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I've been driving an '86 Ranger, 2.9, EEC-IV, for a dozen years now. When I first got it, it had a blown motor so I put in an (honest) junkyard low-mile motor out of an '87, which worked fine. The truck would consistently pull 28mpg going down the highway at 70 with the AC blowing cold. Several years back, with 170K on the motor, I pulled it out and wound up rebuilding it--had the time, money, and place all at the same time. Rebuilt was done right, right parts, right machine shop. Events mostly beyond my control had the vehicle sitting for three years after that, without the engine being run any much. Once I got it back on the road, the fuel economy was a lot worse--21 on the highway. I've been driving it like that since, but lately the CEL is on, and I've got a Code 12 (idle out of adjustment), and the fuel economy has gotten worse. Engine has 50K max since rebuild.
Compression is dead even at 189psi across all six. No obvious vacuum leaks anywhere. Recent tuneup, incl. O2 sensor. Fuel injectors have been pulled --two replaced--and bench tested and all flow fine. CTS is within spec. Replaced MAP sensor. EGR functioning correctly.
There are a couple of things I'm thinking might be the problem. First is the evap system. I can't find any information on it. Vehicle is obviously running rich somehow, that'd be the first place I'd look. Replaced the in-tank fuel pump right when I put vehicle back on road, and believe I got all the plumbing there right. Maybe I didn't? Does anyone have information on the evap system, component locations, and tests?
Second is the exhaust system. With 300K on the cat, and with a prior problem of two bad injectors and a defective O2 sensor, I'd be surprised if the cat is working. Would it be clogged enough to cause the problem? There are also a couple of small holes in the headpipe between the Y-pipe and the cat, downstream of the O2 sensor. Are these causing the O2 sensor to read false? I'd replace it right off the bat except that after 22 years that's going to be a job for a muffler shop, and I'm figuring on replacing the cat anyway (be a good enviro) at the same time. Don't want to shove a new cat on to kill it right off the bat with a rich condition.
Third is there might be an internal coolant leak somewhere. I had a run of defective radiators--replaced 3 in 3 years, and a heater core again as well--dammit I change my antifreeze like I'm supposed to--but still am having to add coolant, maybe 1qt per 1000 miles. Is this a big enough coolant leak to cause my driveability problem? Should I bother to try and fix it first?
Fourth is is whether or not it makes sense to get a breakout box to try and figure out what is going on. I've got access to the right 60-pin unit, but damned if I can find anywhere information on what the pinouts are and what the circuit voltages are supposed to be during normal operation. Does anyone have that information, or should I bother?
I'm sort of stuck fixing this problem myself. Most nobody in town wants to jack with a vehicle this old, and all claim a lack of technician experience with EEC-IV. Any advice would be greatly appreciated.
Thanks--Dan White
Compression is dead even at 189psi across all six. No obvious vacuum leaks anywhere. Recent tuneup, incl. O2 sensor. Fuel injectors have been pulled --two replaced--and bench tested and all flow fine. CTS is within spec. Replaced MAP sensor. EGR functioning correctly.
There are a couple of things I'm thinking might be the problem. First is the evap system. I can't find any information on it. Vehicle is obviously running rich somehow, that'd be the first place I'd look. Replaced the in-tank fuel pump right when I put vehicle back on road, and believe I got all the plumbing there right. Maybe I didn't? Does anyone have information on the evap system, component locations, and tests?
Second is the exhaust system. With 300K on the cat, and with a prior problem of two bad injectors and a defective O2 sensor, I'd be surprised if the cat is working. Would it be clogged enough to cause the problem? There are also a couple of small holes in the headpipe between the Y-pipe and the cat, downstream of the O2 sensor. Are these causing the O2 sensor to read false? I'd replace it right off the bat except that after 22 years that's going to be a job for a muffler shop, and I'm figuring on replacing the cat anyway (be a good enviro) at the same time. Don't want to shove a new cat on to kill it right off the bat with a rich condition.
Third is there might be an internal coolant leak somewhere. I had a run of defective radiators--replaced 3 in 3 years, and a heater core again as well--dammit I change my antifreeze like I'm supposed to--but still am having to add coolant, maybe 1qt per 1000 miles. Is this a big enough coolant leak to cause my driveability problem? Should I bother to try and fix it first?
Fourth is is whether or not it makes sense to get a breakout box to try and figure out what is going on. I've got access to the right 60-pin unit, but damned if I can find anywhere information on what the pinouts are and what the circuit voltages are supposed to be during normal operation. Does anyone have that information, or should I bother?
I'm sort of stuck fixing this problem myself. Most nobody in town wants to jack with a vehicle this old, and all claim a lack of technician experience with EEC-IV. Any advice would be greatly appreciated.
Thanks--Dan White
