misses upon aceleration

first off this forum has been great but i have tell you you ive searched for misses on acceleration found alot but no one has reposted with there findings and what fixed there problem. mine idles great but with little acceleration it misses at full throttle it takes off like a rocket. feels like ign problem ive just replace the fuel pump as i just purchased this blazer in non running condition. i have good fuel pressure 62lbs with key on and 61 running. ive replace the plugs with ac delco. the wire were replace by the previous owner and the cap and rotor looks clean inside and out. ive looked at the cpi and no signs of washing. i hope to find this problem without replacing a ton of unneeded parts. ive seen alot of this in this forum . please give me your findings on this problem from your own experinces thnks

Year and engine?
Any codes or check engine lights?
Double check secandary ign for good hot blue spark to all plugs.
Can you find the missing cylinder?
Pull plugs and check for wet or mashed tip and plug gap or crack on side on any of them and check compression?

im sorry its a 96 4.3 w compresson just checked all 150 to 162 it has 182k miles no check engine light. idles great but on slow take off it misses , if i hit the throttle then it will take off great . at cruz you can feel the miss

Engine miss.
Go over secandary ign.
Get it on a good engine capable scanner and check for missfire history and what cylinder is missing?
Also cofirm good fuel pressure.

ok here we go the fuel checked again 162key on and 160 running ive installed new ac plugs , cleaned the maf. looked at the cap and rotor and the look clean. i hate to have to replace parts that are not needed like mose of the shops are my area. scanned and found 1,3,6 cly misses has anyone had this problem and knows what fixed it instead of the the trail and error thing. i hope to check the wires weds when i return home with a meter. they were relaced by the previous owner when he had a no start problem the sold it to me. runs good until you accelerate then misses bad:crying:

Check fuel pressure good hot on the road on a pull.
You should have 64-65 lbs under load.
Good Ac Delco plugs?
look at plugs and plug gap.
Check dist cap and wires and for good hot blue spark to all plugs.
What codes no does it have?
What is camshaft retard setting?
What is missfire history like a steady miss or ramdom missfire?

is there any chance that the person who changed the plug wires may have mixed up some wires possibly causing the firing order to be off? The order should be..165432. Driver side of engine is 1.3.5 front to back. Passenger side is 2.4.6 front to back. Driver side of distributor cap,#1 IS IN THE MIDDLE #3 is in the front and #5 is in the back. Pass. side of cap is 2.4.6 front to back...coil is last after#6. but if your sure the miss is intermittent, then this probably isnt your problem

ok here is the deal i replaced the cap rotor and wires ive already did the plugs still ran the same. codes radom iss 1 3 6 cly. i unpluged the maf sensor ran better but still little miss not as bad then unpluged the map sensor ran like a raped ape. so i cleaned the map senor and rehooked up both it runs better but still little miss only on acceleration. question is do you think the map sensor is the cause of this. the map is 44.95 ive already put a 29.99 cap and 49.99 wires and 33.oo plugs than were not need not including 300.00 for the fuel pump.

ok here is the deal i replaced the cap rotor and wires ive already did the plugs still ran the same. codes radom iss 1 3 6 cly. i unpluged the maf sensor ran better but still little miss not as bad then unpluged the map sensor ran like a raped ape. so i cleaned the map senor and rehooked up both it runs better but still little miss only on acceleration. question is do you think the map sensor is the cause of this. the map is 44.95 ive already put a 29.99 cap and 49.99 wires and 33.oo plugs than were not need not including 300.00 for the fuel pump.

Proper testing before throwing parts at it.
Check fuel pressure and all senser readings.
Check camshaft retard setting.


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 and fuel pressure testing guide line.
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.