OBD2 Check engine light on for a few seconds then clearing and not storing.

Ok I have run into a new one on the Prowler that I am going through. Recently I did a full service, new fuel pump, new timing belt, battery, new plugs new everything. Car had been sitting for almost 4 years and it's very unhappy, these things are weird and parts are hard to come by but I got a deal about 10K under market for the condition because it was sitting and I like a challenge. 

When I got the car I found a bad fuel check valve and bad fuel pressure on cold start. New pump went in and car was happy. then I started getting a evap error which I tracked down to a bad elbow on the EVAP system.

Now I have a different problem. About 1-2 minutes into every drive the car will start to stall out like it has bad fuel or low fuel pressure,  check engine light comes on. Car will stall or keep running if I hit the gas and then be happy for 50 more miles or till I get home. It never happens twice in a single drive.

Every single time I get a CEL when it stalls or shakes but it clears up immediately after the engine gets back up to speed. So no code is stored so I can figure out what the heck is going on. 

This is not normal behavior right, I keep thinking its 12v dropping to the ECU, but I would not get a CEL when the power drops out. But only once and always a few minutes into a drive. I thought it was a bad ground which these cars are known for so I upgraded the ground cable, no change in behavior but much better idle when sitting at a light for some reason. 

I am stumped is there any tool or suggestion for how to proceed. FYI I think the ECU is keeping the smog checks in memory because it passed the OBD2 check out here in California and if it was dropping power that would be reset I think. 

I'd check 2 things first, misfire counter and O2's for proper switching and heating. After that, a dropping crank signal needs to be checked out.

You need to data log it. 

can't you connect an OBD2 bluetooth reader, and have a copilot check what happens while using torque app or something similar?

If the light comes on, it WILL store codes for at least that trip.

I had a Chevy that would do this, the CEL would come on for extreme misfire but there was no stored code. Ended up being a failing distributor on that one - plastic distributor was falling apart and causing the rotor to wobble.

Possible your code reader isn't full featured enough to catch it? I've got a cheap reader and a nicer one, and the nicer one routinely shows manufacturer specific codes that don't appear at all on the generic cheap reader. 

If the ECM was powering down, you actually might get a CEL when it comes back on depending on how they have the lamp check routine set up. If it lamp checks on power up, you'll briefly see the CEL just like when you key on. 

The fact that you had a notable change in operation by fixing the ground strap is pretty interesting to me and makes me think there's a high chance something else in the electrical system could be marginal. ECMs don't handle low voltage well, and in some cases ground noise spikes can knock them out or cause erroneous sensor readings. There's an SAE spec for this, I think it's something like 500mV peak to peak if you're reading with a scope. Might be worth checking ECM ground path and case grounding, if its externally grounded.

In reply to Ranger50 :

I was also thinking it could be an O2 sensor issue since 1-2mins into driving is just about enough time for O2 sensor warmup.

With an OBD2 reader on the car the code should be visible if you maintain power to the ECU after the problem occurs.

So I am hooking up a lead to the Ecu to confirm power is staying true to the box this weekend. I will also check the O2 sensor signals bu since the car runs just fine in closed loop mode and does not throw a code. 

I deliberately induced a code by venting the gas tank to atmosphere and it appears to hold that code with a restart so so my guess is the ECU is still OK but still need to dig in. 

Also I am borrowing a logger OBD2 setup to test out and see if I need to buy one with that I should be able to capture data at the point of failure off the port as long as it is provided by the ECU. 

Sounds like a bad ECU or bad power/grounds to the ECU.  Considering it happens at 1-2 minutes in to the drive could also be some sensor that is reporting a weird out of range value as it runs through its range during warm up.  Could be something dumb like a bad solder joint that opens at a certain temp and then once something expands enough it closes back up or a sensor that is being ignored during warmup that is waking up too slowly.

I agree with the other folks that before parts cannon it needs to be logged, watch your values being reported to the ECU and make sure they always stay line line during this transitional period.

Could it be coolant temp sensor related?

Does the prowler have the ability to display codes through key cycling like other Mopar  products?

I know on my Jeep I was able to get codes from the dash display that weren't being read by my scanner (foxwell nt630) I had to cycle the key on-off-on-off-on (I think that's the right number of times), and then the dash readout displayed the codes. 

My 2007 Jeep GC  would intermittently cutout, usually on longer drives, sometimes stall and pick right up, or a few times it stumbled and ran rough, but almost always recovered on its own. What I found when looking at the data was that the PCM run time since last reset was always from the stumble, so no codes were stored. It was essentially acting like the PCM had lost the constant 12v. I tried bypassing the TIPM module with a lead from the battery to the 12v constant for the PCM with no change. I tried replacing the PCM, the TIPM, the BCM, and bypassing the TIPM, with no success. 

What I ended up finding was that the additional codes indicated a communication issue with the TCM. Further investigation found the issue is actually in the harness or connectors (not sure which). In my case I solved it by rerouting the PCM harness over the A/C lines instead of under. Im not sure if rerouting the harness changed the tension on the pins, or something else, but I went from stumbling after approx an hour, driving 180 mile from Mass to NYC without any recurrence. 

TL:DR - try to get the car to display codes on the dash in case there are ones present the scanner can't read (TVM, etc). 

So I have more info but its even more confusing. 

I noticed a drop in fuel pressure that corresponds on my gauges with the timing of the stalls, not a lot its like the needle is jumping down and back up. So I did a old trick where I cycled the key three time and let the pump run to pressure on startup. Zero stalls immediately after doing this.  Which makes absolutely no sense because I have pressure on startup and the car is not dropping pressure over 1-3 minutes sitting with the pump and car off after priming. It appears that the ECU is not loosing power and the CEL light is just the car saying it stalled, no codes are actually being stored. Which is so weird but this is a 1st generation ODB2 system and modified from another car to use in this one. 

Short answer right now I have zero codes, I have driven the car about 4 times with the key trick and it does not stall. If I don't cycle the pump I get a stall. I am a little lost not. Air bubble leaking in to the system and then getting to the injectors after sitting is the only thing I can think of. 

I also took some slack out of the wiring harness, apparently other people in Prowlers have seen similar issues and had that fix it. Also clean all the ECU pins and the grounds around the ECU just to be safe. 

Clogged fuel filter is the problem. So need to find one because they are NLA 

burning my infinite wisdom I took the car out today because the weather was nice. Motor overheated in my way home. In the tow truck now. 
 

No bad bearing noises and no check engine light so I caught it quick enough but zero coolant in the car. Apparently I hit something on the freeway and punched a hole in the bottom the of the radiator or in the lower nose hard to tell. Again NLA part.  
 

cursed I tell you. Most break downs and problems I have had in a car in decades after buying it. Luckily cheap to fix myself. 
 

car starts up happy as a clam 

For the fuel filter, I can only find a reference to this pickup sock:

https://www.summitracing.com/parts/mop-04897416ab/make/plymouth/model/prowler

If that's not it, bypassing the stock filter and installing a generic inline filter is always an option.

GameboyRMH said:

For the fuel filter, I can only find a reference to this pickup sock:

https://www.summitracing.com/parts/mop-04897416ab/make/plymouth/model/prowler

If that's not it, bypassing the stock filter and installing a generic inline filter is always an option.

I think I'd put in a generic/universal fit fuel pump from the parts store with readily available parts.

As long as you have the end caps intact, any rad shop can make you a new core.

Ranger50 said:

GameboyRMH said:

For the fuel filter, I can only find a reference to this pickup sock:

https://www.summitracing.com/parts/mop-04897416ab/make/plymouth/model/prowler

If that's not it, bypassing the stock filter and installing a generic inline filter is always an option.

I think I'd put in a generic/universal fit fuel pump from the parts store with readily available parts.

As long as you have the end caps intact, any rad shop can make you a new core.

Its going to get a new one with a bypass for sure. Apparently there is some "guy" in the midwest who repacks the originals for around 50$ and if he has quick turn around times then I may do that just to keep it as stock as possible and avoid any future California shenanigans.