So I had the air suspension on the old 93 Mark some 5-6 years ago - it suffered from leaky front airbags and solenoids, which after replacing (along with a compressor) made the car quite a pleasure to drive. My 96 was converted to coils before I bought it, and it was nice to have the maintenance free aspect but I did occasionally miss the novelty of the adjusting ride height and the self leveling trait due to varying loads. The ride characteristics also seemed much better with the air suspension which I also came to miss.
Now, this 98.
I bought it and the original owner had the front two air springs/shocks and compressor replaced before I got my hands on it. It doesn't leak (that I can tell), but there are still some gremlins that I'm trying to hunt down. I wanted to present my findings and thoughts here for whoever's left that has any experience with these. This will be a fairly long winded and detailed post, so bear with me.
Background on the system and its operation, for those not familiar and potentially looking to weigh in -
The system has four air bags (one at each corner) each with a solenoid to allow air in or out, three ride height sensors (front corners and one at the driver's rear to measure rear ride height), the compressor, and a control module. The system maintains two different ride heights - city height and parked/freeway height (1/2" lower than city height). It's supposed to pump itself up to city height after you open and close the driver's door, then turn the ignition on. It maintains that height until you get to freeway speed (60-65 MPH), then it vents to parked/freeway height. It will maintain that height until the car slows down (48 MPH or so), after which it will pump back up to city height. It also adjusts to changes in loading to maintain a level stance (e.g. you dump a bunch of weight in the trunk so it pumps up the rear to compensate).
If the suspension control module is trying to raise the car and after 90 seconds doesn't see the change completed, it triggers a "check air ride" warning and disables the system until next key cycle. If it is trying to lower the car and doesn't see the change completed after 45 seconds, it does the same.
Now for my symptoms.
Item one - the car doesn't always pump up to city height after I get in, close the door, and start the engine. I don't get a check air ride message on the message center. It doesn't vent back down to parked height after I get to where I'm going, shut the engine off, and exit the car/close the door. If I take the car up to freeway speeds and maintain it for a few minutes, it will eventually trigger the check air ride warning. I can drive this way for at least a couple hours, and it wasn't low when I parked the car (did this on my way home from Michigan with it).
Item two - most of the time (maybe 60-70%) it will pump itself up after I start the car (as it should) and it acts normally while driving in the city. If I take it up to freeway speeds and allow it to lower, but return to city speeds, it will raise the car again within a couple minutes, and it continues to act normally without triggering any warnings.
Item three - sometimes, if it doesn't pump up after I start up and get in, I've shut the key off and restarted the car while waiting at a traffic light, and it pumps up right away.
Item four - I initially suspected a bad or intermittent relay. I bought and installed a used one off a guy parting out another 98 locally, and there was no change - so I am assuming the relay/connection to the relay is not the problem here. The compressor is new, so I also assume that is not the problem.
Item five - if it behaves normally, it will always trigger the check suspension warning after I've had it at freeway speeds for 5-10 minutes.
My understanding was problems with the components would trigger the suspension warning message 90 or 45 seconds after a commanded event, due to the pump/vent timeouts. My suspension warning messages always come on at weird times, several minutes after any commanded changes in ride height.
I bought two new rear air bags when I bought brake parts, just for the heck of it. Is it possible there's a slow leak at certain ride heights in one of them, which causes the suspension to see the rear of the car go low after a few minutes at freeway heights and throw the error? If so why would it do that instead of just pumping back up; does it not make adjustments to ride height at freeway speeds? Part of me is leaning towards an intermittently faulty suspension control module (which I understand is rare), or connection to it. I jiggled the wires to it a little but there doesn't seem to have been any change in symptoms.
I've been combing through the troubleshooting articles on the archived versions of Eddie Spinks's americanairsuspension.com (https://web.archive.org/web/20101116...III%20AREA.htm
) for ideas, but all seem to point to that 45 or 90 second timeout which isn't leading me anywhere that I can tell. Sadly I don't think that air suspension test tool is available for loan anymore either!
Maybe I should just get the new rear air bags in and see what happens...