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escobar, April 29, 2015 in <i>Powertrain Tech</i>
worth a try !!
Would not be the first time a plug was bad right out of the box
True, I went ahead and swapped #3 and #4 cylinder plugs around. While I had them out, I noticed that the cylinder 2 and 3 plugs were bone white on the ceramic end, where the #4 misfire was like brownish. I also did a leakdown test and it was fine, so I know its not the valves. Could the EGR valve be bad and cause it? Its making a odd exhaust sound under the car, like a puffing sound. I dont know if thats from the misfire or what. I'll take a video of that tomorrow.
have you been for a ride after changing the plugs?
yea I drove it up and down the street and the CEL never came back on but it was still idling a little rough. I'll have a full day tomorrow driving it and I'll see what cylinder the code comes in on. thanks GBL!
Get A Plug Just in case, Let me know
will do. I'll let you know what I find.
so after swapping plugs around it came back in on cylinder 4, so I know the plug is good. Im gonna make a compression test gauge until my buddy returns mine and check that. After that I guess it could be a injector or something electrical where its not sparking good enough I guess. It was idling rough on first start but after it warmed up it was smooth again. very strange.
Ok take a long shank screw driver and put it on the injectors, put your ear to the top
You should here the injector clicking test all 4 of them for clicking. They should all sound the same.
If they all are clicking add a bottle of Sea Foam fuel system cleaner and run that through the system
let me know if it helps.
ok I will try that. I was able to confirm it is cylinder 4 by removing the coil wire and no effect on engine idle. I checked for resistance across all injectors and they all read 20.5. Had to work late tonight so I couldnt do the compression test but with all new rings I doubt thats it...
Just to cover all the bases a compression test should be done
Could be an intake leak
You said it has good power under load? Did you swap the coils?
I will have my comp. tester back this weekend and will check that. I have swapped coils, plugs and injectors and it still comes in on #4. I did a leakdown test and the valves checked out ok. Im gonna buy this http://www.northerntool.com/shop/tools/product_200391521_200391521?cm_mmc=Google-pla&utm_source=Google_PLA&utm_medium=Automotive%20%3E%20Fuel%20Line%20Tools&utm_campaign=Performance%20Tool&utm_content=205107&ci_src=17588969&ci_sku=205107&gclid=CjwKEAjw5pKtBRCqpfPK5qXatWYSJABi5kTxInFXqRgFzkZeDd1PGBaWzPU-zxTZZfUgW8YYaUmXUBoCUcXw_wcB
and check the injector. if compression is good, what else is there to check??
Is the skip all the time or at low speed only?
Did you listen to the injectors with the screw driver?
did you move the injector from cyl 3 to cyl 4?
do the compression test.
spray some carb cleaner or Mass air flow cleaner at the intake
manifold see if the engine sound channges
the noid light will tell you if the injector is firing
but won't tell you if it is clogged
skip is pretty much only at low speed. it bogs down every now and then when im accelerating. I did listen with a screw driver, they are all clicking. Resistance is the same across all injectors. I did swap the injectors and coil packs and plugs, still came in on cylinder 4. Used the NOID light and the coil pack and injector is firing properly. I get my compression tester back tonight, I'll let you know what the results are on that. I took the air box cover off and let it pull air with no filter and it started to stall. I'll shoot some MAF sensor cleaner on it.
On a side note, my AC acts funny. When the engine misfires and the cel blinks, my AC will stop blowing cool air. It will take about 30 seconds before it gets cold again. It doesnt happen much. about 2-3 times a day but its odd.
ok so I just did the compression test, 210 in #1, 210 in #2, 210 in #3 and 180 in #4. That is exactly right at the 15% margin so I guess that is what is causing the misfire. 180 doesnt seem bad, that is what I had in all the other cylinders to start with, but with the new rings it went up. I did a wet test and the psi went up to like 240 so I know its the rings. What options do I have beside pull the engine again?!
How many miles on the engine, the low compression would effect the cyl power and make the idle a little lumpy but should not cause a skip
is the AC always affected when it skips Are the heater controls run by vacuum ? check for a vacuum leak
it has 180,000 miles. i'll check the vacuum lines again. I replaced all the rings, I wonder why that cylinder is lower than the rest? Initially #2 had the low compression. maybe defective rings? Alot of work to pull the head and and oil pan back off. damn
Sorry how many miles since your rebuild? did you check the cyl bores for taper and wear, how were the ring grooves in the pistons, if the cyl bore is out of round it can take a while to break in
you could have a leak in a vacuum servo or some where else.
its been about 1000 miles since the rebuild. I did not check the cylinder walls, everything looked fine and I didnt have any of those tools. I knew I had a bad valve and plug threads so I just fixed that and put it back together, The ring grooves looked just fine, no difference between any of them. This is hard to believe, is there any tricks or anything to lower the compression in the other 3 so the misfire goes away?! I really dont want to have to pull the head and pan off to mess with the piston again.
The 15% difference is not the skip We are missing somthing.
Can you bump the Idle to 1500 then Disconnect the coil aand see what happens?
ok ill try that. you really dont think that 15% difference is causing it? I dont know what else it could be.
If you clear the code and you are on the highway under load when will it send a code?
if every thing else is good and the compression is 15% low it should not set a misfire code.
typically I will clear the code and drive and it will only come back in when its idling.
Good info, with the code cleared it will not set the code when you are putting the power
to it and the power is good?
if that is true then the compression is not the issue
thats true, after today I think its a electrical issue of some sort. I was driving to work today and the CEL starts flashing for about 30 seconds, my AC stops blowing cool air and my power drops. Then it stops flashing and AC blows cool and my power comes back. Im baffled. I know a good mechanic who used to work at ford and has the $2000 scanner, he said he will take a look middle of next week hopefully. He said it could be the fuel rail clogged, because the #4 injector is last in line. I think i'll take the rail off this weekend and blow it out and clean it real good to eliminate that as well. I'll keep you all in the loop as the saga goes on!
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