QuestionMy car is a 95 Cadillac Fleetwood which has the LT-1 which is stock with 75000 miles, recently my car has been running extremely rough in all weather, it has been happening for a while but recently it has be getting exponentially worse. The car still runs, but at lower rpm especially in higher gears the car runs so rough that the entire car shakes in drive from 55- about 70 however shaking less as I travel at higher speeds and dissipates as I accelerate. Thinking that it was maybe the injectors I started putting in fuel injector cleaner which had no noticeable effect. And even more recently there has been a dramatic drop in my fuel efficiency, I was getting about 24-25 MPG when it was all normal then it slowly lessened to about 20-22 MPG, but within a month and about 300 miles it now gets about 14-15 MPG(note all these are highway fuel efficiency observations). The amount of gas that is used during city driving has lowered from 17 MPG to 14-15 MPG. I have taken it to a couple paces and each say it might be something else one says the injectors, another the oxygen sensors, and another said that it might be the EGR since that the diagnostic system says that sometimes that it is not operating properly, but this has not happened for a while and the car has been getting much worse over a short period of time. About 5000 miles ago I replaced the Opti-spark, the plugs and wires, coil, and water pump due to it not starting in wet weather. Hopefully you may be able help me, I would really like to do a road trip for spring break but if the car keeps acting like this I may have to rent one.
the codes that i get off the On-Board Diagnostics system are
Powertrain Control Module (PCM) Codes
00-44 ....................... Left oxygen sensor under voltages (closed loop operation)
and it sometimes pops up this one but it seems to happen pretty randomly when i start the car
Powertrain Control Module (PCM) Codes
00-32 .......... EGR open command did not change fuel mixture during off idle operation
Could the EGR cause this or is it injectors,or the oxygen sensor,and if it is the oxygen sensor then why is it not not poping on the the check engine light all the time, i reset the codes and drove like 200 miles and the car drove very rough but no lights
Thank You for your time and your help
AnswerChris,
Good choice of cars, I have a modified '95 Fleetwood myself. Assuming that you've gone over all the work you recently did to make sure there's no problem there, the first thing I'd do is check out the EGR system. Make sure it is working properly. It may not be the ONLY thing wrong but it's not only a pretty common problem but it certainly could be contributing to your problem.
As for the code 44, first verify there's no exhaust leaks on that side of the engine (cracked exhaust manifolds and/or broken/missing bolts were common on the LT1's). If you find any of these, fix them first because the exhaust is drawing in outside air and making the O2 sensor "think" it's lean.
Next, you'll need to do a cylinder balance test. Hate to say it but for this, you'll probably need an engine analyzer. You want to verify that the ignition system is working properly. Most shops at the very least, have an ignition secondary (KV) tester which will give you at least some preliminary info.
After that, if you want to check the injectors, you'll need a fuel pressure gauge, and an injector tester. With this, you can test both flow and leak-down of each injector.
Beyond all of this, you should be looking over the entire engine for loose or broken vacuum hoses and fittings, as well as burned or chaffed wires.
