Rough Idle when warm under load 99 suburban

Figured I'd repost with a different title - I know the intake has been discussed in detail and I really appreciate the information I've gleaned from this site. My questions do go beyond the intake, yet I think it may be related to my idle problem.

I too am faced with the leaking intake manifold on a 99 gmc suburban.
I think mine is leaking from the front just below and to the right of
the t-stat housing, unfortunately I pretty sure it the intake gasket
and not the T-stat, dry as a bone up there. The leak has gotten a bit
worse, brought it to a mechanic who replaced the water pump which I'm
sure had failed, fluid everywhere....
I am now at the point of deciding wether to fix it or dump it. I've
got ~120k on it now and it's had the fuel pump done, decent tires.

One of the existing problems is during the warmer months it idles rough and sometimes even stalls at
idle when in gear but at a stop, put it in park and it runs smooth. I
wonder if this could be related to the leaking manifold gasket, if
it's leaking interally too. The only other thin I can figure might be
causing problems is the remote start, astroflex/start mv801, the
install was obviously a butcher job, as I've traced the wires, one went
to the coil and was just twited on an taped, no solder... Recently there are times when it just won't start, if I disconnect the battery and reconnect it starts right up, I do believe this is related to the darn autostart and plan on removing that, at least while troubleshooting.

I also see that the temp doesn't get over 130 what's the normal t-stat
open temp 195? During the cold weather it seems fine, other than having to add coolant. I'd really like to get a handle on the stalling before tackling the intake manifold.

1999 5.7L k1500

Hi Jim:

Sounds like all the symtoms my 97 Suburban had, and it was the intake gasket. I did repace it about 50000 mi earlyer. The new one was a Felpro steel renforced. No problems since. Kind of a pricey gasket at about a hundred bucks but thats a job I do not want to do a 3rd time.

Anyway my 2 cents

Good luck

Yes, the RS will make the truck start when you hook up the battery when there's no hood switch installed. Your truck should run much warmer than 130. It should be 200-220

The temp must be the thermostat or the sensor, I'll replace both during the gasket job. No hood switch on the remote starter. I replaced the starter yesterday and got the same click no turn over. After reading more on this site it seems quite common for the battery cable + to be the cause, I'll investigate that more today. 8F with the windchill, the starter was easy until my fingers stopped doing what my brain was telling them, had to warm up for 10 minutes in between bolts:eek:

Thanks for the feedback on the rough idle gasket issue, that makes me feel like it's worth delving into. Did you perform any other maintenance while in there, fuel pressure regulator, injector cleaning, de-carb? Normally I'd leave well enough alone but don't know if the plenum should be part of the job.