1996 taurus gt misfire

[pontiacfanactic]

Have a code PO305. Replaced coil. Plugs and wires. Checked front injectors. They make that correct clicking noise when listened to with a long screwdriver touching their bases. Attempted to listen to rear injectors. Only could touch outer two and they make more of a swishing noise. CEL will blink after driving higher speeds but will return to steady on when engine is turned off and rested for a few minutes. Does have new fuel filter. Newer pump. Newer Cat. CEL came on when driving at highway speed with cruise control on. Engine is a 3.0 not flex. Any ideas?

[shorod]

I'm curious what you consider a Taurus "GT" as that model never existed from the factory.

Anyway, have you checked compression on cylinder #5? Does the engine idle and run smoothly, or does it seem down on power?

-Rod

[65comet]

All 3 engines that year were 3.0 liter. You already said it wasn't a flex, but was it a 24 valve Dual Over Head Cam (DOHC) Duratec, or the Single Over Head Cam Vulcan? The Vulcan will just have "3.0 OHC" in large letters on the engine and the Duratec will also have large letters indicating it is a 24v DOHC.

[pontiacfanactic]

Sorry it is a GL. Not a OHC. Cleaned intake with Seafoam per label directions. Noted smoke on top of engine toward firewall during cleaning. Was not oil. Possible intake gasket leak? Had at garage and he said he read code for another cylinder and compression varied there. HE thought valve or piston problem. Added Restore and changed oil at same time. Will check compression today. Still hear a miss. Not a big sounding miss. Mechanic's code reader read another cylinder miss than what Auto zone reader had. I read 5 and mechanic had 2 or 3 I can't remember now.

[pontiacfanactic]

Oh and Shorod it does seem to have good power yet but does not keep CEL light off when going out on test drive at highway speeds for a minute.

[pontiacfanactic]

OHC not DOHC.

[shorod]

You might see if the shop can do a cylinder leak down test instead of or in addition to the compression test. A leakdown test would help identify if the issue is a gasket/head, valve, or rings/cylinder wall issue.

And, 65comet, don't forget about the V8 option also available in 1996.

-Rod

[65comet]

Yes, though he definitely knew he had a 3.0, so I disregarded the 3.4L V8 for this thread. But I guess I should have mentioned it anyway for future readers.

[pontiacfanactic]

Tested all cylinders for compression. All tested good. Noted # 3 to have a wet look to spark plug. Moved spark plug to a different cylinder. Removed plug wire from coil at # 3 and did not notice a change in idle sound. Still a misfire heard. Checked spark to that cylinder and even replaced plug wire. Still a miss. Checked coil resistance and noted it to be out of specs. Brought coil back to parts store and tested replacement. Same out of specs. Loaned fuel pressure test kit and checked fuel rail pressure. Did not register. Listened to injector above cylinder # 3 and did not make click noise as front injectors. Ordered new injector. Will be here in am.

[shorod]

Sounds like you're headed down the correct path.

Does the parts store have a noid light set in the loaner tool program? If so, you might want to borrow that and check for injector pulse to the injector before installing the new fuel injector. Confirm that you have pulse before voiding the refund option for the new injector.

What's a bit confusing is that the plug for #3 was wet. Apparently that fuel injector is stuck partially open.... Good thing you already replaced the fuel filter.

-Rod

[65comet]

There are many videos on YouTube for bench cleaning injectors. It does take a bit of DIY tool/fitting work. I just wanted to mention that option in the thread as it can be a lot cheaper than replacement if several are very dirty and someone feels they have the ability to do that kind of work. Also look for bench testing videos, since cleaning isn't always the only issue.

[pontiacfanactic]

Replaced injector on # 3. Tested Ohms on all injectors and that one did not register which means it was bad. Put everything back together and did sound a little better but still a rough idle. Took for test drive and noted a distinct misfire with acceleration but not constant. CEL came back on after reaching highway speed for a few miles and did start to flash but returned to steady on when lowering speed to 40 mph. Did return to flashing after stopping at stop light and starting to accelerate. Checked light again is PO305 misfire. Did clean injectors DIY with carb cleaner. Does seem to have more power but does bog down at times when gas accelerating along with that boom sound from engine that happens a few seconds apart and only when stomped on and is not constant when driving. Will be bringing it to a mechanic with a scanner in morning to see if he can pinpoint what it is. Any ideas if he can't figure it out?

[shorod]

I'd be examining closely the condition of the spark plug on cylinder #5 to see if it shows signs of unburned fuel or a lack of fuel. I'd also break out the cylinder leakdown tester to see how healthy the combustion chamber seems to be.

-Rod

[pontiacfanactic]

After mechanic checked all kinds of things that I didn't tell him I replaced. It turned out to be a crack in the insulator of the spark plug. Should of listened to you guys. Thanks for the help. I will heed to your advice much closer next time.

[shorod]

I'm glad to hear you got it figured out and it wasn't anything major. Thank you for following up on your thread!

-Rod