A/C condensation & fuel economy

Okay, I've got a '91 XJ, 4.0, auto w/ A/C obviously.

Problem #1 is the A/C condensates inside the Jeep with very little condensation outside. It drips out from under the dash and under the vents for the back seats. It is bad enough that it will puddle up significantly on the passenger side. You can also hear water moving around in/under the dashboard when cornering. I'd like to figure something out before my floorboard starts to rust and before summer gets here.

Problem #2 is I had to reset the distributor and I don't think I ever got it right. I generally get about 8/12 mpg. Sometimes when running the A/C I can average 18-20 mixed driving, with a lot more highway than city miles. My question is does running the a/c affect timing, fuel delivery or anything else that should improve my fuel economy that much?

I have already tried quite a few times to get the distributor set right, but it doesn't seem to change anything (fuel economy, idle, stumble off the line with throttle).


Shane

TeXJ said:

Okay, I've got a '91 XJ, 4.0, auto w/ A/C obviously. I generally get about 8/12 mpg. Sometimes when running the A/C I can average 18-20 mixed driving, with a lot more highway than city miles.

Shane

Click to expand...

I'm running my ac full time to increase my milage !!!


You sure this isn't backwards?

There is also a drain hose for condensation under the right side by the firewall IIRC...I bet it's plugged up and thats why you have the moisture inside and not out.

red91inWA said:

I'm running my ac full time to increase my milage !!!


You sure this isn't backwards?

There is also a drain hose for condensation under the right side by the firewall IIRC...I bet it's plugged up and thats why you have the moisture inside and not out.

Click to expand...

Found the hose, thanks. Would have never found it, if I hadn't been specifically looking for something like it. It was hidden from view in every possibly way. Found it by feeling around -- when my hand got soaked I found it...


Am I sure what isn't backwards?

Now if I can just figure out the other issues... lol


Shane

I'm positive my mileage isn't backwards. 8 when driving mostly city streets, about 12 (varies from 10-13) when driving mostly highway. I usually use a quarter of tank by about 60 miles (highway) and am down to a quarter of a tank at about 200 miles. When I've used the A/C, and gotten better fuel economy, I can get 100+ in a quarter of a tank which is close to original and end up averaging above 15 mpg. It is not consistent though, the A/C "fix" doesn't always improve the economy but seems to more often than not.

Also, with the A/C on it doesn't stumble as much and is more responsive. Otherwise, it will stumble hard off the line with anything close to half throttle or more and sometimes it sounds like it might be backfiring in the intake, though I'm not positive. Also, sometimes it is difficult to start. But, if I've been running the A/C it fires right up when I try to start it.

There are a lot of things that running the A/C seems to improve, which is why I was wondering if the PCM adjusted anything when the A/C is running. I thought maybe I could use that info to pinpoint the cause(s) of these issues.

Anyway, got longwinded. Sorry about that.


Shane

The PCM may change timing a bit with the A/C on, I don't know for sure. The A/C does put a big load on the engine and the PCM is programmed to compensate for it. If it changes timing I have no idea though.

To set the distributor, pull the cap off (you don't have to disco the wires from the cap), then manually turn the engine over until the mark on the crankshaft is aligned with the "0" mark on the timing cover and the distributor rotor is pointed at the #1 cylinder pin on the inside of the cap. Rotate the distributor until the rotor is perfectly aligned with the position of the #1 pin, and re-install the cap. Any fine-tuning from there will have to be done with a timing light.