Cutting out at 4200rpm

[tucsonxj]

No I don't have an actual number, don't think I ever did.

I did verify the cam sensor sync with the CPS. It is just like the one on the posted Motor Age Garage link above. We were able to look to see if the CPS signal drops out when the cutting out happens, and it doesn't. So I am confident that the distributor is in phase.

It does lean out at higher rpms, so I have fiddled with MAP voltages a little. 5.05, 5.10 and 5.15 don't make a speck of difference in the cutting out. The rpm is pretty consistant near 4000-4200 when it pops, but I did get it to go up to about 4900 once today, but it may not have been over 180 degrees yet.

Other things I have checked:
Fuel pressure is good even when popping.
Ballast resistor bypass relay swapped for another known good relay.
Pulled cover to look at rockers/pushrods. All seems well.
No codes except when forced.

Nexy idea to try:
backpressure from a bad cat

It seems to need more fuel (duh, that is pretty well known from others experience). I don't know how high I should set the MAP voltage to try and compensate, how high are others running. I have seen that Dino ran higher than mine at times but came back down after realizing it was rich. I may have to go with a n adj. FPR, just wish there was an alternative to Hesco's one. Not that I don't like Hesco, just that I am unemployed right now.

I also wonder if the spark is hot enough. I know that nobody seems to run a non-stock coil, but wonder if it would help in my case. What spark gap do people run? Anyone tried the Firepower stuff in Quadratec?

Any other ideas?

Thanks

[crustodd]

Hey Tucson,
I'm having similar problems to what you're having. It has cropped up all of a sudden. I'm running a full MSD, al6 brain, blaster coil, and fatty wires. It has just started happening in spite of this. I just put in colder plugs last week and I'm wondering if I have the gap to wide? Anybody??? Will too much plug gap create the problem Tuscon and I are having? Have you checked your plugs, Tucson? How do they look?

T~

[hatem61]

Tusconxj,
In my opinion, a 0.035" gap won't be too wrong as far as plug gap.
What fuel pressure did you read? under what condition? intake popping makes me feel it could be spark or fuel.
Ignitions normally gives up under load, so does the fuel starvation.
Was the CKP signal clear at the RPM range where it cuts off? I am also concerned with the excessive flywheel runout. Could you measure it with a dial indicator?
Good luck

[RAPTORFAN85]

Don't know if you thought of it but what valve springs are you using?
Valve float can feel like a rev limiter like you said.

It sounds like you have some weak valve springs to me...

[tucsonxj]

That's what my mechanic thought too till her remembered what springs I used. I'm running the mopar perf stuff and the seat pressure was so high it was concerning my machine work guy. He was concerned that I would wipe out the cam. I am going to pull the valve cover tomorrow and re-check the lifter preload. My mechanic friend said there is too much valvetrain noise. I hope I don't have a bad cam. Anyway. I have recently developed a knock. Don't think it's related but who knows. It's a strange one. It knocks once at startup, and again only if I really punch it when idling, and then only once again. Sounds like it is coming from around the distributor/oil pump area to me. My friend said to check the torque converter bolts so i did. Not it. I may drop the trans and check the flexplate to crank bolts too. Doesn't do it at any other time or speed. I will be looking into that as soon as I really have time and can do without my heep for a couple days. Kinda puts the popping on the back burner. sometimes this thing is frustrating, but I love the heep. I've had it like 12 years now. Longer than I have owned any car.

[crustodd]

Hey Tucson,
What pistons do you have in there again? My KB's are noisy until the engine is TOTALLY up to temp. I had read that might be a characteristic of them before I got everything together and sure enough, they're a little noisy for a bit when it's first gettin goin'. I agree the about the Jeep love too. I'm also frustrated by the "teething" gremlins. I think it'll get better as mileage accumulates and the engine seats in more.

Keep at it,
T~

[crustodd]

Hey, I see that you do have forged pistons. That could be a bit of the noise when the engine's not fully up to temp. On the cutting out, is it happening when the rig is parked and you rev it up, or only in motion, under load?

T~

[doublins]

Tuscon,

Did you ever solve this problem?

Mine has developed it, and I can't figure out what it is...

I have ruled out fuel and cam failure, plugs look good, distributor is properly indexed, feels like it's cutting out in top end...

Thinking valve float (but I have performance springs), clogging cat?

What was your problem?

Thanks,

Chris

[superstingray77]

My first 4.7 build started doing this when the cam wiped out hence stroker #2.

[doublins]

My first 4.7 build started doing this when the cam wiped out hence stroker #2.

I replied in the other thread titled something like ¨high rpm misfire¨ or something of the like- I pulled the valve cover last night and all valves are fully actuating, so cam failure is ruled out.

[superstingray77]

Did you measure lift with a dial gauge?
Mine were all still actuating fine (visibly) and the engine was not making any noises but significant lift had been lost leading to a lower and lower power curve until it finally had nothing over 3000 RPM, even without a load on it.

I do not imagine the cam timing could change due to a bad chain/gears, but how about the distributor or crank sensor gear? Possible that its worn causing either a scattered spark or screwy injection timing? Also that shaft play can cause issues.

I do not wish what i went through on anyone
7k later ..... stroker #2 is running great... had this cam nitrided after I got the custom profile cam done by Lunati/Solid lifters, lash is holding spot on for 2000+miles thus far so no noticeable wear yet. I broke it in on Joe Gibbs driven break in oil ( as I did on first one) and ran from 2200-2800 for 25 solid min. Then switched to Brad Penn 1 after 300 miles. Oil still looks great.

[doublins]

Did you measure lift with a dial gauge?
Mine were all still actuating fine (visibly) and the engine was not making any noises but significant lift had been lost leading to a lower and lower power curve until it finally had nothing over 3000 RPM, even without a load on it.

I do not imagine the cam timing could change due to a bad chain/gears, but how about the distributor or crank sensor gear? Possible that its worn causing either a scattered spark or screwy injection timing? Also that shaft play can cause issues.

I do not wish what i went through on anyone
7k later ..... stroker #2 is running great... had this cam nitrided after I got the custom profile cam done by Lunati/Solid lifters, lash is holding spot on for 2000+miles thus far so no noticeable wear yet. I broke it in on Joe Gibbs driven break in oil ( as I did on first one) and ran from 2200-2800 for 25 solid min. Then switched to Brad Penn 1 after 300 miles. Oil still looks great.

I am picking up a new battery for my digital dial gauge tonight so I can measure with that.

I´ll pull the dizzy and look at the gears to make sure... I also had this cam nitrided, i would be very angry if the lobes were fine but the dizzy drive gear got messed up...

More to follow.

[doublins]

Did you measure lift with a dial gauge?
Mine were all still actuating fine (visibly) and the engine was not making any noises but significant lift had been lost leading to a lower and lower power curve until it finally had nothing over 3000 RPM, even without a load on it.

I do not imagine the cam timing could change due to a bad chain/gears, but how about the distributor or crank sensor gear? Possible that its worn causing either a scattered spark or screwy injection timing? Also that shaft play can cause issues.

I do not wish what i went through on anyone
7k later ..... stroker #2 is running great... had this cam nitrided after I got the custom profile cam done by Lunati/Solid lifters, lash is holding spot on for 2000+miles thus far so no noticeable wear yet. I broke it in on Joe Gibbs driven break in oil ( as I did on first one) and ran from 2200-2800 for 25 solid min. Then switched to Brad Penn 1 after 300 miles. Oil still looks great.

I am picking up a new battery for my digital dial gauge tonight so I can measure with that.

I´ll pull the dizzy and look at the gears to make sure... I also had this cam nitrided, i would be very angry if the lobes were fine but the dizzy drive gear got messed up...

More to follow.

Cam wiped. See http://www.jeepstrokers.com/forum/viewt ... 456#p31667