I need to test the ignition system on my 2.5 Ranger. It's still got a rough idle in Park, Neutral, and especially in Reverse. One time when I came to a stop it even idled down so low it shut off. I've been trying to go through the FSM Pinpoint test under Idle Concerns and I've passed all the Pinpoint tests and I'm to the Ignition System. Of course I don't have a Rotunda Engine Analyzer to test the Spark Plug pattern. It started with a bad MAF that had been bad for awhile but only intermittently. I fixed it with a new one, then came the EGR codes P0401 and P0402. I went through the EGR system replaced the faulty parts, cleaned the pipes, installed new silicone hoses, cleaned intake. Then after all that was fixed I got a P0171. We then cleaned the throttle body, replaced the gaskets, tps, and idle air valve, and replaced the front O2 sensor. It was totally ceramic white so definitely it had been running lean for awhile. It still idles rough and especially when you drive and them come to a stop light. It will idle down, lope sometimes, and then clear up. When you're cruising and you're doing about 55mph and hit the gas it will hit like you've got a bad u-joint but it's not a u-joint. Like a hard hesitation. My converter is rattling internally but there's no code for it. I don't know if it could cause all this. But it's not getting too hot. So I want to check ignition. I looked in the pitch black dark and I didn't see any spark arcing. So I just want to know if there is a way to test it to find out if one plug or wire is bad?

 

Have you performed the suggested secondary ignition after dark wet down test?
Have you performed the suggested shift to "N" when coming to a stop, to see if it'll prevent the low rough idle or stall?
Have you performed the suggested vacuum gauge excessive exhaust back pressure test, or any of the other engine condition vacuum gauge tests? If so, post up the results.
You could use a inductive timing light on any suspect spark plug wire to see if spark is going missing.

 

I tried looking at the ignition wires where they attach to the plugs in the dark. I didn't see anything but didn't try the wet down part. I did try shifting to neutral when stopping but it has no effect on the idle or missing. I just received my vacuum gauge today as well as a new rear O2 sensor. I will try and do the vacuum gauge test tomorrow if there is time when I get home. I will also video the gauge readings. I'd like to know more about how to use the timing light on this truck. How does it help?

 

The inductive timing light is one way to get a safe, fast, visual answer to the last question in your #1 post. However, if you don't have misfire codes you haven't posted, no need to look there for the rough running.

Good feedback on trying the shift to "N" test, no difference in idle quality tells us you don't likely have a torque converter unlocking problem when stopping.
So now you can look at other common idle woe parts like a vacuum leak, or at the IAC, which can be acting out but not set a trouble code.
To test the IAC, try disconnecting it while the engine is idling normally in "N", if no change noted, it's not working.
Disconnected, the idle should drop, maybe run rough or stall, if the IAC is working.

If it's not working, try removing & cleaning it internally with a plastic safe spray cleaner, like CRC MAF, or QD cleaners, keeping the electrical connector end up, so crud & cleaner don't run into the solenoid winding end & cause mischief with the windings insulation.
Cleaning to make it work again may not last, it didn't for me & is probably why Ford recommends replacement when they act out but cleaning mine was a good trouble shooting step for me in diagnosing my IAC woes, before replacing mine with a BWD make.

Did you replace the upstream/before cat converter O2 sensor yet?

Let us know the vacuum gauge test results, as it could simply & quickly provide clues on where best to focus your trouble shoot.

Don't start any more new threads for the same problem/s, as it makes it difficult for the forum to follow what you've already done, answers you got & what the results were, thus you get repeated questions for things you've already done that posters don't know about.

 

Ok I've done the vacuum test and I also unplugged the IAC while it was idling. I hooked up the vacuum gauge to the intake manifold fitting that the brake booster plugs in. I had to use some reducer tees to get it all hooked up because I didn't have a tee with 2 3/8" and one 3/16". The youtube video link is: https://youtu.be/nSCHrDdX0no
I also unplugged the IAC while I was doing the video. It idled down when I did that but didn't stall. It idled back up when I plug it in. If you can't tell the vacuum is fluctuating very slightly between 15-17 inHg. According to the Ford vacuum test results that equals retarded ignition timing or it could be read as spark plug gaps too close. I also did replace the upstream O2 sensor and today when I got done I also replaced the downstream O2 sensor. I started this new thread because I thought it was appropriate as I was asking how to do something different than my initial thread. I also did a video of how bad the catalytic converter is rattling. Although no codes have come up you can hear it rattling inside the converter. The one I have is about 3 years old and it's a Magnaflow which has a pre-cat. I remember the original one didn't have a pre-cat. It will definitely have to be replaced but I cannot afford to replace it right now. The best deal I can find is around $180 for a direct fit new converter. I just don't know if it's something that can easily be swapped out at home. Last time I had a shop do it. But it didn't seem to take them too long.

 

Ok, good feedback on the IAC test, seems it's working, as you say idle speed drops when disconnected & picks up again when reconnected, so we can put the IAC lower down on the suspect list.
On the vacuum gauge readings, which link scenario best fits what your seeing with your gauge?
How did the engine do on the plugged exhaust test scenario when you rev the engine?
If you still suspect higher than normal back pressure is affecting idle, you could remove the upstream O2 sensor temporarily to provide some back pressure relief & see how that affects idle quality.
On the cat converter rattling, have you inspected for a loose heat shield?
How many miles on the current timing belt?

 

I just hooked up the vacuum gauge and started it up. It was already warm from driving. I didn't rev the engine. I've not played with vacuum gauges much. I did put it in Reverse and Drive and the reading didn't change. It was fluctuating between 15-17 but mostly steady. I'm not sure what that means. The timing belt and tensioner has probably 30000-40000 on it. The muffler and tailpipe was replaced a few weeks ago because the baffle was broken. We checked the converter rattling and is internal. The shields are solid. I know it was expensive but I went ahead and ordered a new direct fit converter because it's got to be changed no matter if it is the cause. I will tell you that the ignition coils have been diagnosed as being a problem before and never showed a misfire but it was usually missing at driving speed. Coils,plugs, wires were all done at the time of the timing belt.

 

Ok, well it doesn't look like the vacuum gauge is seeing anything mechanically gross going on with the engine & yes I agree the closest vacuum gauge reading match is to scenario 11, retarded timing. SO, what does your timing light indicate is going on with timing when the vacuum gauge is doing it's little flicker?
Yes I could hear it surging, then seem to settle down.

Have you done the clogged exhaust scenario 14 test yet, where you raise the rpm & see if the vacuum reading drops?

Interesting how the vacuum starts low & slowly climbs to a low/normal reading, then flickers & climbs a little more & seems to stabilize & hold steady. Maybe an old engine guy seeing the video will chime in with a clue. My first wag, maybe sticking, or poorly seating valves???

 

My 98 3.0 gave all the symptoms of an ignition problem. In the end, it was a dead fuel injector. The next time that it happened, I checked the fuel injector first. Fuel and ignition share a lot of the same symptoms. 268,900 miles and running strong.

 

I haven't had time to check anything else on the vacuum gauge because it's always dark when I get home. It's aggravating because the past 2 days it actually shut off making a turn. It's running extremely bad. It cannot maintain a proper idle anytime you stop. Anytime you put your foot on the brake to start stopping you can feel the idle lower. I looked over the engine bay on my lunch break to make sure there wasn't anything obvious unplugged and there isn't. I still don't have any CEL, which is amazing with it idling as poorly as it is. It's getting to be dangerous to drive and of course my R/T is taking longer in the paint shop than originally expected so I'm without a second vehicle. I did change the fuel injectors probably 3 years ago with new Denso ones. The old ones weren't really that bad. Can't you hook up the FORSCAN scanner and choose the Fuel Injector pids to see if they are working properly. We did do a fuel pressure test last week and it was right at 65PSI. Fuel mileage is way down about 50 miles off of tank. I'm still waiting on my catalytic converter to arrive. It definitely needs to be changed with the internal rattle going on. I'm not even sure when I'll be off again to check anything. But I'm not sure I can keep driving this much longer. Which side wire do you have to hook up the timing light on to check each cylinder? How will I notice anything is wrong with the ignition using the timing light test? Does it have to be hooked up close to the spark plug because I don't know if I can get into the ones on the intake side.

 

Update. I did still go out and hook up FORSCAN to see if there was any codes. There are no codes or pending codes. This time when I went to start it up it actually wouldn't stay running. It took a couple of times with some help from the throttle to get it to say running. It runs roughest after it's been sitting for awhile and then is started up. I still have a P1000 from when I cleared everything out after fixing the EGR issues. It's been at least 200-300 miles. It says the EVAP is still not ready. So it wouldn't let me complete any of the self tests. I did scan some PIDS while it was running. Egr, IAC, Fuel Injector 1-4 faults, Misfire, Total Number of Misfires, and PIP. Everything was in order, no fuel injector faults, IAC, DPFEGR. It did say Yes on Misfire right after it started up and then went to No. It did say total number of misfires was 38 when I finally shut it off. On the PIP PID it kept cycling from On/Off while running. Under the description of what it describes this PID as it that it monitors the CKP sensor but only while cranking. So I'm wondering if there is a fault there? I couldn't find any information on it. I also went ahead and did the vacuum gauge test but didn't get to video it because it was dark. The vacuum seemed a little lower, maybe because it cooled down a bit since I got home. It was like around 14inHg or 15inHg and then went up to 16inHg. When I pressed the gas it went down to 0inHg and then shot up to 20inHg before settling back down at 16inHg. I didn't get the timing light out. I've never had a crank sensor fail but funny I did order one with a RockAuto shipment I did a few weeks ago because it was a closeout for $9 and it was a new Dorman part. Only problem is that it looks like you've got to remove quite a bit to get to it. So what does the vacuum readings tell you? Know anything about how the PIP PID works? Is it suppose to cycle from On/Off while it's running?

 

I don't see any difference in what we already know from your previous vacuum readings.

You can hook up a inductive timing light inductive pick up to any spark plug wire you want to monitor & watch for missing blinks to note misfires.
Hook it up to the number one plug wire to check timing to see if it's jumping around, or not set right.

Using FORScan I'd also call up short & long term fuel trim, up stream O2 sensor switching, MAF sensor & TPS on the dashboard in oscilloscope mode & watch the traces to begin to get an idea whats going on overall. If fuel mileage is down, then fuel trim should indicate rich, so you don't want to install a new cat converter until you get a good grip on whats going on & right now you don't.

If you don't have an after cat O2 sensor trouble code set, or an indication from the vacuum gauge that you have excessive exhaust back pressure, or some other indication that the cat converter isn't doing its thing, I'd put it lower down on the suspect list for now.

The vacuum reading low, then slowly climbing into the low/normal range is a clue, but you need a engine guy to tell us what his best guess is, I've given mine but I'm not a engine guy.

 

Well I looked at the FSM vacuum diagrams and the explanations. When I accelerated rapidly the gauge went Low and then went higher than normal until settling back down to the normal reading. According to the diagram in the FSM and the reading I did on the gauge it shows a good motor. It did exactly what Ford says it should do for a Normal reading when Accelerating/Decelerating. Also int he Ford manual it says Normal reading is 15-22InHg fairly steady which is what mine read. It was 15-17. Although it ticked up and down for the most part it was steady. I'd say vacuum isn't a problem but I'm not an expert by far. I checked the PIDs and didn't see any readings out of the ordinary even the fuel trim. However, there is definitely misfires because the Total Number of Misfires PID picked up 38 misfires since I started the engine, which had been running a few minutes after I noticed that. I tried the timing light trick but wasn't having much luck over on the intake side because it was hard to get in there and even so the exhaust side with the intake hose on. But of the three cylinders I was able to check the light was normal. It seems to me that it's a random misfire because you can tell when it's misfiring and it's not always doing it. There's one way I can clear that up. It's by changing plugs and wires. I was planning on doing it in the near future back to Motorcraft. Summit has the plugs and wires Motorcraft in stock and I can go get them. I think right now I've got Autolite Platinum plugs in there and the worst wires you can buy from the parts store. I usually try different brands of wires but by far the best I've used has been the NGK. They've even been better than the Motorcraft but a lot more money unless you order them. But that still doesn't rule out the crank sensor. Could the crank sensor be bad and still not show a code? I've got a new one I just don't know how involved it is to change. So is there anyway I can rule out the crank sensor?

 

The vacuum beginning low, then slowly climbing, fluctuating up & & down regularly an inch or so, then finally becoming steady, isn't normal. To me it suggests something is going on with the valves or piston ring sealing, but I'm not experienced enough with engines to know what that is trying to tell us, but bet a engine guru could, so maybe one reading this post will chime in & enlighten us.
To me it seems maybe something is warming up, or getting lubed up, sealing & causing the engine to become a more efficient pump. So things like piston rings, valve seats & seals come to mind for me. What weight engine oil are you using?

On the inductive timing light, you can clamp it onto any handy plug wire, on the coil pack, or plug end, or anywhere handy in between, to watch for missing spark that's in time with a miss.

How did engine timing look when hooked up to #1 spark plug? Was it steady, or jumping around in time with the miss, or surge?

Did you ever use, or rig a stethoscope & have a listen to the fuel injectors, or valves, to determine if one sounds different than the others & if that difference is in time with a miss or surge?

I've chosen to stay with the Motorcraft ignition parts on my Fords, as all have been of good quality.
For it's 60K maintenance I installed the specified heat range Autolite fine wire iridium enhanced center electrode, with platinum pad side wire design plugs & Autolite premium wires on the wife's 2000 Dodge Neon SHOC waste spark ignition & like my Fords with the newer design Motorcraft fine wire plugs, notice quicker year round starts. The fine wire plugs spark gap is staying in spec Way longer too.

Low grade plug wires on our waste spark ignition system have earned a place on your suspect list.
Check the end to end resistance on each one while flexing. Resistance should be about 1K ohms/inch of length & steady when flexed, 30K ohms max, no matter the length.

Did you ever perform the after dark warm idle wet down test of the plug wires & coil packs?

 

When I checked the engine with the timing light it was daytime but it seemed like it was a steady light. The miss isn't always apparent. Sometimes it's so apparent it almost stalls out and sometimes you have to listen to the tailpipe to hear it. But driving it appears to be most apparent when backing up. Then also when cruising for awhile and then coming to a stop, it drops down and feels like it wants to stall. And it has stalled twice coming off the exit ramp going into a turn and then turning at a red light. Every time I get the Motorcraft SP-432 plugs it seems the gap is pre-set too high and they are non-adjustable because of the finewire. The cheap parts store wires I just used because I had a new spare set on the shelf. Is it ok to use a spark plug hole thread chaser? Maybe there's some gunk on the threads and maybe some have loosened up? I remember particular last time I changed the plugs I had a little trouble with exhaust #1 plug getting it to tighten up but I didn't see any problems with the threads. I finally got it in. I plan on going to get the Motorcraft wires and plugs Monday. But even if I do change all that out. It could still be a bad coil. I've had many bad coils since I've owned this truck since new. It causes all kinds of driveability issues but never has set a misfire code. What should the wet down test do at night? I'm going to try that. I wish there was a cylinder balance test on FORSCAN that would make it a lot easier. As far as the oil I always use 5W-30 conventional oil, 4.5qts total.