04 Comp G Tune Up

**streetsmart** · 04-09-2008

Hey there everyone. I am new to this board and I wanted to ask a question. I have an 04 comp g that has around 44k miles on it. It has been sporadically throwing the check engine light on. When scanned it reveals "random cylinder misfire." On the highway the other day I punched it around 80 mph and then it seemed sluggish and the light came on, but instead of being solid this time it flashed for a good period. Again it revealed "random cylinder misfire." I just figured I would go ahead and tune it up myself. I ordered MSD coil packs with PRJ plug wires and NGK plugs. I also ordered a 180 degree thermostat. After some research I ordered the parts but then I read some people saying that these mods are actually worse than the stock AC Delco parts. Do you feel this is correct? Did I waste my money?! Also, this car is bone stock but I was going to change the T-stat anyway to have it run a little cooler. From what I have seen the check engine wont come on unless I went down to the 160 degree T-stat. Should I replace it or leave it stock? I plan on doing more mods down the road, I am just not in a hurry because I have my 01 Wrangler which is my true "toy" (4.5 skyjacker, 35 12.50 mickey thompson claws, blah blah blah lol.) This is my 3rd grand prix and my last 98 GTP was pretty modded and got me 4 tix in 10 months. Sooooo, I am in no hurry to get back into that mess again!

Also, do you have any suggestions on the tune up? I have heard that I will need to loosen the motor mounts, jack the engine up with wood from the oil pan and roll the motor forward to get to the back plugs? Is there any truth to this?

Any input you can give would be greatly appreciated!

Thanks,

Mike

**SyntheticShield** · 04-09-2008

I personally see no problem with the MSD coils, though you will get a wide variety of opinions on that. I think most put them on there with the expectation of some kind of noticeable performance gain and thats not really where their focus is at. Those are more powerful coil pack 48k Volts vs. Stock 38k I believe. Which will give you much better spark at the plugs and might help with fuel economy as well because of the better spark.

The 180* thermostat is fine. 160 would be too low, but 180 is a much better choice. The only thing I would have done differently is run MSD plug wires. Simply because they are much lower resistance than stock, lower resistance than any other after market wires Ive seen and would let you take full advantage of the coil packs. Ive never used the NGK plugs so I cannot speak to those directly.

With regards to doing the tune up, yes you will need to disconnect the upper motor mounts on the engine side so you can tilt the motor forward, but I have never heard of having to jack up the bottom end to do the work or to tilt if forward. Unless the 04's do something differently with the mounts, I dont see that being necessary.

**streetsmart** · 04-10-2008

thanks for the reply! if i do not get the jack stand from underneath how would i get that motor to roll forward? sorry for the questions, i am just trying to learn on the go!

yeah i actually was hesitant on the plug wires but hopefully they work out. i am not expected any gain, i just hope to get it back to normal because it is NOT running well and only avg. 22 mpg in conservative highway driving. that tells me something is wrong.....

**Sabrewings** · 04-10-2008

Put the car in park and rock the car forward (with the upper mounts removed). When the engine is tilted far enough forward, apply the parking brake. The upper mounts are not supporting the engine. They only keep it from moving forward or back. The weight of the engine/tranny sits on the engine/tranny mounts at the cradle. They allow enough flexibility for you to rock it forward (hence why the upper mounts are needed so it doesn't move while driving).

Never heard of someone tilting it forward by pushing up on the bottom. I've heard of someone attaching a strap with a heavy duty ratchet-type system and pulling it that way. Also, to keep it from moving, I've heard of people using the ratchet-strap tie-downs to hold it forward.

**archemedes** · 04-10-2008

on the 3800 I don't need to tilt it, now the old 3.4 dohc engine (from the lumina's) it had to be tilted. Heck even my friend who weighs 275 pounds can get his arm in to do the rear plugs on my engine (including my buick)

**streetsmart** · 04-24-2008

i appreciate all of the feedback that you have given!

i have swapped the coil packs and pulled and replaced the front 3 plugs and wires. i am having one heck of a time getting to the back 3 (especially the 2 plug.) i have removed the front motor mounts and have a little wiggle room. i am using prj wires; should i throw the stock heat shields on these prj wires? it seems a bit restrictive.....

do you have any suggestions on getting to those plugs in the back? can i actually jack the motor from the oil pan with wood?

also, do you recommend i change anything else in this tune up? i have swapped the air filter and i am putting in a 180 thermostat. any suggestions you can give are greatly appreciated!

have a good one,

mike

**SyntheticShield** · 04-24-2008

Back three plugs are best accessed with the engine tilted forward as much as you can get it. There are tools out there to assist with that, and Ive seen and used a rachet strap to do this to get maximum tilt.

I dont know much about the PRJ wires, but when I installed the MSD wires I used the stock heat shields until I can get a complete set of the fiberglass socks.

I would not jack up the motor or should not need to, particularly by the oil pan. If you are doing a tune up, might as well replace the PCV valve. Id go ahead and check the belts as well and make sure they are good. Thats about all I can think of at the moment.

**streetsmart** · 04-24-2008

thanks man,

is there any threshold of movement before i need to worry about damaging anything? i am sort of learning on the fly here.

i will try the heat shields, they just seemed a bit out of place on the new plugs.

**SyntheticShield** · 04-24-2008

The lower motor and tranny mounts will restrict your movement on the engine. The only thing I could see being an issue would be the down pipe and Ive never personally heard of or seen one damaged by tilting the motor too far and as I mentioned before Ive used a ratcheting strap to pull it forward before.

**streetsmart** · 04-25-2008

yeah, i worked again last night and removed the back engine cover mount and also rolled the motor forward. i worked on pulling the 4 wire off of the plug for 45 minutes and it will not break free. i then tried 6 and i am having the same issue and it doesnt help with the o2 sensor there as well.

anyone have any suggestions for getting the wire off of the plug? i have tried wiggling and pushing it in and out with any movement i can get!

**RooK** · 04-25-2008

Twist! If it sticks, the only thing you can really do is twist them and try to brake them loose. Otherwise, get some pliers on the plug boot and pull (have spare wires ready just in case).

**streetsmart** · 04-29-2008

wd-40 did the trick. i sprayed each wire and plug and let sit for about 45 minutes. i came back it the boots came off the plug with relative ease!

the car is running great again. thanks for the input yall!

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