I've been getting this misfire code for quite awhile now. It first showed up about 4-6 months ago. First thing i did was check compression in cylynder 5 and it was fine. I found a air leak that i had for quite awhile between that time that I fixed. Check engine came on went off and came back after I fixed leaks and changed pluggs. Changed the coil, spark plug wires and gapped and replaced the spark plugs after light came on. P0305 is a misfier in cylinder 5, thinking it was the cylinder 5 fuel injector I ripped the plenum off and cleaned and swapped the cylinder 5 injector out with cylinder 6's. Check engline came on strong right after putting it back together and still read codes for cylinder 5 misfire. I reset codes and ran it about 60 miles and light came back reading misfire in cylinder #5, ruling out injectors.

Any help would be great, I am starting to think the only thing left is the valves and contemplating getting a valve job done unless someone says it could be something else. I also removed and cleaned my MAF sensor with MAF cleaner thinking it could be my MAF that got fouled up.

Truck runs rough at idle but I'm not spitting a lot of black smoke out of the exhaust in the morning when I start it up.

help me out? Please? Lol

 

Hi Ed707

You have three threads started for the same problem.

Please only have one thread per question to avoid confusion.

Also when asking for help have in your signature the year engine size what cab you have transmission etc so we do not have to ask for this information.

Information that we may have to offer may change from year to year.

Now that we got that out of the way lets try and help with your problem.



Have you double checked the cylinder you think is number 5 is really number 5?

If so how do you know what cylinder is number 5?

You claim cylinder 5 has good compression Let say you are right and did find cylinder 5
what was the compression for cylinder 5?

Did you check all the other cylinders for compression? if not please do so and report your findings.

I am guessing you have a 3.0 Ford Ranger

If your compression is in fact good there will be no reason to do the heads.

For example a cam lobe could be completely worn down not allowing enough lift yet this would show good compression.

My point is you still have more diagnostics to do before replacing anything.

I would also inspect the injector electrical connector for loose or corroded contacts, broken retention clip or missing connector seal.

BTW if the engine is a 3.0, cylinder 5 should be the middle cylinder on the drivers side.

 

Sorry I'll remove the 2 other posts I have up.

I don't remember what the compression was for cylinder 5 and that was the only cylinder I checked. I new I shoulda checked them all but didnt. I just remember compression was within normal range from specs I got online.

Cylinder 5 is the middle cylinder on the same side the batterie and master cylinder is on the engine right? Pretty sure I just googled a diagram of my engine to find it.

idk where my signature is to put my car info in but here it is.

99 Ford Ranger XLT 2 wheel drive, Flex Fuel, automatic tranny

 

Found my signature, sorry I'm new to these forums just joined and still figuring things out. Idk how to delete the other 2 posts or if I even can.

i checked the connectioms for the injectors, gave them a spray of electrical cleaner and a scrub with a soft bristle brush. Didn't see anything of concern like broken connections ext.

I'm not the most mechanically inclined but not car stupid either and this just has me stumped. A good mechanic friend told me it's not the valves which is why I've been hesitant to do them. Mechanic shops and other threads I've read have stated that the valve seats are a common issue with these trucks and people recommend that 90% of the time

 

The other two threads you cannot delete, Do not worry about them in a few hours those will be long gone in the sea of unanswered threads.

For now do a compression test on all the cylinders and report back all the numbers.

Again there is no reason as of this moment to suspect a valve if you have good compression.

 

Going to do a full compression test today then I'll post what I got. I didn't even think or check the injector seals that the injectors sit in, that very well could be a/the problem. I replaced the spark plugs with NGK Iridium plugs and read a few threads that you should use double platinum plugs instead. If the parts store has my pcv I'll probably change that as it's cheap and I'm sure needs to be changed anyway.

 

Did a full compression test on all cylinders. I used a loaner tool from autozone though and I don't know if the compression tester is calibrated right or not.

Cylinder 1 - 100psi
Cylinder 2 - 80psi
Cylinder 3 - 90 psi
Cylinder 4 80 psi
Cylinder 5 - 80 psi
Cylinder 6 - 80 psi

if I had such low compression in all of my cylinders I'd think the truck would be running like crap and it's not. Just a rough idle. What are the chances the compression tester I used wasn't working properly? I remember checking compression in cylinder 5 the last time, believe it was around 120psi. Definitely above 100psi because any lower it would have caused concern?

I just bought a dvom and was going to test voltage going to cylinder 5 injector as well. Mechanic friend told me it could be the computer sending the wrong signal to the injector causing cylinder 5 injector to not function properly.

what a headache...

 

Well like I said not the most mechanically inclined lol. I read on other threads that you need to remove all of the spark plugs to run a compression test accurately. I didn't remove them all just tested them 1 by 1, replacing them as I went. So that's probably why my #'s were so low...

 

removing the plugs only make it the compression test easier on the starter, you do not need to remove all the spark plugs.

But you do have to hold the throttle wide open while cranking.

And yes a loaner tool may not work that good, but you cannot diagnose anything else until you get a known good compression test done.

So get another kit and try again, make sure to keep the battery fully charged.

 

With those numbers, he's probably not holding the throttle valve fully open.


Edward, when doing a compression test keep cranking until the gauge gets to its highest reading.
You should be getting at least 160 PSI, a healthy engine would be at 170 to 175.

If the compression is still low, add a tablespoon of motor oil (one at a time) through the spark plug hole.
If the compression improves, then you have a ring problem, if it doesn't then you have a valve problem.

How many miles on this truck ?

Also about running rough at idle _ an engine with low compression numbers will idle rough because the engine is running slower.
A slower running engine does not have time to build the proper compression because it can't over come what is ever causing the low compression, eg worn valves or rings or both.

My gut tells me it will be your valves, assuming those numbers are accurate.
The bottom ends of the Vulcan a pretty strong, even with 2 or 300,000 miles, but with high mileage like that, the valves will need attention, even after 100,000 IMO.

 

A worn stretched timing chain could cause low compression across the board.

Yet I think his compression test is suspect and needs to be redone.

 

122,xxx miles on the truck.

i cranked the engine for a slow five count and rechecked the compression in each cylinder 2-3 times. If the compression tester worked properly then those #'s are correct. I'll look for another tester and try it again though. I held the gas pedal down all the way when I was cranking it over.

 

Unlikely on the 3 liter _ very short chain with no guide or tensioner, like the old Chev 350's.
He needs to do the oil test.

 

May sound crazy but I think you could have a broken valve spring symptoms are very similar to what my truck did turned out to be a broken valve spring like to Drove me crazy

 

Maybe if it was only one cylinder, but the low compression is on all 6.

 

Only getting a code for cylinder 5 though. Still not sure about that compression tester. Going to buy one and recheck and do a wet test. If it's still low on compression going to rip the heads of and get my valves done. If compression is low after wet test then going to redo my rings while I'm in there. Real pain in the rear, I have no time to do this in the next 2 weeks so hoping it'll run until I can get to it

 

Does it run rough only when it is cold or all the time

 

Only runs rough at idle and not all the time just most of the time. Got worse today though, check Engine light goes on and off too

 

My truck when it was cold would run real rough for 10 to 15 minutes then smooth out on it's own or I could let it run like for 10 minutes then kill it and start it back up running smooth missing only a little bit would run OK all day till you cut it off and let it sit for a little while then would start back up running rough and it had a broken valve spring it rotates around when it's cold and maybe comes back togather once hot it's all I know but that's what it turned out to be showed misfire on cylinder six change changed out broken spring and ran a lot better still had a mess I believe cylinder 2 maybe doing the same thing now I seem to be having the same troubles again just not as bad

 

Sorry new to this site don't know really how it works doing the best I can

 

Part of compression test diagnostics is to do a oil test then a leak down test this part I agree.

Yes it very well could be a worn stretched timing chain, I cannot think of much else that would take out all the cylinders like that other than a timing chain.

I have replaced many Small block Chevy, Ford and Dodge etc timing chains because of low compression due to stretched worn chains and gears.

Normally I find out how much play a timing chain has on it, anything more than a 3-4 degrees slop the OP should change the timing chain set.

We could check for timing chain slop without the compression test kit yet it is best to wait for the compression test numbers.

 

I'll bet it's just bad valves and seats _ just worn out.
My brother in law had a Chev station wagon, thing coughed and hesitated _ went through everything.
Turned out to be a worn cam shaft not opening the valves to let the fuel in, but more detrimental, the exhaust valves were not staying open long enough to let the exhaust out.

Dad had a big Oldsmobile that a 330 in it (odd displacement).
It jumped a few teeth because the nylon gear on the cam shaft was shot.
There was a steel core, but it was coated with nylon _ it was old and cracked.

One should get 300k on a Vulcan engine and shouldn't have to worry about the timing chain being stretched to the point where it effects compression.
The OP only has 122k on it.

 

Sorry I haven't replied with any updates on the truck, been at work like crazy and haven't had time to really do anything. When I finally had some time off the week of thanksgiving I started to just rip into the engine planning on pulling the heads off and getting them redone. Took me awhile, worked on it for a few days before thanksgiving, pulling the fan clutch was probably the hardest part. Then it sat for a few days, thanksgiving through the weekend, I went back to work and just got the heads off yesterday. Took them to a machine shop today and the guy told me the valve seats were bad. Thats pretty much what i expected, every shop I called said the seats were crap on those engines and every thread I read online agreed. Cylinder #5 had slightly bent pushrods, the exhaust side pushrod was definately slightly bent, very minor but probably would have got worse if I continued to drive the truck. No unusual wear on the rocker arms. Machine shop quoted me $450 to replace all the seats and the seals, resurface the heads and replace any bad valves. Cost me $60 for a fel-pro complete gasket set for everything on the top end. $40 for head bolts and probably another $100 or so for various parts and tools I needed. Also got my torque wrenches calibrated but not going to count that towards the cost of the rebuild as I needed it done anyway. All in all going to cost me around $700 to rebuild the top end if I don't run into any more problems along the way. Cheaper then the $2,200 - $2,500 quote I got if a shop would have did it. I'll post a update when I get it all back together to let you guys know how it went.

 

Interesting about the valve seats, I know they had some problems of them sinking into the head.
Mine is a 99 too (B3000 though, same engine)
When I had my heads done, nothing was mentioned about bad valve seats.
They were re-cut and I bought all new valves _ the guides were replaced too.

 

I've heard it from every shop I've called about my truck. Every one garunteed me it was the seats. Read alot of threads all saying the same. Apparently the stock ford seats aren't that strong and they tend to fail. The guy said the ones he's replacing them with are twice as strong. All of mine were bad, cylinder 5 was the worst leading to the misfire code. He said he actually just did one 2 weeks ago, same thing.