1998 Chevy suburban p0307 help!!!

[theroach51]

Ok I have a 1998 Chevy suburban 1500 2w drive with 168000 miles.i started with a p0300 code, replaced cap rotor wires plugs and replaced old popit injectors with new mfi style fuel injectors.now the code is p0307 it's not the cats because I took them of thinking that's what was causing the problem, checked the egr it's fine, did a compression test lowest was 170 highest was 200 #7 being 195.fuel pump was at 60 with key on and 50 when running, I'm running out of ideas, ecm?? After about a week with new plugs I pulled out number 7 and it looks clean like almost new out of box.I'm not experiencing any hydrolocking.so what else could it be?? I'll post some pictures of number 7 spark plug when I get home.

[Doug_Scott]

Compression numbers seem to be too high for an engine with that many miles on it. It also fails the compression test. Lowest number should be no less than 90 % of highest number. 180 is the lowest acceptable number.

 

The comment about not experiencing hydrolocking is very odd to make. Why would you think hydrolocking would be something to look for when looking for misfiring? Actually if you did experience hydrolocking during engine running that would take care of any misfiring issue on that engine pretty much instantly. It would also end the engines ability to run properly due to the broken piston/broken rod/hole in side of block/broken crank or just about any other fatal engine failure occurring due to the sudden stopping of the piston in the cylinder from the hydrolock.

 

Was the compression test done dry or wet? When you pulled #7 plug to check condition, what did #2 or #8 plug look like when compared to #7 plug? No point in only checking one plug condition to locate a misfire. I would expect a freshly changed plug to look like new for a few hundred miles at least, and all plugs should be similar to each other. With a dual plane intake manifold, you should at minimum check a plug from each plane of manifold. Otherwise you are actually only checking one half of the fuel delivery system.

[lee123]

Just just got mine finished today. Did u clean injector holes? One of the more experienced in this forum told me #7 [which is the injector I was having trouble with is most likely 2 give u trouble because its last. You r not getting fuel to#7. Pull power plug, Check power with noid light I used a test light, make sure when cranking it lights up. Most likely defective new unit. I had to go back in and replace the new one. Sorry, keep us posted.