: Stumped (P0307)

03-20-06, 09:15 PM
I have a '97 115K mi 4.0L that keeps setting this code. Checked the wire and spark plug for #7 cyl and everything seems fine. ( both new OE Delco within the last year) Took the plug out and replaced it with new Delco. Connected another new plug above the engine to the wire and grounded it with a jumper cable, started the engine, the spark was strong.
There is a miss that is noticable and sets the code (P0307) under moderate load. The engine ran great before this problem. Pulled the vac line off of the FPR and there were no drips. When I pulled the plug back out after running the misfiring engine, there was no smell of fuel from it.
Teaching my son the value of diagnosing/repairing/maintaining his own car. This problem has me stumped.

03-20-06, 09:38 PM
Is the injector firing (pulsing)? A noid light or a stethescope will tell.

03-20-06, 10:41 PM
Ranger beat me to it, so instead of saying what he said, I will add... The injector may be plugged if it is firing, and if it's not firing, it may not be getting voltage. If it not firing, check for voltage with a small light bulb (194 peanut bulb works well) and alligator connectors. A multimeter may or may not work, because the pulses are so fast. You should see SOMETHING though, but I've always learned to use a light, not a meter to test an injector. The light will be dim though, maybe 1/5 bright.

03-20-06, 10:44 PM
I can tell you from expirience that a 12v test light will not work.

03-21-06, 01:16 AM
No, not a test light. A very low wattage bulb. Test lights NEVER light up brightly. I learned with a 194 lamp on a Camaro to test injector firing.

If you think it will work better, get a mini mag light bulb, one of the cheap aftermarkets that's $2 for a pack of two. They are 3 volt bulbs. It won't last long, but will be bright.

Ranger, take your test light and put it across your battery. See how long it takes to light up. Both of mine take about half a second to light up and are nowhere near the brightness of a 194. It annoyed me greatly when I was testing fuses a while back, one after another. Took twice as long because the light was slow, bought the second because of that and it sucked too.

03-21-06, 08:42 PM
Thanks. You guys seem to have nailed it! Took the car to the dealer for the fuel rail recall and had them troubleshoot the misfire. They found 3 injectors malfunctioning. They wanted $600 to replace them and the spark plugs. They did replace the fuel rail under the recall. I ordered 3 new OEM injectors but will need to find some info on the removal/replacement procedures for them.

03-21-06, 10:43 PM
It's not difficult, may be even easier if you remove the manifold (easy) and work on it on a table.

04-13-06, 08:51 PM
The injector replacement was a breeze with the new SS fuel rail. Replaced: all 8 injectors, the fuel filter, and FPR. The car runs like a dream again. Have never had a problem with injectors on any other car before. The intake manifold bolts were extremely loose. Tightened them to the designed torque.

04-15-06, 10:29 PM
I can't believe they tried to stick you for $600 on those injectors. Injectors are only about $100 each, and they had to remove all of the injectors to do the recall. Places like that give people like me(an honest mechanic) a bad name.

04-20-06, 09:28 PM
Exactly. Don't think i'll be giving them any more of my buisness. Feel sorry for all the underinformed that get raked everyday. Can they make enough to stay in business without "padding" the bill?