transam1998

iTrader: (5)

Car in sig, I have MSD coils, brand new Magnacore wires, a newer Z06 MAF, put another new set of spark plugs in today, pulled all the coils and ensured spark plug wires were making good connections. I pulled the valve covers and checked all the springs.

I noticed a problem at the drag strip about 3 weeks ago, the car suddenly slowed down 8 mph trap speed. On the way home, I noticed that, when I put it under part throttle load, it feels like one or more cylinders drops out completely. I've been driving the car around, forcing it to misfire, but this thing won't set a #$#@%$ trouble code so I can see what the heck is going on.

I took a day off work and put a tech 2 on it, the stupid thing wouldn't detect any misfires, even though it's falling on it's stupid face and dropping cylinders like mad. I didn't have it for long and didn't get a chance to check the MAF, I did check the TPS, all good there.

I do have a K&N filter, tomorrow, I'm going to pull the MAF and clean it, in case there is any oil on it. I don't know where to go from here, If I don't know which cylinders are dropping, I'm lost.

I still have access to the Tech2, but I would have to take another day off work. There are no shops in this area that will touch my car now, so I either have to drive an insane distance to get help, or figure it out myself.

EPP was my tuner, they have been unwilling to make time to fix my idle which hasn't been right since I had them dyno tune it. So I don't think I will be able to go back there.

I'm so angry now, I can't think straight, anyone have any ideas I can't think of or know of someone close to me that has some expertise? I live in Mattawan Michigan.

WhiteRhino

iTrader: (6)

Have you missed any shifts latlely? It could be bent pushrods, it doesnt say in your sig if you still have stock ones. Which I'm sure you don't. If your positive all the ignition is firing/good, it just sounds like something in the valve train to loose that much power. I had a couple bent pushrods and a slightly bent valve on an a 97 lt1 I had and it never threw a missfire code.

Could you maybe have had valve float and kissed a piston to bend a valve slightly? Just throwing ideas out there.

transam1998

iTrader: (5)

Thanks for the reply! I didn't think of that, I did have hardened pushrods installed, or at least I paid for them. I haven't missed any shifts. This trouble doesn't seem to be RPM related, though. I can make it misfire so bad by putting the car in 6th and giving it some gas, that it won't accelerate at all. I lift off the throttle, misfire disappears, but the RPM never changed.

Sometimes, under acceleration, the car will drop one or more cylinders, then suddenly pick back up breifly before dropping again. This is rare, though. Once it starts misfiring, lifting off the throttle is all it takes to bring the car running on all 8 again.

The only thing I haven't checked or replaced yet, are the injectors. The car has 70,000 on it. I am running cleaner through it with no results. The problem seems electrical. With everything I just said, does it still sound like pushrods? or lifters?

I did clean the MAF today, it didn't look like it needed it, and didn't help.

Forgive my earlier frustration, I'm much calmer now.

Thanks for the help!

99FormulaM6

iTrader: (21)

my car was doing the exact same thing. but i fixed it today thank god, its really annoying and it was really pissing me off.

but, all i did to fix it was new plugs/wires. i also changed the fuel filter too, but after i did the plugs/wires, it fixed the problem.

but, since you have new plugs/wires, and you have MSD coils...i recommed swapping coil packs with a friend and see if that fixes it. Swap all 8 coils first, and if it fixes it, narrow it down from their. It may or may not work, but its a start.

or you could have bent exhaust valve(s), but if you havent missed any shifts, thats unlikely.

done a compression check? any loose grounds?

WhiteRhino

iTrader: (6)

Injectors could cause that as well. You can find them cheap sometimes. When mine went I just got the Ford red tops for a couple hundred.

Another thing. Are you sure it's not detonation/pinging. You say the car misses/loses power and that you had a shop tune the car. The cars knock censors could be yanking a ton of timing and causing it to do that.

Maybe the tune is way off for some reason. What all did they do. Did they do a road tune or a dyno tune? Most just do the dyno tune and all that really is is a wide open throttle tune. If they dont take it on the road or do road testing, the tune could be off.

99FormulaM6

iTrader: (21)

im pretty sure its the same thing i went thru.

car is stumbling when your WOT, sometimes it seems like it clears up, but usually is stumbling/missing. the whole car shakes and bucks when the RPMs are really low (trying to merge on the highway in 6th or something).

but i told you what i did to fix it....and that doesnt seem to be working for you. i would try swapping injectors with someone as well and see if that changes anything.

transam1998

iTrader: (5)

Thanks for all the help guys. The car was tuned last year and has been running great, it's been running the numbers in the signature. It may be detonating now, but it would have to be a failure of some sort, injectors, fuel pump, dirty fuel filter... The tuning has been fine. Filters are so cheap, I'll change it for the heck of it. Who knows, if I see bits of the fuel pump in the filter, I'll know what's wrong :-)

Glad to hear you fixed yours 99formulam6, I feel your pain.
Grounds have all been checked and are clean and tight, all the grounds I know of, anyway. :-)
I do have someone I can trade coil packs with, I will give that a shot. I could change injectors as well.

I guess if it's not injectors, not spark and not losing fuel, that leaves me with valve train, though I would think a drive train problem would either always be there, or would be RPM dependant and this doesn't seem to be the case. I definitely hope I don't have a bent valve, Compression tests are easy to do, though.

Thanks again for everyone's suggestions.

01RedT/A

do you still have cats on this thing? i had a truck kick my *** with misfires one time (funny thing is i was just telling a friend about this about an hour ago. anywho) if your cats are melted down, they wont flow enough exhaust through them, that exhaust backs up into the cylinder, and takes away from your a/f mixture, eventually you get misfires since there is no air to burn. also, it will come and go, and is worse under heavy throttle. jsut something to check. good luck.

transam1998

iTrader: (5)

Thanks for the reply. The cats were the first thing I removed when I started modding the car. I don't miss them much :-)

joshp14

iTrader: (5)

I'd do a cylinder leakdown check, cranking compression, and running compression checks. Also perform a fuel injector balance test with the Tech II and a fuel pressure gauge. I'm guessing your problem will show its ugly face when doing one of the above tests.

transam1998

iTrader: (5)

Thanks for the reply, the injector balance test is easy enough to do, it will just be a pain to get ahold of the tech II again. It will be less of a pain than the running compression test, though. :-)

If I remember right, all the injectors should be between 10 kpa of each other, is this correct?

Thanks everyone for the directions, Now I have enough to keep me busy for the next couple of nights.

WhiteRhino

iTrader: (6)

Keep us updated if you find out the problem.

tc3

iTrader: (2)

if you get ahold of a tech II again the first thing you should do is a power balance test, if you have any cylinder not performing as good as it should you should notice it with this power balance test.

And also check to see if the o2's are switching good and not lazy(ignore rear)
And also check to make sure that sensors such as tps and iac and what not are working correctly with tech II, that should only need common sense...

transam1998

iTrader: (5)

Hmm, I didn't see a power balance test on the tech II I borrowed, but I didn't have time to look through everything. is this the same as the misfire test? I'll bet EPP turned off the misfire tests during my last tune, don't know why I didn't think of that sooner, duh.

I've got the tech II for 5 hours today. That should be enough time. :-) I'm lucky here, the company that helps build and test the tech 2 is in town. I used to work for them, we didn't have the tech II back then, that is a nice piece of equipment. Priced a little high, though.

If I see a power balance test on there, I'll give that a shot, at least I will know which cylinder or cylinders to pick on. I will also do an injector balance test.

I have a friend at a salvage yard, he has a set of coil packs I can borrow to hopefully rule out the MSDs as a problem. That may not be necessary, if I can do a power balance test with the Tech II.

Last will be the compression tests, yuck, I know what it is like to get a spark plug into cylinder 8 :-)

I'll post my results, thanks again for all the help.

transam1998

iTrader: (5)

Ok, I got some results. (and a $4000.00 Tech II all to myself for a couple of days :-) )

The injector balance test passed with flying colors. All started with 340 kpa and all injectors were between 209 and 210 kpa after. Most were 210, only a couple were 209. better than I expected.

We messed around with a scope and a Dyno, but the Dyno wouldn't put the car under enough load to keep me from taching out before the bad misfires started, so I gave up on that idea. When I pulled the car off the dyno, the motor didn't seem right so I ran a quick cylinder balance test and found cylinder 2 was dead. I confirmed this was a coil by swapping with another cylinder. I don't know if this coil has been dead all along or if it just picked this time to fail. Under load, and while misfiring, cylinder 6 is the only one that I can kill and it makes no difference. So I am blaming this one for my intermittent misfires.

I will be calling MSD to see if I can swap these two with stock coils just to test with, I will then have to send at least one of them back. If cylinder 6 is also a coil, I will send that in as well, or continue testing, I can swap injectors or run compression tests.

I'm getting a lot happier now that there is a light at the end of the tunnel, although waiting up to two weeks to get RMA coils back from MSD is going to be a pain, I may just buy some new ones so I have spares in case this happens again.

99FormulaM6

iTrader: (21)

do you have your stock coils to put back on?

98 Raptor TA

iTrader: (9)

I also think it might be the coils, when i had a LT1, i put an MSD coil on it and it actually misfired more at idle especially than with the stock coil.

WhiteRhino

iTrader: (6)

I have seen a couple threads with failing brand new Msd coils. At the time I didn't think of it. You might be able to do a search on here for Msd coils and see what people have to say about them.

transam1998

iTrader: (5)

No, I didn't have my stock coils, in a moment of generosity, I gave them away to a member of this board last year so he could diagnose a misfire :-)

Cylinder 6 also turned out to be a bad coil, it was only cutting out under load, verified by moving the cylinder 6 coil to cylinder one, making the car misfire and cutting out cylinders. Cylinder one was dead after moving the cylinder 6 coil to it.

So I have 2 coils going back to MSD, I also called Thunder Racing and bought two which will arrive Friday. When the RMA'd coils return, I will keep them as spares.

Thanks everyone for their help.