Misfire on #1 and #6. Need Help!
07-10-2009, 10:09 AM
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Misfire on #1 and #6. Need Help! I posted this in the diagnostics setion as well. I recently did a head/cam/intake swap on my car and cannot seem to figure out the cylinder misfire on #1 and #6 cylinders. The car runs fine at rpm above 2500-3000. It made 430 at the rear wheels on the dyno so I am assuming that everything is ok at higher rpms. It does not feel like it is missing at higher rpms either. If you accelerate it from idle it stumbles/misses and feels sluggish until about 2500 then it clears out and hauls. I have done a compression test on all cylinders and they all have good compression (all around 130-140 psi). The O2 sensors are new, the plugs and wires are new, and IAC, MAF, and TPS are new. The only codes I am getting are for the TPS and MAF. The TPS is only showing to be getting .5-.7 volts on my scanner. Is this right? Would this cause a misfire? I have also checked all engine sensor fuses as well. I have checked the injector harness with a noid light to make sure they are getting signal and they are. I am not sure what direction to go next since it does not have dead miss, only at low rpm. All help is greatly appreciated. Thanks!
07-10-2009, 12:14 PM
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Im assuming you have an LS1 and if i recall correctly they have coil packs on each cylinder. In my POS ford daily driver i had the same problem starting with #4. It was a pain in the *** to chase it down because the misfire was never consistently missing or regular in any way. I eventually forked out the 200 and changed them all out. Problem went away totally. Perhaps this may be something similar to your case...*shrug*
07-10-2009, 12:51 PM
#4
Im assuming you have an LS1 and if i recall correctly they have coil packs on each cylinder. In my POS ford daily driver i had the same problem starting with #4. It was a pain in the *** to chase it down because the misfire was never consistently missing or regular in any way. I eventually forked out the 200 and changed them all out. Problem went away totally. Perhaps this may be something similar to your case...*shrug*
Good luck.
07-10-2009, 01:12 PM
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If your problem is consistent then that is a good idea. My packs were $40 a piece and a 6 cyl eng. i think the ls1's are like 80+ right? My way isnt really an economical fix =/
07-10-2009, 02:59 PM
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i pulled the plugs and they were fouled, so i replaced them and the damn thing still misses on 1 and 6. took off the valve covers to check for broken spring, rocker arm, pushrod, etc. and it all checked out good too. i switched the injectors to see if the problem moved to another cylinder and it didnt. also replaced the map sensor since my rubber grommet was cut. no help there either. i will check the coils and also check for vacuum leaks where the intake bolts to the heads. thanks for the help guys. any more suggestions are appreciated!
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07-10-2009, 03:20 PM
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You can switch the coil packs around and test them. Swap #1 & #6 with two you know to be working. See if the problem "moves" with the coil. If it doesn't, try changing out the plugs on 1, 6 again. Might have a small hairline crack. Also, try switching the plug wires around, too. Might be a bad set of wires. Oh, double check that all your grounds are tight. The ones on the back of the drivers side cylinder head are important for the injector and coil grounds.
Good luck.
Good luck.
yeah that is your best bet switch #1 and 6 with another cylinder n see if the misfire switches, n pull the plugs out n see if they are cracked... cause my friend had a misfire and it was because his plugs were either bad or cracked, so small of a crack that you could barely see it... if you have headers then chances are you might of put the plug in there in a slight angle and cracked it... hope this helps...
07-11-2009, 11:26 AM
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will do. i pulled the intake and did not see a gasket issue, so i did a smoke test to look for vacuum leaks. it seems that smoke is coming out around every injector where it mounts to the intake. my next step is to put some new injector o-rings on to try and seal it up. hopefully this works 
08-04-2009, 07:24 PM
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Had a similiar problem, car was running great, but was throwing a misfire code for cylinder #7, switched coil packs, problem still occured, changed plug on the cylinder, still a problem. I'd do a compression test and leak down and you may find your problem like i did. My problem: rings got into the ring land on that piston. Pulled the piston out of the cylinder and pieces of rings just hit the floor. Hope this is helpful to you.
08-04-2009, 10:06 PM
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If you have a code for a throttle position sensor, then of course its going to run like **** and misfire. The PCM doesn't know how much timing to give the car or fuel. And maybe check your valve springs.
