Lazy o2 sensor?

[Vilpo]

Ok, yeah the baro reading is just about correct 110kpa around here.
Thanks NAJ, that could be useful with this problem.

[Vilpo]

NAJ, can you post the "Rich exhaust condition" explanation here?
I replaced the o2 sensor and i put the car on scanner right away. The pulse looked much better right away, switched some quicker than the old one.
Economy was maybe 3 mpg better than before on highway. In city it still seems the same.. And long term fuel trim went to about -30% now. So i guess there is still something not right..

[NAJ]

Not exactly sure what you are looking for.If the O2 is crossing (twice in 8 seconds according to Chrysler) the system is operating normally.
Since you have a driveability concern (poor fuel mileage) without fault codes these are the tests Chrysler wants run in order to narrow down and isolate the cause.
Secondary Ignition and Timing,(including advance) (using a scope)
Fuel Pressure
Coolant and TPS Calibration
MAP Sensor Calibration
Idle Speed Motor Operation (Using the DRB2)
Park/Neutral Switch Input (Auto Trans)
Engine Controller Power and Ground Circuits
Engine Vacuum
Minimum Idle Air Flow
Engine Mechanical
I assume we are working on a 91 3.0L, what is a Saratoga?

[Vilpo]

Ok, thanks. The car is i think an european variation of Dodge Spirit, an AA-body?
One thing i was wondering about is that ignition timing, when i adjust it to 12 btdc, coolant sensor removed. When i reconnect the sensor, timing is about 23 degrees btdc at idle. I also checked it on scanner when i was driving, it went between 20 and 40 degrees btdc. Do those numbers sound normal?
I guess i will also check the powers and grounds for ecu, just incase.

[NAJ]

All I can find on spark advance is "does it advance with rpm?", if so it is ok.
If you follow Chryslers diagnostic sequence for a driveability concern without a fault code and find no problems they say replace the engine controller.
I would suggest that since you have a mpg concern and have been chasing this concern for quite a while that you follow Chryslers diagnostics in order so you do not miss anything.
Step one is to check ignition patterns using an oscilloscope. Basically they want to be sure the ignition system is capable of producing a minimum of 25 kv and that all cylinders are firing in the normal range 10-15 kv. A scope will give you indication of ignition problems(weak coil by looking at coil oscillations, open or shorted wires, resistance problems in the cap/rotor), rich/lean in a cylinder(s)(rich = lower than normal kv, lean = higher than normal kv) or high/low kv caused by a mechanical problem and can narrow down a problem thru the entire rpm range.
Here is the beginning of the "No Fault" Diagnostics. As you complete each let me know and i will post the next couple of tests.
I apologize for the poor image quality, my Son had this manual stored in his toolbox and it got damaged from moisture.

[NAJ]

Here is step 2, checking fuel pressure. The images are from a 92 3.0L MMC Powertrain Diagnostics manual so i am not sure if the fuel line connectors are identical to your 91.

[NAJ]

If some of these pages are not legible let me know which one(s) you need and I will print them out from Alldata and rescan.

[Vilpo]

Ok, thanks a lot!
I will start getting through these things, and let you know what i come up with. Though i'm not sure if i can get a scope to measure the ignition..

[NAJ]

Thats what happens when you use a manual that is 16 years old, scopes were the norm back in the day. I have not used one in about that long.
Purchase a spark tester. OTC, Thexton make them. The OTC looks like a spark plug with an alligator clip for grounding but it requires a minimun of 25 kv to fire. The Thexton is similar but has an adjustable range for kv. Both are less than $10.00.
Both will tell you if the ignition system is strong enough and they are great to have in the toolbox for those dreaded" no starts".

[Vilpo]

Ok, i can see they sell one here that goes between spark plug and the wire.. Would that do?
Could you post the "MAP calibrations" and the "Engine controller grounds" pages for me, i would appreciate that. Thanks.

[NAJ]

If you want to see pics go to Tooltopia.com and type in "spark tester" in the "search box".
You will see 1 made by lisle/thexton that are adjustable and 1 that looks like as spark plug made by K-D (also made by OTC).
The 1 that looks like a spark plug requires 25kv to fire, the adjustable testers will allow you to check the systems total output since you can adjust the kv.
I bought the OTC version on eBay for my son at Christmas, it was around $10.00 with shipping, it was new in package and a "buy it now".
There is 1 on eBay now for $6.00 + shipping. Type in Spark Tester and it is on page 2, the title/description reads "Best_Clip on Ignition Spark Tester".
When using these testers you are supposed to clip it to a good ground, I clip it to whatever is close to hold it in place and run a jumper wire from the clip to - batt.
I will post the pages you asked for.

[NAJ]

Voltage's are listed in a "sticky", "voltage tables" in the "engine management" section.

[Vilpo]

Ok, thanks a lot. I think i'll get a lot of diagnosing done with these..
Actually looking at that tooltopia page, i noticed that the one i found they sell here is simular to the INLINE-type spark testers they sell on tooltopia.

[NAJ]

I just do not know what type of voltage is required to fire the in-line testers.

[Vilpo]

Ok, well i try to find out if that's the only type of tester i can find here..