Random Cylinder Misfire 99 3.4

[nqc2k]

For about 2 years now, my car misfires. 99, 3.4 150k. If I don't let off the gas promptly the check engine light will appear or blink. Its slowly getting worse, now I can't safely pass cars as it won't accelerate as it should. New wires/plugs (ac delco) /coilpacks/fuel filter, cleaned tps, ran STP and seafoam as well as other products through the engine. If I remember correctly, fuel pressure was at 30. This week, I plan to do a new fuel pump and sending unit. Before I do this, any other suggestions?


Thanks!

[Airjer_]

What codes specifically are you getting?

[BNaylor]

Originally Posted by nqc2k

If I remember correctly, fuel pressure was at 30. This week, I plan to do a new fuel pump and sending unit. Before I do this, any other suggestions?

Your fuel pressure sounds too low to me. Best to get that issue resolved since fuel supply issues can cause random misfires.

[nqc2k]

I don't recall exact codes. I'll put in the pump and sending unit and see what happens. Thanks

[nqc2k]

haven't had any free time to put in the new parts in yet, but I was thinking, any chance it could be a semi clogged cat? And any way to test to see if it was? Thanks

[Airjer_]

Unbolt it from the manifold and see if the performance changes. If it does than you are likely on the right track.

[Cre8tive]

I would check your MAF Sensor. I had a similar problem with mine (2000 3.4, 180k). I replaced it and it fixed the problem immediately.

[mcgee139]

It sound a lot like the problem that I had and it was the cam sensor I have a 2001 3.4 and only 135ks on mine. I did all the same thing new plugs,wires injuctor cleaner and every thing under the hood the part was only $78 from the dealer. good luck

[rsnjeter]

same code, similar issues. rough idle, finally quit running, raw fuel odor. replaced throttle control valve and P1 O2 Sensor, no help. replaced fuel regulator (second time in less than 20K miles), and problem resolved. if you can remove the (small) line from the top and blow through the regulator, it is bad. simple to replace. mechanic told me i needed a fuel pump, glad i disagreed. saved about $500.00. now car shifts hard, and that is next project, then the ignition switch, then the power windows, etc, etc, etc. good luck if you own one of these lemons. my 2001 reached 80K miles in 2005, but has only ran long enough at one time to reach 100K today.

[armatac]

I think I have whatever this problem is, but mine is flooding I think

2000, 3.4L V6, 140K
Car started ideling really rough. Got Scanned, came back rich mixture, and multiple misfires. I replaced the plugs and wires, then the first 02 sensor, then the second 02 sensor, then today I went and bought 1 coil pack and moved it through and tried it in each position to see if it was that and the car will just die after about 1 minute of ideling. It runs fine on the interstate but when you get off the gas to take a turn it will stall, and to re-crank involves giving some gas as it seems very flooded.

Could it be a fuel pressure regulator? I have read and it could be the crankshaft sensor, or maybe the idle control thingy.

I just got this car and I can't believe all these problems I have read. It really doesn't bother me too much as I would just try to come here and fix it now that I have found this nice resource.

[rsnjeter]

definitely sounds like the fuel regulator if it has symptoms of being flooded like the old carburated engines. remove air intake hose at throttle body and have someone hold gas pedal to floor and crank the engine. be careful, as gas may gush oui of the throttle body as the butterfly valve opens. fuel regulator is in front of throttle body--brass housing attached to fuel rail with fuel line coming into bottom and smaller line attached to top. it takes a 24mm wrench to remove the fuel line. good luck.

[armatac]

That was it,

If I had done this first it might have saved me some dollars,

thank you very much for your help