Stumped...need fresh ideas!!!

[car62]

car(mustang with 2300)misses when coming off corner,doesnt clean up til it come back to an idle...sometimes 1 lap til the miss starts,sometimes 4 laps,sometimes 10 laps...lately it has been 1-2 laps.

here is a long list of what has been changed to try and cure the issue:

radiator
fan
complete cylinder head x3
head gasket
bottom end x3
intake manifold
carburetor
new fuel line
fuel fittings on cell
new fuel cell
new electric fuel pump (Holley red and blue)
all new wiring,new cables
new switches and push button
unhook tach completely
unhooked all gauge lights
starter
solenoid
battery
alternator(new,and unhooked/unwired)
distributor
module
coil
plugs and plug wires
checked cam(2A) and ignition(36A) timing

now for the strange part....

when we pulled the carb off to change the head a couple months ago,under the carb in the intake it was black under the carb,like it has been really hot..so we changed intake as well(carbed not EFI)

took complete head off another engine(no issues with this head)and put it on our bottom end...been fighting same issues last several weeks..pulled carb off yesterday,intake is black again under carb.

anyone got any ideas???

the sound it makes when it "misses" is like it dropped a cylinder or 2...sometimes if the throttle is played with,it will go away for 1/2 a lap.

[racerman]

Are you getting your fuel at the track? I've had problems with that before, so I tried getting it out of a fresh barrel a couple weeks and my problem was fixed. Usually though there is more people with bad running cars.

[car62]

no,fuel is bought down the road from a pump,alot of other racers get their fuel there as well as 2 of our other cars and nobody is having problems.

[racerman]

Maybe a ground to the engine has corroded? The black under the carb sounds like reversion from the misfire. That's odd, as much as you've changed.

[jatchis]

Have you checked the header/exhaust to make sure you don't have something clogging up one of the primaries? The black under the carb could be exhaust being pushed out when the intake valve opens if it's not evacuating a cylinder properly.

What do the plugs look like?

[return to dirt]

i think you need an efi intake:D. it sounds like a posible exhaust problem like others have suggested. did you do anything to it before it started acting up?

olin

[car62]

actually...we had a bung welded in the exhaust pipe about 6-8inches past collector for our crankcase vent system...we run the 1998 ranger cast iron manifold...well for 1 reason or the other,we capped the bung and quit using it for the crankcase vent system...also there was a crack about 1/4" parallel to the weld on the pipe...so i welded that up.

hmmm...maybe i better pull it all apart and look at it...see if something is plugged up.

[dirty white boy]

sounds like a stopped up catalytic converter....know theres not one but thats how it would act,...even turn inside of carb black if ran long nuff

[Headhunter]

Are you sure the cam timing is correct? If you change the head. carb. and everything else and put the cam in with the same location nothing will change. If the cam is opening the intake too soon you will blacken the intake. Is this a solid lift head or hydraulic? Lash too tight?

The plugs will tell the story, do they all look the same? What color are they? If they are all black then it may be a fuel or exhaust problem. If only one is black then look at the exhaust port.

[car62]

yes the cam timing is correct...advancing or retarding it does not change the miss...all 4 of the plugs are exhaust colored.

the head is a hydraulic head.

[Foghorn]

When you had the carb off could you see black coming up the intake runners? If so was it one cylinder or all four? If it is all four then I would look at your exhaust system. Do you run a muffler? Also you mentioned doing some welding on the exhaust system. Maybe you have a large piece of slag hanging in the pipe that is getting hot enough to ignite some unburned fuel coming down the pipe and the flame is coming back up the pipe. I know that might be a stretch but with your combination of jets and timing it is possible.

[car62]

yes it is in all 4 runners..and the spark plugs are white in color with exhaust soot on them that wipes right off.
yes there is a muffler,we are going to change out the entire exhaust system today.
stupid thing runs great in the shop,and free revs fine,but total different beast on the track.

[Headhunter]

Have you tried to close up the gap on the plugs to see if that helps?
What fuel are you running? If it is a higher octane than you need it may not be fully burned when the intake opens.
Hotter spark plug?
When you changed heads did you use the same cam? Maybe it was ground wrong.
Have you cleaned all the engine and cable grounds?
Maybe pumping up the HLA's?
Ignition timing marks off?
Bad wire or connector on the positive side of the ignition?
Bad switches.
Electric fan?

Just tossing out a few ideas...

[84Dave]

As has been stated here, the black in the intake manifold could very well be reversion. If so, the reversion will/can 'crap up' the induction mixture and cause misfires. Again, as stated here, carefully check your entire exhaust system. Is the muffler relatively new? Is it collapsed on the inside? Weld a short piece of small tubing into the exhaust pipe, put a pressure gauge on it, and check for excessive back-pressure @ WOT? -Dave-

[car62]

ok,pulled the entire exhaust system off the car today and replaced with complete system off another car that was new last year...when the exhaust came off problem car,all 4 exhaust ports are a very light gray in color...almost white.

[Headhunter]

I'm wondering if your not a little to lean and getting some detonation......

[car62]

exhaust wasnt the fix,running Dorton 350 with 75 and 76 jets...bumped up to 79 and 80...didnt change anything except made engine load up in pits....totally stumped!!!

[drtlvr]

I use like 62's in my Parker 350. 4.5 power valve. Have you tried jetting down? What about the coil breaking down?

[84Dave]

Time for a wide-band O2 sensor in the tailpipe to see what the AFR is doing? -Dave-

[Dan32]

we run 68 jets 70 are as big as we have ever had ur choking the engine jet it back !!!

[car62]

been running same jets for 4+ years and never had an issue

[youngengines]

Seems like a lot of jet to me, unless a lot has been done to the carb. Rich will miss up high for sure. And, if there is any "pullover " going on it would be amplified. JMO

[Wrencherer]

Check the red flapper valve in the accelerator pump make sure it is not ripped also ceck the power valve

[car62]

we have 4 Kieth Dorton 350 carbs and a 500 carb....all carbs have been on the car,jets have been played with from 65-80 with no results other than 77 up loads up,we have used PV block and different power valves,every squirter from 21 to 31...4.5psi at carb with Holley Blue and Red with and without regulator.

[Headhunter]

Hydralic head? I'm thinking that maybe you have HLA that is pumping up and holding the valves open if it is Hydraulic. Oil pressure to high or pressure releif not working right? Last thing I can think of is fuel system. Either a colapsing/clogged pickup tube, clogged vent or bad fuel line. bad regulator.

[car62]

we have changed heads,3 different heads that all turned 7200+ when they were on other shortblocks,but just in case,went with new lifters and followers,set to .035 as we do on everything else...no change.

went through fuel system and replaced EVERYTHING (fuel cell,all lines,filter,fuel pump,fittings)...


again this is a miss that picked up last season just prior to mid season and has gotten worse and worse..id really be shocked if someone threw out an idea we havent already covered.

i also dont think a fuel issue is the cause for inside the intake manifold to turn black.

[Headhunter]

One common denomonator,,, the short block. that goes back to oil pressure maybe a cracked block or cylinder wall.

And yes a fuel system problem can on occasion cause that. You go lean and get pre-ignition causing hot spots on the plug, head and piston tops and when the fuel hits it it fires back into the intake igniting the fuel in the runners.

[Racedad]

A long shot here,but have you looked at the water pump?Rarely we see a loose or eroded impeller.Would fit with the symptom of sarting after a few laps on the track and gets worse.Coolant temp sensor in the block,maybe head area is hotter(too hot)?
Last time I saw it on a 4.0 Jeep,would run fine all day in the shop but overheat within a mile going down the road.

[car62]

headhunter and racedad...appreciate those 2 ideas...waterpump is something we have not looked at...we did have a different block in there,and upon pulling intake for tech,we saw some water droplets in intake runner #2...so we changed blocks....that was last season...i th9ink its time to pull out one of the backup bottom ends and put in there for next week.

[Milford Motorsports]

If I find half a fly in my rice,i'm sending it back!

[jatchis]

I'm not even sure rice is relevant to this conversation. We're talking about a Ford, not a Toyota ....

[steveshawjr]

we had a guy at our track wit ha wired issue like yours his turned out to be a bad crank. the crank had started to twist witch in turn was messing up cam timming and so on.. probly not you probelm but nothing seems to work so i thought id throw it out there.

[Dirtman29]

Probably a very long shot here, but have you checked inside the distributor cap for any moisture? Happened to me yrs. ago after cleaning up an engine compartment, car ran like crap after. Had water in the cap.

[car62]

yes,even changed distributors 3 times,modules,harness plug,rotor,you name it...the haunted mustang from hell!!!

[Dentman]

Sounds like you need to roll the car over a few times to shake it up a bit...
I had an enduro car that had a similar problem. It was traced back to a broken motor mount that was allowing the motor to move on accel causing one of the harness wires to ground out periodically and temporarily on the firewall. Perhaps you have an unsecured wire doing the same thing somewhere.
I'm a Toyota guy so don't hop on me, but maybe you have a worn crank keyway or pulley or something that is moving back and forth under accel/decel causing the timing to go out of range, then back.
On the Toy 22R engine, the timing chain tensioner relies on oil pressure. If the pressure drops from starvation in the turns (broken oil pick-up, broken gasket, slosh etc.) the tensioner can retract allowing the chain to whip and the cam timing to jump around. Perhaps you are having a similar issue, only it is causing your hydraulic lifters to starve for a few seconds and keeping the valves closed or partly closed.
Or perhaps the framistat is no longer attached to the connecticazoink. That would require a transplant...
Good luck with that. Hope this helps.
Dentman

[Dan32]

u tried changing the exhaust?? is it stoped up?