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1999 Gmc Safari Check engine light


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gpaaske
New User

Nov 26, 2008, 2:40 PM

Post #1 of 9 (4721 views)
1999 Gmc Safari Check engine light Sign In

1999 GMC Safari, 4300 V6, AWD, 140,000 miles. Check engine lite comes on, running rough...smooths out, check engine lite goes out (usually when starting). Starts to run rough, lite comes back on. Used to be off more than on, now on more than off. Been a great van, but not a everyday driver until just recently. Probably drove it once a week for the last seven years. Diagnosed twice as the #5 cylinder misfiring, although both times the mech could not make it come back on after clearing it. About 18 months ago a mech ran a bunch of stuff thru the fuel system in an attempt to clean a injector, and this worked for awhile. Also have recently run 2 bottles of the $25 GMC fuel system treatment, paying strict attn to the instructions. Now the problem seems to be getting worse. I don't want to get talked in to a new fuel rack unless I'm sure. Any comments would be appreciated. Thank you


way2old
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Nov 26, 2008, 3:56 PM

Post #2 of 9 (4710 views)
Re: 1999 Gmc Safari Check engine light Sign In

How long since last complete tune up? Including filters? Just wonderin'.



Being way2old is why I need help from younger minds

(This post was edited by way2old on Nov 26, 2008, 3:57 PM)


Loren Champlain Sr
Veteran / Moderator
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Nov 26, 2008, 5:00 PM

Post #3 of 9 (4704 views)
Re: 1999 Gmc Safari Check engine light Sign In

Are you still coming up with the P0305 code? It is possible that the injector is partially plugged. If so, the cleaner that you put in the tank will very rarely clean it. The spray pattern of the injectors is very important. We use a Snap On Motor Vac to clean the injection system and have had very good results with plugged injectors, assuming they are electrically sound. Also, you should check the resistance of the injector. Wouldn't hurt to check compression, just to be sure it isn't a mechanical problem. Don't forget Way2olds advice...plugs, wires, cap, rotor, ect. Could be a secondary ignition problem, just as easily. I'm also assuming that the engine has been checked for a vacuum leak on that cylinder?
Loren
SW Washington


Jeff Norfolk
Enthusiast
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Nov 26, 2008, 5:01 PM

Post #4 of 9 (4703 views)
Re: 1999 Gmc Safari Check engine light Sign In

Are you losing any coolant?
Jeff


gpaaske
New User

Nov 26, 2008, 5:57 PM

Post #5 of 9 (4697 views)
Re: 1999 Gmc Safari Check engine light Sign In

April '06, 23000 miles ago


gpaaske
New User

Nov 26, 2008, 5:59 PM

Post #6 of 9 (4695 views)
Re: 1999 Gmc Safari Check engine light Sign In

No...no coolant lost


gpaaske
New User

Nov 26, 2008, 6:07 PM

Post #7 of 9 (4692 views)
Re: 1999 Gmc Safari Check engine light Sign In

Thanks for your points.....am taking this girl to a mech next mon, 12/1, will print your reply and show it to him. In the meantime, after looking at old paperwork (and its hard to make out this handwriting) I think it says error code 300. This is from Dec '06 17000 miles ago. Make sense?


Loren Champlain Sr
Veteran / Moderator
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Nov 26, 2008, 6:09 PM

Post #8 of 9 (4690 views)
Re: 1999 Gmc Safari Check engine light Sign In

P0300 is "Random cylinder misfire". Which, could be most anything. What pointed to #5 cylinder?
Loren
SW Washington


Jeff Norfolk
Enthusiast
Jeff Norfolk profile image

Nov 27, 2008, 9:07 AM

Post #9 of 9 (4679 views)
Re: 1999 Gmc Safari Check engine light Sign In

The reason I ask about the coolant leak is that these engines have a history of leaky intake gaskets. You mentioned that one of the code was a #5 misfire. When these intakes leak they will leak on the front or the back. They can leak a bit into the intake port and cause a miss. On this motor the front cylinders are 1 and 2. The back are 5 and 6. So if there is a leaky intake it could be the culprit for a cylinder specific misfire. Good Luck
Jeff


(This post was edited by 10-5-6-6 on Nov 27, 2008, 9:04 PM)






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