The symptoms are when coming to a stop or as i take foot off brake to start,the truck will have a motion similar to warped rotors. If i put it neutral it rolls to stop smooth as silk,so just does this when in gear. Plenum's been done couple years ago,just did new wires,cap,rotor,plugs,coil,iac,tps and map sensor. Also recently did the cat and new upstream 02 sensor(denso). Timing cover was leaking so did timing set and new harmonic balancer. Fuel pressure at 47 psi. Compression numbers are well above spec for truck with 211,000 miles. It runs fine all other times except for slight miss #8. couple mechanics think its a valve not seating. Sorry this is long winded. Any ideas would be greatly appreciated. Forgot to mention this started immediately after rear differntialrepair and i asked them to adjust rear drums. Thanks in advance!

 

Do anything about the cat?

How do your tires look? Brake pedal pulsate at all?

 

Magnaflow cat replaced along with denso 02. The annoying jumpiness seems more engine related. Tires are almost new. It's only noticeable at less than idle speed like pulling slowly out of garage or last couple feet of stopping at stop sign or inching ahead at red light. Actually feels like your bouncing up and down. Once i am at dead stop it quits bouncing/jumpiness. Runs smooth on highway and around town speeds. No pulsing in pedal.

 

Hhhmmm...... Have you tried giving the engine a seafoam treatment? If it's just something carboned up, that may help..... (sure won't hurt.)

 

HeyYou, I got a CEL while letting truck idle. Was same old #8 misfire that shows up 3 or 4 times a year. Seafomed it after work and seems a little better. Still can feel miss. Seems like it runs smoother the hotter the outside temp. Freeze frame data also ECT at 147 F. Thinkin that should be higher as truck was running for about 20 minutes,unless i didn't notice CEL earlier. Maybe a big stick of dynamite! #8 plug wire is stretched over valve cover and wouldn't make it if it was 1/8 in shorter. Idk? And thanks.

 

Done anything with your plenum? Vacuum leak there would give you a miss. Clogging cat also affects #8 first..... Might wanna do a compression/leak down test as well, and see if there isn't a mechanical issue there.

 

Got a solution to this jumpiness problem today. Replaced champion plugs with NGK coppers and my truck no longer has the symptoms described above. I had put 2 new set of champs and one set of autolites over the last six months with no satisfaction. I can't believe how well my truck likes the NGK's. No rhyme or reason technically speaking, but got results by dumb luck. Oh yeh, pushing 218,000 miles now.

 

The jumpiness with my 99 never completely went away and have just been living with it until recently. Replaced the TPS with OE one off my totaled 2001 ram. Had a BWD one on there from couple years back that did get rid of surging at idle and while cruising. Apparently it was giving a choppy signal at idle speed, because no more watching the hood jump up and down
while coming to a stop. Kudos to the guys recommending staying with OE when replacing sensors! 228,000 miles now.