runs ruff when cold

[tamnative]

This has been an ongoing issue for about a month.When I start the engine after it has been sitting and is cold it runs ruff for about a minute then smooths out and runs fine. I pulled a P0304 code (cyl.4 missfire) but I do not get a CEL.
I checked the plugs and they were ok but I changed them and the wires anyway as it just turned 50k and the plugs were original. I could live with a little cold ruff idle but the code throwing bothers me. The truck is a 2000 xlt 4x with auto trans. and 4.0 engine. This is my second 4.0 ranger but I have only had it for about 6 months.
Thanks Jeff

 

[SenorNoob]

Reads like the code had something to do with a problem that doesn't exist anymore or the check engine light doesn't work (Easy test. Just turn the key over without starting and look for the light) and there is an issue that stops once things warm up.

Does the check engine light work? If yes I'd clear the codes and drive for a day or so and check it again. If not I'd try to find out what causes a misfire only when cold. How long after starting does it continue? That could be a big indicator of cause.

 

[tamnative]

The check engine light does work,I have cleared the code several times over the last month but the issue still pops up,but not every time I start it. It only happens when cold and does not last more than a minute and does not always throw a code. After I changed the wires and plugs it ran great for about 2 weeks with no issues than it started up again.
As said the running ruff when cold doesn't bother me as much as the throwing of a code.

 

[snake]

try some injector cleaner like 44K and see if it clears it up. Or switch the injector over to another cylinder and see if the code follows over to that cylinder. If so replace the injector. Also wouldn't hurt to run a compression check when the engine is cold.

 

[tamnative]

try some injector cleaner like 44K and see if it clears it up. Or switch the injector over to another cylinder and see if the code follows over to that cylinder. If so replace the injector. Also wouldn't hurt to run a compression check when the engine is cold.

I have used a bottle of Chevron Techron and it hasn't made any difference. I did do a compression check and all was good there, of course it only has 50k miles on it so I expected the compression to be ok. If I go through the trouble of switching an injector I would just replace them all,they are not that easy to get at. I would like to narrow it down before I go that far.

 

[SenorNoob]

Just throwin this out there cause it's pretty unlikely but, could it be something shorting when it's cold enough to frost? Or does it not have to be that cold?

Edit: Just re-read your last post. Sounds like it is definitely spark-plug/wire/coil-pack related. Do you have a plug wire getting on the exhaust or something? Did the old plug from cylinder 4 look significantly different than the other 5?

 

[freedom5]

This has been an ongoing issue for about a month.When I start the engine after it has been sitting and is cold it runs ruff for about a minute then smooths out and runs fine. I pulled a P0304 code (cyl.4 missfire) but I do not get a CEL.
I checked the plugs and they were ok but I changed them and the wires anyway as it just turned 50k and the plugs were original. I could live with a little cold ruff idle but the code throwing bothers me. The truck is a 2000 xlt 4x with auto trans. and 4.0 engine. This is my second 4.0 ranger but I have only had it for about 6 months.
Thanks Jeff

I don't know if the 4.0 has a separate Engine Coolant sensor from the temp guage sensor like my 2.9 but I had a similar problem which was rectified when I replaced the engine temp sensor. It's the three wire sensor that controls the idle speed when the engine is cold. Correction ( it's a two wire connection) Freedom5

 

[SenorNoob]

There are 2 separate parts on the 4.0 as well. In-fact the same 2 parts. At least according to O'Reilly's website.

 

[tamnative]

I wanted to keep as many people as I could posted on this issue I have been having with my truck. I have done alot of research since then and gotten nowhere. The problem didn't come back until last Friday 4/17 then it came back with a vengance. When I left work to go home it missed very bad and I wasn't sure i was even going to make it,so after all the things I did before here is where i'm at. I must say that this truck is a bitch to work on,I have a F-350 with a 6.0 and I didn't think there was any room under that hood, they really packed it in there on this one I couldn't get my hands around anything. Well I replaced the coil pack and it didn't change then it ran better then I let it sit, and it ran crappy again. No codes. So I looked for vacuum leaks. Found all the manifold bolts not to torque specs.,tightened all bolts,upper and lower to 18lbs. (shop manual states 12 lbs.lower 17 lbs. upper) ,still ran bad until it was hot then ran normal. I let it sit for a few hours and then started it again and let it idle for a minute before putting it in gear, it still has a good miss. I am going to take it to a shop tomorrow and well see what they find. I will keep you posted as all my research on this has turned up nadda. PS still no codes.

 

[snake]

Id swap #4 injector with another on the engine and see what cyl it throws a code on tomorrow. Same with the sparkplug wire, move it to another cyl and check codes. Also check your fuel pressure for giggles

 

[tamnative]

I took it in to a shop Monday and by Thursday they still couldn't find a problem, The tech said he thought it was a bad valve and that the shop would not be able to do the work so I picked it up and brought it home. ( I think they just wanted it gone ) I talked to a friend at work whom I found out today was a certified ASE mechanic and gave him a run down,after some thought he said it wasn't valves and explained why.Then he said he would do some research and get back. He found me a few hours later and gave me a few things to check. Crank pos.sensor may be loos or dirty, to much resistance to the injector not allowing it to function properly, small leak in head gasket (not real high on the list but possible) and ...... DOUBLE PLATINUM SPARK PLUGS, but I told him that I just replaced the plugs with Motorcraft AGSF 22 FM Platinum plugs. He said no double platinum. ?! Go buy 1 plug and see what it does they are only $4.99,so I did even though the plugs I just put in are only 2 month old.
Well I came home and started it up to see how it ran and it still missed bad so I pulled the plug ( which didn't look bad at all, nice brownish tan and dry). I replace it with an Autolite APP 103 DOUBLE Platinum,started it up and she ran like a clock. Now being that this has been an intermittent problem I am going to wait and drive the hell out of it over the weekend before I get to excited but it sure rules out a valve job. Now about the plugs:something I never really thought to look at but the Motorcraft plug only had the platinum on the center electrode were the Autolite if you look really close has a contact on the other side also.If you remember the factory plugs are different on the left and right banks and are not interchangeable, this is because one set has the platinum on one side of the plug electrode and the other plug has it on the opposite side.Fruit for thought. I will keep you posted on the progress.