I just re-read your original post again.. it says you are getting a constant 171 and 172. Would you be able to trace the stock wiring as far up as possible to make sure nothing its crossed, broken, etc.

Aw what the hell try unplugging the map sensor too (front sensor on TB) and see if that changes anything too. I read the link provided above. You can test them with a vaccum gauge, but I don't know the number or anything. Again, if you unplug it should hopefully choose the default value although i am still puzzled as to how you got the rich/lean codes with no o2 sensor plugged in.

 

No no, I misposted that, I neglected to mention that I had to drop the misses off at a nail appointment, so being it wouldn't move I chucked the o2 connector back together. Muh bad.

I did at one point disconnect the maf sensor, and to my recollection the idle swooped up and down. I'll do it again tomorrow morning and see what happens.

I did have a thought tho, the rotor in the distributor is worn out and awful, I wonder if that could do it. It skipped my memory but before when I did the tune up, and broke down coming home with my trailer, I fiddled with the distributor (put a new cam sensor in) and broke the new rotor. Luckily I had the old one, popped it in and came home. Just dawned on me before, so I got a new one, Ill put it in tomorrow. I dont see how it can affect fuel mixture other than it running rich, but who knows at this point.

 

I have just read through this entire post. Now, you have a few things going on and, one of those is backfiring which, can be caused by a few things. However, backfiring through the intake was already discussed so, I won't repeat what was said on that as it would be redundant.

What you need to verify / check is your CKPS first. How the system works is, when you start it cold, the PCM is in open loop mode and, there's only a few items being used to start it and keep it running. That's your ECT, IAT, and that's it. The IAC is set to a preset value at the PCM thus controlling it's motor steps to remain open at a preset gap. All the other data is based on values the PCM obtained from the CKPS and CPS and MAP sensor, TPS and other fixed value parameters. Oh, by the way, it's never a good idea to be pulling 12 volt connectors off on a live sensor and / or reconnecting them. You can actually damage them and the PCM input. If you need to test them, always backprobe them with a DMM and read the voltage while operational. FYI on that.

The fuel mix is preset and, at time of startup is very rich. The colder it is, the more fuel is required to keep it running at cold startups. This mode is open loop mode and, it sits in this mode for a pre-programmed amount of time at the PCM. It's running on a timer in the PCM for a few minutes. It's usually 2-3 minutes on the timer. You can see this on a good scan tool when it transitions to closed loop mode.

Now, there's another requirements that must be met before it will go into closed loop mode and that's the ECT temp. It must reach a min, preset temp before it will switch over to closed loop mode and, depending on the year and geographic location the vehicle was purchased, this can either be around 160 - 180ºF. Once it reaches the min target value, the PCM switches into closed loop mode and now begins to use / read the input at the O2 sensor to adjust your fuel trims. This begins to adjust not only the A/F ratio but, it also begins to adjust the timing, the injector pulse width, the coil pulse etc. It's constantly fine-tuning the timing and everything based on sensor feedback.

This is all based off / around the values set forth at the PCM. The PCM uses the CKPS and the CPS values to provide voltage on the timing relationship between the crank and cam respectively. There's also what is called a sync offset value and, if and when you change any of those two sensor (CPS, CKPS) this value must be reset or at least checked to make sure it is not out of sync or, has a large offset. If the value is too large, your timing can go way out and it may lose sync. It can be reset by using a DRBIII tool at the dealer. Since the tool is around 8-10K (for a good one that can reprogram) this is a dealer fix only or, someone that knows the process to re time your cam. This will cause all sorts of issues such as what you've been experiencing.

I would again, check that CKPS to make sure it's not going out of whack. And when they go, it's not just a dead truck where, it won't start and the same is to be said of the CPS. I had it happen and, it wouldn't run right and felt like the timing was way off and yes, it backfired like a ***** through the intake. It would also stall out and ran extremely rough. Then, when restarting, it was like nothing happened. I knew what it was and replaced them both. But, here's another piece of information: when I bought 3rd party sensors, they didn't work. Couldn't, wouldn't start. No go. I had gone to another supplier- same thing. I finally went to the dealer, paid the money and got new ones. Then, they told me right there, about the sync reset. Now, that, I did not know about.

Now, if your diz shaft is worn, it will most likely be eating caps. If the bushing or bearing is so worn, you should be able to move it from side to side and, if it's that worn, it's going to be eating your cap. It will move up and down- that's normal. What to look for: broken contacts, scraping, twisted rotor, cracked rotor, damaged at the pop rivet, loose blade contact at the rotor, broken spring-loaded contact or cut in half laying on the CPS. But, in this case, it would not be intermittent and, it would certainly not affect your fuel trims.

The other thing that I had happen that caused THE SAME EXACT SYMPTOMS as you was a fault in the coil driver circuit at the PCM.

How this works, is, under normal operating conditions, the PCM switches the ground to the coil ON/OFF in sync to your cam as well as the injectors. If, the PCM chip is dead (or intermittent) and is not switching the ground, the voltage is applied 100% throughout the cam rotation thus causing arcing inside the cap thus causing misfires, backfires, out of time conditions etc etc. I had this happen not too long ago in fact and had to get a new PCM.

Now, to check this it's very simple. You will need to get an LED test light. Place one lead to chassis ground (use the headlight ground) and one goes to ground at the coil. Run it. Note if it pulses on off. If it's not- your PCM needs to be replaced and, if this is the case, I can point you to the top of the line place for obtaining a new one that has a lifetime warranty and uses MIL rated components. They make it, they test it and, they are not rebuilt junk.

Ok, so that aside, we now have to look at this so-called lean running condition. Yes, the fuel pressure is correct at 50 psi and, you did the right thing by running a fuel gage inside the cab to verify under load conditions that the fuel pressure did not deviate more than the OEM allowed ±5 psi. It's safe to assume that your pump is not the issue and, it's probably not mechanically relating to injectors either. It is most likely rooted at the PCM fuel trim level.

Now, if it's running lean, it will pop and backfire and, that lean / rich condition is controlled in part at the O2 sensor circuit at the PCM level. The other indication that it may be your O2 sensor is that you've reported a no-volt condition. In addition to that, you've also reported a rich running condition such as the case of seeing smoke come out the back.

This is an indication that you need / should check / or simply replace both O2 sensors with NTK sensors that are rated for the heat and are very reliable as compared to Bosch sensors. I had used Bosch and had issues with them. I now only tell people to run NTK sensors as I have yet to have an issue with them.

Look into those systems and, from the sounds of it, you may simply have a faulty O2 sensor.

 

damn. ^ that's good stuff.

 

Whoah guy! I have probably read and reread that post about 50 times in the past day. Thanks a ton for the info. Point taken about the plugging/unplugging.

The crank pos sensor is interesting, I took it out once and cleaned it, awhile back. Whatever it is it seems to be getting worse, either worse it just reacting worse to the colder weather.

The cam pos sensor is new, I wouldn't even know how to test the ckps, it's so impossible to get to.

Now, it is changing into closed loop as it should, I noticed that when I had the scanner on it. The coolant temp sensor is new and Im assuming working properly, perhaps even no better than the old one I replaced haha. I unplugged the air temp sensor this morning before my trek for firewood and started it, didn't seem to run any different.

Now here is an idea, that maybe can narrow something down? It runs like crap from startup to after switching to closed loop, so that would I guess tell us that it runs awful both on the PCM's settings and the 02's settings, which is why Im thinking it may not be a bad upstream O2. What do you guys think about that logic? When I noticed it ran like utter garbage at startup in open loop (I used to just let it warm up for 20 mins before leaving) that's when I shifted my attention to whatever aids the fuel/air mixture before closed loop.

I'm going to replace that rotor later, not that I really think it'll do anything, but needs to be done anyway. Dhvaughan, I actually did have an intake leak, good eye. It was pretty mean too, looks like I didn't notice it when I did the plenum but the corner of the gasket by the pass side front cyl was ripped, but I siliconed it w/ the valve cover off and it was all better the day I had the scanner. Really thought I would have had it fixed with that, but it wasn't really any better that I could see. I then emptied a few cans of carb cleaner all over it and I found nothing at any joint. This thang is crazy.

 

IF it's running like crap in both modes, (which is not a surprise), you can't really narrow it down to anything until you start testing each component one at a time and by using the process of elimination. Also, I noted that you changed both O2 sensors and you still received a no-volt condition. If the oxygen content is low, the voltage output is high; if the oxygen content is high the output voltage is low. The PCM uses this information to adjust injector pulse-width to achieve the 14.7–to–1 air/fuel ratio necessary for proper engine operation and to control emissions. So, after thinking this through, it's probably not your O2 sensors but, it may be due to a gross vac leak.

Again, just so you know, you should never remove a sensor and run it w/o it connected. It's fine to remove some sensors with the harness attached such as you would when testing the IAC for pintle movement but, it's never a good idea to run part of the circuit without a load / sensor on it. That's not going to give you what your looking for and, when pulling one, it affects everything as they all work together as a system thus throwing everything else out of whack at the PCM level. Then, it has to relearn in order to create a new baseline.

I also noted that you did your plenum. That means that you've removed the intake. If you had a major intake vac leak it would cause backfiring due to a very lean mix. How you can test this is NOT by pouring carb cleaner or any other chemical onto the intake but by either using propane and listen for idle increase or, use a rubber hose up to your ear while probing at the gasket interface as well as all of your injectors. Those are prone to causing leaks.

Also, check the O-ring seal at the IAC motor in the back. Run a Vacuum test. Healthy engine should read 17-22 and no needle bouncing. If there's a leaker, remove the intake and re-do the whole thing properly and use a good gasket by Felpro. There's a section on here that lists out all the steps for creating good seals at the intake.

You may also have a failing IAC that's allowing tons of air to blow past unmonitored and, it's leaning out the mix. To check this, remove it and power on the key to <ON>. watch for movement in the pintle. If no movement is noted, it's shot. They can be bad out of the box. I had to buy two just to get one that actually worked. But, since you report that the idle is not high, that's probably not the issue.

I would also be looking into the 101s as in the ignition wiring. Start by rewiring the ignition wires to this: http://autorepair.about.com/cs/faqs/l/bl654h.htm and by making sure that all of your plugs are good / not cracked at the insulator thus arcing over. What kind of wires are you running and, if they are only 7MM wires, they should be wired per that bulletin.

Also, check that cap for damage. Start there first.

Update: Based on the information you provided, I think that one or more of the following systems may be where your problem is rooted:

-Intake leak: It was removed to fix plenum: possible intake gasket leak or, plenum leak- vac leak thus leaning out mix- backfire and runs bad. However, in my experience, if there's a leak that bad, it always runs bad and is not intermittent.

-Ignition system / new wires and cap, were changed: possible miswire / arcing / thus induction crossfire / backfire rough running. However, it was noted that there were no misfire codes. In this case, it's leaning more towards another system.

-CKPS: The PCM interprets the sensor input to determine the crankshaft position. The PCM then uses this position, along with other inputs, to determine injector sequence and ignition timing.

-CPS: The PCM uses the signal from the camshaft position sensor to determine fuel injector sequence. Once crankshaft position has been determined, the PCM begins energizing a ground circuit to each fuel injector to provide injector operation. If that system is not working properly, it is quite possible that the ground circuit is not being switched ON/OFF thus not allowing fuel to enter into the chamber, thus causing a lean running condition thus causing no voltage to be seen at the O2 thus the backfiring and rough running condition. Either one of those sensors would also explain the intermittent running condition more so than the previous mentioned systems. What was the reason for changing out the CPS in the first place?

 

This thing is killing me. Ran rich almost exclusively for the past few days, then last night after clearing the codes again, ran a 171 after that. Surging and backfiring in both conditions.

I did the propane thing, I have heard of that, but it didn't seem to do me any good. Even held right by the butterfly on the TB didn't make a jump or RPM alteration at all. I've been using the carb cleaner with a straw sprayer for years, anything that blocks the air even momentarily spikes the RPM and has been proven beyond effective at finding even minute leaks.

Im going to start at the begining again with this thing I think. Good point about the vacuum gauge, that's my next step, grab one of them and take a peek. I'd REALLY like to remove any further vacuum leaks from the possible causes for a few reasons, but mostly because redoing the intake/plenum isn't something I'm looking to do again in the freezing cold haha.

When your CKPS went south, did it throw any codes? I know they are supposed to, but what's the possibility (read: probability) of it causing such a rukus under the hood without throwing a code?

My thought process now since you outlined what is working at startup pre 02 kick in is if I can remove vacuum issue from the list, I'll go through those sensors you listed first as it's never running well, just inconsistent on whether rich (maybe 10% of the time ONLY recently) or lean, almost always.

Man if you were closer to NJ I would give you my first born child to take a look at this pile. Thanks again!

 

NO- no codes for that, only the CEL for misfire due to out-of-timing condition.

I am going to be very close to you soon. I will be across from NY come two weeks in Danbury, CT.

Here's a quick test: plug ALL ports going to the intake. Note how it runs.

IF no improvement is seen, and, your positive it's running rich, you may have a problem with either leaking injectors or a blown injector coil driver circuit at the PCM level.

When this happens, one of two things happens:

It either fails to switch the ground ON or OFF thus causing a lean or rich mix.

Did you check your plugs?

How about the plenum leak test?

Plenum Leak-Test

-remove the PCV and breather from valve covers
-place both hands over both holes
-with engine running, not vacuum at your hand on PCV

results:

If vac is present, your plenum is leaking.

How about the o-ring test?

O-ring test
-place a rubber tube up to your ear
-with engine running, probe around each injector 100%
-note hissing / air sound

Results: if hissing is heard, you have a leak

How about IAC gasket test?

Test
-with cold engine, START engine
-propane into back of TB at the IAC
-note idle change

Results:

IF idle goes up, you have a leak

 

Now, focusing on the fuel injection system now, let's just assume that you have one or more leaking injectors, this would cause it to run rich. Now, the indication of this is to pull the plugs and check for soot like material.

This will tell you if it's running rich. One thing to also take into account is the so-called lean code that you've also experienced. Well, we could say that a blown O2 sensor would also cause voltage hi / low swing at the PCM input thus causing it to go lean / rich at random. But, you stated that those were new. Now, if they are Bosch, it's possible that they are not working correctly. In that case, we would replace them with NTK- FYI

Let's just say that those are working fine. Another thing that would induce a rich running as well as a lean condition would be a intermittent injector driver circuit. The EFI system would have to be tested with a DRB III tool at the dealer in order to diagnose this.

 

I can't thank you enough, I have to finish up a Mercury I'm working on tomorrow morning, I'll sneak out for a few minutes and run those tests and post back with the results. I am going to try and get a vacuum tester tonight too if I have a chance. I just have the Dodge here at my house @ the moment, and if I travel outside of my neighborhood I have to do so under the cloak of darkness (bad inspection sticker). The cops here don't mess around when it comes to fund raising.

If (and I hope it isn't) the plenum is bad I think Im going to hold off and get the Hughes kit. I was in a pinch last time and needed the truck back on the road the next morning to move ourselves, so I just got a FelPro kit, but if the plate is bent or distorted and I didn't see it, better just to do the job twice instead of more.

Thanks!