NEED HELP 2004 Envoy won't start

[S Tucker]

I will give as much information as I can..first of all I am not a mechanic, so I guess that means I really should have taken by Envoy in to have it serviced...but I didn't!

About a 2 weeks ago I replaced the spark plugs..seemed pretty straight forward (I-6 engine). I think I have everything gapped right. Only problem I had was with the very front one, there is a plastic cable tray I had a hard time getting off and then back on. Everything seemed to be fine, but after a few days I noticed the car is idling rough in gear. In Park, seems pretty smooth-sometimes when I put it in gear it is rough, kind of shaking. (turning a/c on\off doesn't seem to affect issue). Also sometimes stopping at stoplight has same symptom-really rough. But this doesn't happen all the time, and when in park always seems to be ok. So we went on a 5.5 hour (each way) trip, again most of the time just fine, occasionally rough idle.

After getting back from the trip, the vehicle wouldn't start, finally turned over and ran fine for about a week. Then a few days ago it wouldn't start at all. This is where I am at now.

It cranks, and cranks, and cranks, like it is going to start, but never does. Check engine does come on but no codes (I have a scanner). Friend said it sounded like the variable timing solenoid, so we replaced it (it was kind of gunky, but the screens looked ok). Still it won't start. So now I am wondering what to do next? Could it be the camshaft sensor? Or is there something else I should check. Thanks for any help.

 

[Mooseman]

What spark plugs did you use? These engines are very picky and like only ACDelco 41-103. And you DO NOT gap them as you will damage the irdium tips.

Also, did you disconnect the battery while changing the plugs? Did you clean the throttle body? You have to clean it if you disconnect the battery and isn't a bad idea either way to clean it. Lots of threads on this here.

 

[S Tucker]

Thanks for the response I basically went back through everything last Friday (4days ago). I did have the correct plugs. I reseated all the spark plugs and cleaned out the fuel body. The battery was disconnected while I did everything. As far as the gap....this is one thing that REALLY FRUSTRATES me. I looked at a few forums, several people say NEVER EVER gap iridium plugs..you might break them, etc. And they should be gapped correctly out of the box anyway, some people say it doesn't even matter if they are gapped correctly because the new plugs are so good. But on the other hand I see on a lot of forums that you should ALWAYS check the gap, ALWAYS follow the manufacturers specs. Even the plug manufacturers website says that the plugs are made for several models so you should always check the gap. It is just frustrating to find polar opposites on something that I should be straight forward. Do you gap the plugs according to mfg specs or not? So I did gap the plugs, out of the package they were off about .014, if I remember correctly.

And now there is even more to the story...After checking the spark plugs again and cleaning the fuel body, the Envoy still wouldn't start. I could smell gas on the plugs after cranking, so I take that means there is fuel getting to them. And then this last Sunday I replaced the camshaft position sensor. And the Envoy started up. I drove it around town some on Sunday, still seems to occasionally idle rough in gear, but it started several times. It also started fine Monday morning and throughout the day, then Monday night, it quit starting again. I have made a cursory examination of cables, connections, just what I could see easily and it all looks ok. Iit still won't start.

I have an appointment with service center in a couple of days. It has been over a week without it starting so I am giving up at this point.

 

[gmcman]

So everything ran fine before you changed the plugs?

I'm going to try to save you some $$$ as the shop will do this anyway.
Since your plugs are all fuel fouled now, you need to replace the plugs again.

If your check engine light is on, there is a code. Not sure why your scanner isn't picking it up.

You may not have had a coil pack wire connected fully or you may have lost a spring under the coil pack and nothing is contacting the plug.

Go get some new 41-103 plugs and DO NOT gap them. If they are a few thousandths out don't sweat it. Every 41-103 plug I have bought was within .005 if not better. There is a way to slightly gap the plugs and it involves moving the side electrode only but you generally don't need to do this, never pry or best not to even touch the delicate iridium tip with a hard object.

Also don't crank down on the plugs, they are only snugged to about 15 foot pounds, or 180 inch pounds.

Coil pack bolts are even more delicate, only gets 89 INCH POUNDS of torque. Check the coil packs to ensure they are still seated and you don't have a snapped bolt.

Check all the coil pack harnesses to ensure they are fully seated.

Did you by chance spray anything on top of the motor? Just asking because liquid can get trapped inside the coil pack connector and not drain out, quickly shorting the coil.

After you get the new plugs, check the coil pack inside the boot to see if the spring and tip are still there.

 

[Chickenhawk]

I hate old school thinking with new technology. Yes, you do NOT need to gap the new plugs. As long as they seem about the same and weren't crushed in shipping, put them in without gapping.

The reason we say this is simple. There is a CORRECT way to gap plugs, and an incorrect way. Most people do the incorrect way, which will work on the old school plugs. On the new iridium plugs, you will wreck them. Thus, because we do not know a person's mechanical skills, we simply say not to gap them.

Anyone who thinks a few thousands of an inch is going to make the slightest bit of difference has not done too many plug changes in their life. I have seen plugs running quite fine - but simply worn badly - and the gaps are WAY off the recommended setting.