R Holland Posted May 19, 2014 Report Share Posted May 19, 2014 I bought a 1996 Regal Gran Sport with the 3.8L V6. The car currently has 135,000+ miles on it. The car ran fine when I initially bought it. After putting on about 2000 miles on it, the engine is running rough and takes like 3 to 4 tries to start the engine. The original owner had the car serviced up until 57,000 miles when she gave it to her daughter who didn't do anything to the car other than having the oil changed once in awhile. I did do a tune up when I bought it to include plugs, wires, PCV valve, air filter and both O2 sensors. The engine threw a code and I replaced the MAF sensor. Engine was still runing good at this point. Then is threw a code for random cylinder misfire. I found a bad coil pack and replace all three as a set. Engine ran fine. Then it began running rough. So I replaced the fuel filter and car ran fine for a day. The I replaced the fuel pressure regulator and the car ran fine for a day. So I replaced the fuel pump, fuel pulsator and all rubber fuel lines at the tank and on the evaporator canister. Car ran fine for a day. So now I replaced the upper and lower intake gaskets and plenum, the gaskets were shot and falling apart. I also replaced the IAC as that was pretty fowl with carbon and the spring was fairly well corroded. I also replaced the o-rings on the injectors. Engine is still hard starting and running rough. I checked the injectors with a meter and get between 13.2 to 13.5 ohms on them. The fuel pressure is reading 32 psi at idle and fluctuates a bit between 30 to 32 psi sometimes. Shouldn't the fuel pressure be higher? I checked the shop manual and it says 37 psi. Bad pump out of the box or is there something else causing a restriction? Should I just go ahead and replace the injectors? Any help with this would be appreciated. Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted May 20, 2014 Report Share Posted May 20, 2014 Fuel pressure is supposed to be 48-55psi key on/engine off and 3-10 psi lower than that w/ the engine on. Since you're a bit on the low side, I would suspect the "new" fuel pump is not up to the task or that something related to the new pump is causing the pressure to be low. This is assuming your test gauge is giving you accurate readings. What do you get key on w/ the engine off? Does the pressure hold after you prime the system? Generally speaking, it shouldn't bleed down more than 5psi in ten minutes time. Quote Link to comment Share on other sites More sharing options...
R Holland Posted May 20, 2014 Author Report Share Posted May 20, 2014 The fuel pressure at idle is 32 psi and there is no fuel pressure when the engine is off. It seemed like I had better pressure before installing the new pump, but with either the old or the new pump I still had/have this rough idle and hard starting. I'm curious if the fuel pulsator could be the issue? I've heard people removing this from the fuel circuit because of pressure issues. The test gauge is new. The fuel pump is a Bosch unit. Quote Link to comment Share on other sites More sharing options...
ron350 Posted May 20, 2014 Report Share Posted May 20, 2014 Exactly what fuel pump did you install? Quote Link to comment Share on other sites More sharing options...
l67ss Posted May 20, 2014 Report Share Posted May 20, 2014 Check ur icm Quote Link to comment Share on other sites More sharing options...
R Holland Posted May 20, 2014 Author Report Share Posted May 20, 2014 ron350, I replaced the fuel pump with this unit: http://www.rockauto.com/catalog/moreinfo.php?pk=977691&cc=1021374 Quote Link to comment Share on other sites More sharing options...
ron350 Posted May 20, 2014 Report Share Posted May 20, 2014 Before you throw rocks at the Bosch fuel pump put your old fuel pressure regulator back in and see if the pressure goes up. For a fuel pump I would only buy AC Delco locally because of all the trouble people have with brand new pumps even Delcos. These pumps are supposed to have a check valve in them that prevents gas from flowing back through them. One of these fuel systems in good shape should hold 40 PSI over night if the injectors are not dripping. ACDELCO Pump EP375 Quote Link to comment Share on other sites More sharing options...
R Holland Posted May 21, 2014 Author Report Share Posted May 21, 2014 So far I found one injector that is bad. But the main issue is down below. There's barely any flow coming from the fuel line. I'll have to disconect the line to the filter and see if the issue is a clogged filter, which was replaced 2 weeks ago, or if I need to drop the tank again and see if the pump is bad or the connection from the pump to the fuel line is leaking somewhere. At least I've narrowed it down. Quote Link to comment Share on other sites More sharing options...
ron350 Posted May 21, 2014 Report Share Posted May 21, 2014 Sounds like a good start making sure the fuel lines are open. Once I saw a 3800II fuel rail that had a clog just past the fuel regulator in the u-bend. Quote Link to comment Share on other sites More sharing options...
R Holland Posted June 5, 2014 Author Report Share Posted June 5, 2014 Okay, so I pulled the fuel pump and found that the fuel pulsator wouldn't stay on the pump. Pulled it out and installed a piece of fuel injection line. Fuel pressure now runs at a steady 45 psi at idle. Engine started up and ran fine for about 2 minutes and then began running rough again. The car sat for a couple of days and when I went to start it up, it took a few trys. Engine still runs rough at idle and when I took it around the block, engine stalled when I slowed down. Cooling fans won't come on now unless you disconnect the lead from the temp sensor. Everything I've been reading says it's either the MAF sensor, which was replaced or the crank sensor in regards to the rough idle and stalling. That still doesn't explain the issue with the cooling fans. Now I'm wondering if the ECM is going bad. I'm about ready to throw a molotov cocktail at this POS and watch it burn. Anyone have any ideas? Quote Link to comment Share on other sites More sharing options...
ron350 Posted June 7, 2014 Report Share Posted June 7, 2014 Wow your Regal is not playing nice. OK things that will cause bad idle without setting a code on a 96.Regal 3800II. Bad gasoline. Poor ground connections at the block and poor positive connection at the starter. Bad injectors. I think GM had a recall on bad Bosch injectors in 96 and I know they have a ECM reflash update to prevent intake manifold explosions. The bad batch of Bosch injectors will drip gas after the motor is turned off which can cause a large explosion when cranking the car. I know all about this because it happened to my 96. Vacuum leaks. The corrugated steel EGR pipe cracks along the bottom and causes a vacuum leak. Gummed up Idle Air Control passage. Bad Temp Sending Unit. If the ECM does not see the resistance it expects to see from the temp sensor the motor will run like crap. The unit is two sensors in one with one working the temp gauge and the other goes to the ECM. You can have the dash temp gauge working and still have a bad sensor. Bosch O2 sensors. Bosch spark plugs but they usually set a code 0300 misfire code. Quote Link to comment Share on other sites More sharing options...
ron350 Posted June 7, 2014 Report Share Posted June 7, 2014 Forum is not working properly? Quote Link to comment Share on other sites More sharing options...
R Holland Posted June 7, 2014 Author Report Share Posted June 7, 2014 Thanks for the info Ron. I put the scanner tool on it again today and got back 2 codes, P0118 and P1115. Both are related to the temp sender which I had just replaced when I did the intake gaskets. I'm now curious if the sensor is bad out of the box. I did notice that some of the cables from the battery look questionable. I guess I'll just replace them if not for anything else, preventative maintenance. Quote Link to comment Share on other sites More sharing options...
ron350 Posted June 8, 2014 Report Share Posted June 8, 2014 I don’t know how my posts look to you but they look like a long paragraph to me. Every thing is all messed up, the forum would not let me in for a couple of days and now will not let me edit. Now I can only us Quick Reply when it let me. The Engine Coolant Temp Sensor wires need to be inspected for brakes or scraped insulation. The plastic engine cover will cut into the wires insulation just above the thermostat housing. The Yellow and Black wires are the important wires that go to the ECM and the Green wire feeds the dash gauge. The dash gauge catches ground through the threads of the Coolant Sensor so don’t us too much Teflon tape on the threads. Quote Link to comment Share on other sites More sharing options...
R Holland Posted July 13, 2014 Author Report Share Posted July 13, 2014 Okay so here's the update on the Buick so far. Replaced the crankshaft position sensor and the car fires right up and runs pretty decent. There were no codes associated with the sensor, but after reading through quite a bit of posts, I figured why not try it. The cooling fans come on now and no more codes for that thanks to ron350 sending me a good used temp sensor. The parts store one just didn't cut it. There still is a slight miss at idle though. I put the scanner tool on it and saw that the TPS sensor would read .4 volts and then drop to zero or shoot up to .8 volts periodically while idling. These spikes in either direction correspond with the engine miss at idle. So I guess replacement of the TPS is the next step to getting this car back on the road. Quote Link to comment Share on other sites More sharing options...
R Holland Posted July 20, 2014 Author Report Share Posted July 20, 2014 Okay so I replaced the TPS unit with a new AC Delco and the car ran fairly decent. It was still missing here and there at idle. My guess is that the gas is pretty old now from sitting in the garage basically since February. Went to the gas station and put in some 93 octane and drove it to work. There was some hesitation until I got out on the interstate. Once I cleared out what was in the gas line, the engine ran really nice. Purred at idle when I got to work. So I'm hopeful that the engine work is complete. Now I need to replace the valve body on the transmission. More fun. Quote Link to comment Share on other sites More sharing options...
R Holland Posted July 21, 2014 Author Report Share Posted July 21, 2014 Okay, so after doing a complete tune up, replacing all coil packs, ignition modual, plenum, intake manifold gaskets and just about every sensor known to man, I'm still getting a Random Cylinder MIsfire. So, burn it? Take it to the dealer to check the computer? Quote Link to comment Share on other sites More sharing options...
Nas Escobar Posted July 21, 2014 Report Share Posted July 21, 2014 Are your spark plug cables in the correct firing order? This happened to me once, where I accidentally plugged in the cylinder 5 cable in cylinder 3. Check to make sure they're all in the right order. This one is pretty easy to overlook, especially if your coil packs don't have the numbers on them. Remember it's the odds on the firewall, the evens on the header panel (where the lights are). So it should be 1, 3, 5, in the back bank and 2, 4, 6 in the front bank, and well... just trace the cables from the coils to make sure they are in the right order. The coils should be in this order. Quote Link to comment Share on other sites More sharing options...
R Holland Posted July 21, 2014 Author Report Share Posted July 21, 2014 Nas, the spark plugs are in the correct order. I did the tune up initially when I bought the car and the car ran great for about a month and then just went down hill from there. I'm pretty much done with this POS and am scheduling a trip to the dealer for them to try and figure out what's wrong. Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted July 23, 2014 Report Share Posted July 23, 2014 the dealership will not diagnose a car that old and be able to fix it. they will probably try to get you to trade it in on a new car. I bet it's just bad grounds or battery or something that you could find that they will try to rip you off and never fix Quote Link to comment Share on other sites More sharing options...
R Holland Posted July 28, 2014 Author Report Share Posted July 28, 2014 I checked the cables and they don't show corrosion. The battery is relatively new, 1 year. I'm not showing a power drop on the cables from the battery. Car runs good for awhile and then will either jerk like the transmission is locking up or run like total crap. Stalled the other day for no reason while driving down the road. Other times it starts like crap and then smooths out and runs fine. It's not showing any codes. The engine does run much better than it did when I started having issues, but quite honestly I'm just tired of screwing with this car. I have a 1984 Trans Am that never had the level of issues that this car does. Quote Link to comment Share on other sites More sharing options...
ron350 Posted July 29, 2014 Report Share Posted July 29, 2014 Sounds like it is time to trade it in. Quote Link to comment Share on other sites More sharing options...
R Holland Posted August 12, 2014 Author Report Share Posted August 12, 2014 Okay, so the dealer had a shot and found a bad wire from the TPS sensor to the computer. They replaced the wire and also found that the MAF sensor I had replaced earlier this year was toast. So engine runs good now, however now I have a hot starting issue. Takes like 3 to 4 tries to get it started after turning it off within say 30 minutes. Starts fine when the engine is cold. Quote Link to comment Share on other sites More sharing options...
R Holland Posted August 13, 2014 Author Report Share Posted August 13, 2014 Okay, so finally after months of work on this car, I believe it's finally done. Today I replaced the IAT sensor ad the car starts every time, even when it's hot. Car runs smooth and idles decent now. Thanks for everyone's input and to ron350 for sending me a part. Hopefully now I can enjoy driving this while I rebuild the transmission on my Trans Am. Quote Link to comment Share on other sites More sharing options...
ron350 Posted August 14, 2014 Report Share Posted August 14, 2014 Great news. Can you please give more information about replacing the Idle Air Temp sensor? Some one recently had a thread about replacing the IAT sensor and curing a odd RPM problem? I had no idea the IAT sensors could cause so much trouble. All I knew was if you forgot to plug it in the air conditioner compressor would not work. Quote Link to comment Share on other sites More sharing options...
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