Here's a weird one........on a Neon 4 cyl..valve bent??

[diesel4me]

Off topic subject,being non GM, but thought I'd relate this anyway...Friend put a timing belt on a late model Neon today---was towed in with a shredded timing belt...its a 4 cylinder ,with 4 valves per cylinder,an "interference" engine...he warned the owner chances were good the valves hit the pistons,and it might be junk,but he told him to go ahead and put a new belt on it,and see what happens next.....He tells me after he installed the belt, (and he's done a lot of them,and does them correctly),he said it started right up,ran and sounded perfectly normal,and it ran great for at least 5-10 minutes,till it warmed up good--then one cylinder started misfiring out the exhaust.....said he's never seen an engine run fine at first,then act like the valve bent or stuck AFTER running it for awhile like that................................................................................I would think a bent valve would have made it skip from the get-go.....he ruled out bad plugs,wires or injectors,he replaced the wires and plugs and the injectors being involved is doubtfull,as it ran fine at first--after the misfiring started,it had some slight lifter noise too...I wondered if a valve stem bent and got hung in the guide after it expanded when it was run??--we doubted a piston failed because it had no blowby really,but pulling off the plug wire on that cylinder has little effect,so its probably low on compression......................................................................................................He is going to have to pull the head and see I guess,but I told him if it were me,I'd just replace the engine with a salvage yard one--probably be cheaper in the end...but he said the customer isn't willing to go that route..yet!...anyone have any ideas or opinions about why it ran great at first,then started skipping?.....I would assume anything mechanical that might have been wounded would have shown up instantly...hate to see him rip it all apart and find something stupid was to blame,like a hunk of carbon or something...

 

[73k5blazer]

I did a couple Neon head gaskets a few years back.
I might check if the belt skipped a tooth after it was running a a bit.
Do a compression check, for sure. Simple procedure. Head gaskets blow on the neons all the time. They are famous for warping, so don't just put a new gasket it, check it flatness, if it's out of spec at all, you have to have it planed. Some shops will sell a thicker head gasket for these engines that claims to compesate for slightly out of plane, they don't work.

I can tell you why I stopped doing them. I only did the 2 for friends of my wife. I said no more, I absolutly HATED working on these things. No space at all. My knuckles were bleeding for days after doing one.

 

[63chevyll]

I've actually had bad injectors on many new Chryslers, even a few neons recently.

So, what does the compression test say?

 

[Fordum]

Lost compression out the exhaust plus valve noise, sure sounds like an exhaust valve stuck open.
Not sure I have ever seen a Neon engine, but I would stop at the valve cover and check things over before pulling the head.
It might have just damaged the rocker arm instead of the valve, and it finished coming apart after it ran for a while.
Bent rocker might jam the valve.

 

[diesel4me]

My friend had to quit at 6 pm last night,so he wont be doing more work till today on it--I'll post back with the compression test results--or the carnage report,he may just yank the head off it,rather than take a compression test,seeing he already knows one cylinder is likely low on compression without needing a gauge to verify it.........................................................he knows Neons eat head gaskets,he's done plenty of them!.................................................................................................I find it hard to believe a valve bent more AFTER being run awhile,but I guess anything can happen...it'd be nice if he did find a rocker arm was what failed or something easier to fix though.............................................................................................................after I found out the PT Cruiser uses the same engine as the Neon ,I'm not as enthused about them as I once was--always thought they looked cool,that retro look is appealing,but they should have made them a bit taller,taller,RWD,and put a 318 V8 and a 4 speed on the option list ,it would make a cool little hot rod...but to slap that body on a Neon and ask 10K more for it when its basically the same car underneath,is a ripoff,IMO--just like the new VW Beetle-- being plopped on a Jetta chassis at a much higher price....

 

[496truck]

I'm betting the valve tweaked just enough to seal almost all the way. And after running a while and the gasses just slightly escaping then carbon building and creating a hot spot and burned the valve. It can happen that quick.

 

[diesel4me]

No update yet--he had to move on to other cars he has to fix,while the owner decides if he wants to fix the engine,or just swap another one into it..or junk it!....I bet 496truck has the answer,I figured much the same thing,or a valve stem bent just enough to make it rub hard on the guide after it warmed up and got stuck ....I'll post up with any post-mortem updates if he ends up fixing it.......................................................................................................my friend is having a bad week with timing belts--when I saw him yesterday,he was struggling to install one on a Subaru Outback--worst one he said he ever did too--had to borrow special tools to keep the cams aligned,and it took me and another helper plus him,to hold the belt from moving as he went to put it on under the tensioner............................................................................................first one he ever did,and claims it'll be the LAST one too!...it LOOKS easy enough,and is much more easily acessible than most FWD's with the engine going sideways,but you need to be an octopus to install it--belt is 3 feet long,and goes around multiple gears and idlers,one of which is hydraulic and you must pin the plunger in place with a metal rod...took him all day trying to install it without the special tools,the cams kept moving a tooth off ,after getting it on,had to try again like 6 times!.........................................................................................I have vowed to never own anything with a "rubber band" instead of a timing chain--chains were bad enough!...I'm dreading the day the timing belt snaps in the '93 Caravan 3.0 I drive ,its got 90K on the original one,and I am expecting to be walking home one of these days when it blows...I hear they are a real bastid to install too,and the water pump is driven off it....I consider that arrangement completely retarted...a few drops of coolant weep out of the weep hole in the pump,and bam,your belt jumps time,and on many engines,the valves kiss the pistons,and its a "kiss of death"....I'm sure some engineer got a bonus,for this clever way of ensuring folks have to buy new cars sooner,or have to replace an engine.............................

 

[black dawg]

those twin cam subaru belts can be a bitch till you get the hang of getting the belt on there.

 

[black dawg]

what did he find out?

 

[ChadRay13]

I would highly suggest doing a leak down test before pulling the head. That'll tell him for sure if a valve is bent and which valve.

 

[diesel4me]

My friend hasn't been able to work on it yet---had other cars to get out of the shop first,and the owner still hasn't decided whether to continue repairing the Neon,or just get another vehicle yet...................................................................................................he's already determined at least one cylinder isn't doing much by pulling off the spark plug wires with it running,so its evident that one is the one thats low on compression.............................................................................