BodybyFisher Posted May 13, 2008 Report Share Posted May 13, 2008 I was thinking about this before. I am somewhat like the tortois in my thinking, I plod. I was so locked into doing the compression testing that I overlooked the PSI readings.. I am much too a linear thinker these days, not sure why.. 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...
MIke D Posted May 15, 2008 Author Report Share Posted May 15, 2008 FYI, we are waiting for a scan tool to figure out what's wrong. My dad's goes up to 97 (i own a 99STS). As soon as wee find out we will be posting and update. Thanks... Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
KHE Posted May 15, 2008 Report Share Posted May 15, 2008 Not sure why you need a scan tool - the car has built-in diagnostics. Based on your fuel pressure readings, I have to believe the fuel pump is in the process of dying... 33 psi is too low. You NEED to locate the section in the manual that describes how to isolate the fuel pressure problem to either the fuel pressure regulator or the fuel pump itself. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
MIke D Posted May 15, 2008 Author Report Share Posted May 15, 2008 Based on your fuel pressure readings, I have to believe the fuel pump is in the process of dying... 33 psi is too low. You NEED to locate the section in the manual that describes how to isolate the fuel pressure problem to either the fuel pressure regulator or the fuel pump itself. We tried that.... If you read one of my previous posts the diagnosis tree does not make sense. The part where you let the car sit for 10 min and look for a psi drop does not direct you to a logical NEXT step. It said does it drop more than 5psi in 10 min. No it does not... so it tells you to go to number "X" that number asks if it dropped more than 10 psi in 10 min. Well if my answer was no to the 5 then why would it be a yes to more than 10.... So the answer is no again. so then it says replace the fuel filter and check lines for any opstructions. We did that and it still happens... What is wierd is that it's only too low on slow acceleration. Not when the car is sitting at idle which is when it occurs the most.... Not sure why you need a scan tool - the car has built-in diagnostics. As far as the car diagnostics. It says everything is running fine. then once in a great while it will pop a PO300 Engine miss... That's it... Not why or which bank of the engine is Miss firing... All the other diagnostics in the FSM says to plug in a scan tool... Engine missfire, Fuel injector, And 3 or 4 others that could cause it... I left the books in boston with my dad because that it where the car is. I can't do anything in an apartment parking lot.... Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
KHE Posted May 16, 2008 Report Share Posted May 16, 2008 Based on your fuel pressure readings, I have to believe the fuel pump is in the process of dying... 33 psi is too low. You NEED to locate the section in the manual that describes how to isolate the fuel pressure problem to either the fuel pressure regulator or the fuel pump itself. We tried that.... If you read one of my previous posts the diagnosis tree does not make sense. The part where you let the car sit for 10 min and look for a psi drop does not direct you to a logical NEXT step. It said does it drop more than 5psi in 10 min. No it does not... so it tells you to go to number "X" that number asks if it dropped more than 10 psi in 10 min. Well if my answer was no to the 5 then why would it be a yes to more than 10.... So the answer is no again. so then it says replace the fuel filter and check lines for any opstructions. We did that and it still happens... What is wierd is that it's only too low on slow acceleration. Not when the car is sitting at idle which is when it occurs the most.... Not sure why you need a scan tool - the car has built-in diagnostics. As far as the car diagnostics. It says everything is running fine. then once in a great while it will pop a PO300 Engine miss... That's it... Not why or which bank of the engine is Miss firing... All the other diagnostics in the FSM says to plug in a scan tool... Engine missfire, Fuel injector, And 3 or 4 others that could cause it... I left the books in boston with my dad because that it where the car is. I can't do anything in an apartment parking lot.... I'm confused - does the car misfire more at idle or on light acceleration? Your earlier posts indicated it misfired/backfired on acceleration. That information along with the low fuel pressure tells me the fuel pump is on its way out. The low fuel pressure reading is a HUGE clue to the puzzle . The scan tool that the manual refers to is a $3000+ Tech-2 which most DIYs don't have access to. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
MIke D Posted May 16, 2008 Author Report Share Posted May 16, 2008 I'm confused - does the car misfire more at idle or on light acceleration? Your earlier posts indicated it misfired/backfired on acceleration. That information along with the low fuel pressure tells me the fuel pump is on its way out. The low fuel pressure reading is a HUGE clue to the puzzle . The scan tool that the manual refers to is a $3000+ Tech-2 which most DIYs don't have access to. When I come to a stop it will idle fine for about 30 seconds.. then one quick miss.. then another and another. it will get progressivly worse the longer i sit there... I start to go and it clears right up. Once or twice a month I can get it to do it on acceleration. But it has only backfired 3 times in the last 4 months... we too think it is the fuel pump but at $400 we want to be sure first... We are waiting for a friend to swing by my dads shop. He has a tech 2, he's the one who fixes "lemon car's" for saturn and others.... He seams to know the little things to check too... Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
MIke D Posted May 17, 2008 Author Report Share Posted May 17, 2008 Well it's all Fixed. My dad ran the car for a few days with the FP gauge taped to the windshield. No drop in FP at all even when it stackfired again. So he took it back to the shop and did another Top engine cleaner (tec) but this time didn't use the "spray can" that GM sells but a liquid concentrate out of a bottle. Let it sit for an hour. Started it back up. Filled the shop parkinglot (and part of the road) with white smoke and waa laa. Car is running good. So my original attempt at fixing it was the correct one. (which is what our "lemon law" friend told us to try first) It's just that I had a coil go dead at the same time... which meant that what i thought was one problem was really two... I will meet him in CT to swap cars back. I can"t wait.... On a interesting side not. Boston dealers has asked congress to look into gas stations tampering with the fuel "mixture." Turns out they have had numerous (new and old) car being brought into the dealer for a slight miss fire and sometimes a backfire... Here is one of the audio snipits on the story http://multimedia.wbz.com/m/19890946/bad_g...amp;seek=36.018 And the story from WBZ news radio http://wbz.com/Trouble-in-the-gas-tank-/2160021 Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
JimD Posted May 17, 2008 Report Share Posted May 17, 2008 So you had a valve being held open by carbon? Something that WOT therapy could take care of. Glad you got it fixed. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
MIke D Posted May 17, 2008 Author Report Share Posted May 17, 2008 So you had a valve being held open by carbon? Something that WOT therapy could take care of. Glad you got it fixed. I do WOT's all the time. I love merging on highways... Someone said once, drive it like you stole it! Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
MIke D Posted May 18, 2008 Author Report Share Posted May 18, 2008 Just picked the car up and it's back... I knew it was too good to be true.. Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
BodybyFisher Posted May 19, 2008 Report Share Posted May 19, 2008 Just picked the car up and it's back... I knew it was too good to be true.. Could it have been fixed for a couple of days? Have you done the WOT procedure?, I DO NOT MEAN, GIVING IT WOT ENTERING THE HIGHWAY, I MEAN THE PROCEDURE, HAVE YOU DONE THE PROCEDURE? 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...
MIke D Posted May 19, 2008 Author Report Share Posted May 19, 2008 Just picked the car up and it's back... I knew it was too good to be true.. Could it have been fixed for a couple of days? Have you done the WOT procedure?, I DO NOT MEAN, GIVING IT WOT ENTERING THE HIGHWAY, I MEAN THE PROCEDURE, HAVE YOU DONE THE PROCEDURE? what is the procedure? Start it in manual first and go? cause i held it wide opn till i was going more than double the speed limit. Had to test out the new rear shocks too.. Yeah, I "HAD TO" Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
lothos Posted May 19, 2008 Report Share Posted May 19, 2008 what is the procedure? Start it in manual first and go? cause i held it wide opn till i was going more than double the speed limit. Had to test out the new rear shocks too.. Yeah, I "HAD TO" Here's a post I found from JasonA: WOT = Wide Open Throttle. WOT in itself is basically flooring the accelerator and enjoying the ride. The procedure, the "WOT procedure" as it's usually called, consists of more than that though. It means pulling the gear selector down into 2, accelerating to about 80 at full throttle, then backing off the accelerator and letting the engine slow the car down, to say 40. Then do it again a few times. You'll likely see a lot of black (carbon) out the tailpipes -- this is good. It's literally cleaning your engine out. After you stop seeing junk from your tailpipes, your engine is relatively clean, and simply proceed to drive the car hard every now and again. Nary a day goes by that I don't hit the accelerator hard for a scream up to redline. Most of my driving is actually pretty slow, but if I turn out onto an open stretch of road, or get a free stretch of 2-lane, opening it up a little bit helps to keep the carbon deposits at bay. WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn. Cheers! 5% discount code at RockAuto.com - click here for your discount! Link to comment Share on other sites More sharing options...
BodybyFisher Posted May 20, 2008 Report Share Posted May 20, 2008 Thanks Lothos, I do that 10 times in a row, once a month The deceleration sucks junk from the combustion chambers including valves due to the high vacuum 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...
MIke D Posted May 20, 2008 Author Report Share Posted May 20, 2008 Just got to do it 8 times in a row here. No smoke out the back (shouldn't since I just did 2 TEC treatments). However the problem is still there... Cop didn't see it, I didn't do it! 93 STS 225,000 Miles 99 STS 111,000 Miles Link to comment Share on other sites More sharing options...
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