod is moving up and down but the rocker isn't moving? Without pictures, it's hard to tell. Mabe a retainer failure?? If the valve keepers start to pull through the retainer it will lower the seat pressure and cause the valve to bounce on the seat , hence the miss at anywhere past idol. If that is what it is DO NOT RUN THE ENGINE ANY MORE!!!! If the retainer finally fails it will do SERIOUS DAMAGE!!! You maybe a very lucky man but we realy need pics!!!!
 
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