KHE Posted November 24, 2010 Report Share Posted November 24, 2010 Someone with a '91 service manual should be able to confirm the minimum fuel pressure spec. Another possibility is a failing fuel injector. A Tech-2 scanner hooked up to the car will show what cylinder(s) if any are misfiring. Observe the misfire counts and see what cylinder(s) is misfiring. One possibility is there be a fuel injector that has a running short in it and once it heats up, it won't deliver fuel to the respective cylinder(s). The injectors are expensive and you need to use the OEM injectors or there will be a fuel imbalance. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
adallak Posted November 24, 2010 Report Share Posted November 24, 2010 The injectors are expensive and you need to use the OEM injectors or there will be a fuel imbalance. I have replaced the original injectors with refurb. Ford injectors for Crown Vic, Mustang, etc. I paid $150 for a set and did not notice any difference in performance or fuel economy. Many 4.9 owners have done the same. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
bschelle Posted November 24, 2010 Author Report Share Posted November 24, 2010 I ordered a set of reman injectors for $137. I should have them early next week and will post back how it goes. Will I mess up the engine if I drive it the way it is? Link to comment Share on other sites More sharing options...
Ranger Posted November 25, 2010 Report Share Posted November 25, 2010 I doubt it. Link to comment Share on other sites More sharing options...
adallak Posted November 25, 2010 Report Share Posted November 25, 2010 I ordered a set of reman injectors for $137. I should have them early next week and will post back how it goes. Will I mess up the engine if I drive it the way it is? By the way, as far as I remember, to lift up the fuel rails you do not have to remove completely PS pump or anything else. Just loosen them up and you will see a way to lift the rails. The new injectors probably came with o-rings. Use them instead of old ones. Clean the are around the injectors with a brush, before lifting them up. My engine was a mess because of several oil leaks. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
bschelle Posted November 25, 2010 Author Report Share Posted November 25, 2010 I ordered a set of reman injectors for $137. I should have them early next week and will post back how it goes. Will I mess up the engine if I drive it the way it is? By the way, as far as I remember, to lift up the fuel rails you do not have to remove completely PS pump or anything else. Just loosen them up and you will see a way to lift the rails. The new injectors probably came with o-rings. Use them instead of old ones. Clean the are around the injectors with a brush, before lifting them up. My engine was a mess because of several oil leaks. This is the second set of injectors since I have owned it. You are right about the PS pump, I didn't have to remove it the first time. Link to comment Share on other sites More sharing options...
CarlaValentine Posted November 25, 2010 Report Share Posted November 25, 2010 Just throwing this out there as a thought...does the 91 OBD system have the same diagnostic capabilities as later OBD1 models? Specifically I mean could a power balance check be done on this car by disabling the injectors one by one? Link to comment Share on other sites More sharing options...
adallak Posted November 25, 2010 Report Share Posted November 25, 2010 Just throwing this out there as a thought...does the 91 OBD system have the same diagnostic capabilities as later OBD1 models? Specifically I mean could a power balance check be done on this car by disabling the injectors one by one? Yes, it does. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
KHE Posted November 25, 2010 Report Share Posted November 25, 2010 You will eventually find the problem by continuing to throw parts at it but it is going to get expensive... The injectors could be bad but they may well not be. A scan tool that is able to monitor the misfire counts could easily pinpoint the problem. I would find out what is actually done to remanufacture the injectors. If it is just new o-rings and cleaning, that may not solve the problem - particulary if the injector coil has a short in it. I believe that model also has the ability to turn off individual injectors from the climate control panel - when the problem occurs, turn off the injectors one at a time. When you turn one off that DOES NOT make the engine run worse, that is the problem injector. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
CarlaValentine Posted November 26, 2010 Report Share Posted November 26, 2010 You will eventually find the problem by continuing to throw parts at it but it is going to get expensive... The injectors could be bad but they may well not be. A scan tool that is able to monitor the misfire counts could easily pinpoint the problem. I would find out what is actually done to remanufacture the injectors. If it is just new o-rings and cleaning, that may not solve the problem - particulary if the injector coil has a short in it. I believe that model also has the ability to turn off individual injectors from the climate control panel - when the problem occurs, turn off the injectors one at a time. When you turn one off that DOES NOT make the engine run worse, that is the problem injector. That's exactly the test I was talking about. Link to comment Share on other sites More sharing options...
bschelle Posted November 28, 2010 Author Report Share Posted November 28, 2010 I put the new injectors in yesterday morning and it is back to running great. You people are the best! Thanks for all of the good advise. Link to comment Share on other sites More sharing options...
BodybyFisher Posted November 28, 2010 Report Share Posted November 28, 2010 So what was your prognosis? Do you have an ohm meter?, check each injector's resistance Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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