Ed Hall Posted July 21, 2009 Report Share Posted July 21, 2009 While on a trip driving towards San Diego, my 93 Allante suddenly started bucking as though the gas tank was running empty on fuel. I still had nearly 1/2 a tank of fuel. I managed to get the car off the freeway and to a gas station. I thought it might be a ground issue so I got a piece of wire and clamped one side down to the engine and the other side to the shock tower. However, it made no difference. I decided to take the chance and continued on my trip. After several miles, the bucking seemed to clear up. About 2 hours from San Diego, I got hungry and parked the car so I could eat. About 1/2 hour, I returned and started the car and the problem was even worse. It took me about 15 tries to get engine to run. I finally got the engine started, put it into gear and smashed the throttle to the floor to get the car rolling. Once I got back to the freeway, the engines horrible bucking slowly cleared up. I made it to my destination in San Diego but who knows if I'm going to be able to drive it tomorrow. From previous posts, I have not been able to fix the warm hard starting problem. Gas mileage around town is also horrible and much worse than my 82 Chevy Suburban. I have replaced the FPR, spark plug wires and fuel filter. I don't believe the problem is the Idle Speed Controller. I thought that was the problem at first and disconnected it but it continued to buck in idle. Basically, it idles from 500 rpm's to about 2000 rpm's. The engine keeps dying and does not want to start back up again. Also, I have no codes. Link to comment Share on other sites More sharing options...
joeb Posted July 21, 2009 Report Share Posted July 21, 2009 bucking can be the same as dying from lack of fuel flow. fuel pump, fuel filter. happened to me. car died. towed home. ran fine. did it again 2 weeks later. towed again. turned out to be crud in the gas and clogged fuel pump pickup. never use old gas from a seldom used boat fuel tank. Link to comment Share on other sites More sharing options...
Ed Hall Posted July 21, 2009 Author Report Share Posted July 21, 2009 Update: The following codes are present as history: P032 ..... Open MAP Sensor Signal P041 ..... No Cam Reference Signal from Ignition Control Module P071 ..... Intermittent MAP Signal P095 ..... Engine Stall Detected The way the engine runs is if someone is turning the ignition on and off at a frequency of 1 second. Link to comment Share on other sites More sharing options...
Jan Olsson Posted July 21, 2009 Report Share Posted July 21, 2009 Update: The following codes are present as history: P032 ..... Open MAP Sensor Signal P041 ..... No Cam Reference Signal from Ignition Control Module P071 ..... Intermittent MAP Signal P095 ..... Engine Stall Detected The way the engine runs is if someone is turning the ignition on and off at a frequency of 1 second. Seems like you have a problem with the MAP sensor or the connections/wires to it. I believe that a bad MAP could be causing all the problems. I'm not sure if the P041 is caused by the engine stalling as well but I would start with the MAP-sensor. Link to comment Share on other sites More sharing options...
Ed Hall Posted July 24, 2009 Author Report Share Posted July 24, 2009 UPDATE: Thanks for all the help. Turns out, the problem was most likely was the Manifold Absolute Pressure (MAP) sensor. I drove the car back home on the 200 mile trip without incident last night. I was lucky that this was the problem because it was a relatively easy sensor to change out and I was able to do it in the hotel parking lot. The problem with the bucking came on suddenly so I figured most likely it had something to do with the computer rather than clogged injectors or CAT. The engine was also not missing so that ruled out fuel problems, spark problems or EGR problems. I have already put in new coils, new custom made MSD wires and a new AC Delco FPR. So it came down to a bad Crankshaft Position Sensor (CPS), bad MAP sensor, bad PCM or bad ground. I ruled out that it was a bad ground by using my battery jumper and connecting one end to the engine block and the other to the negative battery terminal wire. This made no change so I knew that this was not the problem. This new MAP sensor however has not fixed the previous hard warm starting problems and bad city economy. It still takes lots of cranking to get the car started and once started, I can smell raw fuel out the exhaust. I also notice that when driving on the freeway going downhill, the engine does a slight amount of surging at minimal throttle level. I have not put in new spark plugs so I’m going to try that next. Link to comment Share on other sites More sharing options...
MrEldo97 Posted July 24, 2009 Report Share Posted July 24, 2009 For the hard hot starts and poor fuel economy try swapping out the Fuel Pressure Regulator. Link to comment Share on other sites More sharing options...
Jan Olsson Posted July 24, 2009 Report Share Posted July 24, 2009 For the hard hot starts and poor fuel economy try swapping out the Fuel Pressure Regulator. Ditto that! Link to comment Share on other sites More sharing options...
Ed Hall Posted July 24, 2009 Author Report Share Posted July 24, 2009 For the hard hot starts and poor fuel economy try swapping out the Fuel Pressure Regulator. Since I replaced the FPR about a year ago and noticed no improvement, is there something else that could be wrong that would produce the same exact symptoms? Link to comment Share on other sites More sharing options...
Jan Olsson Posted July 24, 2009 Report Share Posted July 24, 2009 No other codes? The engine could be running in open loop mode all the time. How's the temp? Link to comment Share on other sites More sharing options...
KHE Posted July 24, 2009 Report Share Posted July 24, 2009 For the hard hot starts and poor fuel economy try swapping out the Fuel Pressure Regulator. Since I replaced the FPR about a year ago and noticed no improvement, is there something else that could be wrong that would produce the same exact symptoms? Leaking injector(s)? Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Jan Olsson Posted July 24, 2009 Report Share Posted July 24, 2009 If the engine is smoth running then we can propably exclude leaking injectors. Then the engine would miss/run rough. Wouldn't it? Link to comment Share on other sites More sharing options...
Ed Hall Posted July 24, 2009 Author Report Share Posted July 24, 2009 No other codes? The engine could be running in open loop mode all the time. How's the temp? No other codes have come up since installing the new MAP sensor. The check engine light does not come up so that must mean it's running in closed loop. The temperature always runs between 98 and 105 degrees celcius. For the hard hot starts and poor fuel economy try swapping out the Fuel Pressure Regulator. Since I replaced the FPR about a year ago and noticed no improvement, is there something else that could be wrong that would produce the same exact symptoms? Leaking injector(s)? I performed a pressure check several months ago and it held pressure for a reasonable amount of time with the key off so I don’t believe the injectors are leaking. If the engine is smoth running then we can propably exclude leaking injectors. Then the engine would miss/run rough. Wouldn't it? The engine idles with a slight lope to it. It’s not completely smooth. My brother in laws N* engine idles much smoother but it’s the lower performance version. Another thing I should mention is the engine surges ever so slightly at freeway speeds while at extremely light throttle positions. I don't know if this is normal or not. Link to comment Share on other sites More sharing options...
Jan Olsson Posted July 24, 2009 Report Share Posted July 24, 2009 No other codes? The engine could be running in open loop mode all the time. How's the temp? No other codes have come up since installing the new MAP sensor. The check engine light does not come up so that must mean it's running in closed loop. The temperature always runs between 98 and 105 degrees celcius. For the hard hot starts and poor fuel economy try swapping out the Fuel Pressure Regulator. Since I replaced the FPR about a year ago and noticed no improvement, is there something else that could be wrong that would produce the same exact symptoms? Leaking injector(s)? I performed a pressure check several months ago and it held pressure for a reasonable amount of time with the key off so I don’t believe the injectors are leaking. If the engine is smoth running then we can propably exclude leaking injectors. Then the engine would miss/run rough. Wouldn't it? The engine idles with a slight lope to it. It’s not completely smooth. My brother in laws N* engine idles much smoother but it’s the lower performance version. Another thing I should mention is the engine surges ever so slightly at freeway speeds while at extremely light throttle positions. I don't know if this is normal or not. About the only thing left is the TPS. Works like the acc.pump on a carburettor. It can be out of whack or defect. Any problems with shifts at the wrong time/harsh shifts etc? I think we can rule out any fuel related problems. Pressure is ok, no leak down. MAP changed, IAT ok, temperature ok. A TPS could cause incorrect idle/idle speed etc. Link to comment Share on other sites More sharing options...
Jan Olsson Posted July 24, 2009 Report Share Posted July 24, 2009 I had occasionally high idle problems. Could be 1300 rpms, 2000 etc. No codes. I pulled the connector to the TPS and sprayed it with WD-40 and it has worked fine until recently. Now I get shifts at odd speeds, almost right but about 10 km/h slower speed than usually. The funny thing is that I visited my parents the other day and my fathers Volvo 960 (with automatic transmission) threw a TPS code. It did just the same things. High idle, wrong shift points, bad idle quality. He changed it to a unused one (the old one was filled with oil, propably residues from the intake) and the problem was solved. It threw a code though. A bad TPS/wrong adjustment could cause poor fuel economy too since it can make the PCM think that the car is accelerating (wrong throttle angle) Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 24, 2009 Report Share Posted July 24, 2009 Have you put a fuel pressure gage on it, and look to see what happens when you turn the key on?, I think the early NSs had a secondary fuel pump switch actuated by oil pressure, when the the fuel pressure relay malfunctioned. Maybe the cranking, gets oil pressure up enough to turn on the fuel pump? 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...
Phillip Posted July 24, 2009 Report Share Posted July 24, 2009 Have you considered a vacuum leak? I have never had this problem with a N*, but I have had many of these symptoms occur when vacuum hoses start to leak. Link to comment Share on other sites More sharing options...
Ed Hall Posted July 24, 2009 Author Report Share Posted July 24, 2009 About the only thing left is the TPS. Works like the acc.pump on a carburettor. It can be out of whack or defect. Any problems with shifts at the wrong time/harsh shifts etc? I think we can rule out any fuel related problems. Pressure is ok, no leak down. MAP changed, IAT ok, temperature ok. A TPS could cause incorrect idle/idle speed etc. There are no problems with the shifts. It shifts well and at the right time. I did go into the computer and looked at TPS readings while pressing on the accelerator but did not seeing anything out of sorts. I originally thought the bucking was caused from a defective TPS. Link to comment Share on other sites More sharing options...
Ed Hall Posted July 24, 2009 Author Report Share Posted July 24, 2009 Have you put a fuel pressure gage on it, and look to see what happens when you turn the key on?, I think the early NSs had a secondary fuel pump switch actuated by oil pressure, when the the fuel pressure relay malfunctioned. Maybe the cranking, gets oil pressure up enough to turn on the fuel pump? Yes, I have. When I turn on the key, the fuel pressure immediately goes to 40 psi. However, I do have a defective oil pressure sending unit. My oil pressure is always maxed out. I should get a new oil pressure sendor unit but the hard starting problem existed before the sending unit pooped out. Have you considered a vacuum leak? I have never had this problem with a N*, but I have had many of these symptoms occur when vacuum hoses start to leak. What's the best method to test for vacuum leaks? I have not looked into this. Link to comment Share on other sites More sharing options...
Jan Olsson Posted July 24, 2009 Report Share Posted July 24, 2009 There are no problems with the shifts. It shifts well and at the right time. I did go into the computer and looked at TPS readings while pressing on the accelerator but did not seeing anything out of sorts. I originally thought the bucking was caused from a defective TPS. I miss OBD-I I can't check those things anymore Link to comment Share on other sites More sharing options...
KHE Posted July 25, 2009 Report Share Posted July 25, 2009 Ed, Unless you performed a leakdown test on the injectors with the Kent-More tool to activate the injector for a specific period of time and then watched the fuel pressure gage for identical pressure drop for each injector, I wouldn't put much faith in the fact that the system holds pressure for a reasonable amount of time correlating to non-leaking injectors. I would lift the fuel injectors and fuel rail out of the manifold and then thrn the ignition to ON and let the fuel pump pressurize the system. Look at the bottoms of the injectors and of there is any fuel droplets hanging on them, replace them. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Phillip Posted July 25, 2009 Report Share Posted July 25, 2009 To check for vacuum leaks, start by listing for a wistling sound. Next use a vacuum guage to confirm that there is sufficient vacuum. Given the severity of your performance problems, it should be fairly obvious, although in my experience, when I am looking for an ignition or fuel problem, it is easy to miss the vacuum lines. I wouldn't hold out a lot of hope for this, but given the age of the car, it is worth ruling this out early. Link to comment Share on other sites More sharing options...
coolnesss Posted July 25, 2009 Report Share Posted July 25, 2009 To check for vacuum leaks, start by listing for a wistling sound. Next use a vacuum guage to confirm that there is sufficient vacuum. Given the severity of your performance problems, it should be fairly obvious, although in my experience, when I am looking for an ignition or fuel problem, it is easy to miss the vacuum lines. I wouldn't hold out a lot of hope for this, but given the age of the car, it is worth ruling this out early. In a car of that age, I would find each end of each vacuum tube and snip off the end about 1/2 inch or so, and then put the now-virgin tube onto the apparatus it's connected to. With heat and over time, the tips harden and don't seal as well. This has improved the running of several cars I've had over the years. It's good preventative maintenance, even if it doesn't solve the problem. Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 25, 2009 Report Share Posted July 25, 2009 To check for vacuum leaks, start by listing for a wistling sound. Next use a vacuum guage to confirm that there is sufficient vacuum. Given the severity of your performance problems, it should be fairly obvious, although in my experience, when I am looking for an ignition or fuel problem, it is easy to miss the vacuum lines. I wouldn't hold out a lot of hope for this, but given the age of the car, it is worth ruling this out early. In a car of that age, I would find each end of each vacuum tube and snip off the end about 1/2 inch or so, and then put the now-virgin tube onto the apparatus it's connected to. With heat and over time, the tips harden and don't seal as well. This has improved the running of several cars I've had over the years. It's good preventative maintenance, even if it doesn't solve the problem. Good tip, and exactly what I used to do, as they cracked at the ends 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...
Ed Hall Posted July 25, 2009 Author Report Share Posted July 25, 2009 I checked the resistance on each injector and they all were around 13 ohms. I then did the injector drip test by turning on the key but did not find any dripping injectors. I then put the intake manifold cover back on and went to start the engine but it locked up. Apparently, the engine got flooded. I don't want to take the spark plugs out so I was wondering how much time it will take for the gas to evaporate. Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 25, 2009 Report Share Posted July 25, 2009 I checked the resistance on each injector and they all were around 13 ohms. I then did the injector drip test by turning on the key but did not find any dripping injectors. I then put the intake manifold cover back on and went to start the engine but it locked up. Apparently, the engine got flooded. I don't want to take the spark plugs out so I was wondering how much time it will take for the gas to evaporate. Explain locked up, that sounds ominous 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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