Topic: Idling very rough and has no power

[cmb516]

I changed the injectors since I was going to switch to ford injectors anyway but it is still running the crappy.  The injector that came out of the cylinder with the white plug did have crap on it so I thought that would be the problem but that is not it.  Could you walk me through how to check the pressure at the rail?  Thanks

[cmb516]

Also since my exhaust manifold is cracked could I have a bad O2 sensor causing this and would a code be thrown if I had a bad sensor because I have no codes after replacing plugs and injectors

[sharpxmen]

I changed the injectors since I was going to switch to ford injectors anyway but it is still running the crappy.  The injector that came out of the cylinder with the white plug did have crap on it so I thought that would be the problem but that is not it.  Could you walk me through how to check the pressure at the rail?  Thanks

can't remember if you mention it or not - do you have a schraeder valve on the fuel rail? if you don't know what that is - it is a fitting that sticks upwards in the middle of your fuel rail between cyl 2 and 3, usually has a plastic cap screwed on it - to get an idea where it is look at my thread about installing an adjustable fuel pressure regulator in the Member's Projects section - i hooked up the adjustable FPR to the schraeder valve (but that was on a YJ, some TJs have that as well). Let me know if you have it and i'll tell you what you need to put together a fuel pressure check gauge.

Also since my exhaust manifold is cracked could I have a bad O2 sensor causing this and would a code be thrown if I had a bad sensor because I have no codes after replacing plugs and injectors

unless you have a big chunk missing i don't think the crack can cause such a problem especially that is isolated to 2 of the cylinders. I would still do a compression test if the fuel pressure checks out. Since you changed the injectors i assume that they were not the issue in this case (of course assuming that is not a case of a bad set that you put on or that 1 or 2 of the 4 you just installed are bad).What injectors did you use? that is also important (post a P/N).

[cmb516]

I do not have that valve on the fuel rail in the middle, the injectors I put in were ford 19 lb injectors design III that I bought off a guy on jeep forum.

[sharpxmen]

I do not have that valve on the fuel rail in the middle, the injectors I put in were ford 19 lb injectors design III that I bought off a guy on jeep forum.

those injectors will not work on your Jeep, replace them immediately with appropriate sized injectors - they are flowing roughly 17% less than what the stock ones are - this has been covered many times here, please read the FAQ about injectors on this site.

So that being said, changing the injectors with the 19# ones didn't provide any answers

[cmb516]

So i took the ford injectors out and put the oems back in.  Anyway when I took the ford ones out the one that came out of the cylinder closest to the firewall had gunk all over it and it had only been run for about a min to see if it would run any better why would it fill up with crap that quickly?  When I took the factory ones out the first time that one had crap on it too so I am wondering why that is happening to that one only?

[sharpxmen]

So i took the ford injectors out and put the oems back in.  Anyway when I took the ford ones out the one that came out of the cylinder closest to the firewall had gunk all over it and it had only been run for about a min to see if it would run any better why would it fill up with crap that quickly?  When I took the factory ones out the first time that one had crap on it too so I am wondering why that is happening to that one only?

can be a bad intake valve. Take the compression, it's fairly easy - buy a compression tester or rent one (they are about $15 for a cheapo, you don't need a brand name). you need to take out all your spark plugs and screw in the comp tester in the cyl one at a time. crank the motor about 7 times on each cyl and write down the results. do it cold and then warm up the engine and do it again. If one of the cyl is low compared to the others squirt some oil in it (couple of oz is enough) and take the comp again - if it gets to the same level as the other ones then the rings are the problem, if it's the same then there's a valve or valves that don't seal.