At about 30 to 40 mph under steady accelerator pressure I am getting what feels like a cyclinder not firing, might happen 2 or 3 times in 20 miles. Never notice it when accelerating, or at freeway speeds. No CEL coming on, it is not coughing or sputtering it's just a quick miss, doesn't register on the tach. The only idea I have is maybe a sticking valve? but I am not sure how to test for that.

So I am looking for ideas

As always any and all help greatly appreciated

 

Well, here's some good into on sticky valves -

http://www.robisonservice.com/servic...n_fouling1.pdf

The trouble is, it's not real easy to test for sticky valves. I had this problem and took the truck to a good indy shop and told them what was wrong with it (because I had already gone thru other diagnosis and a guy on another forum helped). I took it there because I didn't want to go thru the trouble. They told me it was everything else in the world while they kept it and drove it for a couple of weeks. They finally gave up and told me they would check for sticky valves for $500. I ended up bringing the truck home and doing a valve job myself. It probably was going to need a head gasket soon anyway, and I took my time and did a thorough job. All that being said, you should be seeing misfire codes. Mine was P0308, and P1316. Number 8 cyliner, exhaust valve.

 

Well that is certainly a good description of what I've got happening, looks like a valve job is in my future

 

There are some products claiming to help fixing sticky valves, give them a try first. Had the same problem, happened to be a broken valve spring.Good Luck

 

I have that ocassional misfire too, seems like all 8 cyl's miss a beat then go right back to normal firing. I also read somewhere it can be a bad igintion module?

 

The problem with those products that claim to clean sticky valves is that they only work on the intake valves, and are burned up by the time they get to the exhaust valves which are the ones that tend to stick on the D1. I've heard the same regarding the ignition module, can cause some firing flakiness. It's always less painful to eliminate the obvious before easing in to the catastrophic, have you gone through all the standard ignition components and ignition troubleshooting, injection & fuel delivery etc ?? Mine was doing the same thing, just a slight skip here and there at 40mph when just a little more throttle was needed to go up a mild hill, Champion copper plugs and some decent wires took care of it.

 

I ran a can (don't remember which one) of one of the cure all's through a tank of gas about 1-1/2 weeks or so ago and the missing has gone away completely. In the past year I have replaced most of the engine electrical so I have some confidence that the missing was not coming from there. Time will tell if it was just a sticky valve that needed a little cleaning or if the real problem is just waiting for the right time to show it self. The truck is a daily driver for my son, so I am hoping it holds it together until this summer when school is out so I can park it for a week and do the heads, oil pump, etc and then he will be ready for the next school year.

 

I am glad it worked for you. Also remember the quality of gas is very important too...never put regular in and if that product has worked for you repeat it once a while.

 

Well the miss is back with a vengance. Truck ran great for almost 2 weeks and then today started missing again except now it is much more pronouced - like the truck is almost stalling. It seems to only be happening at 1100 rpm, I drove it around tonight and can almost make it happen at will by going up or sometimes down through1100 rpm, I thought maybe the TPS was at fault so swapped with an old one I had but still same results. I've got no codes showing up on the dispaly.

 

Strange, if you have valve related issue you must get a misfire code. I suggest checking the pressure on each cylinder. Yet if it comes and goes, it may not show in your pressure test.