fuel injector question and missfire issues

[wangmauler]

Alright everyone, So this is my issue I need some help on - Right now, I don't have a job and no money to put into this, so I need to do this dirt cheap, without a mechanic.

My engine ('98 ford explorer sport)is a v6 running on 4 cylinders - This all happened a few months ago, right before the winter started. I did a compression and leak-down test myself, and everything was okay, no leaks and compression was good in all cylinders.

I brought my truck to 3 different mechanics, 2 of them I know well, and they are usually very good with repairs and cheap. NONE of them could figure out what was wrong, I know they all replaced different parts, and tested different parts, such as basically all the sensors relating to the cylinders and firing, including spark plugs, wires, and all that jazz. I had a list of stuff they replaced but lost it.

So my MAIN question: I was just wondering how I can disconnect or turn off the electronic fuel injectors for the two cylinders that are not firing? the exhaust smells badly of unburnt fuel, and I know its not good for the catalytic converter. Plus it might save me a bit more gas too, as I get around 8 MPG as it is now.

I have to check which cylinders are miss-firing/not firing, as I don't remember which two were doing that lol. Anyways, thats my MAIN question.

My sub question, is does anyone have any idea WHY two of my cylinders are not firing? any more help would be great. Like I said, I know its not a compression issue, i know its not a leak, (vacuum lines were checked too), I know it's not the fuel injectors for each cylinder, its not the spark plug firing unit(also forget what thats called, as I bought a new one that worked in another explorer fine, but didnt solve the issue), its not a gasket, and not a cracked manifold, and I'm fairly sure its not a piston ring or O ring anywhere, as the leak down and compression tests I did came out spot on fine.

Thanks for any and all help all!

 

[wangmauler]

bump

 

[wangmauler]

Bump 2x...

 

[2000StreetRod]

No promises

I suspect the reason that you haven't received any responses is that it's difficult to come up with a possible cause that hasn't already been tried. I'm certainly no expert but I'm willing to try while making no promises of finding a solution.

First, what engine do you have? I'm more familiar with the SOHC than the OHV because I have an SOHC.

Second, I prefer to find the problem rather than disabling the faulty cylinder fuel injectors.

Third, what are the current and specific diagnostic trouble code numbers being reported via the OBD port? If you have not cleared the codes recently using a code reader or by disconnecting the battery then I would like you to obtain the current codes. Diagnosing a difficult problem using old codes can be very nonproductive.

 

[wangmauler]

Alright, so my enigne is a 4.0L 6 cylinder OHV, I brought it to autozone to run fresh codes(disconected the battery), and I get missfire reading - cyl 5 missfire. This was the same error I was getting a few months back too, same cylinder.

I also tested again, today, just to be sure, I moved a spark plug from a working cylinder to the 'broken' ones and then brought it to autozone - first off there was no noticeible difference, still felt like cylinder were missfiring, and the codes say the same thing.

I hope that helps out. I just need this thing to get to job interviews really, right now its really tough lol.

 

[2000StreetRod]

P0305

Please confirm the DTC is:
P0305 Cylinder 5 Misfire Detected
and there are no other codes such as:
P0300 Random/Multiple Cylinder Misfire Detected

If your only code is P0305 why did you state in original post "is a v6 running on 4 cylinders"? Are there indications that another cylinder is misfiring? If so, what are they and which one?

What were the compression numbers from your compression test? Was the test done with the throttle wide open? Were all of the spark plugs out at one time or just the one being tested?

 

[wangmauler]

I'm getting a P0305 Cylinder 5 Misfire Detected, but its acting now like there is another missfire, but doesn't read on the codes, I totally forgot to post about that lol. I have soo much less power now.

the compression numbers were about 165 PSI for each cylinder, +/-7psi, 171 being highest and i think 163 for the lowest. I had one spark plug(obviously) unplugged, and had the compression tester in that, and tested all 6 clyinders, and tested it both wide open and idle, got about the same readings - as far as wide open, I didnt let it run for a long time wide open, just enough to rev the engine to about 5k rpm, and then back down to idle.

Like i said to, I also had a few mechanics work on this, and they ran the same compression (and they also ran leak down tests, including cleaning with seafoam), and everything came out okay, no leaks or cracks or bad compression.

I'm thinking of just taking it to another mechanic i've heard is really good around here, and just having him figure out WTF is goin on with this thing. I dont care if it's fixed or not, just that I know what the friggin issue is lol.

Any ideas?

 

[2000StreetRod]

Compression & injectors

The typical causes of misfire are ignition, injection and compression in that order.

Your numbers for a dynamic compression test are higher than I would have expected for an OHV with only a 9.0:1 compression ratio. But since all the cylinders are approximately the same I agree that it doesn't appear that compression is the problem.

Did you "read" the spark plugs when you performed the compression test? Did the plug in cylinder #5 look abnormal?

Have you confirmed that cylinder #5 is actually misfiring? If so, how did you determine it was?

Did you replace the spark plugs after the SeaFoam treatment? Some members have reported misfires after a SeaFoam treatment. Apparently the carbon deposits released foul the plugs. Are you using Bosch platinum plugs? Some members have reported misfires with them.

How do you know the problem is not a bad injector? Have they been removed and flow tested? Did you swap them around? Have you added fuel injector cleaner to the tank?

I suspect that for this problem the only way a mechanic will know for sure what the problem is will be by fixing it.

Has the crankshaft position sensor been replaced recently? If not, try disconnecting and reconnecting the electrical connector a few times to clean the contacts.

 

[jelkins]

this problem ever get fixed??? i am having a similar issue .

 

[csnider14]

My 99 OHV is doing this exact same thing. Please tell me someone figured it out!

 

[pcrband]

fuel injector issue

Hey there I have a similar issue and I'm a technician of 7 years at chrysler. Not sure if it's the same for you but you need injectors probably. Mine started stumbling at cold starts injectors were leaking down into cylinders now they are leaking all the time. So it stumbles at idle but if you floor it it will work fine because it's burning that extra gas . Just pull plug wires while it's running and see if you here a change in the idle. If there's no change when you pull the plug that's the cylinder that's not running