Help please! P0340 code; common problems have been ruled out!

[zpstang96]

Hey guys, I'll try to make this short. I've done my research as to avoid wasting anyone's time, so some help would be appreciated!

-1996 GT with a 4v B-head motor, Teksid block .020 over, Kellogg stroker crank, Manley rods/pistons.
-Using factory GT harness and ECU; harness extended for coolant/TPS sensors, etc. CEL is on and turning up the P0340.
-Cam sensor, alternator, and crank sensor are new. There is continuity in the wiring for the sensors (checked), and the alternator is performing fine (also checked, diodes are not causing CEL). Wiring checked for short to ground and short to power--nothing found.
-With the cam sensor plugged in, the car runs like crap. It idles horribly and dies on occasion. Throttle response is extremely poor and it lags at low RPM.
-With the cam sensor unplugged, the car runs nearly perfect. From what I've read, this points to a timing issue between the crankshaft sensor and the camshaft sensor trigger.

This is where my Dad (former mechanic; did the swap with me) and I have come to a partial dead end. He thinks that when the machine shop dialed in the cams, the trigger or reluctor for the cam sensor was moved out of position. The cam timing (mechanically) is correct, but the computer is seeing the difference between the position of the crankshaft and the position of the cam sensor trigger. I am trying to give the machine shop the benefit of the doubt, as they are extremely reputable and have been building these engines for a while.

Can these problems be caused by anything else?? We're guessing that the only way to see if Dad's theory is correct is to pull the timing cover, which we would like to avoid doing until we absolutely have to.

Stupid question, but I have to ask: Can my tuner who dyno'd the car bypass or delete the cam sensor? Or at least clear the CEL?

Also, can someone explain to me how: The car made 310hp/304tq on a Mustang Dyno at a 9.5:1 compression ratio with the cam sensor plugged in, and the poor throttle response/idle. I'm having trouble seeing how it made those numbers when it was running so poorly. I'm guessing at WOT/high RPM these problems are insignificant?

Unrelated Question: The car is actually running quite cool, but the fan is on 90% of the time. Could this be a bad coolant sensor? The CEL only returns the P0340 though, nothing else.

Thanks in advance!

 

[iamtheshaner]

So it runs like it's out of time. The CMP sensor is known good. You have no opens, STG or STP in the wiring. You've attacked the infamous noisy alternator and it still runs like garbage unless you force it into bank fire by disconnecting the cam sensor.

Can these problems be caused by anything else? - Not really. It's either out of time or the PCM thinks it is
Stupid question which must be asked - Is indeed a stupid question. I'm sure someone out there can pull out CMP but this is a textbook example of tuning out a problem and you certainly don't want to go that route
Also, can someone explain to you... - Fascinating to say the least. Under WOT you are in open loop....which to my knowledge still incorporates sequential injection timing and ignition. If this is NOT the case, and Ford chose to "double fire" the coils and go bank fire under WOT it would explain why it's runs well under WOT. I'm probably missing something...but these are my thoughts at the end of a Monday.... Also, I can make a Mustang dyno say anything I want. They are fantastic tuning aids but the load correction is such a huge variable that just unstrapping the car and restrapping it could throw your #'s off by 10+hp EASY. They are NOT very consistant dyno's and they certainly aren't accurate unless it's been calibrated recently. I love mine but goodness it's a picky little bastard. Rule of thumb is tune with a Mustang, brag with DJet.

I can't remember if the primary cam sprockets are bolted or pressed onto these motors. If somone here can chime in with this answer I can tell you whether or not the pickup was incorrectly set by the machine shop. The pickup for the CMP is cast into the sprocket. If it's bolted and keyed - HIGHLY unlikely the sprocket shifted and I would STRONGLY recommend you double check your base valve timing. If it's a press-on and the machine shop had it off for some reason - it very well could be sending BS to the PCM but that would also conclude that your base timing is off because you use marks on that sproket to set base timing.

So pretty much however you crack this egg your timing is off.

Any other source of RFI such as that from an ignition coil or other aftermarket electronics could very well set your CMP code but they should not result in any driveability issue like this. Are your CMP circuits still twisted 1 twist per inch and covered with a grounded metallic shield?

Your issue SCREAMS base timing off. Textbook example, actually. A difference in compression between the two banks will confirm this with 100% certainty. I'm guessing the intake cam(s) aren't phased to the exhaust correctly. Setting the main chains on these motors is so stupid simple I'd be shocked if anyone with any sort of skill (your dad) could screw it up.

 

[iamtheshaner]

After more thought I don't know how a machine shop could screw up sprocket phasing and/or intake and exhaust phasing. Regardless, the best advice is, unfortunately, to reset and check thrice your base valve timing. The comment I made about your ignition coil was directed at a COP system which I suppose you probably don't have with a 96. Even more the reason why it runs like garbage when the PCM fires your injectors in pairs or by bank. I just don't see it being a PCM or CMP circuitry issue because sequential fuel delivery and misfire monitor is basically all that input is used for. So if it runs better when the PCM fires them in groups it says to me that the specific timing is off which must mean the valve timing is off because there is no way the crank trigger wheel is off or wobbling because it would run crappy all the time if at all

 

[RIO RED SNAKE]

Sorry to hear Zacher, looks like you may have to pull the cover, I do NOT think your tuner can bypass the cam sensor issue nor delete the CEL short of pulling the bulb out of the cluster. I am curious as to how the car would run/last with that sensor unplugged full time and if there are any side effects of that.

And as for the dyno, numbers are numbers, weights, percentages etc all can be tweaked not saying it was not an accurate reading but anything is possible, i thikn that under WOT everything seems to run ok just because everything is firing and trying to make full power and who knows, maybe the timing etc syncs up at full power. But again i dont know, weird issue though, i am sure you have googled this to see if others have had this issue but goodluck man.

 

[zpstang96]

After more thought I don't know how a machine shop could screw up sprocket phasing and/or intake and exhaust phasing. Regardless, the best advice is, unfortunately, to reset and check thrice your base valve timing. The comment I made about your ignition coil was directed at a COP system which I suppose you probably don't have with a 96. Even more the reason why it runs like garbage when the PCM fires your injectors in pairs or by bank. I just don't see it being a PCM or CMP circuitry issue because sequential fuel delivery and misfire monitor is basically all that input is used for. So if it runs better when the PCM fires them in groups it says to me that the specific timing is off which must mean the valve timing is off because there is no way the crank trigger wheel is off or wobbling because it would run crappy all the time if at all

Yeah, the only way I could see the machine shop screwing it up is that the cam gears are fully adjustable. So they could possibly degree the cams in mechanically correct but incorrect in accordance with the crank trigger (I suppose that's possibly with adjustable cam gears?). In response to your first comment/post, I'd be inclined to think that the PCM thinks it is out of time rather than it be actually out of time, especially because the car runs so well with no cam sensor. Literally it idles perfectly and drives just like my 2v motor but with more power. Either way, this all leads to pulling the cover and double checking everything, I guess I can't get away from that.

Thanks for your help :beer: I'll be keeping the thread updated as soon as I make some progress with this.

Sorry to hear Zacher, looks like you may have to pull the cover, I do NOT think your tuner can bypass the cam sensor issue nor delete the CEL short of pulling the bulb out of the cluster. I am curious as to how the car would run/last with that sensor unplugged full time and if there are any side effects of that.

And as for the dyno, numbers are numbers, weights, percentages etc all can be tweaked not saying it was not an accurate reading but anything is possible, i thikn that under WOT everything seems to run ok just because everything is firing and trying to make full power and who knows, maybe the timing etc syncs up at full power. But again i dont know, weird issue though, i am sure you have googled this to see if others have had this issue but goodluck man.

The only thing I could find was a guy on a mark viii forum having the same problem. He said he unplugged the cam sensor and it ran fine, which led me to unplugging mine just to see what would happen.

But yeah I was pretty baffled at the numbers after I saw the car run. The car was tuned by Pro Edge but Dad trailered it up for a day while I was up at school because they had an opening, so I never actually saw it run until I got home and went to drive it.

But to answer your curiosity...I've been driving it around with the cam sensor unplugged all the time and it's doing just fine. I am also wondering how this would fare long term, but from what I can tell, the PCM just defaults to firing the injectors in groups so the car still runs with the sensor unplugged. I'm still fairly cautious with it, but the car feels great with it unplugged and is a monster from 4500 RPM+.

 

[iamtheshaner]

It has adjustable cam gears on it??

If this is the case I wonder how the CMP pickup is incorporated.

The presence of an aftermarket adjustable cam gear makes me even more inclined to believe it is out of time.

Either way your next step is to pull the front cover or the LH valve cover at the very least to investigate this adjustable cam gear. Advancing the intake cam a bit will promote high RPM V/E and if this were the case I'd expect it to run better with the CMP disconnected.

 

[zpstang96]

Bump! Pulled the driver's side valve cover today and it looks like when the engine is at TDC and the cams are aligned properly the reluctor is one tooth off compared to the cam sensor.

Should the reluctor be lined up with the cam sensor at TDC? I have some pics below

Blue arrow is the cam sensor, red arrow is the reluctor

Better angle in this one

Turned the crank 360 degrees

Edit: Just looked at the factory cam gear that came with the timing chain and the adjustable cam gear looks to be set up properly, as the keyway for the cam is a tooth off of the reluctor. No idea where to look now