For the past couple of months I've been getting a rough idle after my car has warmed up. For the past week or two its started not wanting to start when its warm as well. I was told that if I unplug the maf it will throw it in open loop and should run fine if its a sensor. Well I tried that and it still didn't run right. I replaced the coil yesterday along with the coolant temp switch.

It only runs rough at idle after it gets warm and smooths out as soon as I put it in drive and give it some gas. It accelerates fine and runs great so long as I'm moving. Seems like I mainly get this problem idling around parking lots.

 

Which coolant temp sensor (its not a "switch") did you replace - the one in the driver's side head or the one in the water pump housing? Have you scanned it for codes? Have you looked at the PCM with a scanner to see if its getting the correct coolant temp reading?

Unplugging the MAF sensor does not put the PCM in "open loop". The PCM simply defaults to speed-density mode, rather than mass air. Everything else stays the same - stays in closed loop, all the normal sensors are used. Simply proves the problem is not caused by the MAF sensor.

 

I replaced the sensor in the water pump. The other one is just for the gauge in the dash, correct? I haven't had it scanned for any codes but its not giving me a light. I guess I could take it by autozone and let them scan it but they don't have anyone who knows what they are doing. I'm hoping its just something like the coil wire but I think it would run bad when it was cold as well if it was the coil wire.

 

A friend of mine with a 97 was having very similar sounding symptoms and it ended up the TPS (throttle position) sensor

Does it run rich, or blow black smoke when it does start and run poorly? It could be the fuel pressure regulator, when the internal diaphragm fails it will allow fuel to be sucked through the vacuum tube and can basically flood the engine

 

I have noticed the oil has smelled like gas the last few times I've changed it but I figured it was an injector leaking down. I had planned on replacing the regulator but just never got around to it. I'll check it out tomorrow if I can get to it.

 

Sounds like its running rich, possibly due to a faulty coolant temp signal, or problems with the O2 sensors in closed loop.

 

Might want to check your injectors. If you can test the rail pressure for a leakdown worth a try.

 

So I changed my fuel pressure regulator last night because the line smelled like gas. I also replaced all the vacuum lines with new hose. I'm still having the same problem though so I rented out a scan tool today. Lucky for me I just got my first ses light this morning. It was a code 36 so it looks like its the distributor. I've noticed that the problem seems worse when I park on a hill so I'm thinking the fuel pump may be weak as well. I don't have the money to replace the distributor right now so I have a few questions:

1. Can I keep driving the car until the opti completely craps out without doing any damage? It really doesn't run that bad except for an occasional rough idle and hard start.

2. Would I be able to get away with just replacing the cap and rotor or do I need to buy a distributor as well?

3. What distributor cap and water pump do you guys recommend? I've heard of the gm units being bad right out of the box.

 

Bad Iac. Took it apart and put it back together after pulling it out a second time and the car starts on the first or second try every time now. I guess after I pulled it out the first time and saw how carboned up it was I should have replaced it then. Resistance checked out though so I decided to just clean it. Have another on order.