pearlwhite97sts Posted February 28, 2008 Report Share Posted February 28, 2008 ok heres the deal my car (1997 sts) starts fine but runs rough until its warms up if i try to go anywhere until then it has very little power. the engine sounds fine to me but there is a very faint knocking coming from its left side, also when i give it a quick burst of gas it does not react immediately, there is a tiny pause and a gasping sound. i have no clue, do you? Link to comment Share on other sites More sharing options...
pearlwhite97sts Posted February 28, 2008 Author Report Share Posted February 28, 2008 ps i just bought this car so i know very little about how its supposed to run, and the knocking sounds like its coming from the trans axle Link to comment Share on other sites More sharing options...
TDK Posted February 28, 2008 Report Share Posted February 28, 2008 pearlwhite97sts, You should probably start by using the onboard Diagostic Information Center (DIC), to find out if your car has any trouble codes either current or history. I believe you press OFF and WARMER on the heater controls with the key on. You will see various systems display and then with the up/down buttons - the codes (if any) can be displayed for you to report back to us. If you press certain buttons, (I forget which ones), the codes are erased. However, if the problems still exist, the codes will re-appear anyway. There are a few potential problems that are more fundemental and hard to diagnose or detect with a sensor that will generate a code. For example; the Fuel Pessure Regulator (FPR) is a relatively inexpensive, simple spring/vacumn-diaphragm pressure-control valve that can leak through the diaphragm over time can cause a very rich fuel condition (which is sometimes leaned out a bit when warmer). You may have other codes that are related, such as oxygen sensors, or other such conditions, that this sites members can comment as to what might cause a "cluster of codes". Keep in mind that Caddy's like clean power to deal with all the instrumentation. Therefore it may be wise to ensure the battery, cables and ground connections are all in good condition. Pull the codes and report back. Good luck! Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
Logan Posted February 28, 2008 Report Share Posted February 28, 2008 Its a looong shot... Common on the 3800 series engines. Dust and fibers from the air cleaner can collect on the MAF (mass air flow sensor) wire. Its enough to throw off the calibration and cause drivability issue. A common 3.8L no code drivability issue. Next I would check fuel pressure. Next I would check for sticking EGR. Next I would check for sticking IAC. If those check ok. Throw a Tech 2 on it. That will show the problem alot faster then the IPC test. Logan Diagnostic LLC www.airbagcrash.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
pearlwhite97sts Posted February 28, 2008 Author Report Share Posted February 28, 2008 current codes: pcm p0135 ipc u1255 rss c1783 rss c1785 pzm b2471 Link to comment Share on other sites More sharing options...
TDK Posted February 28, 2008 Report Share Posted February 28, 2008 pearlwhite97sts; The following is an oxygen sensor code: DTC P0135 HO2S Heater Performance Bank 1 Sensor 1 This seems like the best bet and relatively easy and inexpensive as well. It seems like the other codes are not specifically engine related, but more like suspension codes. You can search on the codes and there are links to these codes as well. Since I finished a jumbo Margarita, I'm no good from here out tonight... Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
pearlwhite97sts Posted February 28, 2008 Author Report Share Posted February 28, 2008 TDK, how do i check these things? i tookd a six month auto course but that was in high school so i only learned the basics Link to comment Share on other sites More sharing options...
pearlwhite97sts Posted February 28, 2008 Author Report Share Posted February 28, 2008 have fun Link to comment Share on other sites More sharing options...
TDK Posted February 28, 2008 Report Share Posted February 28, 2008 pearlwhite97sts, The Oxygen senors are on the exhaust manifolds (total of 2) and perhaps one further down the combined exhaust pipe before the catalytic convertor. They basically tell the computer how much oxygen is in the exhaust (it needs to be a certain amount for proper combustion under various conditions). The computer adjusts the fuel/air ratio with this information - along with the air flow data into the engine, rpm, air temperaute, various load factors and lord knows what else. These Hot O2 sensors (HOS) are primarily zirconium oxide on a chip/substrate (if I recall correctly for insitu-types) that are relatively simple and reliable, but corrode, contaminate and wear out over time. Since you know what you want, then any GM mechanic could be told to go right to it and change it out. You could change it as well (and most assuradely) if you had a Field Service Manual along with some hand tools and determination. This is not a tricky tinker-adjustment, but moreover just replace it with the right part. However, (and trust me on this), there are wiser persons on this site that you can consult. Good Luck, Add power to leave problems behind. Most braking is just - poor planning. Link to comment Share on other sites More sharing options...
pearlwhite97sts Posted February 28, 2008 Author Report Share Posted February 28, 2008 how do i check the iac and egr (?fuel pressure release?) also do you know what this means: ipc U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)? thanks alot Link to comment Share on other sites More sharing options...
pearlwhite97sts Posted February 29, 2008 Author Report Share Posted February 29, 2008 how much damage would 2 extra liters of oil do over one oil change period? Link to comment Share on other sites More sharing options...
Ranger Posted February 29, 2008 Report Share Posted February 29, 2008 how do i check the iac and egr (?fuel pressure release?) The FSM would have the procedure to check the IAC valve, but usually the IAC circuit just needs to be cleaned as you clean the TB. EGR will usually set a DTC if out of range. Not sure what you mean by "?fuel pressure release?" Link to comment Share on other sites More sharing options...
pearlwhite97sts Posted March 1, 2008 Author Report Share Posted March 1, 2008 i forgot to say FPR but i figured it out anyways Link to comment Share on other sites More sharing options...
BodybyFisher Posted March 1, 2008 Report Share Posted March 1, 2008 how much damage would 2 extra liters of oil do over one oil change period? Do you mean that you are using 2 liters of oil during the oil change interval? How many miles is that? 4,000? So that means you are using a quart every 2,000 miles which is good. (give or take liter/quart & mile/kilometer). Did you replace the O2 sensor? 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...
pearlwhite97sts Posted March 1, 2008 Author Report Share Posted March 1, 2008 i changed the oil last night and there was about 9 liters in the car and im replacing the O2 sensor tomorrow, any tips for the right bank (rear) manifold O2 sensor? Link to comment Share on other sites More sharing options...
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