Odd 3.4 DOHC problems

[Upgrade]

Heres the deal: 1995 3.4 DOHC Lumina LS

 

Exhaust stinks like unburned fuel. Car is hard to start (have to flutter the gas pedal to get it going). Idle is rough and high (1100 RPM's) once it is running. Timing is right on. Gas mileage sucks. New plugs and wires. All the plugs and wires are connected and firing. Car will drive but it is shakey and idling high. The other day I was driving it and it started running like crap so I shut it off for a minute then restarted it and it ran fine except for the service engine soon light. Had to drive it a bit further and after a few miles it did it again and after shutting it down and starting it, it ran fine. I tried getting codes from it by jumping across the two contacts under the dash but the light never came on. Can anyone offer any suggestions? I have Monday and Tuesday to get it fixed.

[JS91Z34]

probable causes stuck injector/injectors, Bad fuel pressure regulator, MAP sensor, TPS, IAC motor, Low manifold vacuum, Mass air flow sensor. Try one of those and see what happens.

[96montyZ34]

possible EGR valve problem.

[JS91Z34]

possibly :?

[Robby1870]

you cant jump the connectors on a '95....wont work. You gotta go to a dealer and let them check them. yeah it sounds like a MAP or even crank position sensor going out

 

Robby

[nriesen]

my car does the same thing, i dumped a bottle of injector cleaner in it with 93 octane, it ran fine. Now, next tank is 93 octane, and no injector cleaner...runs a lil rough again....weird. I had codes 35 and 43, but they havent been back since i cleared em about 2 weeks ago.

[95GTP]

I have the same problem now. I have no idea where to start. It was running fine then started to chug/rough idle with real rich fuel smell.

 

No visable leaks, all vacuum hoses seem to be connected.

 

WTF??

[JS91Z34]

Mine was an O2 sensor problem. I replaced every sensor in the car. Car runs good again. You could also try checking/changing plugs and wires. Just a thought!

[CPSMonteZ34]

Don't worry about the MAP, they stopped with the 94. 95 went to MAF with IAC and EGR being the most suspect in situations like yours.

 

Since the computer is throwing a code, it's likely sensor trouble. Unless someone you know has a personal electronic computer scanner, any shop with a diagnostic scan tool will be the only place you can go. That's the safe way to go before you bother replacing sensors like Russian Roulette hoping to find the right one.

[95GTP]

upgrade. check out this link, ita about my problem and what some of the ideas are

 

http://www.efi-street.com/phpbb2/viewtopic.php?t=8649

 

Im going to change the fuel pressure regulator and intake gaskets again

 

also I have never found anything weird about the 3.4L motor symptoms unless its running without any problems, now thats weird!

 

==95GTP

[Slade901]

All I can say is that you may have a failing cat. It barely allows your exhaust to pass through the cat chambers. The cat is suppose to burn those unburned gas but failing cat will cause this problem on your exhaust.

 

Bad cat is usually a common problem and mostly mis-diagnosed ALL the time.

 

Disconnect your O2 sensor and start the car and note the IDLE and car's performance before removing the O2 sensor and after removing the O2 sensor.

[95GTP]

here is the deal. i was just about to send out my injectors for a rebuild when i decided to try and blow through it. Guess what? air went through the bad one. its stuck open! Looking for a deal on an injector now, looks to be about $80 for one.

 

I still have to replace the cat since I know it crapped out. Time to get out the sawzall!!!!!

 

==95GTP

[JS91Z34]

80 bucks for an injector is worth it if its the new design!

[95GTP]

What new design? Im looking into remanufactured ones for $47. I dont know if its wise to get one new design injector and have 5 old ones. Wont there be a major imbalance on fuel flow? Wont one cylinder get more fuel and run hotter that the other ones? If I could afford it I would replace all of them at the same time, Right now I'm freekin broke thanks to the 3.4l money monster.

 

==95GTP

[JS91Z34]

I'll be honest with you. The new design I'm speaking of is injector durability. Yours being a 95 might already have them. The older ones like what was in my 91 were junk. There was something about the design. I'm still researching different components of these cars. Finding out whats a bad design and whats not. Your not the only one the has an injector problem. Realistically speaking the motor is not at fault. The electronic component is. The 3.4L(LQ1) is not a bad motor. These motors are so opinionated by other people its sickening. I'm pushing almost 50K(in 1 years time) on mine, and the only time I was underneath the hood of my car was when the power steering line broke.It wasn't the motors fault. I'm getting ready for 2000 mile trip tomorrow in my Z34. I have complete confidence that this motor will get me to where i'm going and back.

 

If you got an Injector that was dumping more fuel into one cylinder, the computer will see that and try to compensate for it. That one cylinder will run cooler than the others. If it were an extreme rich condition in that one cylinder, The computer is going to lean out all the cylinders to get the proper air/fuel ratio required. The new design is just a flaw that was fixed with the older ones to prevent premature fouling or shorting. There still the same injector, just made better with different materials.

[95GTP]

I just sent all my injectors in for clean, test and recondition. I have a 50/50 chanc the stuck injector might free up, if not they will get me another one, all balanced with the same spray pattern and flow rate.

 

I see what your saying.

 

==95GTP