Please help! My truck has been running awful it starts up at 1400 RPMs then after 8 seconds drops to 400-800 and sometimes will die,then settles around 1100. Starts back up with P0357 and P0353 code every time it does this, some mornings starts fine. Has thrown 5 P035x codes at once but these two always come up. Ive replaced spark plugs again, tested new coil packs, inspected wire harness to coil packs up to connection before PCM, and put dielectric grease on and in boots. Still got the miss for last 3-6 months HELP PLEASE! 2000 5.4

 

What plugs did you use? You cant really test the coil on plugs.. (You dont have "coil packs") Where did you buy them? Was it doing this before you changed all this stuff. If so you might have an internal engine problem.

 

I'm asking this because I don't know........... Can you use a cheap Calibrated spark gap tester to test coil over plug ignition?

tool such as this: http://www.amazon.com/gp/product/B00...pf_rd_i=507846

or http://www.amazon.com/gp/product/B00...pf_rd_i=507846

Would this be able to test the strength of the coil?

Thanks
Pax

 

Have you checked the PCV valve? I cracked the vacum line to mine & it was ideling all erratic! Also clean your IAC sensor.

 

The only way to test them is to run the stress test a the dealer. Lot of time they test good on thost things but under a load its a different story. Answer my questions if you want help. What plugs? What coils? whas it doing all this before you replaced them?

 

Running Motorcraft spark plugs, and the COPs I got from Autozone. It all started with a single P0304 code last christmas, then 4 more P0300 codes in the next few months so I replaced the all. Ran fine for a few weeks another code, fix it, a few weeks later another, then after all were replaced I started getting these P035x codes. They come and go. For instance it really got bad when it was around 12 degrees idled good on startup then died. Started back up ran fine. Next morning same thing. Then it ran fine for 3 days, very subtle miss. Rained today didnt noticed anychange in the way it ran just small misfire. but tomorrow morning will probably run bad again. Ive checked for vaccum leaks behind PCV, looked at wire harness, everything looks good. Cant figure this thing out!

 

Check for air leaks??

 

Have you replaced your fuel filter lately?

 

might be able to lend a little assistance, with the P0357 & P0353 codes, are they the only ones that are continuously returning? If so, read post #7 that Jbrew posted here : https://www.f150online.com/forums/v8...y-circuit.html

 

I changed the fuel filter Dec. 09 when the original problem started. I looked for leaks couldnt find anything. And I saw jbrews post when I searched this problem, my harness was right against the accumulator so I tied it back, and I have changed number 7 and 3 with known good COPs and still throwscodes for these 2. About 6 months ago, before I replaced all COPs, I noticed water getting in so I sealed it up at the firewall.

 

Swap the injectors with known good ones see if the miss moves if it dont then compression test those cylinders

 

Ill try the injectors this weekend, also gonna clean the IAC. Have you ever heard of any wire harness problems causing this?

 

My brothers honda had that particular wiring problem and also coming from a parts guy just because you bought them new doesn't make them not be defects and I've been there 4 yrs

 

sure. The odd thing is you have 2 on opposite sides of the engine. No real common wiring..

 

Yeah I was wondering about the harness, justseems strange for so many to mess up at once.3 and 7 mostly, but will usually have another one with them just not always the same one. Ive heard that the Auto Zone COPs arent that great and noticed that the biggest problems I have are in the morning when its cold outside. Just wondering if it has anything to do with crap electrical COPS shouldve went with Global buy needed them ASAP.