QuestionQUESTION: I have a 96 Seville STS - love the car. bought it with 103,000 miles and it now has 227000 miles. It got to running rough and was hard to start. My mechanic (independent, but a Caddy trained mechanic) tuned it, new plugs, wires, we changed out one coil, O2 sensors, and some other sensors. Starts like a champ, runs as smooth as glass, hardly know it's running, all the power is there - but the gas mileage is now about 18 mpg on the interstate and about 15-16 in city driving. I was getting 27 to 28 (even hit 29 mpg once) interstate at 65 mpg and around 20-22 around small city, close in rural driving. My mechanic is buffaloed. All the codes read that it's on the top of it's game. What are we missing? what should we be looking for? Obviously, too much fuel is going through the system - but no black or white smoke out of the exhaust and no fuel leaks. Thanks for you help.
ANSWER: IS or HAS the CHECK ENGINE light on the dash ever illuminated while driving the vehicle ?.
If it HAS, Do you know what CODES appear when you access the computers ?.
Is there anything that is not working correctly with the vehicle ?.
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QUESTION: The CHECK ENGINE - or Actually, the "Service Engine Soon" light was on and off intermittently. I checked with my mechanic and he said he didn't write down the codes when he checked them - the only indications were that there were multiple misfires. The plugs are brand new, wires were recently replaced, he put in a fuel filter and an air filter and a fuel pressure regulator. O2 sensors were also recently replaced. He said the Air intake sensor was indicating that it was running hot, but when he turned off the AC it appeared to be within range. He also said that he didn't do anything with the MAP sensor. He said all vacuum levels seemed right according to engine specs. I asked if the catalytic converter might be a problems and he indicated only if there was some kind of blockage - but that would also reduce the power due to back pressure - and it does seem to have all the gutsyness it always had - for a nearly 2 ton vehicle, this baby screams. There doesn't seem to be anything else wrong with the car other then the struts could use replacement, but at a parts cost of close to $2000 plus labor for a 13 year old car, they are not that bad. Does that help any?
AnswerOK, Here is how to retrieve the codes from the computers.
1. Turn ignition switch ON. Do NOT start the engine.
2. Simultaneously push and hold the OFF and WARMER (^) buttons on the
climate control panel for 3 seconds and release them.
3. Watch for a combination of LETTER & NUMBERS followed by either (H) history or (C) current after EACH code displays.
4. After all the codes display the display will show PCM?
5. Turn OFF the ignition switch.
6. Tell me what codes display and if they are HISTORY or CURRENT.
