Need Some Help Diagnosing Misfire? After Car Is Hot

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jbelcourt

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You can feel it when stopped, like a "putt putt" feeling real quick and then it'll go away or it'll just happen really intermittent. Once she's good and hot, if I shut it off and start it back up a few minutes later, it runs like absolute crap for a a good 20 seconds and then it's normal but still does the intermittent putt that I assume is a misfire. Once in a blue moon, it'll stall or really try to on that initial hot start up but giving it gas pushes through it and it's fine. Non of this happens 100% of the time though. I can drive to work then a couple hours later run to lunch and it's fine. It's usually after a lot of drive, park, drive, park etc and when she's nice and hot.

I ran a Cylinder Balance Test three times and all three times I got a 90 (passed) code.

Earlier in the day today, I tried pulling one wire off the coil pack at a time when the car was just a little warm and it got pretty damn rough regardless of which plug I pulled. After doing all three balance tests (engine going under high load on and off for several minutes multiple times) and the car was nice and hot, it was doing it's putt putt feeling so I started pulling plug wires one at a time once again. This time, there was hardly any noticeable difference in the motor function regardless of which plug wire I pulled.

I'm kind of to the point that I think it's two old coil packs on their way out. My car is at 206,5xx miles and they're the original packs.

I ohm tested them this morning while car was warm and pulled primary of 1.6, 1.7 (passenger) and 1.6, 1.6 (driver) along with secondary of 14.9 and 14.6 (passenger) and 15.1 and 15.4 (driver). I'm not knowledgeable with multi-meters, so, if I'm suppose to touch my two test leads together first and get a resistance reading (.9) and subtract that from my results on the primary readings (1.6), then I'd fall within the specified range of .3-.9 (.7). If not, and I understood that wrong then it's actually 1.6 and it's showing it's exceeding specs during heat soak and it's probably the cause.

I'll attach a video from last night when it was really acting up and then today as I'm doing the wire pull test.

Any insight would be greatly appreciated. I'm tired of chasing this issue.


FYI, I tested fuel pressure while idle and revving a few weeks back and it was good. Spark plugs were changed last weekend (it was happening with the newer 764's I put in and it's still happening with the 103's I just put in). Plug wires are new Motorcraft. Oil was changed less then 1,000 miles ago. Fuel filter and air filter changed within last 2,000 miles. MAF cleaned as well. IAC replaced last year along with TPS a few months back. Compression test was done a few months ago and all fell between 140-153 dry. Motor mounts were just changed less then 1,000 miles ago. I've changed so many things, including canister purge valve and cleaned the throttle body, etc etc etc and my fuel mileage never really gets over 15.3 on average as well.


Issue
[video]https://youtu.be/Sc1mfZrxl8w[/video]

Testing
[video]https://youtu.be/WT2cspUsMJY[/video]
 
Hmmm, I have been checking for leaks and haven't found any. I'd think a vacuum leak that bad would be pretty audible. Obviously I could be wrong though. I need to figure out how to do a good vacuum leak test.

On that note though, I was able to pull some coil packs off (F5LU-12029-AA) and I swapped those in. I think both of my packs were weak because when I swapped these in, there was an obvious miss and before it was more of a weaker feeling with intermittent miss. With these coils in, I was able to trace it to cylinders #4 and #8 only. I could pull the plug wire off the coil and it made no difference at all in performance while the others made the car run terrible. I flip-flopped the wire on the coil pack top to bottom (since they're technically interchangeable) and the miss followed so I knew it wasn't that coil pack I put on. Had a spare set of wires so I tried different wires and still the same.

Pulled the spark plug for #8 and the tips were fouled pretty obviously. Switched the plug and tried again and now only #4 was missing. Checked #4 plug and switched, all was good. I switched to Autolite 103's a few weekends ago and apparently it was too cold for the tune I have. I posted a picture of them, with less then 100 miles put on it, and one of the guys confirmed that is what it looks like if the plug is too cold. I put the 764's back in all around, with the coil packs I switched in, and it seems to be running perfectly fine.

I didn't drive at all today, so, after it's hot that could be a different story. I'm thinking I had more then one underlying problem rear up at once though. Weak pack(s) and plugs too cold. Maybe there is a vacuum leak but I definitely don't hear it.
 
So, car has been running better since the coil pack and plug switch. I haven't had to drive it after its hot until this morning though.

Got to work, did some computer stuff for about 15 minutes then jumped back in the car to run to the bank. Started right up, like usual, and started stumbling. Put it in reverse, all was well. Drove fine.

Still have that underlying issue apparently.

To the guys that said vacuum leak....

Back end of last year, some of you might remember when I was cleaning my egr port and dropped that terminal brush into my intake. We fished it out with a magnet and string but not before I had broken every single bolt loose and was ready to take the intake off. I never tried to break the gasket, or move the intake what so ever. I was on the last bolt when he fished it out.

My question is, do you guys think it could be a leak at my intake from me breaking all the bolts loose?

I'm not sure what else to think it might be at this point. My brother thinks it's the crank position sensor but then we remembered about the intake, so..
 
I suppose it's possible. The gaskets have silicone seals with torque limiting washers.
 
driller said:
I suppose it's possible. The gaskets have silicone seals with torque limiting washers.
Click to expand...

I'm going to try smoking the vac system this weekend and see if I can find any leaks. I don't know what else to try at this point.

I thought it was fuel related but my fuel pressure ratings are fine and I even checked it while it was acting up. Someone else who saw the video who builds motors said it looked and sounded like a leaking injector but I did three cylinder balance tests and not once did a cylinder fail.

I just can't figure this problem out...
 
IMRC plate can suck vacuum.... especially at 200k
Its were I would look.
 
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