Page updated on 04-24-2018

98 Grand AM - Hard to Start - Rough Idle

08-14-2007, 11:41 AM
I have a 1998 Grand Am GT 2.4L Manual Transmission. 118K miles on it.

Over the past week, my car has suffered the following, all started at the same time:
1. Hard to start. It always starts, but some of the time you have to give it gas to start. before the problem, it would start easily without pressing the gas.
2. Rough idle. For about the first 30 seconds after it starts, it runs hard. The Idle engine speed changes constantly.
3. After the first 30 seconds, the idle speed is pretty constant, but does vary from about 500rpm to 1200rpm. I will be sitting at a stop and see the engine speed change. I have never seen this before this problem.
4. While driving at a constant speed, the engine will hesitate. By this I mean that the car will be going at a normal speed, then for a split second it seems to slow and then pick right back up again.

Other notes:
1. The check engine light is off. No codes to read.
2. It seems to have a harder time starting when it has been sitting in the sun or after it has been driven, but it does have the problem when it is cold also.
3. The spark plugs were changed around 80K miles (currently 118K miles on it). The fuel pressure regulator was changed about the same time. The car does not have spark plug wires. The module that plugs into the spark plugs is original.
4. The car has yet to actually stall, although it has comes close.

Do you have any idea where to look for this problem? I don't know enough about the system to figure out where to look.


08-14-2007, 05:42 PM
Welcome to AF.

I'd say change the boots on the plugs and get your ICM and coils coils tested.

Also your idle troubles could be from the above and your IAC(idle air control).
Sometimes you can remove it and clean it up , making idle and starting better. See the below link.

Idle Air Control(IAC) Testing Replacing for 99+ (

(the link says 99+, but it is relevant to your 98 also)

08-28-2007, 11:40 AM

Thanks for the reply.

I haven't had a lot of time to work on the car. I have taken off the IAC and cleaned it, but that didn't help. I ran the test described in the link and the rpms stayed the same when I turned on the AC. The IAC on my car has a rubber piece that stops the air flow instead of what is shown on the picture for the 99.

My car has the Integrated Direct Ignition (IDI). I took off the IDI and visually inspected the unit and I didn't see anything wrong with it. I checked the spark plugs and they look ok. Can you change the boots on an IDI?

What is an ICM? and how do I get the coils and ICM tested?

Some other things I have noticed.
1. I can start the car without the need to give it gas, but sometimes it cranks longer before it starts.
2. When I start, I get white exhaust from the mufflers.
3. I still don't have a check engine light on.

Anything else you can recommend would be greatly appreciated.

08-28-2007, 10:28 PM
ICM is the ignition control module.

and the boots are replaceable.

09-06-2007, 10:38 PM
ECU uses a lot of parameters to make right fuel/air mixture depending driving conditions. If you just have rough idle, a bad ICM may responsible for this. However, if you have idle and hesitation problems together, it is more likely that your TPS is bad. Since IAC is to contol air when the throttle valve is almost closed and thus it is less related to hesitation at driving conditions. To check the TPS, take off and measure resistance between two pins. If the ohm change smoothly when you rotate the sensing part, this part is good. If not need to replace.

09-07-2007, 09:49 AM
Just testing the ohms isnt all thier is to test the TPS.

See Here....
Throttle position sensor-Testing & Replacing for 99+ Grand Am's (
It will work for the 98 GA too.

crazy Jim
09-09-2007, 09:03 AM
sounds like a simple vaccume leak to me....

09-09-2007, 02:11 PM
yeah you could be right thier too Jim.

10-17-2007, 01:02 PM
The problem has been fixed. I had to bring to it to a local repair shop and they replaced the Fuel Pressure Regulator.

I want to thank everyone for their replys. Even though I wasn't able to fix it myself, I did learn some more about my car and how it works.

Add your comment to this topic!