HELP still have high rpm miss

[lx50]

i replaced everything i could think of electrical,replaced valve springs,cleaned injectors.
what else could be making my car miss,it runs great till 4000 and the farther the rpms go up the worse it gets.

[tmoss]

Did you replace the TFI AND the coil pickup (inside the distributor)?

[5.0Droptop]

fuel pump and filter?

[lx50]

yes i replaced fuel filter, not the pump because i had a gauge hooked to it and it reads good,and it goes to reserve,and i have replaced the whole distributor, it didnt help it so i put my old one back in.

[5.0Droptop]

my old pump made good press at idel. it was under load it couldnt keep up. have someone rev it several times with gauge on it and see if press drops. It should go up not down.

[lx50]

fuel pressure does go up.

[5.0Droptop]

ok rules that out then. And you ruled out the dizzy. So now looking at plugs what kind and what gap? What wires and what cap and rotor? What coil and how old? Checked for vaccume leaks? Vac leaks make it go lean especially if its a mass air car. Also if mass air have you cleaned the maf meter wires? is it definatley a miss and not clutch slipping if its a 5 speed.

[lx50]

autolite double platnum,accell wires.
cap,rotor,coil all new stock equipment.
motor is stock,no mods,ec for headers,offroad h-pipe,flows.
just thought id let you know that too.

[5.0Droptop]

have you tried differnt plugs? I have heard the platnum plugs can cause issues.I run regular autolite plugs.... But its just a guess.

[Joel5.0]

have you tried differnt plugs? I have heard the platnum plugs can cause issues.I run regular autolite plugs.... But its just a guess.

Second sljccj suggestion, I went back to regular autolites 2 days after wasting $48 on a platinum set. Any chance of getting it scanned for codes? My 2¢. LUK

[lx50]

have had it scanned no codes,and have tried regular plugs

[ho50ca]

High rpm miss is definetely ignition. Fuel pumps and related will show as a flattening out of power up high or, in exteme cases, detonation.

Recheck plugs, wires, etc. and gap them at .045. I use NGK V-grooves as they have proven unkillable with all forms of artificial aspiration. Check your wiring connections to the coil, etc., i.e. perform a serious wiggle test on everything to simulate road shock.

Check your grounds. A faulty ground path on an EEC IV car can wreak havoc with things. There's one at the EEC, just replace the ones from the head to the firewall as they rust from the inside out.

Lastly, there is a slim possibility the EEC itself, or its main connector, has crapped out. It's not a likely fault but, with cars this old, unlikely things surface. There is no practical way to really test this other than re and re.

Also, ditch the Accel wires and put some Motorsport ones on there. Accel's have had very poor durability, in my experience, and MS wires have survived the most grueling torture tests.

You can also just plain old scope the car and see what's happening real time. This art is rapidly being lost by shops, even though a modern scope is a fabulous diagnostic tool. I guarantee if you'd done that first you'd be dollars ahead now.

[lx50]

High rpm miss is definetely ignition. Fuel pumps and related will show as a flattening out of power up high or, in exteme cases, detonation.

Recheck plugs, wires, etc. and gap them at .045. I use NGK V-grooves as they have proven unkillable with all forms of artificial aspiration. Check your wiring connections to the coil, etc., i.e. perform a serious wiggle test on everything to simulate road shock.

Check your grounds. A faulty ground path on an EEC IV car can wreak havoc with things. There's one at the EEC, just replace the ones from the head to the firewall as they rust from the inside out.

Lastly, there is a slim possibility the EEC itself, or its main connector, has crapped out. It's not a likely fault but, with cars this old, unlikely things surface. There is no practical way to really test this other than re and re.

Also, ditch the Accel wires and put some Motorsport ones on there. Accel's have had very poor durability, in my experience, and MS wires have survived the most grueling torture tests.

You can also just plain old scope the car and see what's happening real time. This art is rapidly being lost by shops, even though a modern scope is a fabulous diagnostic tool. I guarantee if you'd done that first you'd be dollars ahead now.

this may sound stupid but what do you mean by scoping the car??
and i have tried other wires than accel and it didnt help either.
i have took it to many people here ,and nobody seems to know what it could be.
somebody said it could be the mass air,i dont see how but i guess anything is possible.
like i said the car ran great 1 nite i took it to 6500 ran great,next day it started the missing crap.

[ho50ca]

A scope is an oscilloscope and is capable of accurately measuring any series of repeated electrical events in the engine. Modern ones rely far less on the skill of the operator and have fantastic software/firmware for diagnosing difficulties.

Well, you took it to 6500 rpm on stock valvesprings? They were killed by that, no surprise. The 6250 rev limiter probably saved you from fragging the motor right there. Have you checked the compression or done a leakdown test? You may have dinged a valve or burnt some. This often happens when stock valvesprings are used and it can materialise unexpectedly after a period of thrashing.

What springs did you replace them with? Please don't say stock ones. If so, check the seat pressure. Minimum acceptable is 85 ft pounds and I wouldn't be happy under 100.

P51C

[lx50]

yes i replaced them with stock ones,but the same prob,had comp test around 150 pounds per cyl.i had a 91 lx5.0 all stock and i took it to 7000 all the time with no prob,i still think its something electrical on this 89 lx 5.0.