Hello, my 96 Grand Caravan 3.8l all of sudden became a gas guzzler. The check engine light is on. Any idea what might be the problem?

 

You'll have to give us more details and find out the code that is generating the check engine light. Cycle the key from off to on (not start) 3 times within 5 seconds leaving it at on on the last cycle. Now count the flashes of the check engine light. All codes have two digits. Each digit is separated by a pause, Each two digit code is separated by a longer pause. A code 21 would be flash, flash, pause, flash. Should finish with a code 55. This is called the key dance and lets you read your OBD codes without a scanner to narrow down the cause of your problems.

If this doesn't work head to an AutoZone or the like. They will read your codes for free with a scanner.

You say gas guzzler. What kind of mileage change? Any symptoms like hard starting, an engine miss, hesitation, poor acceleration, pulling one way, heavy raw gas smell? Any maintenance done just prior to this? How old are the spark plugs, O2 sensors, etc?

 

+1, Would need more information. Codes are very helpful.

 

thank you for the quick response, i did what your on cylcling the key. What is got was a
flash, flash flash, flash flash, flash, flash flash flash flash flash, flash flash flash flash flash.

Not sure what this mean, it is 1-2, 2-1, 5-5? or is it 122155?

 

Looks like 12,21,55

12 just means you've disconnected the battery in last 50 starts. Regardless if you disconnected the battery you can disregard it. By itself it won't turn on the check engine light.

21 indicates an O2 sensor fault. To determine which sensor is at fault head to an Autozone or similar store and have them read your 4 digit powertrain codes with a scanner. Most do it for free. This code will determine which of the two sensors is at fault and which fail mode they are in. The O2 sensors are key components in determining air/fuel mixture and this plays a big part in what fuel mileage you get.

55 just means the test is complete.

Odds are you'll be changing the upstream O2 sensor since it is the primary sensor in determining the air/fuel ratio. The downstream sensor is only acts as a monitor. Stay away from Bosch sensors. Stick with Denso or NKG sensors for the best results.

What you get with the key cycle are 2 digit MIL codes. They are good for a quick read on what might be wrong. A scanner will read the much more precise 4 digit powertrain codes. This set of codes is far more comprehensive and help steer you closer to the actual fault.

 

thank you very much for the assistance. I will do what you advise me. Thanks again.

 

Can you pls tell me the location of the upstream and the downstream sensors? Is there a picture diagram somewhere that I can use to have a visual aid. Thanks again.

 

Upstream - on top of the exhaust manifold right behind the engine
Downstream - in the exhaust pipe aft of the cat converter.

http://autorepair.about.com/library/faqs/bl744h.htm

 

Ok, sorry it took so long. I replaced both O2 sensor and i thought it was going to fix the problem. I drove less than 2 miles and the van used 1 bar on the gas meter. Any assistance would be appreciated.

 

Check engine light still on or did it reset? Can't determine anything driving 2 miles. Fill it up and use at least half a tank then fill it again and determine your mileage. Don't count on the overhead display. What mpgs were you getting before the problem then when you noticed it guzzling?