Mechanics

#1 CYLINDER MISSFIRE

1996 Pontiac Grand Am

Engine Mechanical problem
1996 Pontiac Grand Am 4 cyl Front Wheel Drive Manual 165000 miles

ok ! What I have is a 1996 pontiac grand am 2.4L dual overhead cam, electronic ignition. (IDI) " Intergrated Direct Ignition". System
its running very rough, getting bad gas milage. When I get off the freeway and come to a stop it stumbles and then picks back up. It does it at a stop light also, lacking power.

i hooked up my " OBD2" code reader, and it gave a reading of " P301" #1 cylinder Missfire Detected

#1) Replaced Plugs & Boots and coil housing

#2) I placed a ohm meter between #1 & #4 on the coil tower and it read 5.0 ohms the same between 2 & 3 and no reading between coil and cover Plate

#3) switched coils around to see if it was the coils. Still shows #1 Missfire

#4) I checked my ignition module by connecting a test light (at the module) between bat. Pos. Terminal to the coil(Terminal A) and terminal B or C. When cranking engine light blinks. According to the book tt that should eliminate the module from being bad. But to check for open or shorted circuit in the coil wiring harness. I didnt do that. How do I do that? And where do I do that?


#4) put a ohm meter to no.1 injector, the reading was within specs described in book.

#5) I Disconected the electrical connector to the (IAC) " idle air control valve" started engine and pulled off each injector connector to the injector and there was a noticable difference in idle change


i didnt have a spark tester light so I couldnt test that
from what I described you have any advise or instructions besides " take it to the shop"

thank you
Avatar
Lowrunner
March 22, 2008.



Im thinking your fuel injector is plugged up swap fuel injectors and see what happens

Tiny
Spade007
Mar 23, 2008.
When I pulled each injector wire off the idle droped and started sputtering the same on each cylinder

Tiny
Lowrunner
Mar 23, 2008.
Check coil housing and see if it is cracked if that aint it check fuel pressure and regulator

Tiny
Spade007
Mar 24, 2008.
If the fuel regulator was faulty wouldnt it affect all cylinders?
Coil tower not cracked

Tiny
Lowrunner
Mar 25, 2008.
Fuel regulator might be on its way out might not be supplying enough pressure to that injector. Try also a compression test on that cylinder might have a bad intake valve or a stuck valve it will make the engine run rough

Tiny
Spade007
Mar 26, 2008.
Ok ill do a comp. Check this weekend, if its not low ill also try swaping injector with another one from a different cyl. Ill also check the fuel pressure regulator as you mentioned. Ill get back to you when ive done these tests.

Thank you for your replies, much appreciated

Wally

Tiny
Lowrunner
Mar 26, 2008.
Ok I did a compression test. #1 cyl only read 30 lbs. The rest were at 150 lbs. I also did a wet test(oil squirted in cyl.) On no.1 cyl But made no difference, still read 30 Lbs. In wich if I remember right that indicates the valves. Is that right?
Now the other question I have is: the car has 200,000 mi. What would be advisable: pull the heads and have just the valves for that cyl. Replaced or redo both the heads? What csares me about redoing both heads is on the older v8's I remember from long back is when you redo heads and put them on old lowerend you end up taking out the oil rings! What do you think?

Thanks for your reply
Wally

Tiny
Lowrunner
Mar 30, 2008.