knock sensor?j

[tahoe nick]

Truck missing under load or uphill. New everything, still missing. 97 2dr 5.7 vortech

Took it in for scanning,couldn't diagnose. Tech said he thinks poppet valve isn't letting enough fuel in when necessary.

Another possibility mentioned to me is knock sensor gone bad. Never heard of this but would like to try before the spider. Anybody ever?

 

[lesterl]

Check fuel pressure.

How many miles?

 

[tahoe nick]

125k. Trying to keep from having to replace spider

 

[lesterl]

So no codes were stored?

 

[tahoe nick]

Scanner plugged in idle, no miss. Kept it plugged in,went for a ride and got it to miss. Showed random, intermittent misfires on 3,5, and 6. Going uphill on the interstate and then letting it shift into OD causes it everytime. Also when pulling my 16 ft trailer with lawn equipment it misses even more often. And it's running rough after first starting. New fuel filter, and ran 2 seafoams and 1 ac Delco fuel system cleaner from dealership prior too swapping ff.

 

[lesterl]

Hows the distributor drive gear looking? They can get kinda wacky..... Whens the last time you did a tuneup? Particularly the cap and rotor (USE ONLY AC DELCO parts for these....)

 

[tahoe nick]

As in first post, new everything. Been down the checklist. This is what I'm down to: knock sensor, spider

 

[lesterl]

Crate Engine? New everything doesnt tell us what is new.. Is PCM new? Fuel Pump? Rear Axle? (not that the axle tells us but new everything can be read many ways and I usually side on the cautious, plus New does not mean Good...)

 

[tahoe nick]

By new I meant new plugs, wires, distributor cap and rotor button,fuel filter, cleaned mass air flow and sensor. I know you answer thousands of posts so you won't remember that this is what you suggested in earlier post months ago. B ut the problem remains. And scanner only shows intermittent missing only while driving uphill and shifting into OD or pulling my 16 ft landscaping trailer. Then would $ettle back down . But just last night going uphill, I downshift get to top, and it really goes to vibrate and missing and doesn't settle out. I limped home but whatever it was completely gave out. Without having it scanned yet,any guess on this so I'll have something to look for?

 

[MO Viet Vet]

Never have seen a fuel pressure test result?

 

[lesterl]

Check the distributor drive gear for wear, also check the sensor in the bottom of the timing cover for damage.

Also like Ron said some fuel pressure readings would be good before even messing with checking those..... Reading @ key on engine off (prime), crank, and running idle pressure if it will run, if not unplug electrical off MAF and see, or spray some carb cleaner into intake and see if will fire off....

 

[tahoe nick]

Good. Compression test also good dealership said its BC I don't have cats and o2 sensors are bad. But cats have been off for years and this "missing" and rough idle are new. No codes for misfires showing