OK, i've been messing with this for a while now, and think I'm going to SNAP!!! Ever since I got my car it would slowly creep upto 240-255 range at idle, then out of now where it would drop back to 220. Then start th process again. When I say jump I don't mean it slowly falls back down, like the way it came up. I mean this sucker DROPS like BOOM its back to 220. I figured maybe the thermostat was sticking, so I replaced it, didn't help. Then I tried the fan sensor, because it was coming on sorta late, still no help. My car is fine while moving, never jumps and stays cool. But the minute I get to a light or drive through, it gets back to the 220 spot fairly quickly depended on how long I've been driving. Then once at that mark, it starts creeping up. Any ideas or similar problems.

 

How do the spark plugs look? Are they white? You may be running lean. Anything from dieing fuel pump, clogged fuel filter or failing fuel pressure regulator could cause it. Sounds like you have hit the easy stuff. Try some of these and see if it helps. I would hook a guage up to fuel line before tackling that fuel pump. PITA to change. Alot of people never change the fuel filter though.

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91 Camaro RS 5.0L Black Convertible 700R4
** Added so far **
*GM Wonderbar
*Alston SFC's
*Turbo City Inj Spacer
*Dual Snorkel Air Filter
*March Performance Pulleys
*GM 3.42 Gears with OEM Zexel
*Edelbrock headers
*3" High Flow Cat
*3" Dynomax Exhaust
*Walbro 255 lph Fuel Pump
***Future 330hp Vortec Crate with LT4 hotcam and 454 TBI

 

Yeah lean.......I never really even thought to look to much into that. Might as well give that a try. thanks for the advice

 

Ever thought of a faulty gauge or sending unit ?



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver 14.82 @ 91.1 (faster than Ed)
Reader's ride -> My Ride

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

Got all the air out of the cooling system? Verify that temp with a known accurate guage(mechanical is best).


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, current red metallic paint. Lots of other stuff...
82camaro

 

I'm with "82camaro" on this one. Did you make sure that it is full of coolant? My beretta did this once and I was losing coolant from a leaking head gasket.

 

I have a sending unit that I'm going to put in, but I dont think its that beacuse I saw a few bubbles in the overflow tank when I popped the hood after it was running a little hot. As for air in the coolent system, yeah I have all air out of it, and I even double checked that. I do fear it might be the head gasket starting but I don't know..... :-( I think I'm going to put the sender unit in this weekend and do a complete coolent flush and keep my fingers crossed

 

Sounds like head gasket or cracked head kinda symptoms. That's not good.

 

Dude, my car does the same thing. It runs fine if I'm doing 35 mph+. Under that, and the temp just climbs. From what I've been led to understand, this is a common prob with these cars. GM built them to run hot (less emissions). Rule of thumb- Stop and go driving= car can run hot.

Later

 

My car only runs hott on the freeway, I guess because I dont have overdrive, so I have higher rpm's. Every Camaro that I have seen has some sort of cooling problem. But that's just the way these cars are. I love the WINTER!