Check engine light mystery - Diesel Forum - TheDieselStop.com
Power Strokes 1994-1997 General Technical discussion of topics related to vehicles powered by the Power Stroke engine in 1994 through 1997 models.

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post #1 of 16 (permalink) Old 04-26-2018, 03:17 PM Thread Starter
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Check engine light mystery

I have a check engine light mystery. This is a 1996 7.3 with about 220k on the odometer.

When first started on cool mornings (45 50 degrees), after about a half-mile of driving, the check engine light comes on and the engine runs very rough. This lasts for about 20 seconds, and then the light goes off and the engine runs fine. The rest of the day its fine. On a recent warm morning (60+ degrees), the light came on at exactly the same spot away from the house but the engine ran fine.

I would describe the rough running as similar to an old breaker-point ignition with a bad condenser. Loss of power and lots of sputtering.

I thought this might be temperature related so I threw an oil temp sensor in it (OEM) as they are cheap and easy to do. After that was the warm morning when I got the light but no performance issues.

There are no problems later in the day.

My regular mechanic could not find any codes, so I took it to someone who specializes in Powerstrokes and has a code reader that should pick up Ford codes, and he did not get any codes either. I should add that this second check was done after two more incidents, so any chance that the first code reader cancelled the codes should not be an issue.

Since this only happens on cold-engine startups, I still think its temperature related.

Finally, Horrible Fright Tools has a cheapo code reader for about $50. If I kept one of those hooked up, do you think it would show a code during another episode?

Any ideas? THANKS!

96 F250 2x4 x-cab, E4OD, 4.10, broken US Gear e-brake, ugly red & white paint, missing a hubcap, needs shocks and a good bath.
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post #2 of 16 (permalink) Old 04-26-2018, 04:45 PM
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If the check engine light came on it will store a code that can be retrieved.

And no that Harbor Freight code reader will not be able to read the code.

If you want to do it yourself on the cheap check into ForScan. It is a free program that you can run on a laptop. Then all you need to purchase is a cord to connect into the OBD II port or a bluetooth connector if your laptop will accept it. I prefer the cord that I got off of Amazon.




96 F250 PS XLT 4X4 long box, 5sp,4.10, manual hubs,pyro+boost guages, Dark Toumaline, add a leaf, Dale's TYMAR, and HX hose, downpipe, coolant filter, Luk clutch
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post #3 of 16 (permalink) Old 04-26-2018, 08:11 PM Thread Starter
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Thanks, Bugman. But the Ford specialty shop can't pull a code with their reader that reads Ford codes. I'll try ForScan.

96 F250 2x4 x-cab, E4OD, 4.10, broken US Gear e-brake, ugly red & white paint, missing a hubcap, needs shocks and a good bath.
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post #4 of 16 (permalink) Old 04-26-2018, 09:18 PM
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The only other thing that I could think of would be a faulty dash light that is grounding out and lighting it up.

96 F250 PS XLT 4X4 long box, 5sp,4.10, manual hubs,pyro+boost guages, Dark Toumaline, add a leaf, Dale's TYMAR, and HX hose, downpipe, coolant filter, Luk clutch
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post #5 of 16 (permalink) Old 04-26-2018, 09:31 PM Thread Starter
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Quote:
Originally Posted by bugman View Post
The only other thing that I could think of would be a faulty dash light that is grounding out and lighting it up.
But that wouldn't explain the rough running.

Is there any possibility that a coolant temp sensor is bad? Would that cause this?

96 F250 2x4 x-cab, E4OD, 4.10, broken US Gear e-brake, ugly red & white paint, missing a hubcap, needs shocks and a good bath.
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post #6 of 16 (permalink) Old 04-26-2018, 10:17 PM
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The coolant temperature wouldn't have anything to do with it since it isn't monitored by the PCM.

It could be a wiring harness going to the injectors or the pass through connectors on the valve cover gaskets. The connectors have a bad habit of getting burnt and shorting out. You can unplug the connectors on the valve covers and inspect them or if it is running bad and you are in a location where you can unplug them one at a time you might find the bad side. If the engine is running and you unplug a connector and it doesn't change then that is the side that I would do some good inspecting on.

There are also some test that you can do from the IDM connector if you are handy with a volt/ohm meter. The test will measure the resistance from the connector to the injectors and if there is a problem with the valve cover connectors you should see it.

Here is the bulletin that has that test.
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File Type: pdf GB_Tech_Bulletin_103_Ford IDM_Module_Replacement.pdf (710.5 KB, 17 views)

96 F250 PS XLT 4X4 long box, 5sp,4.10, manual hubs,pyro+boost guages, Dark Toumaline, add a leaf, Dale's TYMAR, and HX hose, downpipe, coolant filter, Luk clutch
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post #7 of 16 (permalink) Old 04-26-2018, 11:32 PM Thread Starter
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Thanks, Bugman. The glowplugs and undercover wiring were just replaced with OEM goods, but that doesn't mean the connections are OK or that the external harness is good. Unfortunately, catching it when misfiring will be a challenge as the misfire only lasts about 20 to 30 seconds.

That's a great bulletin. THANKS for putting it up. I have a good quality VOM and will follow through on that. The shop that has the truck now is a Powerstroke speciality place; the owner used to be an instructor for Ford. He says he can't get a code. He's going to try to replicate the problem in the morning when it's cooler. If he can't get something and the wiring from the IDM checks OK, I may have to resort to the dealer (Ugh. I just hope there's an old-timer working there and that they still have the proper code reader!).

96 F250 2x4 x-cab, E4OD, 4.10, broken US Gear e-brake, ugly red & white paint, missing a hubcap, needs shocks and a good bath.
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post #8 of 16 (permalink) Old 04-27-2018, 06:36 AM
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If it is a Powerstroke specialty shop and there are PSDs in the parking area and on the lifts then their code reader should pull codes.

There should be no need to take it to Ford.

Do you have an EOT gauge installed?

Did this happen before the installation of GP and harness?


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2002 F-250 4x4 CC SB 7.3 PSD w/4R100. 182,000 miles.
NOS Black CPS. ScanGauge-II, AIC, Bilstein 5100, Stancor GPR, Marinco Mod, B&W Turnover Ball, Michelin Defender LTX


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2002 F-250 4x4 SC LB 7.3 PSD w/ZF-6. 177,000 miles.
NOS Black CPS. ScanGauge-II. Bilstein 5100. Stancor GPR. Walker BTM. Noco Mod. Michelin Defender LTX 285/75/16.

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2000 F-250 4x4 SC SB 7.3 PSD w/4R100. 164,000 miles.
NOS Black CPS. Rebuilt Fuel bowl w/gold spring, 6.0 Cooler, Walker BTM, Stancor GPR, Michelin LTX M&S2.
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post #9 of 16 (permalink) Old 04-27-2018, 08:07 AM
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It could be like my shop as well just have 1 diesel mechanic which is myself and the rest is gas engines mechanics they don't touch the diesels i do
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post #10 of 16 (permalink) Old 04-28-2018, 05:55 AM
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Check your oil level. Very low cold oil will do that. Don't ask how I know.
AaronSEIA

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97 F250 4 door shortbed, E4OD
DIY intake
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post #11 of 16 (permalink) Old 05-16-2018, 09:45 PM Thread Starter
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Thanks everyone. Here's an update:
The independent diesel shop pulled a P1668 code, which is an IDM-PCM communication code, but the problem remains intermittent. As I wrote in the o.p., it's only just after startup in the morning. The rest of the day it's OK. I was headed into town just recently and it happened again, check engine light and very rough missing. I was just blocks from the shop so I got it in there. The tech grabbed his computer and as soon as he started the computer, the engine quit acting up and ran fine. (Perhaps it was afraid of him :-) ) He could't get any codes, and all the diagnostics checked out OK.

So the current theory is sticky injectors. That seems like a possibility considering the symptoms. I'll run a couple of bottles of Stanadyne injector cleaner through it and see what happens. And I'll make the Stanadyne fuel treatment a regular feature of this truck's diet. Only time will tell if that's the answer.

ArcticDriver: Yes, it did happen before the GP replacement, and no I don't have an EOT gauge, but I did replace the sensor.

Thanks again to everyone who contributed.

96 F250 2x4 x-cab, E4OD, 4.10, broken US Gear e-brake, ugly red & white paint, missing a hubcap, needs shocks and a good bath.
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post #12 of 16 (permalink) Old 05-17-2018, 06:11 AM
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Quoted from a different thread:

Quote:
Originally Posted by SmokeyWren View Post
DTC= P1668
Circuit = PCM/IDM
Condition = PCM/IDM diag. communication error
Probable causes: Open/shorted EF or FDCS wire, open IDM grd.

Hmmmmm. Nope, doesn't mean anything to me. But I suspect you need a scanner/diag tool that can also read the IDM codes. IDM = injector driver module, so if the IDM cannot talk to the PCM, the truck is not going to run.

Usually when you have a code that includes something about the IDM, all it means is that the under valve cover (UVC) clips need replacing. That's a cheap fix that I'd try first. The part number for the UVC retainer clips is 2C3Z-14A163-AB, and it cost only a few bucks for the three clips in the pkg.


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2002 F-250 4x4 CC SB 7.3 PSD w/4R100. 182,000 miles.
NOS Black CPS. ScanGauge-II, AIC, Bilstein 5100, Stancor GPR, Marinco Mod, B&W Turnover Ball, Michelin Defender LTX


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2002 F-250 4x4 SC LB 7.3 PSD w/ZF-6. 177,000 miles.
NOS Black CPS. ScanGauge-II. Bilstein 5100. Stancor GPR. Walker BTM. Noco Mod. Michelin Defender LTX 285/75/16.

SOLD:
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NOS Black CPS. Rebuilt Fuel bowl w/gold spring, 6.0 Cooler, Walker BTM, Stancor GPR, Michelin LTX M&S2.
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post #13 of 16 (permalink) Old 08-25-2019, 07:35 AM
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Wondering if you resolved the problem. My 96 is doing almost the same thing.

Black 1996 F-250 7.3L E4OD Crew Cab SB 2WD
Line-x coated fiberglass bed cover
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post #14 of 16 (permalink) Old 08-25-2019, 10:29 AM
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If you do have the P1668 code, I've attached the pinpoint tests for that. You'll need the wiring diagrams and connector pinouts from the EVTM (Electrical and Vacuum Troubleshooting Manual). The tests mention connecting a breakout box and unfortunately most folks don't have one (like me). Where it mentions to connect the breakout box but leave the PCM disconnected, you can probe from the specified PCM Connector pin to the other specified test point. Where it mentions to have the PCM connected to the breakout box, you would have the PCM connected to the truck's wiring harness and would have to probe the appropriate pin through the back of the PCM connector (or through the wiring insulation not recommended). In any case, the tests along with wiring diagrams will give you an idea of what they are looking for in the tests. Cheers!
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File Type: pdf P1668 Pinpoint Tests.pdf (395.7 KB, 3 views)

97 F250 SC 4x4 (CA model), E4OD, 4.10 LS,
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post #15 of 16 (permalink) Old 08-25-2019, 01:06 PM
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I had a similar problem with my 95. At around 45 degrees and lower truck started fine but after 1/2 mile would run rough and die. Let it sit for a minute and it would start again, once warm it ran fine If I plugged it in before driving or let it warm up for 5 min it did not have the problem. I could not find anything wrong so took it to local Powerstroke shop guru. His advice was to change for 15w-45 to a lighter oil so I went to Rortilla 10w-30 and never saw the problem again. If you do a search this problem comes up every year or so no one has found the answer yet. If you are running 15w-40 try a lighter oil. let us know if it works.
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Early 1999 F350 AUTO 4x4 CC LB DRW 4.10 6.0 trans cooler, Front hitch, 2,000 hubs/ brakes, Bilstein shocks/steering stabilizer, Diesel site coolant filter 203 thermostat, EBV delete, new O-rings, new Oil cooler, RIFF RAFF FRX, Glow plug led, Pillar gauges, Lighted cupholder, Painless wiring fuze block, Harpoon/hutch mods, Removed axle blocks. Air bags, 5 wheel hitch, In bed 7 pin plug. Spare tire key delete. KLHANSEN on speed dial. 75,000 as of May 2019
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