2001 3.5L Intrigue Code P0300

Hello all! First I want to thank everyone on this board. You have already helped me with a serious problem with my wife's 2001 Intrigue, and I did not have to post a question to fix. Every light, Service Engine, ABS, Traction, Security, ETC was on. After reading several post about the ignition switch, I pulled it out yesterday, and replaced it. That cleared most of my problems. I now have a Service Vechicle Soon light on and the car has a miss. It acts almost like it is a gas problem. When I drive it, pulling out and getting up to highway speed, it will bog down and you have to let up on the gas, then it will start to pick up speed slowly, and will run standard speeds. It is giving only one code. That is a 0300, which is a random cylinder misfire. I have just replaced the plugs and checked the boots in the last two months. Also, I have changed the fuel filter(the old one was not clogged). And I as stated, I replaced the ignition stitch yesterday. Can someone please give me a starting point and figuring out why the car is bogging down and throwing the 0300 code. Thanks again to everyone for the help so far.

Have you checked your fuel pressure? You can probably rent a gauge briefly from an Auto Parts store, or I actually bought an inexpensive one from Harbor Freight. Low fuel pressure could definitely cause that sort of behavior. I dont know what sort of numbers the 3.5 is even supposed to run though. If memory serves mine was testing at between 35-40psi when running at idle.

Another thing that could cause that sort of behavior is a clogged catalytic converter. Especially the power at only half-throttle or so business. Most folks say to crawl underneath the car and give the cat a couple good hits and listen for rattling or anything that sounds like something stuck in there....I dont know of a good way to test that though.

My next question is: is the random misfire something that has been happening for a long time? Or did it just start? I briefly dealt with a random misfire, but the first time it threw the code was just after I had gotten gas. I attributed it too some bad gasoline and threw the works at it (Seafoam and HEET if memory serves) and cleared the code and it never came back.

Thanks for the info. The missing has been going on for a while. The Ignition Switch I replaced Saturday fixed 5 other codes the car was throwing. I don't remember all of them at this moment, but one was a Oxygen Sensor. Prior to me replacing the Ignition Switch, it was not only missing, but would randomly die, even at speeds of 40 or 45. So, I will get the fuel pressure checked ASAP. I have done the "Knock" test on the Catalytic Converter, but did not hear anything loose. I also checked it at night to see if it was glowing. Seems I recall that if they were clogging up, they would turn cherry red. Again, thank you for replying, and I will get the fuel pressure checked ASAP and will post the results here. I am also going to recheck the Plug Boots, as I did not replace them when I put new plugs in. I did inspect them, but maybe I missed a pinhole or something. Thanks Again!!

I would think the plug boots would exhibit similar problems as plug wires. Typically when plug wires are b ad youll have a miss a low rpm under heavy load, but if you floor it, it will run smooth. At least thats how they act some of the time haha.

Something else I thought of that you can try...

Try unplugging the vacuum line from the fuel-pressure regulator. It will be on your fuel-rail, cant recall where exactly without looking at mine, but it looks like this:
http://info.rockauto.com/SMP/PR223_FULL.jpg (part of it will obviously be inside the fuel-rail)

If for any reason there is gas in that vacuum line, your FPR is toast, but they usually dont cause problems like what youre having. The reason I say unplug it, is that if memory serves it should max out your fuel-pressure, which might do away with, or at least change your symptoms around a little bit.

I did not get to work on it at all yesterday afternoon, but am going to get to it today after work. I will check the vaccum line as well. These generic codes will drive a man crazy. I use to love working on cars back in the day, but that was before all of the computer crap. There is a sensor for everything now, but the generic codes really do not narrow it down a whole lot. Thanks again for the help and I will post the results. Thanks!!!

I did not get to work on it at all yesterday afternoon, but am going to get to it today after work. I will check the vaccum line as well. These generic codes will drive a man crazy. I use to love working on cars back in the day, but that was before all of the computer crap. There is a sensor for everything now, but the generic codes really do not narrow it down a whole lot. Thanks again for the help and I will post the results. Thanks!!!

At least troublecodes give you a starting point. :)

As far as the random misfire code goes, what spark plugs did you put in? Did you gap them to .052"? Standard copper plugs work OK at first, but don't last too long and all Bosch plugs do the same thing with that engine. The OE NGKs plugs work best. The NGK number is PTR5C-13 (or stock #7740). The AC-Delco number is 41-980. The latter is just the former in an AC-Delco box except they have a GM p/n stamped on them instead of an NGK p/n.

FYI! I pulled the plugs and boots off of the front side after work this evening. It has Bosch Platinum + 4 Plugs in it. The front side boots look ok. Could not find any Pin holes or cracks in them. I was looking for the fuel pressure regulator as it was getting dark. I unplugged a sensor that is located on the Throttle Body and drove the car down the road. It did not miss or cut out at all. I don't know if I stumbled on a bad sensor by luck, or if it has just changed the system enough to fool me. I will post what else I find. And Ruley73, you said the Bosch plugs were really not that good for this car? If so, I will make sure and get the NGK or Delco and put in. Thanks for all of the help!!
Edited!! The sensor I unplugged was the throttle position sensor or one of the air sensors. I looked for a picture of this engine after I unplugged the sensor on this board, found a similar, but not quite the same engine, and going by that, it was one of the two. The sensor was mounted on the firewall side of the throttlebody at the top, it had two vaccume lines on it as well. But this was not the "fix" I drove it again after it got to dark to work on, and it started missing again!! Just wanted to let everyone know the car is toying with me!!! LOL

FYI! I pulled the plugs and boots off of the front side after work this evening. It has Bosch Platinum + 4 Plugs in it. The front side boots look ok. Could not find any Pin holes or cracks in them. I was looking for the fuel pressure regulator as it was getting dark. I unplugged a sensor that is located on the Throttle Body and drove the car down the road. It did not miss or cut out at all. I don't know if I stumbled on a bad sensor by luck, or if it has just changed the system enough to fool me. I will post what else I find. And Ruley73, you said the Bosch plugs were really not that good for this car? If so, I will make sure and get the NGK or Delco and put in. Thanks for all of the help!!

Yep, I'm willing to bet those Bosch +4 spark plugs are at least a good chunk of your problem. The boots usually don't need to be replaced, but I did have to replace a couple once because oil leaked into the plug openings and made them brittle and crack. My wife's old car was a '99 Intrigue GL with the 3.5. I also learned the hard way the Bosch Platinum (regular, +2, +4) plugs are junk; especially in that engine. The Bosch Super or "Copper Plus" as they call them now are actually OK plugs, but since they are just standard plugs they won't last much more than 20,000 miles. Since replacing plugs is a chore on this engine, I'd only use what I know is best for it and that is the NGK/AC-Delco plugs. They should come pre-gapped since that part number is specific to that engine, but always double check them anyways.

One other thing I'd do is pull out the MAP sensor (squarish looking, post throttlebody on intake plenum w/3 wire plug) and spray some carb cleaner in it a few times. It is in a bad place (near PCV lines) and get oil in it quite a bit.

Well, it was not the sensor I mentioned in my last post. After I posted my last, I looked for the fuel pressure regulator while I was pulling the front three plugs, following the fuel rails, and I did not find it. It's like that old saying, "If it had been a snake it would have bit me" but I will relook and pull the vaccume line and see if there is any gas there. I think I will take your advice and go ahead and replace the plugs with what you suggested. The boots were in good shape, very flexable, no white pin holes. I will also go ahead a clean the MAP sensor as well. It is going to be something simple I know, but it sure is aggravating to find. The ignition switch was, thanks to this board, a very easy repair considering how many codes that one switch cleared when it was replaced. Onward and upward! I will not get to work on it this evening as my wife has to work a ten hour day. I will try to change and check everything including the fuel pressure by this weekend and will post the results then. Thanks for all of the help everyone.

You ever stop at a convenience store and get some bad directions? Well thats what happened when I told you where the FPR was, its on the complete opposite side of where the fuel lines run in. I decided to take a couple pics for ya. Quality isnt the greatest, cellphone was within arms reach.

http://members.localnet.com/~jester87/Image000_3.jpg
FPR is in basically the center of the pic, mine is goldish (and kinda dirty) with the vac line running into it. Has the silver metal clip holding it into the fuel rail. On a sidenote, Id hold off on replacing it until youre sure its causing problems, its about a 50 dollar part.

http://members.localnet.com/~jester87/Image001_2.jpg
Since I suggested checking fuel pressure, I might as well show you where. This is the front side of the fuel rail. What youll need to do is unscrew that plastic cap (looks like a big tire valve stem cover) and then underneath is where youll attach the fitting from your gauge.

Thanks LittleHoov! That is a good picture. And I was looking on the other side right before dark last night. I will have time hopefully, before dark tonight to pull the vaccume line of of the FPR and see if there is any fuel in it. I am not going to replace anything yet, before I rule out the FPR or to see what the fuel pressure is. I am going to change the plugs soon, and put Delco back in. I will let everyone know what I find. Thanks again!

MAF sensor. -clean it.

do a search on this forum after you sign in for P0300 -note that code also clears all previous codes.

Yeah cleaning the MAF sensor is a good idea. On the 3.5 its in the air intake tube. Cant miss it.

Thanks guys! I have already cleaned the MAF sensor. I found the link last week on how to clean it and took care of it. I also found the FPR last night after my wife got home and pulled the vac line off. There was no gas in the line. So, onward and upward. Just to be sure, I am going to go ahead and put the Delco plugs back in the car this weekend, and recheck the boots. I will be checking this board often to see if anyone has come up with something I have not checked or replaced already. Thanks again for all of your help. Have a great day!

Ok, just got through installing new plugs, Used the NGK's. I reset the trouble code, drove down the road, felt a slight miss, drove home and rechecked trouble codes. I am now getting a PO131, which is 02 sensor circuit low voltage bank 1, sensor 1, and a PO171- which is System to lean Bank 1, and the original PO300. That is all of the time I have today as I have to be somewhere in a little while. Thought I would post and see if anyone had any more thoughts. Thanks everyone!

Ok, just got through installing new plugs, Used the NGK's. I reset the trouble code, drove down the road, felt a slight miss, drove home and rechecked trouble codes. I am now getting a PO131, which is 02 sensor circuit low voltage bank 1, sensor 1, and a PO171- which is System to lean Bank 1, and the original PO300. That is all of the time I have today as I have to be somewhere in a little while. Thought I would post and see if anyone had any more thoughts. Thanks everyone!

I'm convinced that checking your fuel pressure is the next step. Low fuel pressure would cause a constant lean running condition. That could trigger all of the codes you've seen so far.

I'd also check the harness going to the upstream O2 sensor (located on top of rear exhaust manifold) and make sure it looks ok.

Thanks Ruley73! The fuel pressure was the next thing I was going to get checked. I do not have a gauge, but a friend of mine does, so tomorrow after work I will get that checked, I will also check the harness on the rear exhaust 02 sensor and see if I can detect anything wrong there. Thanks, I will let the board know what I find.

Thanks Ruley73! The fuel pressure was the next thing I was going to get checked. I do not have a gauge, but a friend of mine does, so tomorrow after work I will get that checked, I will also check the harness on the rear exhaust 02 sensor and see if I can detect anything wrong there. Thanks, I will let the board know what I find.

I wanted to make sure you check the right 02 sensor. It is the upstream (pre-catalytic converter) sensor that is located on the top side of the rear exhaust manifold.

I'm also wondering if you have or have recently had an aftermarket alarm installed? There is a TSB (TSB # 02-06-05-004B) out regarding alarm systems intermittently shutting off and turning on the ignition circuit (occurring within milliseconds and are often unnoticed by the driver) causing the P0300 code and premature failure of the catalytic converter. I'm guessing the cat. con. failures are due really high temps caused by a prolonged lean running condition.

No, there has been no aftermarket alarm installed. I will make sure to check the correct 02 sensor and wiring harness as well. I will let everyone know what I find. Thanks again for all of the help!

the cat could be plugged still,do you get a foul rotten egg smell occasionally?

the random misfire code is common, so common in fact someone made an entire web site dedicated to it

http://www.random-misfire.com/

Sorry about taking so long to post, but I just now got the fuel pressure checked. With the ignition switch on, but not started, I get 40 pounds of pressure. When I start the car it drops to 38 psi, and after I cut the engine off it drops to around 32 psi and stays there. I left the gauge on for around 10 min after I cut the engine off to see if the pressure would drop to zero quickly. Anyway, I have also checked both o2 sensors, or rather the wires. I have a DVM. Does anyone know what the o2 sensors should read,(voltage) when you start the engine? I have got to check the cat converter somehow, even if it means cutting it out and driving the car without it to see if it improves. I am at the point of having to try to shotgun the problem, I just do not have the money for a lot of expensive parts that I do not need. Thanks again to everyone who have offered help, and if anyone can think of anything I may have overlooked up to this point, please leave a post. Everyone have a great weekend. Thanks!!

Sorry about taking so long to post, but I just now got the fuel pressure checked. With the ignition switch on, but not started, I get 40 pounds of pressure. When I start the car it drops to 38 psi, and after I cut the engine off it drops to around 32 psi and stays there. I left the gauge on for around 10 min after I cut the engine off to see if the pressure would drop to zero quickly. Anyway, I have also checked both o2 sensors, or rather the wires. I have a DVM. Does anyone know what the o2 sensors should read,(voltage) when you start the engine? I have got to check the cat converter somehow, even if it means cutting it out and driving the car without it to see if it improves. I am at the point of having to try to shotgun the problem, I just do not have the money for a lot of expensive parts that I do not need. Thanks again to everyone who have offered help, and if anyone can think of anything I may have overlooked up to this point, please leave a post. Everyone have a great weekend. Thanks!!

That fuel pressure is just a little low, 41-47 PSI is the spec. I'm assuming that spec for is key on engine off, but my source doesn't say. What you could do temporarily is remove the upstream O2 sensor to check the catalytic converter, and see if its clogged. I would also replace the fuel filter if you haven't done so already.

hey ruley73. Could a bad MAF cause these problems? I know the OP cleaned the MAF but these sensor are known to go bad on the 3.5L Intrigue. I know before I traded my Intrigue in, I had to replace the MAF because it kept throwing a code, even after cleaning. I replaced mine with a used unit from E-Bay.

Just a thought...

hey ruley73. Could a bad MAF cause these problems? I know the OP cleaned the MAF but these sensor are known to go bad on the 3.5L Intrigue. I know before I traded my Intrigue in, I had to replace the MAF because it kept throwing a code, even after cleaning. I replaced mine with a used unit from E-Bay.

Just a thought...

Yes, it is a possibility. FYI it is the same MAF sensor used with the 3100 or 3400 engines in the 1997-2003 Pontiac Grand Prix, 1997-2005 Buick Century, 1999-2005 Pontiac Grand Am/Oldsmobile Alero, 1997-1999 Oldsmobile Cutlass, 1997-2005 Chevy Malibu/Classic, 2000-2004 Chevy Monte Carlo/Impala/Lumina.

The MAF sensor is not specific to the 3.5L unlike most other parts for this engine. If you can find one of these vehicles to temporarily swap and see what happens, you could quickly rule this out.