Engine: 2.8L MPFI V6.

So heres the situation. I just recently rebuilt the intake up on the motor. Last summer, the car ran perfectly fine. When I brought the car home, ran perfectly fine as well. After I rebuild the top end of the motor, car is running into some strange problems...

1. Junky fuel economy: Last summer, I was averaging 400+ to a tank of gas, sometimes getting close to 500. I babied it. I still do, and now my gas mileage has dropped to 336 to the last tank, and I almost ran it to the bottom of the gauge. I smell fuel sometimes, not often. I cant tell whether it is out of the exhaust, or motor. There is no sign of gas leakage around the injectors, or the fuel lines to the right of the motor that feed the injectors either.

2. The engine, when in either neutral or drive, at idle when stopped seems to vibrate the car and the idle seems to go to 500 or so, rather than the 700 or 800 that's normal. Certainly didn't seem to do this last year. I think the cat is what is making the noise, but the car is virtually identical to it as last year, so I don't think that the cat is what is causing the whole problem. The seat seems to vibrate a bit, as well as the dash and all of the interior, and it definately seems that the motor is the culprit.

3. The engine is throwing a code that is intermittantly coming on and off. It happens while cruising around 70-80, comes on for around 3 minutes or untill I slow down a lot, then it just goes away. The car keeps driving as if it didnt come on, and at that speed it is hard to hear a misfire or something like that. As far as I know, unless you drive around with a code reader on the motor and save the code when it pops up, then the code is erased the moment it goes away. Can I brake fast and pull over/ put it in neutral and turn it off while the code is still on, then ground out the diagnostic connector and see what shows up? I dont really have access to a code reader right now, and would hate to have to buy one. I guess I could rent one at like parts source or something like that, but the less $$$ to fix the better.

These are the main symptoms that are showing. Like I said, it didn't run like this last year. The oil is clean, no antifreeze is leaking there. While I rebuilt it, two vacccum lines broke, the little plastic ones, I think they carry the fuel vapour from the carbon canister. I drilled out where they went into slightly undersized, and then stuck the lines back into the rubber area where they broke. They seem pretty tight, and I hear no hissing from the lines. I plan on smoke testing it relatively soon, as right now those are my number one culprits on the list. I know that these motors absolutely hate vaccum leaks.

The second part is the aftermarket parts that went onto it. I bought a MSD street fire coil that is definitely rated higher voltage than the stock coil. I put bigger taylor cable thundercore or something like that wires on it as well. MSD cap and rotor kit also are on there, with NGK V power spark plugs (the spark plugs didnt come gapped to the V6 specs. MY book says 0.045 thou, if thats wrong let me know, and I will re gap them and re post.). The timing is set at the factory 10 degrees. Other than that, everything is basically stock.

Thanks for reading, and hope people have some possible solutions for this. I still am able to drive the car, but the fuel milage sucks and I hate the rattly noise. I am thinking of plugging the stock coil back in to see if it makes a difference by any chance, its worth a shot. IF there is something that I can put on those vaccum lines, like a glue or something, let me know as well, I will try that first.

Thanks a lot

Ben

 

Just read a post about timing... does this car have to be in drive to time it? That may explain the idle being low and shaky at stops. STill doesnt/shouldnt cure fuel issue...

 

Hey man. I dont know much about this motor. Sorry.

I do know, and you must be careful, how to check for vacuum leaks. Very carefully go around your intake/vacuum lines with an UN-LIT propane torch. If there is a leak/vacuum, it will idle up your motor. The more you give it the higher rev you will get. A old timer showed me the way. He actually used ether. lol. Barely have the torch open. Just a slight hiss.(NOT LIT, JUST GAS) You will know right away as the motor will speed up. Other ways Ive seen guys do it is with a cigarette, Wave the smoke around fittings/lines and watch what the smoke does. This is harder to do cause the running engine will blow the smoke away. Anyways. Good luck.

 

No, car does not have to be in drive to time.

 

Thanks for the tips guys. I will try and get this thing working a little better tomorrow. I Will try the propane torch and see if that works out for me. If it is leaking, can i seal it with something? What would be recommended? I have a feeling I wont be finding those plastic lines soon...

Still stuck on the fuel economy, and engine light though. I will wait for more info on that,although I think I will try and turn it off while the car is in neutral with the light on and ground the diagnostic connectors out and see if a code pops up.

 

Okay, so I have done some work over the past couple of weeks. I took the aftermarket coil off, and it seemed to help a bit. then I drove it more and the engine lights are back on.

Went over the whole intake vaccum lines etc with carb cleaner and propane, no leaks found. Took it to school auto shop and took it one step further: put a smoke machine on the intake. No leaks found, then the egr valve started smoking like a train, so I replaced that. Thought it was good, then on the drive home, engine light came back on again.

Finally had them on long enough to get the codes.

12, obviously, the system is working,..
34 and 44 - one is o2 sensor reading lean on the left bank, and the other is low voltage from MAP/MAF sensor with the side note high vaccum detected. (dont know which sensor its talking about, the code says MAP sensor, but I read on here that the V6 doesnt have both, only the MAF... let me know so I can test one/both).

So im still stuck with an up and down idle, and crap fuel economy.

Problem escalated in oak ville. Drove on a 1 and a half hour cruise, and stopped at a tim hortons. Came back out, and the car started, but hesitated on the throttle. Then it started stalling real bad. Got back to the car show, and it got running again. Took it up to the highway, and it sounded like bad misfiring and really hesitated under normal throttle conditions. Then, I took the wrong on ramp, so came back around to the street at 50kmh again and came to a stop. I put it in neutral so I could keep the rpms up, and then when I went to go and put it in drive, the car barely moved, backfired real bad and then died in the middle of the intersection. Trailered it home, and changed fuel filter, still didnt run. Put spark tester on it, no spark. Changed back to aftermarket coil again, and boom.... started right up. Took it for a test drive, no hesitation, but the codes are still there.

Any input on this? hopefully now that I have more info, I can get some more responses.