1998 Ram 1500 Hesitation
#21
10-17-2008, 02:02 PM
1998 Ram 1500 Hesitation
Dear 12341234 (long answer),
I own a 1999 ram van 1500 5.2 and have just cured the identical problem. A forum member named Curmudgeon had this problem on a 1996 Caravan 3.0 and he found a TSB to correct it. It is TSB 18-12-98 Mar 10, 1998. The TSB directs the replacement of the black/green sensor wire for the forward oxygen sensor. The repair kit gives you a new wire with appropriate pins and sockets for insertion in the PCM and O2 sensor plugs.
I bought the kit to see what the wire was like but ended up making a somewhat different repair to the full size Ram Van 5.2 because the color codes are different. On our 5.2 the forward O2 sensor wire is tan/yellow and the rear is the black/green.
The problem is simply that the O2 sensor signal is a low voltage, high source resistance signal and for this to reach the PCM accurately the wire must have excellent insulation resistance. Chrysler used regular engine harness wire and its hot insulation resistance is not quite up to the hot location near the cat converter, particularly as the wire insulation ages , the connectors become dirty and the aluminized heat shield placed over the wires corrodes or becomes dirty.
To really make the problem severe the same cable bundle carries 12 Volt power to the O2 sensor and minute electrical leakage between these wires and the O2 signal wires fools the PCM into thinking the engine is rich so the PCM leans the injectors until the engine stumbles. This was a big problem for us when towing and going uphill. Here the wires also get hot like during a hot soak and the motor would go lean and misfire as if the ignition or fuel systems were in trouble.
To make our repair:
1. I purchased some TFE Teflon clear tubing just large enough to slip over the pins of the O2 sensor connector.
2. I disassembled and cleaned all the sensor connectors.
3. Installed about 18" of the new Teflon tubing over the old wire insulation.
4. Replaced the pins into the connector making sure the Teflon slipped into the silicone rubber seals.
5. Reconnected the sensors.
6. Purchased NAPA foil/fiberglass insulation tape over the bundles in place of the deteriorated ones.
Car now runs really well, much better than ever before and gas mileage is improved. Driveability is perfect and the hot start hesitation is gone.
There are many ways this repair could be performed but the overall solution is to prevent crosstalk between the O2 sensor and signal ground wires and the 12 volt O2 sensor heater leads. I removed the harness from the car to do this repair but this may be an excessive amount of work and risk of secondary damage.
Tom
I own a 1999 ram van 1500 5.2 and have just cured the identical problem. A forum member named Curmudgeon had this problem on a 1996 Caravan 3.0 and he found a TSB to correct it. It is TSB 18-12-98 Mar 10, 1998. The TSB directs the replacement of the black/green sensor wire for the forward oxygen sensor. The repair kit gives you a new wire with appropriate pins and sockets for insertion in the PCM and O2 sensor plugs.
I bought the kit to see what the wire was like but ended up making a somewhat different repair to the full size Ram Van 5.2 because the color codes are different. On our 5.2 the forward O2 sensor wire is tan/yellow and the rear is the black/green.
The problem is simply that the O2 sensor signal is a low voltage, high source resistance signal and for this to reach the PCM accurately the wire must have excellent insulation resistance. Chrysler used regular engine harness wire and its hot insulation resistance is not quite up to the hot location near the cat converter, particularly as the wire insulation ages , the connectors become dirty and the aluminized heat shield placed over the wires corrodes or becomes dirty.
To really make the problem severe the same cable bundle carries 12 Volt power to the O2 sensor and minute electrical leakage between these wires and the O2 signal wires fools the PCM into thinking the engine is rich so the PCM leans the injectors until the engine stumbles. This was a big problem for us when towing and going uphill. Here the wires also get hot like during a hot soak and the motor would go lean and misfire as if the ignition or fuel systems were in trouble.
To make our repair:
1. I purchased some TFE Teflon clear tubing just large enough to slip over the pins of the O2 sensor connector.
2. I disassembled and cleaned all the sensor connectors.
3. Installed about 18" of the new Teflon tubing over the old wire insulation.
4. Replaced the pins into the connector making sure the Teflon slipped into the silicone rubber seals.
5. Reconnected the sensors.
6. Purchased NAPA foil/fiberglass insulation tape over the bundles in place of the deteriorated ones.
Car now runs really well, much better than ever before and gas mileage is improved. Driveability is perfect and the hot start hesitation is gone.
There are many ways this repair could be performed but the overall solution is to prevent crosstalk between the O2 sensor and signal ground wires and the 12 volt O2 sensor heater leads. I removed the harness from the car to do this repair but this may be an excessive amount of work and risk of secondary damage.
Tom
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