Rough Running 95 SR (3.5 DOHC) When Hot/Under Load

[RyanY]

I haven't seen a cap like that on my 95, so maybe it's a SOHC-only component.

I just replaced the coils and the power transistor on mine, since I was having an intermittent misfire when the engine was warm. The heat of towing my tent trailer through 126 degrees in Palm Springs on the way to MOD failed to make it reoccur, so it was apparently one of those ignition components that fixed it.

[Shovel]

I haven't seen a cap like that on my 95, so maybe it's a SOHC-only component.

I just replaced the coils and the power transistor on mine, since I was having an intermittent misfire when the engine was warm. The heat of towing my tent trailer through 126 degrees in Palm Springs on the way to MOD failed to make it reoccur, so it was apparently one of those ignition components that fixed it.

That's also interesting..   since the idea of the cap is to protect other parts from either misreading or burning out,  and you have no cap and your stuff apparently burned out.     So maybe it was added later to improve reliability.   

Anyway then if 95's don't have it then it's not something to check but I learned some stuff while reading the circuit diagrams (in this 1999 FSM) so it wasn't all a waste to think down those lines. 

For the coils themselves if you have 3 coils you don't absolutely need to know the correct resistance value of them you just have to play the one of these things is not like the others game.      The heat component could be a problem or could not..  magnetic fields themselves are not affected by temperature but the core is and the windings themselves are,  so without getting too scientific an increase of 100 degrees F can make a good coil 20% less efficient.    If the coil has some damage like from corrosion because its potting cracked or some of the coils welded themselves after getting too hot from an electrical fault,  that additional loss could be more significant but usually that coil will still read differently even when cold.   Usually.   

Those Ford V6 coil packs are usually easy to diagnose for bad because the potting is visible and most of the time if the coil has failed the potting will crack.    I don't know why, like if it's a crack first that lets moisture in and makes it fail or if the extreme heat of the coil stretches and cracks the potting but whenever I see a bad running Ford V6 that uses one of those six-pack coils I turn the mofo over and look for cracks first.    I don't know if ours telltale that way    

[RyanY]

The '95 FSM backs up the lack of a capcitor, at least for the 94-95 3.5 models.

[Shovel]

It's funny how similar those diagrams are,  even down to junction #20 where the cap would go if it was there.   (Or, where it was added for later years)   

Speaks of the consistency in engineering and documentation.   

[IncorpoRatedX]

Might be a reliability mod to add the cap. Most of the 4 cylinder cars have a cap.

[JohnnyBfromPeoria]

It just figures that my FSM doesn't have a section 16, it just isn't there. So, I don't have a coil testing procedure that is referred to in section 13A-146. I may just do a visual on the coils in the morning and end up replacing all three. If that, plus the wires-n-plugs don't clear this up, I'll have to wait for Pa_Jero to get back from his weekend away to try the power transistor and MAF he has as spares. At least those are external and are easy to get to.

During reassembly, I'll check wiring for continuity and short-to-ground, clean each connection with electrical contact cleaner, lube with a touch of dielectric grease and cross my fingers. Plugs will get anti-seize on the threads and dielectric on the wire boots. From what I can see so far, there's no oil fouling in the spark plug tubes; the engine's pretty clean, compared to many (not Shovel's).

All this is taking away from my regularly scheduled programming of polishing and waxing the paint and wiring up an obnoxious amount of lighting on the front. Not to mention, cutting into my beer time. O.K., it's not really doing the latter.

John B.

[JohnnyBfromPeoria]

I'm just taking a break - don't have any definitive answers to my questions yet, but I'm on "Reassembly Trail." Because I like to just spend money, I went ahead and replaced all three coils. The potting looked good, I only was able to test the leads on the coils where they connect to the vehicle's harness, and all six, the new and old, measured the same at around 1 ohm. That doesn't mean much, since the other end fires the plugs, but my leads aren't long enough to reach into the boot. Some of the plugs looked good, some were just alright, but no paired plugs (firing from the same coil) told me anything special.

I added two grounds, from the vehicle firewall to bolts at the back of each head, 10 gauge. Not that it'll do anything, I just felt like doing it.

I removed the throttle body completely and used product-specific cleaner to degack (TM: Shovel) every bit of its interior. Hopefully I didn't mess it up too badly.

I spent some time on my intake plenum. Many of you probably remember I had new bushings made for the butterfly shaft. These are holding up well. Since I wasn't really in on the whole idea of how things work at the front of the shaft, I did not understand why I had a mean vacuum leak where that shaft exits the front of the plenum. I understand it much better now. I have a spare butterfly section I've been hanging onto for a while and it paid off today. I got to looking at the front linkage and decided to remove it to see if it was in better shape than the one on my truck (it was, a little). After cleaning the front part of the plenum up, I noticed a small drift pin and it was like somebody hit me in the head with a punch (kidding) when I was able to drive the pin out and take out the front bushing, which is made of some space-age plastic. Inside the casting of the plenum, the bushing has a ridge where there's supposed to be an o-ring. Neither of my plenum sections had one. I hauled out my handy Harbor Freight metric o-ring assortment and found an appropriate size, applied it in the proper place on the bushing, reinserted the bushing and drove the drift pin back in. Suddenly, no more end play in the shaft, and it should be much more vacuum tight, at least until the cheap p.o.s. o-ring deteriorates.

While I was wasting time doing all that stuff, my intake gasket set showed up (like magic) at my side gate, so now I guess I'll have to put the plenum back on and try to remember where everything fastens back together. I guess I did it before, years ago, so how hard could it be, really...?

So far I've only snapped off the PCV valve (Auto Zone had one in stock, $3.79, and 1.5 miles away). Cleaned the EGR valve and passages (weren't bad). Created some new colorful words but didn't throw anything. The day isn't over.

John B.

[S298WP]

Any news on of the cap was the culprit?
I think my 98 has the same cap, and I'm at a dead end finding a similar problem....

[JohnnyBfromPeoria]

Any news on of the cap was the culprit?
I think my 98 has the same cap, and I'm at a dead end finding a similar problem....

Uhh, mine is a 95, and as mentioned above, it doesn't have one.

John B.

[JohnnyBfromPeoria]

I just had possibly the most bizarre thing happen to me. It's a Sunday morning, a fine day for a test drive to verify my repairs. Anyone who lives here on a day like today could tell you, it's just nice. So, I drive east on a 45 mph road that has lights/stop signs every mile, the mighty SR's running great. I head south, then east on the freeway at 65+, no problems. I go to the drive through car wash and start by vacuuming and wiping the inside down a touch, then pay my money and head into the tunnel and engage the motorized track that pulls the cars through. About half-way through the tunnel, the car ahead of me, maybe two car lengths, decides it's time to throw 'er in reverse. Yep, the reverse lights came on and she hauled ass backwards right into the front of my big beautiful, half-clean truck. This halted her backward progress immediately. She being of confused stock, did not pull forward at all from that point and my truck continued to push her through to the end of the tunnel where she pulled over to allow me to get her information. Needless to say, this confuses car wash equipment, and the overall result of that was lousy. I had the car wash place give me another go-around and they upgraded my wash to the $15 "super-duty" wash, for which I was able to thankfully opt out of the tire shine. I don't want that shit on there when I basically live on a dirt lot.

In case you were wondering what happens when an Acura MDX backs into a Gen 2 with a 2" body lift and the optional, yet somewhat snazzy grill guard on the front, it will kinda destroy the Acura's bumper, tailgate and trim. I'll let professionals assess the damage to my truck, as it might be there, I just can't tell. I'm not a professional. She's insured. She has a nice ass and wasn't wearing a wedding ring. And she owned the car a total of four days, I think she said.

Oh, the truck seems to run fine now. That job was kind of a pain in the ass. Glad it's over with.

John B.

[Shovel]

She has a nice ass and wasn't wearing a wedding ring.

About half-way through the tunnel, the car ahead of me, maybe two car lengths, decides it's time to throw 'er in reverse.

[Canyonero]

That brings an entirely new meaning to "hot/under load"...

[JohnnyBfromPeoria]

Thanks, guys. I decided to try emissions again, since last time I failed hydrocarbons by a little and carbon monoxide by a lot. This time I passed both of those and failed oxides of nitrogen by 2X the limit. Typically that means a vacuum leak (Eric found a leak at the brake booster line and I didn't check it after he scooted the line back into place) or a failure of the EGR, which I doubt is likely because A) I cleaned the poop out of the entire system and B) Modern Monteros, and I'm including my 95, don't rely nearly as heavily on EGR to reduce NOX as the carbureted versions. So, out comes the propane torch to check for obvious vacuum leaks. Better not be at the front of my stinking plenum again.

I also discovered a weird problem that has to do with drivability and my new LED turn signals/flasher combo. When cruise control is set, activating the turn signal kicks the cruise off. Also, if I'm cruising along normally with my foot on the gas on the highway and use a turn signal, the engine starts to miss a bit. WTF is up with THAT?

John B.

[RyanY]

I've had an NOx failure due to a gacked (TM-Eric) up EGR valve before, although if your EGR system isn't functioning properly you should be getting a CEL on and an EGR code. If you're ECU isn't yelling at you about that then you're probably on the right track with the vacuum leak tracking.

[Crumb]

 What a nice way to meet a girl, hope that works out for you.