LX 470....Help...Help

[Quick]

'99 LX 470 with 191,000 trouble free miles upuntil few weeks ago and now I can't get a break

First, a month ago was an oil leak straight onto the exhaust and the culprit was Valve covers (changed since)

Second, the on and off starter issue and that seems to act so random that we just can't duplicate the dang problem, I know I am going to get stranded one of these days

Anyway, the problem I need help with is:

Ever since I got the truck back from Valve covers replacement, I have noticed every time I take off from a dead stop, the truck seems to hesitate and if I keep the foot down and once passed the 1000-1500 RPM, all is well

Also when standing at the traffic light, the whole truck seems to shudder/vibrate with very little RPM variation (some but not much).

There are no engine light on but I will still take it to Autozone to see if I can get some codes?

Tomorrow I am taking the truck back to the mechanic who did the valve covers but can someone here give me pointers as to what it could be or where to look?

Vacuum leak?

Coils/plugs but at higher RPM truck is fine?

Help greatly appreciated.

 

[re_guderian]

...
Coils/plugs but at higher RPM truck is fine?...

My money's on this. They don't always throw a code right away when they go, and I've had it be days or weeks until it happens. BTW, a code reader, either Bluetooth via the Torque app or a cheap-o from harbor freight is a good tool to have. I've had coil packs go, and a loose spark plug cause similar issues.

 

[PADDO]

Have you had a chance to do a slow and methodical check for loose hoses and connectors? Look for a hose loose on the air box plenum, check the power steering idle up switch vacuum line nipples weren't accidentally busted, check the integrity of the injector connectors, coil packs, confirm the air intake system plenum is still in one piece - I guess just give everything a good eyeball and check connectors for tightness. And grab a code reader too, there might be a stored code or two in the system.