Gentleman,

I have a 1990 Cadillac Allante (4.5L engine). About a year ago, it developed a miss and I repaired it by replacing a fuel injector. About 3000 miles later, it happened again and then failed a Calif Smog test. This time, because it is so labor intensive, I replace all 8 injectors with new OEM Standard brand units. The miss was gone and the car breezed through the Smog check. However, I noticed that there was a decrease in fuel mileage. In fact, when I actually checked it, the local driving was down to 9MPG and the highway was at about 18MPG (averaging about 14.5mpg). This represents a 25% decrease from the previous (15 city and 22 highway) with the old injectors. The car machine specs exactly where it is supposed to and there are no obvious signs of rich or unburned fuel (exhaust, pipes, etc.) I considered replacing the fuel pressure regulator, even though I can see no real reason to do so other than process of elimination. Then I found out that it is no longer even made, factory or aftermarket. I don't even know if that is the problem. So....your thoughts, ideas, or ????? Any help would be greatly appreciated. Thank you, Pat

don't suppose you have access to any scanners that work with it? a good log could shed light on it.

Thank You Robert,

Well, I do have several friends that own commercial shops and can provide scanning, and I will look into that at the proper time. I was hoping for some 'good old fashioned' diagnosis, or perhaps to hear from someone that had a similar experience and was able to resolve it. I do not drive the Allante often (about 4K year), so I can take my time with it. But I do use it on several long trips a year and I need to be confident that it is running correctly. When I see this type of fuel efficiency, it gives me pause that something else might be wrong. I do not want to drive it from LA to San Francisco and have a problem, since parts for this are very difficult to get. I appreciate your input....Pat