Imperial Home Page -> Repair->Fuel -> 1981-1983 Tips -> EFI Diagnostic Tips
Symptoms: Low power, Pops through throttle body
Your symptoms sound like a really lean mixture; there are only 613 things that can cause this, so let's get started.
1. Check all the gaskets and fasteners associated with the "air cleaner" assembly and its covers. Any way that air can enter this enclosure that does not pass through the air flow sensor on the "snorkel" will make the car run too lean, especially when it is cold and the O2 sensor has not taken over the fuel/air ratio management. Often with anything more than a tiny leak here, the car won't idle at all.
2. Check all the vacuum hoses on the system. There are a jillion of them, and they are color coded, with the legend on the left fender near the hinge. Pay special attention to the ones that come directly from the intake manifold - like the PCV, Power brake, and canister hoses.
3. If you don't find anything loose or any missing gaskets, verify that all your electrical connector contacts are clean and gripping their mates firmly. You can get an excellent contact cleaner from Radio Shack. Take each connector apart (study it to see how it releases FIRST) and then clean both halves, making sure the metal parts are clean and bright, and that the spring tension is good in each contact. Look inside the air cleaner and verify that the ground wire under the mounting screw is clean and tight.
4. Check your PCV and EGR valves for proper operation, and good sealing to their hoses and mounting points. The PCV valve should rattle when you shake it, and its hose to the base of the throttle body must be in good condition and securely fastened. To check the EGR valve, put an extra piece of 1/8 tubing on its little dingus and suck on it while the car is idling – it should stall immediately - if it doesn't you are going to fail smog the next time, and it may (or may not) be related to your current problem.
5. Your O2 sensor may have failed. These only last about 75,000 MI, so you might just take a chance and replace it. They're cheap and easy to change, and available from NAPA. Be very sure they look up the right car - this is called the 5.2L EFI or EFM engine, also coded E43. They should give you an OS101. A useful diagnostic trick is to take the lead from the CCC to the O2-sensor loose from the sensor and hold the end in your right hand with the engine idling, thoroughly warmed up. If you touch the battery positive post with your left hand (you won't get a shock, this is only 12 volts, trust me), you should notice a distinct change in the idle. Then touch the negative battery post and there should be another change in the idle. If there is, you've proven that your computer is awake and paying attention. Further on the O2-sensor, it is often worth while to drive the car with it disconnected. This should richen up the mixture, and you might find your problem completely disappears. Either way, we'll learn something.
6. A bad TPS (Throttle Position Sensor) can cause this. If you have a service manual on the car, we can lead you through a process to check this with a VOM. If you have neither, I recommend you get both, if you are going to continue to maintain the EFI system yourself.
7. A bad fuel flow sensor or airflow sensor could also cause this; unfortunately the easy way to eliminate these is to exchange them for known good units.
8. A non-stock exhaust system has been reported to cause drivability problems
on these cars - is your car still running the factory exhaust?
This page was last updated on August 26, 2001. Send us your feedback, and come join the Imperial Mailing List - Online Car Club