Occasional miss now idle issues.

[tw205]

95 ranger 4.0. You know the ones with OBDII a year early. Had a miss that would happen once in a while. I noticed it a idle. It would be lower than normal. It would clear up quickly, then run fine. I rescued this truck after setting a few years following some vandalism. Been driving it for a couple months. I figured the plugs needed changed anyway so I put new plugs and wires on but it didn’t help. It’s my first non OBDI so I don’t have a code reader yet. Researching found it to be an issue for the 95 being I or II. Mine does not have non OBDII compliant statement on the emissions tag so I’m hopeful a OBDII reader will work. Mfg date 8/95. CEL is on as I have no cat and right bank has a broken connector on the O2. Today the miss never happened but my idle seems to stick on high. Never at a consistent level and sometimes it will come back down to normal but not always. Pulled the IAC cleaned it and re installed. Then it started whining when I accelerate. Put a new one in and now no whining but idle is still sticking on high. Can’t find any vacuum leaks. Gonna go try to read codes tomorrow. See what happens.

 

[tw205]

Did a smoke test this morning. Found a vacuum leak at the EGR mount. Hope that’s my idle issue.

 

[rusty ol ranger]

Did a smoke test this morning. Found a vacuum leak at the EGR mount. Hope that’s my idle issue.

More then likely it is

 

[tw205]

Got the vacuum leak at the EGR valve to mount sealed up but found another leak. The EGR tube going into the plenum. Very slight leak. I imagine the steel tube has an O ring or something to seal it against the plenum but I haven’t tore into it to find out. The idle is much better. Settles down to 800 rpms when it warms up. Unplugging the IAC didn’t change idle so I’m sure it’s leaking some but I’m undecided on tearing into it.

 

[tw205]

No joy. Was still effecting the idle. Re thunk this situation. PO had cut the tube between valve and plenum and between exhaust manifold and first monitor port. The damn think leaks everywhere. I removed the tube from the plenum and put an expandable rubber plug in it. Sealed perfect. Filled the exhaust tube with exhaust sealant and squeezed it closed. Let it dry over night and it sealed up as well. Took it out for a trip to my brothers house. 60 mile round trip. No more idle troubles. I think I got er whipped.

 

[tw205]

While got the vacuum issue fixed and my idle is good I do still get intermittent misfire. Got a descent code reader and set it up for live data watching for misfire on all cylinders. Didn’t take long to act up and gave me misfire on 4,5,6. Not all the same amount but all three misfire. Being a waste fire system I swapped 1 with 5 and drove again. When it misfired again it was 4,5,6 Ohms tested the coil Primary’s .07.08.07. Nothing on secondary’s. Yes I set Ohms to 20k. Should be 6,500 to 11,000. I got nothing. I’m thinking my coil is bad.

 

[Shran]

Have a spare coil to swap in? Good part to have on hand...

Does your resistance drop to zero or does it just stay on 1 (infinite)?

 

[tw205]

Primaries hold at .7 or .8
Secondary’s never move. OL.

No spare. This is my first 4.0. But I’ll be pickin when I’m at the yard.

 

[tw205]

This has been a roller coaster ride. Initial issue a little intermittent rough idle at start up when warm. Being neglected by PO I put some Lucas injector cleaned in it. A day or two later when accelerating to highway speed it started sputtering like it had a dead miss. Straightened out quickly but then it would do this on occasion. Put new plugs and wires in but still doing it’s intermittent dead miss. Checked codes but nothing about a misfire. I would watch live data and see a misfire on 4,5,6. Not equally and in a quantity that didn’t seem to match the feel of the misfire. Tested the coil as previously reported and was confused at the results. 1 method said test 12+ to all three grounds for primary’s. That’s seems fine. Then test grounds to plugs for secondary’s. This is were I got failures. All registered OL. Nothing. Others said test plug to plug for secondary’s , this showed good. So I’m somewhat confused by now.
I’m not getting any misfire codes so I investigated how the ECU determines a misfire. To my surprise there is no monitoring of the spark. It monitors the crank sensor for rpm changes. Wow. So a misfire isn’t necessarily a lack of spark. It’s a lack of power on the power stroke of the piston. One element of the equation fuel/air/spark is missing. Now I’m thinking, this started after I put the injector cleaner in it. Perhaps my misfire is from a lack of fuel not a lack of spark. Maybe the fuel system cleaning out is loosening deposits and plugging the injector. I took it for a drive and intentionally hit the rev limiter under load to hopefully reach maximum injector flow. Maybe just a coincidence but it has not had a misfire since. I took it for a 40 mile run, didn’t misfire once. Got a can of seafoam this time and added to a full tank. Put about 80 miles on it and no misfires. I’m keeping my fingers crossed that I have resolved the issue. I would welcome any input all y’all might have. Understanding words have meaning and having to properly use words to describe or report an issue can either find the trouble or send you into a bottomless rabbit hole.

Edit. My redneck speak :
Y’all is singular.
All y’all is plural.