94 B4000 Rough Idle & shuddering @ 50mph

[msppdx]

Changed fuel pump, fuel filter changed 4 months ago, cleaned MAF, ensured no vacuum leaks and no fuel rail leaks & FPR checks good as well as return line. Compression check good. No codes except rarely get 157 MAF voltage low. Idles fine in park and rough in drive,. No power up hills and at 45 -55 mph shudders until I kick off throttle, yet returns quickly on steady throttle. Just wondering if anyone thinks it is Auto xmission or engine problems. Thanks

 

[PanamaExpat]

My truck was doing that off and on when I first bought it. Turned out I had a loose plug wire. Also did you check to see if the lower intake bolts were tight? Seems like another common issue on the 4.0.

 

[msppdx]

Just bought it 6 mos ago and it had a little rumble @ 50mph. The plugs, wires and coil pack are fairly new and check good. #4 cylinder had carboned up but not wet and the rest were light hazy and equal.

 

[PanamaExpat]

Does it sometimes stall out at traffic lights? Second time I'll ask... Have you checked the lower intake bolts..... If you don't believe me do a search here on the site and you will see what kinds of issues that causes. Some guys have reported that they were hardly even finger tight. I had 4 loose on mine.

 

[msppdx]

Well, it is my sons truck so reluctantly I am now involved again. Manifold bolts were good. Found bad coil pack for cylinder 1, replaced and found plug wire for cylinder 4 bad at rear of engine. Replaced. Now have power back. I have driven it with no shutdowns but he said it has happened to him 4 or 5 times. Alas it is still shuddering fairly good at around 50 mph (of which I hear is a common Ford tranny fault) Again no codes or lights to narrow down.

 

[Jay'94]

I had almost the same problem. Was shudering and shaking the whole truck under load, usually up hill, didn't idle well when 1st started then once floored under load would clear up, POOR fuel economy, had a couple shut-offs, no power. I had changed plugs within 5,000 miles, but checked them anyway. Didn't find anything. So I ran codes=nothing. As the truck is a '94 I just started replacing components calling it preventive maintenance if it didn't fix it; O2 sensors, coil pack, IAT, clean and inspect air tube, don't remember what all else. Finally I was 2 miles from home at store, it started but missing all the way home=fed up, looking for a new truck. Ah wth, check the plugs. #3 electrode=GONE! Replaced=all good. I & several others figure it was a bad plug from get go, it was somehow cracked and just took time to fall apart. I'm running autolite DP and I'll stick with them, even though this problem. I've had it happen before with a Bosch SP in a Harley. Figure just get a bad one every now and then. I do however keep 2 spares in the truck at all times now.

 

[msppdx]

ok... changed Throttle Position Sensor.... No help. Tested ICM..... failed. Installed new ICM and power was upped and shuddering went away at 50mph. Now it sometimes shuts off at stopping especially after down hill and a slight missing now and then when driving..
Fuel pressure regulator? Pressure checked right on. Injectors?