I have a co-worker with a 99 that has a 3800 series II with 75K on it. There has been some recent issues with it:

It takes a little while to start, about 4 seconds of cranking, when it does start, it idles very rough and requires manipulation of the throttle to keep it from dying.

The temp gauge spiked to max, stayed there until I told her to shut it off, I then checked coolant, it was fine once it restarted the gauges went to normal. She stated it has done that a few times over the past few weeks. The gauge deal to me, may or may not be related but leads me to believe its computer related. Thoughts??

 

Scan it for codes. Has the plugs and wires been changed recently? What about the fuel filter, has it been changed? Check the fuel pressure. Did the fans come on when the temp was rising? Might need to bleed the coolant system and top it off. Could be several things causing it to run rough, thus the need to scan for codes.

 

It sounds to me like you have 2 issues going on here. First I will adress the cooling. There is a small purge valve on the top of the T-stat housing, start the engine up and when the needle peggs over open the valve up with a standard screwdriver. You should get a little steam out of it. OK maybe a lot but keep it open till there is some water/coolant comming out. Also make sure to keep an eye on the water level since this is removing the air and filling the block with new coolant. The needle should drop about as soon as you start purging the air out of the system. GM manual says you may have to do this as many as 5 times to get all the air out.

The starting issue sounds to me like a going bad but not yet dead fuel pump. I had an Alero do the same thing, replaced the pump and the problem went away.

To check if it is the pump turn the key to "ON" but dont crank the engine, listen for the pump to prime up, once the pump stops turn the key "OFF" then "ON" again quickly. This will cause the fuel pump to prime the engine again. Do this 3 or 4 times and then crank the engine over. If it starts up normally then it is fuel pump time. If not check the plugs and wires for signs of bad fuel, oil or other spark plug issues. Also check or replace the fuel filter if it has not been done in a while... That is $12 well spent.

Massey

 

I will check on the cooling issue. She has no loss of coolant, and all things look good from a gauge perspective. I have not seen a check engine light on, but scanning is an option. Plugs, wires etc. look to be a few years old. It seems like the issue is only on start up and idle, until it reaches operating temp, then everything is normal. I will check filters and pump as for now that seems most likely to me.

 

When you popped the radiator cap off the radiator you relieved the pressure that was preventing the water flow. Doing that is similar to the purge method I mentioned but not in the right location. These engines are higher up than the top of the radiator so air can get trapped above the water line and cause a vapor lock situation. Purge the car on level ground, engine running and radiator cap off.

Massey

 

Thanks, so far there has been no repeat of a temp problem.

 

Glad to hear that all is well.

Massey