Question : Service Engine Light???!!!!

[PerfectCreature]

Okay, so this is the story of events that led up to the "Service Engine Soon"
I blew my headgasket. Decided to get new heads.
This is a 2003 Pontiac Grand Am. 3400 SFI.
It got the following parts installed.

Wot-Tech
3400 Cylinder Heads (2003-2005)
Stage 1 Porting
Spring Pockets: Stock
Milling: Yes-Regular
Valve Job: Yes

LS Blue Springs
LS1 Valve Spring Seats .553'' OD Guide
Valve Stem Seals for LS1 Seats .553'' OD Guide

Pace Setter 88-1474 Exhaust
Fel-Pro Fel-Pro ES74017 Head Bolts
FEL-PRO HST9071PT1 Head Gasket Set
ACDelco 213-802 Oxygen Sensor
ACDelco AFS113 Oxygen Sensor
Bosch 09362 Spark Plug Wires
ACDelco 41-101 Iridium Spark Plugs (6)
ACDelco GF578 Fuel Filter
ACDelco CV892C PCV Valve

He had to make me a new Heater Core to (Something-He never told me) hose and told me I need to replace both of them before winter.

They installed all of that, everything was fine until startup. It had a loppy idle, very jumpy. They poked around, found that they had cracked my upper intake manifold. They replaced the gasket with some cheap Carquest brand cloth/paper looking gasket that no where near looked like a quality gasket. I do not think they replaced the throttle body gasket either to be honest....as the one from Fel-Pro is still stuck to my old manifold.
When they put on the stock manifold, the check engine light popped on, but went away after about 30 seconds.
They had it hooked up to a Snap-On scantool---not sure if it can erase codes automatically?
Anyway, no codes up to this point anymore.
I went back home, got my old stock one. They put that on.
I drove it around awhile, put about 100 miles on it, went to SEARS to get an inspection sticker, asked them to top off the coolant as the mechanic told me it may need some and I should check.
We checked it, and it was dirty. Nasty brown, and very gross. I am speculating that they never cleaned out my intake manifolds like they should have. I had them do a coolant exchange where they hook it up to a machine that just pumps water/coolant through the system. They pumped water through the system until it was crystal clear, then replaced with dexcool.
I drove it about 24 miles, no service engine light. I went to a few peoples houses, hung out, left the car idling, not a smidgen above 200 did the temp gauge move.
I get it back home, park it for about 10 minutes. I go out to start the car, because it needs to be washed for a parade I am showing it in. I go down, in reverse, my mere 200 foot drive way, and I stopped to wait for passing cars. Then I saw it, the Service Engine Soon light. Really upset me to no end that I am still having issues.
I do not have a scan tool, and will be unable to get it hooked up to one until tomorrow, but I was wondering if anyone had any idea to what it is, and if I can run it with that light one.

I checked the RPMs, they stay steady at about 650. It does not overheat, as far as I could tell. The coolant is orange as it should be for dexcool. I did notice some waterbeads on top of the coolant cap, but I assume that is condensation from when it had cooled down a little bit?
Is the PCM not used to all the engines new parts or?
I find it odd, as I drove it home after the coolant exchange and it was fine. I cannot remember if it blinked, or if it just showed up solid like it is staying.
Really frustrated, and looking for ideas-almost just about had it with the car.

[PerfectCreature]

Just another thing, not sure if this makes a difference, but the lights in my dash, and all lights outside dim at idle. Music off, everything off but stock stuff.
Could a bad alternator or battery cause the check engine light?

[PerfectCreature]

Now I am even more stumped.
I drove it down the road, shut my headlights off, and then the light goes away. Turn them back on, it is still off.
The dimming of my lights does not seem to be as pronounced as it used to me.
Any ideas?
Can the code reader read the codes that came on and disappeared?

[3400-95-Modified]

The code does not go away, it will be stored just not active if you do not reset/clear the ECU.. Go to an autoparts store and get that code read... without that you are just shooting from the hip and can only throw parts at it.

[pocket-rocket]

I would like to add that they will only read the code and not erase them. Also you are a glutton for punishment if you are continuing to use Dexcool. That stuff likes to eat gaskets in bi-metallic engines.

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[PerfectCreature]

I was told I had to use Dexcool. I was unaware I could use something else. I know SEARS uses some chameleon stuff, but I was told once before that it was not compatible with my engine.
As for reading the code? Everywhere I went said they cannot read a code once the light is gone.
So, I guess I will have to wait for it come back, or whatever it was trying to warn me about occurs.
Unless I can just buy my own and do it myself?

[pocket-rocket]

You can buy them. Since the code has not been erased it is still in memory and can be pulled. Saying it can't be pulled since the light isn't on sounds like something someone from AutoZone would say.

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[PerfectCreature]

Yeah, that is what I was told. The only place that said they could get it was a dealership, and they wanted $80 to do the scan and print off the code, and look it up and tell me what needed replacing.
So I decided I would pass on them looking at it,

[pocket-rocket]

If you do any diagnostic work of your own I would highly recommend buying an OBD2 scanner. They're an awesome tool to have. You don't have to go expensive or fancy either. Sure, some do more than others depending on price but you get what you pay for. Mine's not fancy at all. I would like one of the more modern ones with an LCD screen that reads what the fault is as well as the code number, but mine works just fine right now even though it's one of those dinosaur units with the 7 segment LED displays and I have to open the book to look up the fault using the code number. One nicer than mine that would suit you just fine could probably be had for that dealership diagnostic fee. It just sucks I spent $150 on it years ago, but at the time it was what was out and it has served me well and done what ive needed it to faithfully over the years.

[PerfectCreature]

Would the Innova 3150 do the job? It has ABS and SRS which I think was mentioned is something needed for the Grand Ams?
I found it online for about $150.

[TGP37]

I know some autoshops will let you use the obd2 scanner for a few minutes to pull the codes. Advance Auto parts, most of them will let you use the scanner device in the parking lot. A little friendly conversation goes a long way.....or get something cheap like an oil change and ask to use the scanner.

It is normal for the lights to dim a little at 650 RPMs. Just the voltage dropping to 12-12.4 volt region. The alternator will produce 13.5-14.5 volts above 800-900 RPM and hits max output potential amps at 1200+ rpms.

[PerfectCreature]

Well, I was able to catch the light while I was near SEARS. They hooked it up, and found code P0300-random misfires in random cylinders. They turned it off, looked it up, and when they started it back up to clear it, they found another code which was, I think P0131-It was Oxygen Sensor Bank 1 Position 1 Running Lean; which was in addition to the P0300 code.
They suspect a few things, but told me to try some octane boost/stabel and that my gas could potentially be bad, which how it sat for 3 weeks without any runnning and there could have been water in it. The fuel filter was replaced also...so I am trying that with hopes it will work, though I don't think it will.
Next thing was a vacuum leak somewhere, which should not be the case, as my idle is fine and runs as well as it should, so far as I can tell. The tach does not jump or sweep or anything unnatural while idling or running.
Next after that they suggested, was my coil packs. Which look to be origional, and I guess are recommended to be replaced every 75,000 miles?

Talked to the shop about the cracked manifold, they won't eat the cost, because they did not do the work, and they do not know how well it was ported and all of that. They are blaming it on a stress fracture because it was placed on once before, heated and cooled many times, taken off, and he says it probably cracked because it had a tiny one from the above scenario. The best he says he can do is-wait for someone to bring in a manifold and attempt to port it like Ben's shop does, or install the new one for free.
I opted for the free install. Kind of lame that he would not come good for it since he cracked it.
Anyway, what are your thoughts on the above codes, and what I have done so far?
I am thinking of having it vacuum checked if the light comes back on, and then, replacing the coil packs if the vacuum checks out like it is supposed too.
Since the car runs fine, should it be safe to drive?

[PerfectCreature]

Eh, light came back on...kind of figured it would happen.
I checked around the engine, and not that it is any coincidence since they cracked my manifold, but I found that the serpentine belt gaurd was broken, epoxied in place. It was kind of hanging, attached to one of the tubes coming off the reservoir tank. I have a zip tie on it for now to keep it from moving.....
I am a little bit more then upset at this point.
Lousy service. Anyway, I will take it to a shop to see if there is a vacuum leak, if not-which I doubt.
I only need 3 coil packs right? How hard are they to change?
Could it also be my cat? I am pretty sure they checked it....maybe they didn't, though....given their history

[pocket-rocket]

The only change interval for coil packs is when they go bad. There is no mileage rating like plugs, coolant, oil, ect.

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[TGP37]

Since the misfires are random, not cylinder specific, I doubt it is the coils.

A cracked manifold will be an issue. Even a hairline crack can leak vacuum and allow unmetered air in, making it run lean. That is a strong possibility to be the cause of the P0131.

Then the lean misfires at idle will set the P0300 code.