Spark Plug Question?

[fatherlarry]

Mike,

We have a member, CG77vette who posted this on in another section. Maybe you can help him? Thanks.

------Spark Plug Question?
Last year I installed Bosch Platinum +4's in my early '86 iron head L98. I recently developed a rough idle condition. I have not had a chance to pull a few plugs to inspect them, but has anyone else had any similar problems with the +4's? Thanks in advance for any input.


__________________
1986 L98 Coupe
Two Tone Silver / Grey

---------------------------------------------------------------------------

[MKOTZE]

Originally posted by fatherlarry
Mike,

We have a member, CG77vette who posted this on in another section. Maybe you can help him? Thanks.

------Spark Plug Question?
Last year I installed Bosch Platinum +4's in my early '86 iron head L98. I recently developed a rough idle condition. I have not had a chance to pull a few plugs to inspect them, but has anyone else had any similar problems with the +4's? Thanks in advance for any input.


__________________
1986 L98 Coupe
Two Tone Silver / Grey

--------------------------------------------------------------------------- Hello CG77Vette, I have had some problems with Bosch Platinum spark plug. What happens is the platinum center electrode breaks at the weld and the piece that breaks off closes the gap and causes a misfire. However, I don't know if that's what's wrong with yours. You need to determine if the rough idle is a true misfire of a cylinder or something else. Does the check engine light come on? One way to check it is to do a cylinder balance test of the engine. This can be done without any special tools if you are careful. If you are interested in doing it yourself get back to me and I'll give you more information. Oh By the way, What did you do about the Bushings for your suspension? :chevy: MKOTZE

[CG77VETTE]

Originally posted by MKOTZE
Hello CG77Vette, I have had some problems with Bosch Platinum spark plug. What happens is the platinum center electrode breaks at the weld and the piece that breaks off closes the gap and causes a misfire. However, I don't know if that's what's wrong with yours. You need to determine if the rough idle is a true misfire of a cylinder or something else. Does the check engine light come on? One way to check it is to do a cylinder balance test of the engine. This can be done without any special tools if you are careful. If you are interested in doing it yourself get back to me and I'll give you more information. Oh By the way, What did you do about the Bushings for your suspension? :chevy: MKOTZE

Hello Mike,
The bushings are still in the box. Since the job would probably take a few days, I will have to find someone local to do the install. If you have time, please send me more information regarding the cylinder balance test. The check engine light does not come on but the engine idles at 400 to 500 rpm in drive and sometimes stalls. Any help would be greatly appreciated.
Thanks,
Charlie

[TopVette]

Mike,

Could the injectors be clogged or staying open?

[MKOTZE]

Originally posted by CG77VETTE


Hello Mike,
The bushings are still in the box. Since the job would probably take a few days, I will have to find someone local to do the install. If you have time, please send me more information regarding the cylinder balance test. The check engine light does not come on but the engine idles at 400 to 500 rpm in drive and sometimes stalls. Any help would be greatly appreciated.
Thanks,
Charlie Hi Charlie, Sorry to hear the bushings are still in the box. I hope you find someone locally. Now about the problem you're having with your car. There are a few tests you need to run to pin point your problem. First lets start with the cylinder balance test. What this test will prove is if all of your cylinders are functioning properly. With the engine turned off remove the cover on top of the distributor- there are three torx headed screws holding it in place. Once this is removed loosen all the spark plug wires on the distributor cap but leave them connected. You also need to disconnect the wire connector that goes to the idle air control motor, located on the right hand side of the throttle body. Now you need to start the car and let it idle. While it is idling you will need to remove one spark plug wire at a time USING an insulated pliers to prevent electrical shocks. When you remove the wire if the cylinder is working properly there will be a significant drop in the rpms. If the cylinder is not working properly there will be little or no change in the rpms. Do all eight spark plug wires and compare the drop in rpms. Unfortunately, the next two test you would need some special tools or have to have access to them. The next test would be to check the fuel pressure with a fuel pressure gauge and also test the fuel injectors. Next you would want to use a computer monitor, like a tech I, to check the data from the cars computer. There is one more thing you could do that may help-that would be to clean the throttle body using carburator cleaning spray. With the engine off you would first disconnect the air duct going to the throttle body. Then you would want to spray the cleaner around the butterflies of the throttle body. It would even be beneficial to use an old toothbrush to help clean this area. Try to remove ALL signs of dirt in this area as this significantly affects the idle. Good luck and let me know how it turns out.:chevy: MKOTZE