[cfurnell]

Sorry if this has been covered before. I searched the forum prior to posting but couldn't find what I was looking for. Here's the deal:

I replaced my timing chain and water pump on my '04 2.7L Intrepid recently. The car ran great before. However, now it "misses" (but it's not actually missing) while driving down the road on occasion and when it does, the tach drops to zero for a half a second, the cruise control goes off, and my check engine light will come on for a half a second. Sometimes if the problem repeats itself enough in a short amount of time (5 times in a minute or so) the check engine light will stay on and it is in some sort of limp mode with my acceleration limited. However, if it "misses" again while in this state, it clears out the check engine light and everything goes back to normal. In the mornings when it is cooler outside or when it is misty/rainy/foggy it is worse. In the heat of the afternoon, it may not do it at all. It is giving me P0121 codes regularly and P0068 codes occasionally. I have replaced the TPS sensor and the MAP sensor. I finally took it to a shop and they told me it is likely a short somewhere in the 5V signal circuit. They told me the only thing they could recommend was to start cutting insulation and looking for obvious breaks, pinch points, bare wire, etc. They were going to charge $400 just to take the intake manifold off, so I said I would give it a shot myself. I looked at everything from the sensors all the way back to the back of the engine and didn't see anything suspicious. Then I looked where the wiring harness goes up to the PCM to see if anything was obvious there. My thinking is that since it ran fine before I replaced my timing chain/water pump, then I may have broken a wire when I bent the wiring harness out of the way while tearing into the front of the engine. But I can't see anything.

My questions are:
1. Would a bad sensor plug (not the sensors- I already replaced those) cause this? I mean, if it's shorting out or going to ground I would assume it would be from the wire making contact with the engine block or frame- not a faulty pig-tail, but I am open to suggestions/input.
2. Could I just bypass the wiring harness by cutting the 5V signal wire at the PCM and routing it straight to my TPS and MAP sensors? I don't have a wiring diagram to see if there is anything else on that circuit, but I assume I could wire directly to anything on the circuit that would be affected by my cutting the original 5V signal wire.
3. Could the 5V signal wire be shorting out somewhere else on my engine that would cause it to affect the signal going to my TPS or MAP? The guys at the shop and the dropping out of my engine seem to point to the problem being related to TPS or possibly MAP sensor signal.

I am not an electrician, but I am decent at turning wrenches and common sense. If anybody has any ideas, I would appreciate hearing them. Otherwise, I'm going to have to take it somewhere for someone else to do what is very likely a pretty simple fix. After successfully replacing my timing chain and water pump I am pretty bummed that it is this that is tripping me up and possibly costing me the money I saved by doing the water pump myself.

Thanks,

 

[peva]

My best guess is an intermittently failing cam position sensor (or a problem with its wires/connector - but most likely the sensor itself). On LH forums over the years, it was discovered that when the cam position sensor is on its way out, the cruise control will start turning itself off (apparently something built into the PCM firmware for some engineering reason when cam sensor signal disappears).

You may want to go ahead and replace the cam sensor and the crank position sensor. Highly recommended to get from dealer only (or NGK aftermarket) because aftermarket sensors (except for NGK for these) are a gamble.

You could disconnect the cam position sensor temporarily and see if the problem goes away while it's disconnected. Be aware that if you do that, the engine won't run above 2500 rpm as the timing runs off of the crank sensor below 2500, and switches over to the cam sensor above 2500. Running without the cam sensor won't hurt anything. But it may save time just to go ahead and replace the cam and crank sensors.

The codes you are getting may be because when the cam sensor is acting up, it is pulling down ("soft shorting") the 5 volt power to all the sensors and the PCM just sees other sensors not working properly but doesn't necessarily know why.

Can't guarantee that it's the cam sensor, but fairly certain.

You might also temporarily disconnect the a.c. pressure transducer connector. That sensor is known for failing and shorting out the 5 volt sensor power bus and causing the engine to cut off. I don't think that is your problem because the cruise control turning itself off points to the cam sensor, but you could rule out the a.c. pressure transducer as being the problem.

 

[cfurnell]

My best guess is an intermittently failing cam position sensor (or a problem with its wires/connector - but most likely the sensor itself). On LH forums over the years, it was discovered that when the cam position sensor is on its way out, the cruise control will start turning itself off (apparently something built into the PCM firmware for some engineering reason when cam sensor signal disappears).

You may want to go ahead and replace the cam sensor and the crank position sensor. Highly recommended to get from dealer only (or NGK aftermarket) because aftermarket sensors (except for NGK for these) are a gamble.

You could disconnect the cam position sensor temporarily and see if the problem goes away while it's disconnected. Be aware that if you do that, the engine won't run above 2500 rpm as the timing runs off of the crank sensor below 2500, and switches over to the cam sensor above 2500. Running without the cam sensor won't hurt anything. But it may save time just to go ahead and replace the cam and crank sensors.

The codes you are getting may be because when the cam sensor is acting up, it is pulling down ("soft shorting") the 5 volt power to all the sensors and the PCM just sees other sensors not working properly but doesn't necessarily know why.

Can't guarantee that it's the cam sensor, but fairly certain.

You might also temporarily disconnect the a.c. pressure transducer connector. That sensor is known for failing and shorting out the 5 volt sensor power bus and causing the engine to cut off. I don't think that is your problem because the cruise control turning itself off points to the cam sensor, but you could rule out the a.c. pressure transducer as being the problem.

I will give it a shot! Thanks!

 

[cfurnell]

My best guess is an intermittently failing cam position sensor (or a problem with its wires/connector - but most likely the sensor itself). On LH forums over the years, it was discovered that when the cam position sensor is on its way out, the cruise control will start turning itself off (apparently something built into the PCM firmware for some engineering reason when cam sensor signal disappears).

You may want to go ahead and replace the cam sensor and the crank position sensor. Highly recommended to get from dealer only (or NGK aftermarket) because aftermarket sensors (except for NGK for these) are a gamble.

You could disconnect the cam position sensor temporarily and see if the problem goes away while it's disconnected. Be aware that if you do that, the engine won't run above 2500 rpm as the timing runs off of the crank sensor below 2500, and switches over to the cam sensor above 2500. Running without the cam sensor won't hurt anything. But it may save time just to go ahead and replace the cam and crank sensors.

The codes you are getting may be because when the cam sensor is acting up, it is pulling down ("soft shorting") the 5 volt power to all the sensors and the PCM just sees other sensors not working properly but doesn't necessarily know why.

Can't guarantee that it's the cam sensor, but fairly certain.

You might also temporarily disconnect the a.c. pressure transducer connector. That sensor is known for failing and shorting out the 5 volt sensor power bus and causing the engine to cut off. I don't think that is your problem because the cruise control turning itself off points to the cam sensor, but you could rule out the a.c. pressure transducer as being the problem.

Actually, it's interesting that you mention the RPM's determining which sensor is used for timing. When I'm driving down the road and it starts bucking, it will quit bucking if I accelerate hard. Maybe it's the crank sensor instead of the cam sensor because when I press hard on the accelerator and my RPM's go above 2,500 it smooths out? I may go ahead and replace them both.

 

[peva]

Actually, it's interesting that you mention the RPM's determining which sensor is used for timing. When I'm driving down the road and it starts bucking, it will quit bucking if I accelerate hard. Maybe it's the crank sensor instead of the cam sensor because when I press hard on the accelerator and my RPM's go above 2,500 it smooths out? I may go ahead and replace them both.

Could be.

 

[cfurnell]

I started my car at lunch and then disconnected the cam position sensor (because I discovered it wouldn't start with it already unplugged :-/ ) and drove it down the road. With the cam sensor disconnected, it didn't hesitate or buck or die at stop signs. I stopped on the way back to work and grabbed another cam position sensor and installed it. It definitely improved the bucking- but didn't completely eliminate it. The improvement was definitely noticeable though. It makes me wonder if the improvement came from unplugging and plugging back in the sensor when I swapped it out. I'm wondering if it is a wiring issue right there at the plug. I grabbed a crankshaft position sensor too, so I'll put that in when I get home this evening and check the wiring at both plugs.

 

[peva]

You know that your timing chain/cams is correct?

I don't know what the chances of using non-NGK aftermarket sensors would be causing any remaining problem. Just keep that in your mind as you continue your troubleshooting.

 

[cfurnell]

You know that your timing chain/cams is correct?

I don't know what the chances of using non-NGK aftermarket sensors would be causing any remaining problem. Just keep that in your mind as you continue your troubleshooting.

Yes, I'm sure my timing chain and cams are right. When it's running right, it runs like a sewing machine. Super smooth. Part of the reason this is so frustrating. Thanks for your help.

 

[cfurnell]

Yes, I'm sure my timing chain and cams are right. When it's running right, it runs like a sewing machine. Super smooth. Part of the reason this is so frustrating. Thanks for your help.

Confused and frustrated this morning. The 60 minute drive home yesterday was terrible. All the same problems but more frequent with my check engine light staying on more than usual. I replaced my crankshaft position sensor this morning before driving back in to work. On the drive in, my car actually died twice on the freeway- actually it didn't die, it just wouldn't accelerate. I thought it had died until I pulled over and realized it was actually still running. It was throwing a P0344 code (cam shaft position sensor) where it never has before when dealing with these issues. I put my old cam sensor back in, cleared the code, and drove it on in to work. It was still doing all the things, but at least it was drivable with the old sensor in. I am going to try to go today to return the Advance Auto sensor and pick up a NGK one and go from there.

 

[cfurnell]

So I read this morning that there may need to be a "relearning" process for a new cam sensor. I put the brand new one back in and disconnected the negative terminal on my battery for about an hour. When I drove it around the block, it did fine for about a half a mile. Then when I stopped at a gas station, it died and threw a P0344 code again. I took it back out and put my old one back in to drive back to work. It is missing like it used to, but it hasn't thrown a code that will stick yet. I'm going to wait til it does and check it. It will be interesting if it is the old P0121 code instead of a cam sensor code. Will update once complete.

*Note- there is no one around who has a NGK/NTK sensor in stock. I would have to wait til next week to get one shipped. I am using other brands to see if I can get anything figured out sooner. I will be shocked if I get a NGK sensor next week and my problems go away.

 

[peva]

So I read this morning that there may need to be a "relearning" process for a new cam sensor. I put the brand new one back in and disconnected the negative terminal on my battery for about an hour. When I drove it around the block, it did fine for about a half a mile. Then when I stopped at a gas station, it died and threw a P0344 code again. I took it back out and put my old one back in to drive back to work. It is missing like it used to, but it hasn't thrown a code that will stick yet. I'm going to wait til it does and check it. It will be interesting if it is the old P0121 code instead of a cam sensor code. Will update once complete.

*Note- there is no one around who has a NGK/NTK sensor in stock. I would have to wait til next week to get one shipped. I am using other brands to see if I can get anything figured out sooner. I will be shocked if I get a NGK sensor next week and my problems go away.

Local dealer part? (more $$?)

 

[cfurnell]

Local dealer part? (more $$?)

I thought about going to the dealer, but just for giggles I ran down to the salvage yard at lunch. I just got back. On the way down there with my stock sensor, it threw a code. I pulled over to check it and it was a P0068. I cleared it and went to the yard and grabbed another cam sensor out of a car on the lot and put it in mine to see what it would do. It looked exactly like my stock sensor, so I assume it was stock also. Once I put it in my car and drove it off the parking lot, it threw a P0068 code too. But then it cleared itself and ran perfectly the 8 miles or so back to the office. But it is also very warm out there today. And it would often run just fine in the warmth of the afternoon. So, at least I'm back to where I started. On the bright side, I could now go pro at changing cam position sensors in a 2.7L Chrysler engine!

 

[PurpleBullet97]

Is anything else electrical occurring when the car bucks?

If I were you, I HIGHLY suggest you avoid any aftermarket sensors for these cars! If the cam sensor doesn't have a Chrysler badge on it - DONT USE IT!

My 97 did the SAME exact thing you are experiencing. It was a mixture of bad crank and cam sensors - except I had replaced the crank with one out of the yard (Chrysler) and the cam sensor was brand new from autobone. 10 miles down the road car stalled and needed towed. This led to an $800+ goose egg chase only for the mechanic to tell me it was the brand new cam sensor that failed. With 10 miles on it. I would highly suggest finding sensors with Chrysler badges on them - I would much rather take a gamble on multiple Chrysler badged sensors out of a junkyard than multiple new sensors from any autopart store!

 

[cfurnell]

Is anything else electrical occurring when the car bucks?

If I were you, I HIGHLY suggest you avoid any aftermarket sensors for these cars! If the cam sensor doesn't have a Chrysler badge on it - DONT USE IT!

My 97 did the SAME exact thing you are experiencing. It was a mixture of bad crank and cam sensors - except I had replaced the crank with one out of the yard (Chrysler) and the cam sensor was brand new from autobone. 10 miles down the road car stalled and needed towed. This led to an $800+ goose egg chase only for the mechanic to tell me it was the brand new cam sensor that failed. With 10 miles on it. I would highly suggest finding sensors with Chrysler badges on them - I would much rather take a gamble on multiple Chrysler badged sensors out of a junkyard than multiple new sensors from any autopart store!

When the car bucks, my cruise control drops, my speedometer drops to zero, and my lights go dim. All of this happens in a half a second and then it all comes back up. It's gotta be killing my transmission too with all the stalls and slams it's creating on it. So, I had originally grabbed a new crank and cam sensor from Advance. The crank is still in there, but I did go to a yard and pull a stock cam sensor from another car. With that cam sensor in it, it's still doing the same thing. Yesterday on the way home I pulled over and unplugged the cam sensor to see if I could get the problem to go away again since I was close to home and didn't need to get it over 2,500 rpm. But this time, about 20ft down the road my car died. Pulled over, plugged it back in, and it fired right back up.

Is it making more sense to anyone else that this might actually be something with the wiring? Should I replace my pigtails to my cam and crank sensors? It seems to make sense that if it were the crank sensor wiring that it would be more subject to variation due to weather and temp since that one is down on the transmission housing and closer to "weather".

 

[cfurnell]

I took a video so you might be able to see what it is doing. Pardon the excessive and annoying commentary.

@PurpleBullet97 @peva

 

[JordanS]

That is super weird. I've never seen an issue like this before. Maybe you have an alternator that's going out.

 

[PurpleBullet97]

When the car bucks, my cruise control drops, my speedometer drops to zero, and my lights go dim. All of this happens in a half a second and then it all comes back up. It's gotta be killing my transmission too with all the stalls and slams it's creating on it. So, I had originally grabbed a new crank and cam sensor from Advance. The crank is still in there, but I did go to a yard and pull a stock cam sensor from another car. With that cam sensor in it, it's still doing the same thing. Yesterday on the way home I pulled over and unplugged the cam sensor to see if I could get the problem to go away again since I was close to home and didn't need to get it over 2,500 rpm. But this time, about 20ft down the road my car died. Pulled over, plugged it back in, and it fired right back up.

Is it making more sense to anyone else that this might actually be something with the wiring? Should I replace my pigtails to my cam and crank sensors? It seems to make sense that if it were the crank sensor wiring that it would be more subject to variation due to weather and temp since that one is down on the transmission housing and closer to "weather".

This is exactly what I was talking about my guy... if I were you I wouldn't be running non Chrysler badged sensors. Period. Take the "Advance" crank sensor out and put the Chrysler one you have back in the car. Test drive it to the junk yard if you have that one close to you, then scrounge 2 of each sensor (2 cam, 2 crank correct mopar numbers!) and hope you get lucky.

Personally, you also now have to question the TPS and MAP sensors you say you just put in the car - because you didn't really specify if they are aftermarket or not.

The problem is you shouldn't have replaced both TPS and MAP at the same time unless they were known working chrysler sensors. One sensor might have cleared both codes (Again. imo 99% of the time it has to be a mopar sensor for it to actually clear the code!) Unless both sensors were obviously needing replaced - !!! - if that were the case I may suspect that - An oem crank, oem cam, oem TPS and oem MAP sensor that are the correct part numbers would get your vehicle running properly again. (I hope? This is assuming your problem IS electrical/Sensor related and not Vacuum related!)

Remember - the computer is screaming at you for a reason!

 

[cfurnell]

This is exactly what I was talking about my guy... if I were you I wouldn't be running non Chrysler badged sensors. Period. Take the "Advance" crank sensor out and put the Chrysler one you have back in the car. Test drive it to the junk yard if you have that one close to you, then scrounge 2 of each sensor (2 cam, 2 crank correct mopar numbers!) and hope you get lucky.

Personally, you also now have to question the TPS and MAP sensors you say you just put in the car - because you didn't really specify if they are aftermarket or not.

The problem is you shouldn't have replaced both TPS and MAP at the same time unless they were known working chrysler sensors. One sensor might have cleared both codes (Again. imo 99% of the time it has to be a mopar sensor for it to actually clear the code!) Unless both sensors were obviously needing replaced - !!! - if that were the case I may suspect that - An oem crank, oem cam, oem TPS and oem MAP sensor that are the correct part numbers would get your vehicle running properly again. (I hope? This is assuming your problem IS electrical/Sensor related and not Vacuum related!)

Remember - the computer is screaming at you for a reason!

I ordered a Mopar cam sensor from the dealership yesterday. It'll be in next week. I'll pick up a crank sensor when I go pick up the cam sensor. I MAY still have the original MAP and TPS lying around. If I can find them, I'll put those back in too. If not, guess I'll be looking for Mopar or NTK for those too. Hopefully by the end of next week I can eliminate aftermarket sensors as a variable. Thanks everyone.

 

[PurpleBullet97]

Thank you for the update please keep us updated!

 

[zerokool]

looks like an output speed sensor from the trans.