Crank Sensor...
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Joined: Jul 2006
Posts: 12,204
Likes: 10
From: Gainesville, Ga.
ouch. i guess i won't be getting one.
Rookie
Joined: May 2010
Posts: 75
Likes: 0
From: Columbus
I am not totally sure about the backfiring, but the fluctuating rpm's aren't good. Mine did that. It would go from 400-700 at idle. I put in some fuel injector cleaner into my gas tank about 3 times and now it is "normal" 
I have a new crank (napa) and cam (mopar); re-synced it with my snap-on. If this crank sensor dosn't fix it, I am going to double check the sync with the DRB 3 at work.
That;s why I am thinking that the crank sensor is bad (aftermarket sucks). Wouldn't be a valve closure problem (just pulled off the valve covers, recent valves done), timing chain isn't an issue (just did, timing is dead on) and according to the engine, the fuel sync is at 0.
Here is what I have done.
When I got it, she didn't run PO said it was timing chain.
So I replaced timing chain, messed up the timing, so pulled the heads 16 new valves and 16 new pushrods. After that, wouldn't run at all; diaged it to be a bad crank sensor. Replaced, still did it, but now to 180. DRB 3 at work scanned saying bad cam sensor, replaced that. Helped it a bit, still backfiring.
Once it hits open loop, it smooths out and runs great. It's only doing this during closed loop, so I thought for giigles i would try computer, replaced that with no success.
From cmkenna's posts on this forum, I have deterined the only sensors used during warm up are the crank, the intake air and the coolant temp.
Intake air and coolant temp work as required by testing, but the crank sensor flunkuates and the spark advance by the computer is approximatly 30-50 degrees, which is the cause for the backfire; IAC will hang open too, as the PCM is telling it the rpms are 300 then 1200 then 400 then 800 then 300 then 1200 then 500, etc.
No codes except exhaust too rich (it pours gas out when its in closed loop, legit the gas steams from the exhaust) and trans temp over. o2 won't affect closed loop, so I am not too worried about that. During closed loop, ti runs on pre-set values.
That;s why I am thinking that the crank sensor is bad (aftermarket sucks). Wouldn't be a valve closure problem (just pulled off the valve covers, recent valves done), timing chain isn't an issue (just did, timing is dead on) and according to the engine, the fuel sync is at 0.
Here is what I have done.
When I got it, she didn't run PO said it was timing chain.
So I replaced timing chain, messed up the timing, so pulled the heads 16 new valves and 16 new pushrods. After that, wouldn't run at all; diaged it to be a bad crank sensor. Replaced, still did it, but now to 180. DRB 3 at work scanned saying bad cam sensor, replaced that. Helped it a bit, still backfiring.
Once it hits open loop, it smooths out and runs great. It's only doing this during closed loop, so I thought for giigles i would try computer, replaced that with no success.
From cmkenna's posts on this forum, I have deterined the only sensors used during warm up are the crank, the intake air and the coolant temp.
Intake air and coolant temp work as required by testing, but the crank sensor flunkuates and the spark advance by the computer is approximatly 30-50 degrees, which is the cause for the backfire; IAC will hang open too, as the PCM is telling it the rpms are 300 then 1200 then 400 then 800 then 300 then 1200 then 500, etc.
No codes except exhaust too rich (it pours gas out when its in closed loop, legit the gas steams from the exhaust) and trans temp over. o2 won't affect closed loop, so I am not too worried about that. During closed loop, ti runs on pre-set values.
Yes: a CKPS will cause erratic idling as will a TPS however, it will also cause popping / backfiring / misfires due to the clocking does NOT meet OEM specs nor does the amplitude and duration of pulse code / voltage sent to the PCM. In my case, I discovered this with both the CPS and CKPS- both were way off OEM spec. I put the old ones back in- fired right up fine.
I know this for a fact because, I went through this last year or so with my truck and, after talking to another engineer (I'm an engineer) who sources parts for the auto industry and defense industry now, and, he told me only OEM parts MEET the OEM specs. With after-market electrical / electronic parts, they are the REJECTS that are sold off at a huge discount to 3rd party brokers which in turn, sell / distribute that junk to Crapa Auto, Auto Blown, Crap Boys and many more retailers / chain stores. Basically, the parts that do not pass or meet OEM specs end up in retail chains. This is why the price is radically different for a CKPS at the dealer. It's not that the dealer is marking it up so much as the fact that the rejects are sold dirt cheap to the retailers.
I also went through this with THREE IAC motors not too long ago. I had to buy three just to get one that worked. One leaked like a siv due to not seating fully and the second one was jamming / binding at the pintle valve.
I've also gone through two TPS as one had a "dead" zone thus causing it to speed up slow down / jerk.
After learning about sensors being iffy (at best), I now buy solely from the dealer.
Go OEM parts for electronics or, if and when going aftermarket (such as for a computer) verify that they do 100% testing to OEM specs or better.
Now, here's another piece of the puzzle that I found: "due to variation" in 3rd party parts, sometimes, you can make them work if they are not TOO far out of what is considered normal operating range. Normally, in OEM parts, they are drag and drop in and they fire right up without the need of a DRBIII or DART tool. In that case you have to use such a tool to reset the offset values and sync values in order to correct the timing. What is most likely going on here is that the timing is out of whack. And, since the entire EFI system is dependent upon that main sensor (the CKPS) as the Master Clock for injector firing sequence and ignition timing sequence, if the CKPS is off, everything will be off.
One other thing to take note of:
If the part is TOO far out of what is considered "normal operating range", it is of no use to try and manually reprogram those values for it's never going to work out in the end.
In my experience and my opinion, the best method is to avoid workarounds and other means to avoid the root problem. I've read about people having to move the plugs by one just to get the timing to match up to the plug which, is really not the ideal way to approach an out-of-timing condition.
The correct approach is to simply address the real-root problem and simply resolve it by changing the non-conforming part out with one that conforms to all OEM specs. Why create more work and potential for other problems by a workaround when a lot of time can be saved (along with frustration) by dropping in a "good" part and be on your way in ten minutes. It takes me ten minutes to change that out vs. spending hours trying to determine how to compensate for it at the PCM level. At one time, my mind ran amuck thinking it was something else before I came to my senses and asked myself "what changed?". A: CKPS. Action: clean and put old one back in. Result: problem solved.
CM
Last edited by cmckenna; May 20, 2010 at 02:12 PM. Reason: More information