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when you disconnected the MAF no cel I’m surprised. I would check fuel pressure. if you have a fuel filter I would change it also make sure your air filter
is clean be sure you have a good 12 volt battery source and connections are tight and clean. good luck and keep us posted.Welcome to the forums!
If you are needing to depress the accelerator pedal to enable the engine start, you are putting the engine into a clear flood mode.
I would first do a visual inspection and take a look at your vacuum hoses. The best method however is to use a smoke machine to check for vacuum leaks. I would make sure that your intake hose past the MAF is not damage.
There is also a product made by CRC that you can use to clean your MAF sensor element. I would do a visual inspection of the MAF to make sure there is no dirt or debris built up on the heated wire elements.
I would also have the CEL scanned to make sure there is no pending codes or that your CEL bulb is not burnt out.
Also that 3.1 engine is also known fo rlower intake manifold leaks causing all sorts of running conditions. Are you noticing any coolant loss?
Other than that, you could check for fuel pressure KOEO.
It would be interesting to see live PID data also while the vehicle is running.
clear flood mode = WOT/foot to the floor. simply cracking the throttle won’t put it there.
To me it sounds like your IAC is questionable. Not starting unless the pedal is depressed = no air getting past the throttle plate, and not staying running unless you keep your foot there makes me think the ECU can’t control the pintle movements in your idle air valve.
To clean your MAF you don’t *need* MAF sensor cleaner. Any non residue electronics cleaner will work. I’ve used rubbing alcohol and I’ve used carb cleaner…many things.
If you can, I would pressure test the cooling system and check for any signs at all of intake gasket leaks. The dirtyonehundred V6 is notorious for OEM gaskets going south.
Does your check engine light illuminate when you first turn the key forward (but don’t start the car)? All cars do a bulb test with the key on engine off. You’ll know if it’s functioning or not.
The Intake gaskets,Dorman sells the kit with everything with new intake bolts and uses upgraded intake gaskets made out of metal.One warning also,make sure you put the push rods in the right spot when reinstalling them or you will bend valves.The push rods are two different lengths,6 short and 6 long.If the fuel pump is bad,don’t buy an airtex and they have high failure rates.Get a Delphi or AC Delco pump instead.The tank does not have to come out on that one I believe,there is an access hole you remove a plate in the trunk area http://www.dormanproducts.com/p-5335-615-205.aspx?year=2001&make=PONTIAC&model=GRAND%2520PRIX%253A%2520SE&engine=V6%2520%252D%25203%252E1L%2520%2528189%2520CID%2529%253A%2520GAS%253A%2520FI%253A%2520N%253A%2520J&parttype=Intake%2520Manifold%2520Gasket%2520Set
Thank you all for the start. I will update a few things that I know already. First, I know the 3100 ALL too well. I had a 96 Monte Carlo and broke it down to the block FOUR times! Believe me, when I say I know the LIM is not here YET!
Also the intake hose after the MAF is in great shape, no cracks or anything like that. I already cleaned the MAF, I used 100% EtOH. I am also familiar with the fuel pump in this car (had access door off to check wiring. The pump could still be a suspect, but seems to be turning on and everything as it is supposed to be.
I know the CEL is working. I also have a scan monitor and that is how I know no codes are there.
I have new battery in there with good, clean connections.
I have not changed out fuel filter or air filter yet. I have not checked fuel pressure yet. I have not checked the IAC yet or for vacuum leaks. So that those are my next variables to eliminate.I’d still recommend doing the cooling system pressure test just to rule out the intake gasket issue.
I would be very cautious using carb cleaner on a MAF heated element. Compare those chemicals to electronics cleaner one day. Each to there own though.
As for your IACV, with it being a 4 wire stepper motor design, it would be handy to have access to a bi-directional scan tool to manually adjust the pintle position.
You could try tapping on the IACV with a screw driver while the vehicle is idling or even use a stethoscope to see if you can hear the pintle moving.You may also want to search online to see if there is any means of testing the IACV with a DVOM at least checking for resistance.
Thanks Dreamer!
One of the first things I did check (because I had such a time with the last 3100 and overheating from head gasket leaks), is the coolant level, which as remained constant for at least 6 months. It may come to pressure testing the system, but right now I don’t think it is involved with the current issue.
My first thought before I “posted” was that the IAC was the issue (I have replaced one before that would not let the car idle down), but I wanted to test it first because, of course, once I put it on it’s mine! Is there a way to clean them? If I remember correctly the pintle has to be set a certain way or something like that. It seems a bit tricky, but maybe I just don’t recall the job.
Anyway, do you think that tapping on the IAC will give me a clue that it is not functioning properly?
Some people will try to clean them with throttle body cleaner, and then use WD40 as lubricant.
However, that is often frowned up on. If you remove the IACV and its all full of carbon, then the choice of cleaning it is up to you.
I have also read that cleaning them can make the issue worse.
Its going to be dependent on what tools are at your disposal to diagnose this issue correctly.
Good luck and keep us posted.
Update – I went through vacuum lines/sources and found nothing leaking. I then tapped on IACV and several other sensors, etc. I checked through plug wires and such, but found nothing wrong (that I could see).
I started the car again and it still was an issue with idling to start off, but then after about a minute or so it started running fine. There has not been any issues with it for the last two days! Starts great, idles great.???? I guess I found something, but don’t know what. I would assume I will see the issue again, but for now, as long as it is not doing it, I can not pinpoint it.
Thanks
I would do a wiggle test of the engine bay wiring as well as tapping on the IACV again for curiosity reasons.
Still, a free fix is always the best fix!
Keep us updated!
My bets are on the IAC based on your description but I wouldn’t rule out an intake vacuum leak on that engine, I know you said you checked the lines but you might want to check the area where the intake meets the cylinder head, here is a video showing my methods of checking for intake vacuum leaks.
http://www.youtube.com/watch?v=9CPqbaSgcok+
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