Question-------------------------
Followup To
Question -
My daughter has a 1998 Chrysler Cirrus 2.5L V6 with 150k miles. It is getting very poor fuel mileage (estimated @ <10 mpg). It has no codes, an independent tune-up shop ran diagnostics with Sun equipment and said that all sensors, etc were showing as operating in the normal (expected) range. He said that it may be eligible for a catalytic convertor change under factory recall (but the recall notice does not seem to relate to anything that would affect the fuel mileage). She has only owned this vehicle since Thanksgiving 2004 (8 months).
It starts fine, idles smooth, seems to run normally in all respects, except fuel mileage. (my daughter does say that there is black exhaust sometimes - I can't verify this nor do I know when it happens).
Recent work includes: new rear brake shoes and hardware, new front brake rotors and pads, spark plugs (Champion Platnium), Distributor cap and rotor (NAPA), PCV valve, Air Filter (NAPA Gold), New spark plug wires (Advance Auto), cleaned throttle body, and repaired vacuum hose to the EGR valve.
At 70-75 mph the tach reads about 2500 rpm.
I mention this because there does not seem to be any obvious problems with the brake system or transaxle operation.
Do you have any ideas for what could be causing this terrible fuel mileage without setting off any codes or having an O2 sensor reading rich (or something)? What and how can I further investigate?
Any advice would be appreciated! Thanks in advance.
Answer -
Hi Ken,
On what basis do you estimate the mpg? Have you checked the accuracy of the odometer? What sort of driving habits does she practice, what type of driving does she do: lots of short trips, mainly in town with many stop lights, jack-rabbit-starts, not coasting up to a stop light/sign? Tires inflated to sticker recommended level? Has it always been this low or did it start to go bad after a particular service? If the catalytic converter is clogged up that will cut the power output of the engine and consequently fuel efficiency will suffer. So if there is a recall and you can get one for free, I'd take them up on that. Are you sure that the independent shop had the test equipment to read all the possible faults codes? Maybe a readout at a Dodge/Chrysler dealer would divulge something the shop missed.
Have you felt the metal surfaces of all the wheels after she has driven it to check for dragging brakes? Is the car burning much oil, which might cause low compression and less efficient use of the fuel? Does the car roll pretty easily when pushed by hand. Roll resistance of the tires could be a factor.
Those are some of the items I would check out. Probably there is not one single reason but perhaps a confluence of several that adds up to a low fuel efficiency situation.
Roland
Thanks, I haven't checked the mileage exactly, but I can drive 10 miles down the interstate and be shocked at how much fuel it has used. This is not a matter of the mileage being 10-15% low. The mileage is only 35-50% of what it should be! Tires are properly inflated. We were trying to figure out if it was always this bad. Several months ago, she put oil in the car and forgot to replace the filler cap. After driving 60 miles she had thrown enough oil on the exhaust manifold to start a small fire. It burned a piece of black corrugated plastic wire loom and the vacuum hose for the EGR. It set off the check engine light with the following codes (138/P1294 Idle Speed Performance, 46/P0401 EGR System Performance) we know that the gas mileage has been poor since but I am not sure of before that. I replaced the vacuum hose for the EGR, cleared the codes, and those codes have not returned.
I had a catalytic converter stop up on a Caravan once, it would build pressure until the engine would not run at highway speeds. I have not felt this symptom (and the recall notice references a structural problem which could lead to leaking and polluting the environment).
I am going back to the shop and ask for a list of checked items (I am now getting interested in transaxle operation as well as the engine). He has a good reputation. I forgot, he got rid of the Sun equipment and is using SnapOn stuff now.
I don't think the transaxle is the problem since the engine rpm (2500) at highway speeds seems reasonable. But dragging brakes could be a culprit. But wouldn't she smell the hot brakes when she stopped the car?
I appreciate your input, it is nice to be able to bounce ideas and get others advice, it assures me that I am not missing something obvious.
Any other thoughts or ideas?
AnswerOn the brakes, it wouldn't necessarily produce an odor depending upon whether there was enough heating to damage some rubber parts or boil off some stray grease. So carefully touching the wheel rims might be the best test of that possibility.
I would try to get a reading of the mileage on a freeway trip where you fill the tank to the autoshoutoff limit on the pump (or even till it tops off for better accuracy) then drive it far enough to get a good numerator and denominator at a roughly constant highway speed, then return to the same pump and see how much fuel it takes to refill it to the previous level.
You might want to do a compression reading on the three front cylinders (the rear ones require dimantling too much gear to make that reasonable to do) just in case she ran the oil too low when the cap was off and caused some wear on the pistons/cylinders.
Roland
