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Old 09-05-2012, 10:06 PM   #1
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Default 1993 cadillac eldorado misfire

1993 Eldorado Misfire

Alright folks here we go. 1993 Cadillac Eldorado with the 4.9l non N* engine in it. Just got done swapping motors a week or two ago and finally got tags so I can drive it. I noticed in my leak checking and letting the car idle and warm up that there was a bit of a shake. Assumed that since the motor hadn't been run for quite a while and is on a different PCM that it may be just learning itself or needed to actually get run up to temp.

Turns out, the minor shake gets worse and turned into a noticeable misfire. I don't feel it very bad when I am accelerating slowly or cruising without the TC engaged but when the TC engages at around 25-30 and the engine is in a lot of torque (1100-1300 RPMs) the misfire becomes pretty violent. It seems like it is almost phantom as sometimes it will run seemingly without the miss, others it will be violent.

I bought the engine out of another eldorado but it was a 1991? I think. It was your standard 4.9L with everything being the same. The only difference was the wiring harness for the injectors was incorrect. In my car the wiring ran for all the injectors into a ten pin plug. In the New motor the wiring ran two separate harnesses for front and back bank with the rear bank containing another sensor. So long story short I just pulled both harnesses and switched them. Worked out great.

It has brand new plugs. Wires look great. (I know I should test them or just replace them, but money and time is tight)

EDIT: Update: I pulled the Rotor, coil, and cap from the old motor (they were replaced soon before the other engine died so they're like new) Seems slightly at idle but still missing under load. EDIT2: Update2: I replaced the plug wires now. Still the same. List of new parts. Plugs, wires, cap, rotor, coil, oil pressure sensor, thermostat, coolant, oil, seafoamed engine, etc. (these are all new parts that I've replaced since swapping engines) Also went out to get it up to speed (55) brought it down to 30 and gave it some gas. Seems quite underpowered.

I have the diagnostics from the car. No Check engine codes. I did pull the PCM data though. This is after full warm up driving then at idle took these numbers.

Things that look weird to me: Intake Air temp? Front o2 cross counts. Power steering - I have full power steering,

pd01 .9 TPS (Throttle Position Sensor) in degrees

pd02 38-39 Manifold Absolute Pressure Sensor in Kilo Pascals (kPa)

pd03 102 Barometric Pressure in kPa

pd04 103 Engine Coolant Temperature (ECT) sensor in degrees Celsius

pd05 100 Intake Air Temperature (IAT) sensor in degrees Celsius

pd08 21-24 Spark Advance in degrees Before Top Dead Center (BTDC)

pd10 13.2 Fuel Pump Feedback Voltage (battery voltage)

pd11 625-675 Engine Speed in revolutions per minute (rpm)

pd12 0 Vehicle Speed in miles per hour (mph)

pd19 0 Power Steering Sensor (kPa)

pd30 4.2-4.3 Front Bank Injector Pulse Width in milliseconds (ms)

pd31 4.2-4.3 Rear Bank Injector Pulse Width in milliseconds (ms)

pd32 .58 Front Oxygen Sensor Voltage

pd33 .48 Rear Oxygen Sensor Voltage

pd34 0 Front Oxygen Sensor Cross Counts (per second)

pd35 2-4Rear Oxygen Sensor Cross Counts (per second)

pd36 128 Front Short Term Fuel Trim

pd37 128 Rear Short Term Fuel Trim

pd38 124 Front Long Term Fuel Trim

pd39 124 Rear Long Term Fuel Trim

pd70 19 Cruise Control Feedback (percent)

pd71 11 Transaxle Pressure Switch (PRNDL Code)

pd72 00 Transaxle Input Speed in rpm (PRNDL P/N Sw)

pd98 30 Ignition Cycles (key cycles on/off)

pd99 1506 PROM Calibration-Engine
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Old 09-06-2012, 07:42 AM   #2
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how long has the fuel been in it and the fuel filter?
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Old 09-06-2012, 07:26 PM   #3
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Car was put away 2.5 years ago with basically empty tank

I put 10 gallons of fresh premium in before starting.

Fuel filter hasn't been changed. I'm thinking on getting a fuel pressure tester tonight and seeing what the numbers are. It doesn't bog down like its not getting gas though. Just misses seemingly on 1 or 2 cylinders.
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Old 09-06-2012, 08:23 PM   #4
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low fuel pressure from a clogged filter can cause a miss. after that i dont know much about your engine but it must have a crank sensor of some sort i would try that if you have one from the other engine. unless its like the truck tbi'* that have the module in the dist, then that same purpose
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Old 09-06-2012, 08:27 PM   #5
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2.5 years of sitting? I'd dump a whole can of seafoam in the tank, half a can in the intake and the other half into the oil. Then go do some italian burnouts.
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Old 09-06-2012, 08:33 PM   #6
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The car sat for 2.5 years before me swapping the engine. I've ran a half can in the tank and half through the brake boost line through the intake. Didn't help too much. Its a distributor ignition system and I replaced the icm as well. Put née AC delco plugs in. Replacing brand new autolites as I've heard that engine is super picky at times. Seems slightly better.

I'll pick up a fuel filter tonight. I'm thinking on pulling the injectors tonight and doing a spray pattern test. Make sure they're all in good shape. I have an extra set from the old motor that I can swap if I need to.

Any other ideas?
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