nikkshepherd

1994 pickup. Meticulously maintained by previous owner for 17 years.

Valve cover gasket slightly leaking so I changed both. Also did PCV, grommet, and hose. Reassembled. Introduce rough idle.

Noticed giant ant crack in intake tube. Replaced. Rough idle fixedish.

Now, it stumbles at a at a very specific range. 45mph-60mph. If I get up to 45, let off and depress again, it stumbles. But only in that range, and only when warm. Otherwise it seems to be idling and running fine.

What ive done in attempt to fix:

-smoke vac lines. No appearant leak.
-checked accuracy of vac lines. Appear to be correct
-replaced plenum gasket with better gasket than first time. No change.
-replaced plugs. No change in idle issue. Slight power improvement.
-unplugged tps while running. Ran like crap.
-stored codes 14 & 13. No current cel
-upped idle screw 1/2 turn. Better acceleration. No change in stumble
-cleaned throttle body and AFM
-new air filter
-new oil
-seafoam in brake booster line
-unplugged egr. No change.
-welded exhaust leak at muffler (nothing to do with this)

I know this topic has been covered numerous times, but each time the fix is something I've tried. Truck ran perfectly prior to me digging in. Is there something blatantly obvious I'm missing here?

cheers

scope103

Did you check base ignition timing?

nikkshepherd

I did not because I assumed since it ran well before starting, the timing wouldn't of changed, but I am very inexperienced with the motor, and with timing in general. Could this be a place to start?

scope103

A timing light is $20 , and is really a starting point for all maintenance. Timing can change with component wear. Or yours might have been right on the edge, and when you fixed the PCV it just went over the edge.

nikkshepherd

Thanks Scope. I'll buy this and give the timing a go. Is it as simple as jumping the diagnostic to get it into timing mode and then rostering the distributior cap? I was reading that 15 btdc could result in more power? Sorry for being a newbie here. Just never done timing other than on a diesel VW rabbit from 1980. Little different procedure. Thanks for the guidance. It is greatly appreciated.

scope103

Yes, you have to jumper TE1 to E1. Otherwise, the ECU is trying to add or subtract based on conditions, and all you want to set is BASE timing. Then just rotate the distributor cap if you need to. The timing figure is on the sticker under the hood (mine is 10° BTDC). I live in California, and failing smog isn't worth any pipe-dream of extra power.

The timing mark should be pretty steady at all points. If it's jumpy, that can indicate bad bearings in the distributor.

nikkshepherd

update:

Set the timing to 10 Btdc. Seems to be a bit smoother now. But the stumble once 4th gear is reached is still present. Any other thoughts? I appreciate the help so far! May try pulling the throttle body and ensuring everything is nice and clean.

MOPARYOTA

hi nikkshepherd.
i had the codes 13 and 14. it was the breakdown of the magnet/pickup coil in the distributor. grab one at rock auto, $135.00, its taiwan made (spectre) but better than paying for a $750. OEM one.
put one in my 93 3VZE and it ran awesome, stumble and random stall power loss is gone!

nikkshepherd

Any advice on checking the current one to see if that is in fact the cause? Voltmeter? What is it suppose to read. Couldn't find in FSM. Thanks!

scope103

Where'd you look?
http://web.archive.org/web/201212070...12onvehicl.pdf

nikkshepherd

Here's some audio of me reving it up with the engine warm. Hoping someone with with a good ear can guide me in the right direction.

childintime

Hey Nikkshepherd, I was just reading through your build thread, looking good. I had a very similar idle problem with my 94 when I first got it. Don't know if you've already checked your compression, but mine ended up being low in two cylinders. Adjusted the valves and that took care of the stutter, then changed out the whole ignition system just for good measure. Runs solid now and has about as much power as you could expect from this engine.
Hope that helps. Good luck!