99 STS. CAME OFF THE HIGHWAY YESTERDAY UPON STOPING AT RED, TEMP GAUGE CREPPED UP ABOUT 4CM PAST 12 CLOCK. ALSO STARTED IDLING KINDA ROUGH LITTLE SHAKY..GREEN LIGHT TAKE OFF NORMAL 2K SHIFT..SAW WHITE/MAYBE BLUISH SMOKE..(DARK TINT NOT SURE COLOR BUT NOT BLACK) GOT TO NEXT LIGHT ABOUT 1000 FEET AWAY..GREEN AND DID SAME SYMPTOINS....AFTER GETTING HOME IN ABOUT 5 MIN FROM ALL THAT...ALL PROBLEMS WENT AWAY. i DONT UNDERRSTAND.
i POSTED A WHILE BACK ABOUT HAVING AN UNKOWN ROUGH IDLE I COULD NEVER FIGURE OUT..AFTER TONS OF READING MY CONLCUSION IS POSSIBLY SLIGHTLY WARRPED HEAD..I SAY THIS BEACUSE 2 YRS AGO MY RADIATOR CRACKED WHILE DRIVING AND TEMP STARTED CLIMBIBNG AND HAPPENED GO ABOUT 1/4 FROM FLAT REDLINE BEFORE COULD PULL OFF. FIXED ALL THAT...AND HAD A ROUGH IDLE EVER SINCE.....JUST RECENTLY ABOUT 3 MONTHS AGO I DRAINED ABOUT GALLON COLANT OUT CHANGED RAD HOSE REFILLED DEX 50/50 EVERYTHING WAS SAME NORMAL SO I KNOW COOLOANT IS FAIRLY NEW SHAPE...SO THIS JST POPPED UP.

*NO COOLANT USE..NO OIL WATER/ OR WATER IN OIL* IDLES VERY ROUGH WHEN ENGINE IS COLD GETS BETTER WHEN WARMS UP BUT STILL THERE. 155K

 

Just wanted to add if anyone can confirm this on our gm engines. I used work for ford and a friend tech of mine said that he knows on ford cobra engine and lincoln 32v intech dohc, that in the heads are coolant senors that monitior temp of coolant and he said if there was any work done to the coolant sytem (watr pump, radiatr, hose change etc) and it was not bleed correctly and air was still left inside, air could surrond sensors and trick the engine in thinking it was hotter and cause it dump more fuel to cause rougher idle/ and or in extreme cases to run in limp mode by shutting sown switching cylinders on and off cause the miss.
So is it possable i have air in system to cause this? Or could i have warpped head from running it to hott?

 

if you did what you said, the engine, heads, etc., should be just fine.
on the engine miss, my vote is on a throttle intake issue or ignition system.






that part about dumping more fuel when hot be incorrect; only if the sensor saw a LOW temp would the computer add extra fuel.

limp mode **camel mode ** if running overheated, yes. but once the overheat is corrected, the limp mode should stop.
as to the warped heads .. I have yet to hear or see a single warped head from Northstar, 4500 or 4100 engine.

 

I agree with Stomper,warped head(s) is unlikely. Aluminum heads warp when engine severely overheat and the severe overheating of a Northstar causes the block to fail, The aluminum softens to a point even "Time-serts" won't hold. You need a way to monitor PCM data when condition occurrs, then you may able to determine why/what is happening. Sometimes it can be caused by poor connection or something with a harness. Try wiggling stuff and see if you can make condition occur the look - there.

 

Well i hope thats the case about head(s) it would be good news then. As for ignition system im almost positive its okay new plugs wires (delco) and even changed the coils, same conditions..i only wonder if the plate under the coils was bad? Should i just bring it to a good mechanic or caddy dealer and let them find out whats wrong-monitor pcm etc.

 

Is your Head Gasket failed It's cause to be a pressure issue.So you should go to your local garage or workshop and get the car hooked up to a Diagnostic machine. Hope nothing major will wrong with your car .




Cadillac STS

 

a bad egr valve? i can check this my self correct for faulty operation/possible cause rough idle? althou i kno i should have it connected and monitiored at shop just very tight budget right now.