engine light

[4xwc24]

I have a 98 gran prix se 3.1 My inspection sticker runs out this month but I can't figure why the engine light won't go off.I took it to AZ and they said that it was egr blocked and a misfire in the #4 cylinder . Since then I changed the sparkplugs and got an egr from the junkyard and put it on.But that light still stays on.I'm running out of time can anyone please help anything would be greatly appreciated

[GPFred]

You need to get the code cleared. Take it back to AZ and have them reset the SES light. That should take care of the problem unless the codes get set off again by another problem. Good luck.

[jimmyv-21]

what was the specific code?

there are several things you can do. for starters, what plugs did you put on? have you replaced anything else such as coil packs, wires, etc? it is important to use gm parts on all the ignition system. however, your problem seems to be a common one on this forum. to find out if it is the coil, you can try switching the coil and see if the misfire moves to a different cylinder. as far as the the plugs, you really should use the stock plugs. when you installed them you should check to see they are gapped correctly and that they are installed all the way in and the wires are securely connected. btw, was it the check engine light or the ses light? in my opinion, it is probably the fuel injector. that has been the prob for many with the gp's. to check if this is the prob. you can swap injectors from one cylender to another. the old school way to check for a bad injector is to put a screwdriver to it and listen for a clicking sound. you can also use a noid light and an ohmmeter. if you are able to find the one that is not clicking, pull it, and the motor should quit misfiring. once you have made it this far, a good injector cleaning or replacement is in order. there are many things that can cause a misfire, but the dirty injector is probably the most common and an easy place to start.

[4xwc24]

Originally Posted by GPFred

You need to get the code cleared. Take it back to AZ and have them reset the SES light. That should take care of the problem unless the codes get set off again by another problem. Good luck.

Do I have to take it back to AZ or can I just unhook the battery?

[4xwc24]

Originally Posted by jimmyv-21

what was the specific code?

there are several things you can do. for starters, what plugs did you put on? have you replaced anything else such as coil packs, wires, etc? it is important to use gm parts on all the ignition system. however, your problem seems to be a common one on this forum. to find out if it is the coil, you can try switching the coil and see if the misfire moves to a different cylinder. as far as the the plugs, you really should use the stock plugs. when you installed them you should check to see they are gapped correctly and that they are installed all the way in and the wires are securely connected. btw, was it the check engine light or the ses light? in my opinion, it is probably the fuel injector. that has been the prob for many with the gp's. to check if this is the prob. you can swap injectors from one cylender to another. the old school way to check for a bad injector is to put a screwdriver to it and listen for a clicking sound. you can also use a noid light and an ohmmeter. if you are able to find the one that is not clicking, pull it, and the motor should quit misfiring. once you have made it this far, a good injector cleaning or replacement is in order. there are many things that can cause a misfire, but the dirty injector is probably the most common and an easy place to start.

I changed all 6 sparkplugs haven't replaced anything else.What do you mean about switching the coil? Do you mean switching some wires around at the distributor or what?and to clarify is the injectors located on the intake and will the car run without an injector thanx for all your help

[jimmyv-21]

i didnt read your post very well. first of all, after you changed the plugs and egr, did the misfire go away? if it did then you solved your own problem. the light will not just go way though, and unhooking the battery does not work in the newer gp's. take it back to AZ and they can clear the code.
but if the misfire is still there, then the code will not just go away no matter what parts you change. to answer you other questions:
the grand prix will have 3 coil packs- no distributor. the coil packs each have 2 stubs on which the spark plug wires are connected. locate which plug/ wire goes to which coil pack(in your case you need the one that goes to the #4 cylender) and remove that coil pack, reverse its position and reinstall it. if the car misfires on a different cylinder, then you know it is the coil pack. if it misfires on the same cylinder, then it is not the coil pack. as far as the injector goes, locate the one that is not ticking when the motor is running. this could be bad wiring at the specific injector location, but more likely is that the injector itself is dirty. pull that injector out- you will have to do this with the motor running so you can listen to the injectors and locate the faulty one. the car should stop missing with the injecter pulled.

[4xwc24]

hey Jimmy I've been having trouble with the ignition sometimes it takes many turns of the key to get the car to start.Would that be part of the problem I'm having with the car .

[jimmyv-21]

if you are talking about it making the engine light go away, it may or may not be a part of the problem. my question to u is: is the car still misfiring? if it is not, then you can get the code cleared at auto zone and the light will go off. if the car is still missing, then we can start to troubleshoot that prob. at least with the code cleared, you will be able to get it inspected.

[4xwc24]

no I can still hear a miss in the exhaust.

[jimmyv-21]

all gp's make that sound. if it was missing you would really feel it under hard accelleration or going uphill etc. Just to be sure, take it to Auto Zone and have them clear the code. that will help narrow the playing feild. if the light comes back on, then we know we know we still have a problem.

[4xwc24]

they told me they couldn't reset it. they said when i fixed the problem the light would go out the codes it is throwing out is p0304 and p0401 is there any underlying problem that could cause these two problems.like a bad coil a bad sensor anything like that thanx again for all your help

[wlkjr]

Originally Posted by 4xwc24

they told me they couldn't reset it. they said when i fixed the problem the light would go out the codes it is throwing out is p0304 and p0401 is there any underlying problem that could cause these two problems.like a bad coil a bad sensor anything like that thanx again for all your help

Maybe what they meant was they can reset it but the trouble is still there and throws the code again. Apparently you still have a problem. The P0304 is the misfire cyl 4 and the P0401 is the egr insufficient flow. You can borrow the Actron from AutoZone (put up deposit) and clear the codes yourself as you work on it. They will probably clear themselves when the problem is corrected.

[jimmyv-21]

i would put money on the dirty injecter. i have found that to be the problem for many others with the gp's. if i were you i would try to have them cleaned. if you want to DIY:

http://www.dans-website.com/cleaning_injectors.htm

another option is the dealer which usually costs around 120.00. you can also use a can of sea foam to a full tank of gas- it works wonders. can be found at almost any auto parts store.

here is someone with a similar problem:

http://www.automotiveforums.com/vbul...=injectors+3.1

another good thing to do is check the fuel pressure. On a Vin "M" 3.1 V6, the GM service manual calls for 41 - 47 psi with vacuum connected at the fuel pressure regulator (FPR). you can usually get the parts for checking the pressure at AZ for about 30 bucks.

btw, gp's seem to prefer mid to high octane gas for best performance. good luck.

[BlueGT02]

the GM 3.1L motor is notorious for cloging the EGR passages in the upper intake manifold(plenum). for a good cleaning you would have to remove this from the car, but you can always try a little carb cleaner.. engine off though, carb cleaner and hot exhaust may remove your eyebrows if you know what i mean.

I also had a 94' GP SE w/ the 3.1L and it had this problem, car would run ok, but if brought up to speed (55-60mph) then brought back down, the MIL light would go on and the EGR flow code would be thrown.Got the passages clean and this problem disapeared

[richtazz]

I agree with BlueGT02 that it sounds like either the EGR passage in the intake, or the EGR itself is causing your issues with the p0401 code. You never mentioned if you changed the plug wires when you changed the plugs. I agree with Jimmy that the injector on cylinder 4 may be your p0304 problem, or it could be a bad plug wire on that cylinder.