90 HBtruck KA24E is misfiring above Idle

[jokeysmurf]

My HB truck with a KA24E is 2yrs on a new computer , ECT, MAF, and O2 sensor, I recently installed 3 fuel pumps to get one that ran more than a tank of gas without being towed. It ran fine as it did adter resurrecting it from severe black smoke from the MAF. Now I have a new dilemma the thing idles smoothly, but shudders when taking off from idle then has aa midfire all through the acceleration to level speed range and at times a notable backfire felt through the gas pedalusually on acceleration. I installed new plugs, cap and rotor as the wires were only 2 years old and not in bad condition i did not replace them. the muffler is also new. also instsalled a new air filter and the fuel filter was replaced with the new pump and screen. i cannot even locate the check engine light, physical location pleae so i can check to see if the former owner removed it? This beast is OBD ! which means only functional tests are available with a scan tool . The Truck is a dead fish above mid rpm range and aoplying gas produces noise with no noted acceleration even with it floored and the mileage wont exceed 18 mpg , now down to 17.6. Im thinkin TPS but the manual describes it as a switch and my scanner confirms it as working. While trying to ascertain the dead fish symptoms i noticed that moving the lever with a small screwdriver on the TPS would improve idle quality. Wrack your brains guys!! I work on Toro Greens and fairway mowers this ones beyond my venue.

9/23 Ok got rid of the misfire and sputter - it was the wires new set cured it but the things still a dead fish. Thinkin mebbe TPS??

[Rev_D21]

Has the distributor ever been out of the truck?

[jokeysmurf]

I have verified ignition timing with a light- nice try this aint no easy fix! I will verify fuel pressure this sun . One thing I Do want though - I cannot find the check engine lite even shined a lite at the cluster do you know the physical location ? As in next to or above on ? Side of cluster,dash, etc.

[Rev_D21]

In 90 they used the LED flashing light on the ECM itself. Since they had no real OBD at all. There is a rotating switch on the ECM which puts it in self diag mode. The red/green flashes will give you the fault code....if there are any. The system is very primitive. I have 3 of these trucks and even the 95 lacks any OBD diag capability as we know it today.

[jokeysmurf]

ok so no light on the dash?? no wonder a lamp ck wont light it up. I know where the screw is and it not showin any codes got the misfire gone but still a shudder coming off idle and a dead fish at higher speeds and upon downshift it holds speed and driones louder as you apply accelerator movement. Any thoughts? also any easy adjustment for the kickdown cable cause it downshifts at 2/3 to 3/4 throttle