camaroeater

Atstart up it idles at 750 rpms. Seems that after driving for 5 minutes, when I come to a stop it still idlesgoodat 750, butif I come to a stop for over1-2 minutes the rpms go from 750 to 550 for 1 sec. and then back to 750. If I just sit and idle, it willdo this every 2-3 minutes. Anyone have and idea what could cause this?

1990NOS!

idle air control....
What about when you get on it--- let off at a high rpm 5-6k, and push in the clutch right away... what do the rpms go to??- really low, does it sink back down gradually, or just drop back to idle within an instant and almost stall?.

camaroeater

I have not tried that and will, but I did punch it andlet off and I could hear the popping sound that is normal from the rear. Also, as I came to a stop I threw it in nuetral and the rpms went to 750. I drove it last night and then this morning, thats it. Could you explain what the above symtoms would be andhow it should react to punching it, then letting off?

1990NOS!

well my car has a cam so it lobes from rpm to rpm--- (700-550) when cold, then when i get to a light it takes a second to drop back down to idle. .. it'll sit at 800-1k for about 10-15secs then just start lobing at about 600pms when at idle temp....

You may just be concerned about nothing... if it's not popping on rev up, any hestitation, or stalling... i wouldn't be worried.

camaroeater

I wonder if O/R midpipes effect Speed Density 5.0's differently than mass air ones?

camaroeater

I got some hesitation on the way back from lunch. When I turned a corner in 1st, a little after I shifted into 2ndI was on the gas and it hesitated for a couple of seconds. Does anyone know what this could be?

Jon82387

You got your 02 sensors back in correctly right?

camaroeater

Yep...Its driving fine...its just that its dieing a start up and the rpms will go from 750 to 650 every once and awhile. I've change the new motrocraft plugs to Autolite 25's gapped to .050", checked timing, cleaned IAC, and new wires. What could this be?

FivePointOhh

ihave the same problem so im curious to find out myself. does your volt gauge jump around too when idle drops down to 550?? mine is out of control when im at a stop light for more than 30 seconds and it goes from 750 to 550 also at start up i have to constantly save it until it reaches a temp 100* or greater.

and 1990NOS!:
i have popping and hesitation until i reach full operating and then nothing. i also experimented on my own with the "bring up to a high rpm and push the clutch in" mine just instantly drops to 750 idle and just maintains unless it idles for a little while until 30seconds ish and it drops to 550 and struggles.

camaroeater

Exactly where mine falls...for two days I had no problem at start up. This morning no problem.
Mine idles at 750-800rpms, but like you said, after about a minute it goes from 750 down to 600 and back to 750. Sometimes it will fluctuate at little back and forth from 750 down to 600 a couple times. My Idle has ALWAYS been at 750. Other than the RPM thing, I have no problems performance wise, I noticed the torque being hurt going O/R, but I notice more power in the high rpm range.

Hey Fivepointohh, my voltage gage drops when the rpms drop.