Persistent Engine Missing

[BrooklynBay]

That's odd since both parts sites show a part with a price.

 

[Aeroguy]

That's odd since both parts sites show a part with a price.

Yes, it also means that I would have to purchase an entire PCM if the ICM was causing trouble.

I checked the I/M monitors... the Catalyst Monitor is the only one coming up incomplete. I know what it does, but where is this located? Is it part of the PCM as well? Could an exhaust leak cause this problem?

 

[BrooklynBay]

Which part are you referring to when you say the catalyst monitor? Is it the O2 sensor or the DPFE?

 

[Aeroguy]

The scanner is telling me the catalyst monitor test is incomplete. Looking at the PCED manual, it's part of the PCM's software to monitor the effectiveness of the catalytic converter. In order to complete the drive cycle for this test, I must:

Start the engine and drive the vehicle for 25 minutes.

• Drive in stop-and-go traffic for 20 minutes, include six different constant speeds between 40 and 72 km/h (25 and 45 mph).
• Drive on expressway or highway for an additional 5 minutes.

Out of all the driving I've done, I'm not quite positive that I completed this exactly as stated. I guess I'm going to try again tonight.

 

[Aeroman59]

Here is the conditions for catalyst monitor entry conditions, from Ford 1996 OBD system operation summmary. Note the vehicle speed change condition only 1mph /2secs.
Malfunction (CEL) takes 3 drive cycles,
I hope you dont have a cat problem you say there is plenty of power!

TYPICAL STEADY STATE CATALYST MONITOR ENTRY CONDITIONS:
Entry condition Minimum Maximum
Engine RPM 1,000 2,100
Engine Coolant Temp 190 oF
Intake Air Temp 20 oF 180 oF
Engine Load 15% 40%
Throttle Position Part Throttle Part Throttle
Time since entering closed loop fuel 30 sec
Vehicle Speed 37 mph 62 mph
Vehicle Speed Change 1mph / 2 sec
Engine RPM Change 500 rpm / sec
Engine Load Change 15% / 1 sec

 

[Aeroman59]

Yes, it also means that I would have to purchase an entire PCM if the ICM was causing trouble.

I checked the I/M monitors... the Catalyst Monitor is the only one coming up incomplete. I know what it does, but where is this located? Is it part of the PCM as well? Could an exhaust leak cause this problem?

I would try to find out why you are not getting any signals from the o2 & VSS, they are both essential for normal engine/transmission control.


The catalyst monitor is performed by the PCM via the O2 sensors. What it does is monitor the waveforms of the front & rear o2 sensors during steady state closed loop fuel controlled engine operation. Because of oxygen reduction within the catalyst bed (in the CAT converter), the rear o2 sensor has a 'flattened waveform' which is what the PCM looks at. When this waveform approaches that of the front o2 sensor, the cel is set. Telling you that the converter efficiency is below state regulated emissions standards. However it cannot complete the tests unless all sensors relative to the test are functional. Not only o2 sensors are needed to complete the test, there are several others which is why you need to get the codes of any malfunctioning sensors & possibly why the catalyst test will not complete.

If the cat is badly plugged up, it will feel very underpowered & will have problems gettiing up through the gears. It will also drastically reduce engine vacuum & air flow from the exhaust will feel very feeble. I dont think it will cause your misfire problem though.

 

[Aeroguy]

Solved

I didn't have any time to deal with it last week, but I ordered a fuel pressure tester Friday and was awaiting it's arrival yesterday when I decided to take another look at the plugs. When I brought the van in to the shop, they had put new plugs in, and since the problem was the same as before, I never had any concern that the plugs were at fault. Upon pulling the rear driver's side plug, I knew there was something wrong... it was tight the whole way out as if there was carbon build-up on the threads. Sure enough, there was... and a nice crack in the insulator. I also noticed the plugs weren't the same as the ones I put in... a different part number. I replaced all six plugs and it started right up. I've been driving it since yesterday and it runs 100% perfectly.

Thanks for the help!

I would try to find out why you are not getting any signals from the o2 & VSS, they are both essential for normal engine/transmission control.

I found out from Actron last week that some '97 Fords don't properly output these results.

 

[BrooklynBay]

Thanks for the update! What brand are the old & new plugs?

 

[whynotthinkwhyno]

Looking at that cracked insulator, I'm surprised it wasn't running hotter than usually. Cracked plugs generally cause hot spots in the heads which also affects the way the engine runs.

I'm having the same problem with my 97. I just haven't gotten around to checking the plugs. I thought it was an intake manifold or head gasket leak, but since the plug wires are lifetime and plugs are the best way to tell what's going on inside an engine- I would've checked those first.