When I've had a miss like you have, it was a spark plug on one car, and a spark plug wire on the other. Running 93 is a waste of money, unless you can hear pinging on regulart. Check for dragging brakes, as the evap code won't cause your problem. Does trans shift into 4th, and does torque converter lockout take place?

 

Yes the trans is shifting through all gears correctly and the TCC is locking. I haven't though of checking for brake drag. I'll do that first thing in the morning. Thanks for the idea marvinstockman!

 

I'd clean the throttle body just as Good Practice, especially if equipped with EGR. Then, check for a linear TPS signal. (low voltage to high voltage as the throttle is slowly opened...no sudden 'jumps')




Last resort? You may have the beginnings of crank or cam sensor failure, or the air gap is wrong (if they have been replaced previously). I don't know how to check that on a running car (usually the sensors totally fail, resulting in a No Start).




++++++++++


At 85 MPH, a car-top carrier is going to cut mileage because of wind resistance, no matter how much weight you take out. (Verified by Consumer Reports testing)

 

I'd clean the throttle body just as Good Practice, especially if equipped with EGR. Then, check for a linear TPS signal. (low voltage to high voltage as the throttle is slowly opened...no sudden 'jumps')

Spraying throttle body cleaner into the intake (duct removed) while accelerating through the throttle range (idle to WOT) did the trick. I'm not sure exactly what component got cleaned (I would say mass air flow sensor on a MAF equipped engine) but these induction systems don't have a MAF?

Thanks for all the ideas everyone!

 

You mentioned the "Auto Store scanner"
Do you know that you can pull the codes with the ignition key? Referred to as the key dance.
I can turn my ignition on - off - on - off - on (without cranking the starter) and the the codes will read out on the LED screen where the odometer is. They will keep showing one at a time until it read END (or is it DONE) I write them down and then go in the house a google them.

Troubleshooting an intermittent misfire can be challenging. Crossfire or short is also a challenge. I can usually see signs of ignition wire leakage as a obvious burn arc spot, but also as a whitish gray almost powder that I think is attracted to the corona of the high voltage going through the wires. Visual inspection is my first thought. If I see any of that and the finance Gods are smiling at the time, I just change out with a good set of ignition wires. If dollars are tight I prefer isolation over insulation, meaning I try to position the wires in the loom so they are not touching anything grounded metal conductive or each other.
If I get lucky to get a code that points to a particular cylinder it makes it much easier. Swap a plug, wire or injector and see if the code follows to the new cylinder. Compression check on suspect cylinder.
Cheers!
Let us know what you find and if you get her fixed, tell us about your magic!

 

Take a spray bottle filled with water, wait till it gets dark, and spray in wires. If you see arching you've found your problem.

There is a sensor in the intake plenum that is something like a MAF, but I'm having a senior moment and can't think of the name. Anyway, they sell special cleaner for these sensors. Go to parts store and ask, as it's probably milder than carb cleaner, which is good to clean the throttle body plate.

An OBDII tester can tell you if you have any pending codes. Torque app and bluetooth adapter (amazon).

 

...There is a sensor in the intake plenum that is something like a MAF, but I'm having a senior moment and can't think of the name...

It is the MAP sensor (Manifold Absolute Pressure Sensor).

 

MAP sensors are just vacuum sensors (air pressure sensors) and do not need to be cleaned. These vans use speed density fuel injection systems so no Mass AirFlow Sensors (MAF) that need cleaning.

I also have an intermittent hiccup that's literally one cylinder missing one time every 5-30-300 seconds or so. It's totally random. I replaced a cracked ignition coil (on the bottom), replaced the fuel injector wiring harness (01-04 vans had it routed it around the driver's side right over the exhaust and it has a 50/50 chance of melting), and plugs/wires twice. I'm wondering if it's the plug wires touching something on the back of the motor. It's never set a code and probably won't, but it's occasionally annoying.

 

My wife's '06 had a hiccup similar to this where it was rather random. I replaced all the plugs and then romped on the vehicle for about 20 minutes (Took the average MPG down from 19 to 12 on a fresh tank) and since then it's been gone. The old plugs were NASTY. (Van has 210K on it, and no records from the PO about the plugs ever having been changed). I've never been able to light up the tires on a 3.3 T&C but I got that to happen when I was beating on it just to make sure everything that might have fallen into the engine when I did the plugs were out.

 

Joel,
How about sending the injectors out for an off vehicle cleaning and flow verification test? That is the FI equivalent to rebuilding the carburetors.

I chased a rough idle, performing all the steps you mentioned. Eventually inspecting my harness, installing heat tape and a slight reroute.
By that time I had already learned about getting to the harness, I was confident to remove the plenum and pull the injectors.

Three choices and snake oil or hoeky service offered at Kemco Tire is not mentioned:

A) remove the injectors and mail them out, about a week return service unless you can find a FI cleaning service nearby for drop off/pick up.
B) purchase a set that has already been cleaned and flow checked off eBay or Amazon. Make sure you get the Chrysler/Siemans (black with gray ID band)(match p/n)
C) you could pull a set out of the salvage yard and send them out for test and tune. Then R&R when they come back.

My local yard "Snake Road Auto Salvage" he wanted a hundred for the set (that was crazy as I could get a set on eBay that was already cleaned for that including s&h). I left them behind and returned the next day with a few eBay printouts and the printout for the cleaning service I was going to send them to. He settled for $30.

DO NOT get the green clones from the Far East (even if you bought them in the West), they are junk. They'll work great for a while, but you may soon have regrets, especially after you threw the originals away. Reports of them cracking, crumbling when trying to remove the green ones, and intermittent misfire after 30+ k miles.

 

Solved

The intermittent miss at steady speed/partial throttle (actually more of a very momentary hesitation) finally got bad enough to cause erratic idle along with even worse intermittent hesitation at part throttle. Additional malfunction codes appeared later also (see list below) I found the cause and fixed it today - EGR control valve. Replacing the control valve cured the problem. I also replaced the EGR valve because I imagine the effects of leaking long-term may have degraded the sealing ability of the pintel on the seat. It's running very smooth now at idle as well as partial throttle. WOT was never affected which is why I suspected this was not an ignition related issue.
For future reference my PCM malfunction codes before repair were as follows.
P1684 Battery Disconnected Within Last 50 Starts
P0172 System too Rich (Bank 1)
P0442 Evaporative Emission Control System Leak Detected (small leak)
P0455 Evaporative Emission Control System Leak Detected (gross leak)

Thanks for all the input from everyone!!!

 

Mike, When you replaced the EGR valve, one thing is a MUST DO. Get a shopvac and suck out both ends that the EGR valve attaches to and verify the tube from the EGR to the top of the engine is squeaky clean. If the soot is packed in the engine port, a flat blade screw drive works best to scrap it clean.

Why do I say this? I once changed an EGR on a 3.8L. Thought that was easy and a quick task. 3 weeks later, that one went bad. Did a search on the web, found a few people mentioning about carbon soot that is packed inside the engine block hole and the metal pipe going to the top of the engine. These will clog up even a 'new' EGR valve in a short time.

MM

 

Since the control valve itself was the culprit, I hope this won't apply but I'll check for 'soot' to be sure the tube and ports are clear. Thanks Mopar-Mofun!

 

thanks for giving input for your cure mike5. question though because i may have similar problem. you said " EGR control valve. Replacing the control valve cured the problem. I also replaced the EGR valve "

i know what the egr valve is but you said you also replaced "control valve". what is that and where is it located?

Mo par mofun also thanks for the info. on using shop vac, sounds more then reasonable.

 

Mike--when you said control valve.....I was just thinking is that the same thing as the IAC (idle air control valve) if so I was thinking IAC was just for idle speed not at 45 miles per hour misses. Is that correct.

someone educate me. thanks.

 

The IAC on our 4th-gen vans is part of the TB.

And this is how the IAC works at various speeds. When your foot is on the pedal, the IAC is basically off. When you release your foot off the pedal to coast, the rpms will drop, but to prevent stalling ... the IAC kicks in. Because no foot on the pedal is having the engine go to idle.

The IAC is just a linear solenoid with a return spring. IF there is carbon build-up or the spring got kinked or both, that 45mph could be at the sweet spot for your troubles. On the older vans and the Magnum V6/V8 engines, the IAC itself was very serviceable and easy to swap out. The ports are easy to clean out with carb cleaner and q-tips. When the IAC was removed, you could verify if any carbon had build-up or the spring aged and kinked. If only carbon on those, cleaner worked really good.

Getting the TB/IAC/TPS all working right on these vans makes all the difference. Then the troubleshooting can determine the real culprit otherwise. Like the computer and shift sequence around 45mph on a slow and steady pedal climb.

 

FabricGator, I've sent a junkyard set of injectors in for servicing. Witchhunter Performance is who I used, great to deal with, though injector servicing is very simple, the value is in the test equipment to properly pulse and flow test the injectors in a safe environment, so anybody with that equipment can do a great job.

What I don't know is how much benefit you get from this off-vehicle service versus just running several tanks of gas with injector cleaner through the vehicle. I've done tuning of another manufacturer's vehicles and knowing the the injectors were working right at the outset was CRITICAL to not wasting your time while tuning. For that purpose, having an established flow baseline was well worth the money for off-vehicle injector servicing. These injectors are ethanol-tolerant but the other vehicles I had used injectors that weren't, and that was a big concern.

 

Cool, I will be curious to hear your report. I was pleasantly surprised when i got mine back from Mr Injector in Idaho, and the performance restoration exceeded my expectations. It is almost like a having a new car... with minor dents and scratches all around.

I have considered getting a machine. I counted and I have over 36 fuel injector that I am counting upon to get us there at any given day. Cars, boats, motorcycles. I get a great sense of satisfaction of having all my equipment snap start to running and idle smooth, so this may in fact be my missing link. Hmm, I have a friend who runs a local garage and used auto sales. Perhaps I encourage him to make the investment and I can just use his stuff on the weekend.:biggrin:

I like the idea of having a junkyard set, I have an extra set for mine. It is great if you can get them for the right price.

 

One other add on TB/IAC/TPS - very often the manufacturer design INCLUDES throttle body air leaks or small drill holes as the base idle air, and then the IAC adds to that. Which is fine until those leaks clog. Then the idle speed becomes totally dependent upon the IAC for air, which makes the idle over-respond to the slightest IAC change. Cleaning the throttle body fixes this and restores original operation.

 

Thanks for the info. MOPAR fun. You said "IF there is carbon build-up or the spring got kinked or both, that 45mph could be at the sweet spot for your troubles." But you also said the IAC kicks in when foot is off the pedal.

So since the IAC kicks in only during idle, then how can the IAC be the potential issue for intermittent miss at steady 45 mph speed (more often going up a bridge) with foot on the pedal at 45mph. Please help me reconcile what your saying or what I am misunderstanding what you said.

thanks again.