Imperial Home Page ->Imperial by Year -> 1981 -> General Information
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Tips from Dick:
General Information Ok, here's some more info (in no particular order) for crazy people who drive EFI Imperials...
1. It is not unusual for the car to surge SLIGHTLY at idle. This is because the CCC is always "searching" for the perfect mixture of air/fuel/spark. The "guru" even showed me the changing readouts on different sensors (temp, O2, etc.) during idle. The reason that this effect is more noticeable on an 81-83 Imp (as compared to "modern" cars) is simply the fact that the CCC is late-70's computer technology. In other words, its little brain cannot process the info. fast enough and therefore causes a delay between sensor data and mechanical action (re-action of engine).
2. As I stated earlier, this system has NO tolerance for air leaks. For example, after fixing my seals, I took the car for a drive around the block. The problem seemed to be only 90% cured. As I stood around watching the engine surge just a bit more than it should at idle, I noticed that the oil-breather to air-cleaner-hose was loose. I pushed it on better, and the idle improved measurably. Another ride around the block confirmed this problem and the car was running 100%. On a carburetor car, this same problem would have a .0005% effect on performance (if at all)!
3. The cars can be prone to "internal" vacuum leaks. This is because Imperial 318s used 360 intake gaskets. (Paper instead of steel). The paper seal can break-down between the lifter valley and intake port, thus a vacuum leak you'll NEVER find. The guru had no idea why the factory did this, but he always uses the proper 318 gasket on any rebuilds. Cars that do this will burn oil on the freeway, but none during city driving (Unless of course there are other problems like stem seals, rings, etc. then, it will always burn oil).
4. Vacuum leaks are also common near the distributor, at the rear of the intake (this applies to any smallblock Mopar). Typically, you see the gasket squishing out from its proper place.
5. It's easy for the CCC to go into what he termed "lean-lock". (runs too lean) Apparently this happens quite often, and can be triggered by almost anything. The only fix is to reset the CCC.
6. To reset the CCC, you don't have to go through all that "rev @ 2500 RPM for 90 seconds" B.S. He says just unplug the white connector and re-connect. The computer will "learn" on its own. I believe him, because I've done it a few times now with no ill effect. The guru is also not the type to cut-corners, unless it's really, really OK. OR: Also consider unplugging the O2 sensor, then disconnect the battery to clear the memory. Run it with the O2 unplugged for a day or two. This will keep it in open-loop mode, meaning it will run a little richer. See if that helps idle, if it does, there is still an air leak.
7. The "lean-lock" problem was caused by the computer's programming. It was told, when in doubt, go lean. Blame the EPA. There was no fix for this problem, and this was the reason for carb.-conversion. The EPA wouldn't grant a wavier to allow the car to have slightly higher HC emissions (only under certain conditions).
8. A slack timing chain will cause lots of grief.
9. An idle that goes down when you step on the brake has a bad throttle stop ground. I knew the brake switch was tied into the idle circuit, but I didn't know it would reduce idle ONLY if the throttle stop lost its ground (corrosion, dirt, etc.)
10. If you run good gas (premium), you can set the timing to 14 degrees instead of 12 degrees. He says the timing was backed off purely for emissions, it will run better at 14 degrees.
11. 1-2 seconds worth of spark knock at the 1-2 and 2-3 shift is normal under hard acceleration.
12. Not having catalytic converters won't cause any driveabilty problems, BUT, not having the air pump injecting air at the O2 sensor (upstream air) could cause a problem with cold weather warm-up. The fresh air helps heat the O2 sensor (it only begins to work above 600 degrees). So if you don't heat it up with fresh oxygen, the computer will be looking at a cold O2 sensor when it goes to closed loop. Once the 70 second timer has "timed-out", the air from the air pump is directed to the converters to help them warm up. However, even he admitted that the problem would be very slight, possibly unnoticeable.
13. Any part (voltage regulator, alternator, a/c compressor, p/s pump, etc.) marked with a silver/black pentastar was tested after being built and performed better than average, thus it was given the silver/black star and destined for Imperial use only.
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