Ignition Coil/ ignition module

Has anyone done this type of replacement on a 1999 tahoe?
I have a real bad studder on acceleration and i replaced my plugs wires cap and rotor but it changed nothing. im hoping it the ignition system? anyone had this type of problem before?

What is the fuel pressure?
Any codes or check engine lights?
What kind of plugs did you feed it?
Have you got good hot blue spark to all plugs?
Any engine miss codes?
What engine and mileage?

Have you checked to see if your timing is set correctly? How was the engine running prior to the tune up?

I gave the truck Ac delco platinums
engine has no codes at all
timing is set by computer the engine ran like crap prior to tune up and still does it was the reason for tune up
engine is vortech 350 i put the new coil and coil module on with no improvements fuel pressure is up to specs engine has 148,XXX miles on it.
Timing does go a little goofy under acceleration could this be caused by faulty distributor?

What engine and engine code?
What are you fuel pressure readings?
Engine cold ranking and engine running on the road and when it acts up or when it does it?
Good hot blue spark to all plugs?
MT

engine 5.7 code R i believe
it does it around 30 and above under acceleration once i reach a cruising speed it is ok as long as i dont encounter a hill
no codes being picked up
good spark to all cylinders
dont have fuel pressure tester to take readings

Can you feel a cylinder miss fire?
I would check the fuel pressure real good and get it on a good engine capable scanner and read out all data and codes.
Watch and check fuel trims and cylinder miss fire and camshaft retard readings.

Rent or borrow or buy a fuel pressure gauge.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.
MT

i scanned it using snapon scanner from work no codes only trouble area i found is that under load when the problem occurs the timing backs way off. yes you can feel it missing it feels like a large anchor being thrown out of the back of the truck skipping on the road.

Did the scanner show any miss fires or high fuel trims?
What reading are you getting on camshaft restard?
Go for a fuel pressure check when it acts up.
MT

not showing any misfires
fuel trim checks out not sure about camshaft
ill need to take the pressure tester along for a ride with me thats the only time it acts up the thing idles smoother than smooth and runs good until i hit a hill or go to pass someone

Yes
Tape it to outside mirror or outside windshield and watch it when it acts up.
Good Luck
MT

i got a 94 caprice and it starts and runs for two or three seconds then it dies

i got a 94 caprice and it starts and runs for two or three seconds then it dies

If you need help on it go to the caprice forum and hit the
NEW THREAD BUTTON.

And give us all of your info on it.
MT

ok got it fixed bad plug last thing io suspected since i just replaced them about 2 weeks ago MT Many thanks for your help your very knowledgable appreciate it. Now i know who to ask more questions too

You are welcome.
Glad you got it fixed and thanks for posting back how it went and the fix.
Sounds like you done a good job on the repair.
MT

ok problem is back once again with a number 6 cylinder misfire checked plugs again they are clean wires are perfect. Is it possible that this is a fuel issue. like the spider and injectors.

Yes but check secandary ign real good first.
Ac-delco plugs?

Switch plug and wire with another cylinder and see if miss moves to the other cylinder.
Check for good hot blue spark to the missing cylinder.
Is the no 6 plug wet or dry on the end?
Also check that cylinder for good compression.
And run a fuel pressure test on fuel pump.
Low fuel pressure or bad maf sensor can cause a engine miss.
Are you getting any codes or check engine lights?

yes acdelco plugs and wires cap and rotor
plug looked dry on the end
tried switching wires and plugs with no difference
checked for compression got the same as number 8 cylinder so i guess thts allright will check fuel pressure.