Gang,
My last posts began with bank1 and 2 lean codes on my '98 4.6. Changed the fuel filter and cleared the check engine light. Truck idels rough on start-up then calms down after about 2 minutes. As soon as it goes into gear the engine starts shaking. When I accelerate, it shakes bad enough that the seats and center console rattle. When I'm not accelerating it doesn't shake. When I turn at low or no speed, the power steering pump seems to put quite a bit of load on the engine and it bogs down and shakes a bit, but not at speed. Acceleration from a stop on an incline is also slow and lacks power.

Now...I've checked all the vacuum lines I can (even under the right front fender well), PCV rattles when shaken lightly, checked all the vacuum connectors and all seems good.

HAVE NOT checked the throttle body/EGR for gunk yet, nor have I cleaned the MAF.

Ideas???

 

Check these... throttle body/EGR for gunk yet, nor have I cleaned the MAF. and get back to us. I think the culprit is most likely hiding in any or a combination of all of those.

 

another thought...the plug wires, while relatively new, are run around the engine like a pile of spagetti! could my shaking be coming from arcing?

 

well, that IS a possibility. Are they aftermarket wires? I still think that the things you mentioned that you haven't done yet hold the problem. How many miles are on the truck? When was it's last servicing? What did they do/replace? Has the truck been acting funny ever since then?

 

Hey I have a 98 with a 4.6 also, I had that problem before where my engine would shake upon acceleration and you could feel it missing just a little bit when idling. The plugs and wires were changed and the problem remained. It turned out to be a plugged fuel injector. It was replaced and I haven't had a problem with it since. You might want to look into that. Hope this helps some.

Greg

 

You need new sparkplugs and or fuel injector cleaner and or coils could be breaking down (usually only shows up after engine running for a while). Could just be the sparkplugs or it could be a dirty/clogged fuel injector fouling the sparkplug(s).

I would have included plugwires, but you said they are new. However, on another vehicle with the same problem it was my plugwires and they were new. To make sure your wires are not arcing, observe the engine running at night to see if it is arcing to eliminate them as the problem.

I had the exact same problem. It was a fouled spark plug.

 

I also had that problem on my 02 (It was a 5.4), was a quick fix for that, the number eight cylinder was not firing, in my case it was a bad coil (Each cylinder has its onwn) coil changed ran great. Also same problem with wifes corisca a few years back, only running on four. I started pulling plug wires, when the engine dies I new I had a running cylinder. When there was no change I new I had the correct coil pack. I bolted on a new coil pack and back to running on all six.

Hope that this helps.

 

the truck has about 70K on it and had a new PCV, O2, and clean injectors, new autolite dbl plat plugs, aftermarket fram (I think) wires about 16 months ago witrh no problems at all. This is not an everyday driver and I bet I only put 1-2k on it since then. No MIL anymore since I changed the fuel filter 2 weeks ago. even when I read the codes, it came up 0171 and 0174 and nothing about a cylinder misfire, egr code, maf code, etc.

 

I would have suggested plugs earlier but I assumed that new wires + new plugs too. My 97 shook like an epileptic for a while under scceleration. New plugs and wires helped immensely. Trans fluid flush was good too. It still idles like a missing diesel though, especially on cold startup. I know I need to clean the MAF, IAc, and throttle body though.

 

Just went through the same problem with my 97 F150 4.6L. First I had the plugs and wires replaced since it had 112K mi. on it. That did not solve the problem...it ended up being a faulty coil pack. Once it was replaced, the roughness went away and she accelerates smoothly again! Very happy to have that problem resolved.