Ford 3.8, Misfire, Recurring P0340

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PhillipP
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Ford 3.8, Misfire, Recurring P0340

Post by PhillipP » Fri Sep 29, 2017 8:24 am

I've been chasing a misfire issue. My other posts reference it. And it's the kind of misfire I cannot ignore if I continue tuning the maf. This is a variable reluctance sensor.

Symptoms include:
- misfire at about 2500 rpm in neutral
- misfire at about 2500 rpm while driving
- no misfire above or below a narrow rpm band at about 2500 rpm
- lean spikes registered on wideband
- severe bucking if driving
- decent shudder during neutral
- recurring DTC P0340

Corrective actions include:
- bench testing alternator and battery at parts store
- disconnecting alternator and drive testing
- checked resistance across primaries on ignition coil pack
- re-tested with 3 different ignition coil packs
- changed plugs, cleaned plugs, gapped plugs, changed plugs, now ngk TR6IX at .028"
- verified spark plug wires are going to the correct cylinders
- cleaned maf sensor with maf cleaner
- cleaned grounds at forward end of engine bay and the one adjacent to pcm
- removed pcm and visually inspected chip sets for obvious defects
- calibration changes to enrich AFR and add spark, up to commanding AFR=13
- testing with original cam sensor, BWD sensor, and new motorcraft sensor
- executed pinpoint test per Ford service manual to step 12, and failed

Problem show case:
video https://drive.google.com/open?id=0Bxg1w ... UlqbDVlVWc
log, Binary Editor, see 141 to 150 seconds https://drive.google.com/open?id=0Bxg1w ... mRiRFd4Vjg
Note that commanded inj_pw, spark advance, maf counts, lambda, tps are all very smooth right until misfire occurs

Pin Point Test procedure: https://drive.google.com/open?id=0Bxg1w ... 0lPOGRYaFk

The next things I can think to do are:
- check the noise suppression capacitor on ignition power is properly grounded
- hook up borrowed oscilloscope and watch the trace on cam sensor output, attempt to observe electromagnetic interference or other anomaly
- start extracting the leads for the cam sensor from the main harness, diy shield with tinfoil and a ground strap

Last resort is to swap in my 2003 pcm, bcm, and key with tumbler. Those are salvaged from my previous car. Aside from the tediousness of swapping tumblers, it would throw a wrench in the token association for my Binary Editor license. It's also not super clear cut at this time that the pcm is the problem. All of which assumes I can put a UVB0 in place of TBX3 without pinout issues.

Odd things noted so far:
- misfire still happened with alternator disconnected, but DTC P0340 did not come up
- misfire is consistently at 2500 rpm with motorcraft sensors, the BWD sensor permits misfire at lower rpm
- engine behaves fine above or below the misfire and I can power through when driving

I'm open to recommendations! This is a brain buster. HELP!

The cam sensor ground, pin 91 at the eec is shared with many other sensors. Could this have any bearing on the problem?
Phillip P SCCA-SCR, Region #79
2006 Ford Focus - DD, 5 gears of blue fury
1985 Chevy C10 - Expendable work truck, 383 cid of carb'd fun
2001 Ford Mustang - My eec-v dillema
PCM: TBX3/RTAI - Flashed to: CHB3/RTA1 - Cal Tool: BE & J2354 -Ford slot maf, 96 mm, ID1000's, NTK AFRM Gen 1
4.3 stroker v6 - eaton m112 - astro 5 speed - 3.27 rear - LOTS of suspension and brakes work

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Paulie
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Re: Ford 3.8, Misfire, Recurring P0340

Post by Paulie » Fri Sep 29, 2017 11:30 am

Have you tried disconnecting cam sensor and driving?
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

PhillipP
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Posts: 17
Joined: Fri Jul 21, 2017 7:46 am

Re: Ford 3.8, Misfire, Recurring P0340

Post by PhillipP » Fri Sep 29, 2017 12:50 pm

I have not tried disconnecting the cps and driving the car. Can I? It's used to control fuel injector timing.
Phillip P SCCA-SCR, Region #79
2006 Ford Focus - DD, 5 gears of blue fury
1985 Chevy C10 - Expendable work truck, 383 cid of carb'd fun
2001 Ford Mustang - My eec-v dillema
PCM: TBX3/RTAI - Flashed to: CHB3/RTA1 - Cal Tool: BE & J2354 -Ford slot maf, 96 mm, ID1000's, NTK AFRM Gen 1
4.3 stroker v6 - eaton m112 - astro 5 speed - 3.27 rear - LOTS of suspension and brakes work

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Paulie
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Posts: 457
Joined: Thu Oct 23, 2008 9:05 pm
Location: Chicagoland

Re: Ford 3.8, Misfire, Recurring P0340

Post by Paulie » Fri Sep 29, 2017 2:30 pm

Yes you can, it will just run batch fire instead of sequential
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

PhillipP
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Posts: 17
Joined: Fri Jul 21, 2017 7:46 am

Re: Ford 3.8, Misfire, Recurring P0340

Post by PhillipP » Fri Sep 29, 2017 8:17 pm

You were right. It does run without the cam sensor. I am guessing the pcm can narrow batch fire down to two cylinders, not unlike how wasted spark works? It was good enough to make it all the way to the good gas station and back. Lots of maf tuning to do upstairs.

Which leaves restoring cam sensor function open ended. May try routing a new overlay harness with shielded 2 conductor wire tomorrow. After UPS man drops it off.
Phillip P SCCA-SCR, Region #79
2006 Ford Focus - DD, 5 gears of blue fury
1985 Chevy C10 - Expendable work truck, 383 cid of carb'd fun
2001 Ford Mustang - My eec-v dillema
PCM: TBX3/RTAI - Flashed to: CHB3/RTA1 - Cal Tool: BE & J2354 -Ford slot maf, 96 mm, ID1000's, NTK AFRM Gen 1
4.3 stroker v6 - eaton m112 - astro 5 speed - 3.27 rear - LOTS of suspension and brakes work

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Paulie
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Posts: 457
Joined: Thu Oct 23, 2008 9:05 pm
Location: Chicagoland

Re: Ford 3.8, Misfire, Recurring P0340

Post by Paulie » Sat Sep 30, 2017 7:03 pm

I have seen the camshaft synchronizer cause this on stock vehicles. Not sure why.
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

PhillipP
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Posts: 17
Joined: Fri Jul 21, 2017 7:46 am

Re: Ford 3.8, Misfire, Recurring P0340

Post by PhillipP » Sun Oct 01, 2017 8:41 pm

Installed the overlay harness yesterday. Did some testing and tweaks today. In short, used some pretty nice twisted pair shielded wire to replace the path for cam sensor to pcm. Signal is crimped to pcm connector. The ground side is teed in with original ground, as that is ground for cam, maf, frps, and oss sensors. Shield is drained at one end only, the sensor side. It was going to be by the pcm, but I ripped the first try at a drain accidentally.

And it made no difference. [expletives, lots of expletives]

When I put the motor back together I did check out the synchronizer. It turned smoothly, no missing teeth where it meshes with the cam drive. Just one stub at the top for the reluctance sensor.

How does the pcm generate P03040? Could a defect in another system cause a false dtc, ie the crankshaft sensor? Kind of grasping here, since driving batch injection without this issue indicates its only the cam sensor something.
Attachments
TBX3 M112 tune1 2017_Oct_01_16-48-06.csv
(521.31 KiB) Downloaded 18 times
Phillip P SCCA-SCR, Region #79
2006 Ford Focus - DD, 5 gears of blue fury
1985 Chevy C10 - Expendable work truck, 383 cid of carb'd fun
2001 Ford Mustang - My eec-v dillema
PCM: TBX3/RTAI - Flashed to: CHB3/RTA1 - Cal Tool: BE & J2354 -Ford slot maf, 96 mm, ID1000's, NTK AFRM Gen 1
4.3 stroker v6 - eaton m112 - astro 5 speed - 3.27 rear - LOTS of suspension and brakes work

User avatar
Paulie
Tuning Addict
Posts: 457
Joined: Thu Oct 23, 2008 9:05 pm
Location: Chicagoland

Re: Ford 3.8, Misfire, Recurring P0340

Post by Paulie » Mon Oct 02, 2017 11:26 am

I would replace the syncro
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

PhillipP
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Posts: 17
Joined: Fri Jul 21, 2017 7:46 am

Re: Ford 3.8, Misfire, Recurring P0340

Post by PhillipP » Mon Oct 02, 2017 2:39 pm

I guess the synchronizer is the next to last thing. Is this one of those things where it's best to buy oem, or are the chinese ones ok? This thing drives the oil pump too, so component failure could be catastrophic for the engine.
Phillip P SCCA-SCR, Region #79
2006 Ford Focus - DD, 5 gears of blue fury
1985 Chevy C10 - Expendable work truck, 383 cid of carb'd fun
2001 Ford Mustang - My eec-v dillema
PCM: TBX3/RTAI - Flashed to: CHB3/RTA1 - Cal Tool: BE & J2354 -Ford slot maf, 96 mm, ID1000's, NTK AFRM Gen 1
4.3 stroker v6 - eaton m112 - astro 5 speed - 3.27 rear - LOTS of suspension and brakes work

User avatar
Paulie
Tuning Addict
Posts: 457
Joined: Thu Oct 23, 2008 9:05 pm
Location: Chicagoland

Re: Ford 3.8, Misfire, Recurring P0340

Post by Paulie » Mon Oct 02, 2017 10:57 pm

If I had a bunch of time and money invested in my car I would spend the extra money for an OEM syncro.
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

User avatar
Paulie
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Posts: 457
Joined: Thu Oct 23, 2008 9:05 pm
Location: Chicagoland

Re: Ford 3.8, Misfire, Recurring P0340

Post by Paulie » Tue Oct 03, 2017 11:27 am

Did you use the tool to align the syncro when you installed it?
1990 Mustang 5.0, HCI, Vortech S-trim, FRPP 42# inj., PMAS MH95, A9L, Moates Quarterhorse, BE/EA, Innovate LC-1.

PhillipP
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Posts: 17
Joined: Fri Jul 21, 2017 7:46 am

Re: Ford 3.8, Misfire, Recurring P0340

Post by PhillipP » Tue Oct 03, 2017 6:56 pm

Talked one of the electrical engineers at work into bring the oscilloscope over. Captured attached waveform images. This test also brought up P0340 and misfires again. Checked at both at the sensor and pcm. Super clean signal.

Ergo the cam, cam synchronizer, cam sensor, and cam harness are fine. All signs now point to pcm internal issues. I can swap it for my 2003 UVB0, but need to overcome token association with VIN. I emailed Clint Garrity about it.
Attachments
misfire.png
misfire.png (5.93 KiB) Viewed 889 times
idle.png
idle.png (4.69 KiB) Viewed 889 times
Phillip P SCCA-SCR, Region #79
2006 Ford Focus - DD, 5 gears of blue fury
1985 Chevy C10 - Expendable work truck, 383 cid of carb'd fun
2001 Ford Mustang - My eec-v dillema
PCM: TBX3/RTAI - Flashed to: CHB3/RTA1 - Cal Tool: BE & J2354 -Ford slot maf, 96 mm, ID1000's, NTK AFRM Gen 1
4.3 stroker v6 - eaton m112 - astro 5 speed - 3.27 rear - LOTS of suspension and brakes work

decipha

Re: Ford 3.8, Misfire, Recurring P0340

Post by decipha » Tue Oct 03, 2017 9:20 pm

check the coil capacitors

PhillipP
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Posts: 17
Joined: Fri Jul 21, 2017 7:46 am

Re: Ford 3.8, Misfire, Recurring P0340

Post by PhillipP » Wed Oct 04, 2017 7:37 am

Decipha, which capacitors are you referring to? There are two prominent electrolytic caps in the pcm. The look fine. Checking capacitance with fluke meters was an exercise in scratching through the conformal coating. Such measurements also require a grain of salt, since its not isolated from any other patch in the circuit board.

Little: 191-200 uF
Big: 6824 uF but ambiguous

So the TBX3 pcm does have capacitance. It also passed the resistance check across pins 85 and 91.I don't have the number off hand. But it still misfires and throws P0340 at 2500 ish rpm.

The only other capacitor I am familiar with is on power to ignition. It is in parallel with the coil pack, to ground, and serves for noise suppression. After installing a shielded wire for the cam sensor, and capturing signal waveform, it's pretty clear noise isn't the problem.
Phillip P SCCA-SCR, Region #79
2006 Ford Focus - DD, 5 gears of blue fury
1985 Chevy C10 - Expendable work truck, 383 cid of carb'd fun
2001 Ford Mustang - My eec-v dillema
PCM: TBX3/RTAI - Flashed to: CHB3/RTA1 - Cal Tool: BE & J2354 -Ford slot maf, 96 mm, ID1000's, NTK AFRM Gen 1
4.3 stroker v6 - eaton m112 - astro 5 speed - 3.27 rear - LOTS of suspension and brakes work

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