Frustrating ignition problem.

[Aeroguy]

I have a '97 Aerostar with 4.0L/4WD. For the last three months my Aerostar has been having intermittent problems with misfiring that has been driving me crazy. Out of a seven-day week, there will usually be one or two good days where there is no evidence of a problem at all... the rest of the week it will idle fine, but misfire for the first 3-5 minutes of driving before curing itself for the rest of the day. About a month ago it had a very bad time when it ran horribly for about ten minutes before lighting up the MIL... a minute later, the problem suddenly went away. I pulled the codes to find that there were two error codes, misfires on cylinders 3 and 6. Since they were both on different coils, I ruled out the coil pack for the time being. The wires and plugs are about 18 months old, but I checked them out anyway and everything looks good. I had an extra wire for cylinder 3, so I swapped it, but there was no change. I tried some Lucas fuel injector and even Seafoamed the engine, but there's been no change at all. I lost a tip for my compression tester so I haven't checked the compression yet, however due to how fast the problem seems to solve itself after driving it a few minutes, I'm thinking the problem lies elsewhere.

Four days ago things got worse... the misfiring no longer goes completely away after a few minutes, but instead misfires at highway speeds. Two days ago I started it up in the morning and it ran horribly before lighting up the MIL... cylinders 3 and 6 again.

Today, I hooked up a timing gun to each of the wires just to see if I could catch it misfiring that way... not a very scientific test, but I did find that cylinder #6 seemed to be occasionally skipping, however cylinder #2, which is on the same coil, seemed to be firing perfectly. Cylinder #3 almost seemed like it was firing faster then the rest of the cylinders, but I really had no way of confirming it. When I was done, I found the MIL went off again, but only for cylinder #3. I called Napa to see if they had a coil in stock, figuring I'd rule that out, however the guy I spoke to didn't seem to think so... he said that he rarely ever sees coils go bad, but when they do, they just die. He said that since the other cylinders that are paired with the problematic cylinders (#2 and #4) are fine, then that rules out a bad coil.

I don't have a whole lot of time to really deal with the issue and what time I did spend on trying to solve it has come up with nothing. On days the misfiring wasn't occuring, the engine runs flawlessly. The problem is now clearly getting worse. Is it possible for a coil to go bad and effect only one of the two cylinders it handles? Should I be looking somewhere else entirely?

I would appreciate any help!

 

[BrooklynBay]

My friend had this issue on his Taurus. My OTC spark tester read a lower voltage on two cylinders just like the code's description. I replaced the coil pack, and it helped. What brand of spark plugs & cables did you use? Did you ever replace the CPS?

 

[Aeroguy]

The plugs and wires are Motorcraft and the CPS was replaced 5K miles ago.
Thanks.

 

[BrooklynBay]

It sounds like it's the coil pack. Less spark energy (high voltage) is going to two cylinders.

 

[Brian A]

Aeroguy

I have a very similar issue with this.

I sent you a pm, I think it could be a coil pack


thanks

 

[BrooklynBay]

Today is Aeroguy's birthday. Happy birthday! Did you make any progress with the ignition issue?

 

[Aeroguy]

Thanks!

Been busy, so I didn't get chance to work on it until the other day. Up until Thursday, my van was running pretty bad... starting it cold, it idled horribly. I'd let it warm up for 6-8 minutes then drive it for about 3-4 before it smoothed out. The last week the MIL went off a half dozen times, mostly right after start-up.

I installed a brand new Motorcraft coil pack on Friday. I reset the computer, started it, and then let it idle for about five minutes (ran rough, but I expected that after resetting the fuel maps). I drove it around a bit and at first I thought there wasn't any change, but then the problem went away completely after the first mile. In addition to that, the engine seemed a LOT stronger. After driving it around for 20 minutes, I decided to bring it onto the highway where the problem had been more consistent, and it ran beautifully. Before it always seemed a bit bogged down at 65mph, but it seemed flawless with the new coil pack. Lastly, the gas mileage went from a maximum of 13mpg to a surprising 17mpg on my 10-mile test trip between city and highway driving. I was happy, but I knew the problem was intermittent, so I didn't want to get too excited.

I've driven it the last two days and it's apparent that it was just having one of its 'good days' on Friday. It still idles horribly at start-up... often lopping badly if you put it in gear too early. After it warms up, it runs better then it did before, so the coil definitely helped, but it wasn't the problem after all. I drove it on the highway today and although it still seems a lot more powerful with the new coil pack, the occasional misfire was there when accelerating above 60mph. Also, the problem is now occurring after even brief period of time when the engine is off. I went to the store yesterday and after being off for 20 minutes, the engine started up with the usual roughness I would normally expect after cooling overnight.

I had an Aerostar years ago that was an absolutely fantastic vehicle... I loved it, but it was totaled in an accident. I spent years trying to find a replacement, specifically the same year and engine with E4WD. I finally found one after three years of searching that was identical to my old one and had an excellent interior, but it had various problems... very loose steering, alignment problems, switches that didn't work, etc. During the first three months I replaced all the bad switches, completely replaced the steering system, and threw on new brakes, tires, and various extras. For six months it ran great, but ever since then there's been one problem after another. I've spent several thousand dollars in parts trying to get this thing to be like my old Aerostar, but I fear that'll never happen.

I really don't think this is being caused by compression or cylinder problems... when the problem first started to occur, it would go away suddenly, as if flipping a switch. In my experience, compression and cylinder problems that occur only when cold go away much more gradually. I had a car once with very bad compression in one cylinder, but only experienced a rough idle... never a misfire. I also had a car with a cracked head, as well as a friend who had a cracked head as well... both cars would backfire under load... not a misfire like I'm experiencing here. However, my next step will have to be a compression test since I really need to know whether my efforts are worth it.

 

[Aeroguy]

I was looking through my tools trying to find the part for my compression tester when I came across my new fuel pressure tester. I bought it last year, but forgot all about it. Just for the hell of it, I connected it to my Aerostar along with a vacuum tester connected to the intake manifold. Key on, the pressure should be up at around 60psi I believe, however the pressure was only 7psi. I started the engine and the pressure jumper to 27psi. It stayed at 27psi without so much as a flicker when I revved the engine and while I pinched the fuel return line. The intake vacuum was at 18.5psi... solid until I revved the engine in which case it responded perfectly as expected.

I then turned the engine off and watched the pressure... it slowly increased to 35psi over the next two minutes, the stopped where it sat stable for the next ten minutes. I restarted the engine and it immediately dropped down to 27psi and held solid.

So could all this be the fuel pump? Why wouldn't I be getting MIL alerts for lean fuel mixture?

Thanks for the help!

 

[BrooklynBay]

Was the fuel filter ever replaced?

 

[Aeroguy]

Yes, the fuel filter was replaced about two years ago... only put about 7,000 miles on it since.

A correction though: I looked up the fuel pressure specs... with the key on and engine off, it should be 35-45psi (mine was 7psi). With the engine running it should be 30-35psi (mine was 27psi). A bit low, but nowhere near as low as I originally thought.

The engine ran terrible when I first started it up... the pressure showed 27psi. After it warmed up, it smoothed out, but still showed 27psi. This makes me wonder yet again if I'm on the right track. My biggest fear right now is replacing the fuel pump and it not being the problem. Another gulp of cash into the money pit...

 

[Brian A]

I may have missed it but have you ruled out the fuel pressure regulator?

another thought is maybe the injectors are leaking down and causing a pressure loss when the engine is sitting. That could be why its hard to strart cold.

I know there are simple tests for this.

 

[Aeroguy]

I pinched the fuel return line closed... if the regulator was at fault for the low pressure, the pressure should have spiked. It didn't, so I don't think it's the regulator.

Also, the fuel pressure held after I turned the engine off. It goes up to 35psi, but then sits there not moving. I left the gauge attached for 20 minutes and there was no pressure drop. If the injectors were leaking, there would be some sort of pressure drop.

I dropped the fuel tank late last night. The pump looks fine... no signs of clogging or an overly dirty strainer.

 

[FORDBOYpete]

37#PSI is nearly ideal system PSI on MAFS systems. Also it's a loop based PSI & will or cannot vary between injectors in a fuel supply loop. IOW All injectors get same loop PSI. injectors or more likely harness attacting clips deteriorate causing issues but irregular pressures between injectors in a typical FoMoCo MAFS/EFI are really not normally possible.

I agree with Brooklyn Bay & suspect coil pack Issues. Coil Packs are located in highly heated location with very little air flow & cooling. Over time they've a tendency to degrade, losing efficiency & performance capabilities.

When replacing your plugs do you use double platnum type plugs? Spark Plugs can bridge gap & over time it gets worse. Matter bridging them may or may not burn completely off electrodes on start up. I've 1 cylinder fouling it's plug every 8-9 months or so. The 4.0L has over 250K on it now. Before using Dbl Platnum plugs it would foul about every 2.5 - 3.0 months. Always the same cylinder, always same condition & problem. My fix has been to R&R the plug & clean it when I feel it starting to foul. My main fix is a fresh 4.0L Cologne V6. I am working on that right now.

I just got an EDU in A4LDs. I've a life beyond wrenching on my own stuff. As with most folks & am chasing $$$'s & spending much of my time "Juggling Bubbles" & "Herding Cats" just to get by nowadays. I'm supposed to be Retired, but apparently I'm "Re-Tried" instead.

Coil packs are insidieous creatures causing seemingly unrelated problems. So are carbonized linen ignition wires all coil packs require. Heat is not our friend.
Good luck & Please keep us advised on this issue.

CIAO
FBp

 

[Brian A]

37#PSI is nearly ideal system PSI on MAFS systems. Also it's a loop based PSI & will or cannot vary between injectors in a fuel supply loop. IOW All injectors get same loop PSI. injectors or more likely harness attacting clips deteriorate causing issues but irregular pressures between injectors in a typical FoMoCo MAFS/EFI are really not normally possible.

I agree with Brooklyn Bay & suspect coil pack Issues. Coil Packs are located in highly heated location with very little air flow & cooling. Over time they've a tendency to degrade, losing efficiency & performance capabilities.

When replacing your plugs do you use double platnum type plugs? Spark Plugs can bridge gap & over time it gets worse. Matter bridging them may or may not burn completely off electrodes on start up. I've 1 cylinder fouling it's plug every 8-9 months or so. The 4.0L has over 250K on it now. Before using Dbl Platnum plugs it would foul about every 2.5 - 3.0 months. Always the same cylinder, always same condition & problem. My fix has been to R&R the plug & clean it when I feel it starting to foul. My main fix is a fresh 4.0L Cologne V6. I am working on that right now.

I just got an EDU in A4LDs. I've a life beyond wrenching on my own stuff. As with most folks & am chasing $$$'s & spending much of my time "Juggling Bubbles" & "Herding Cats" just to get by nowadays. I'm supposed to be Retired, but apparently I'm "Re-Tried" instead.

Coil packs are insidieous creatures causing seemingly unrelated problems. So are carbonized linen ignition wires all coil packs require. Heat is not our friend.
Good luck & Please keep us advised on this issue.

CIAO
FBp

he said he replaced the coil pack

 

[Aeroguy]

Yes, the coil pack was replaced. No change...

I replaced the fuel pump and fuel filter today. Before, the fuel pressure stayed at 27psi... now it stays at 28psi, while randomly jumping to 30psi every minute or so. I drove it to the gas station to fill up and I wasn't even sure it would make it ... runs like absolute s**t. Stuttered and hesitated the entire way.

 

[Aeroguy]

I spent a couple of days testing the fuel system to find out why it's only reading 28psi. Although the fuel pressure regulator seemed fine, I was just about to test it when I thought about the fuel pressure testing tool itself. I hooked it up to my wife's Taurus, which I know is running perfectly, and it too showed 28psi. I ended up making up a mock manifold of tubes and connected it to my air compressor. Both gauges on my air compressor showed 45psi, as did an additional gauge that I hooked up... the fuel pressure tester showed 41psi, so apparently the tester itself was bad all along!

I ran a compression test last week... all cylinders were 180psi +/-4psi, so the compression is good. Vacuum test shows the valves are good and I now know the fuel system is fine.

Today, I drove to the store and noticed it was running a bit worse then it had been. On the way home, there was a noticeable loss of power and when I came to a stoplight, the engine horribly rough... I had to step on the throttle just to keep it from dying. The MIL started blinking various times during the trip. I finally got home and hooked up my scanner... instead of the usual misfires on 3 and 6 I got SIX codes...

P0302 Cylinder 2 Misfire Detected
P0306 Cylinder 6 Misfire Detected
P0353 Ignition Coil C Primary/Secondary Circuit
P0303 Cylinder 3 Misfire Detected
P0230 Fuel Pump Primary Circuit Malfunction
P0231 Fuel Pump Secondary Circuit Low

In addition, after I shut off the engine, it would not restart. This was great news to me since now there was a definite problem to search for. I checked out everything with the fuel system and everything was working perfectly. Then I got to the spark plugs... no spark on any of them. Found there was power at the coil pack, but before I had a chance to go any further, the engine ended up starting. So now I'm hunting blind again.

Now codes P0302, P0303, and P0306 are no big deal... the misfire could be caused by a number of things. However codes P0230 and P0231 are very strange... I checked the fuel pump relay and and fuel pump cutoff switch and found no problems. There was plenty of pressure when I was trying to start it.

The coil pack is brand new, so my next target, before the engine ended up starting, would have been either the PCM or the crankshaft position sensor. The only problem is, I replaced the crankshaft position sensor not too long ago, but well before this current problem started up last January. I'm beginning to wonder if the problem could be the CPS since most of the problems I have been having could be contributed to a bad sensor (besides the fuel-related codes, P0230 and P0231). The only thing that's keeping me from replacing it at this point, besides the fact that it's relatively new, is the fact that I don't remember ever hearing about intermittent problems with one... in my experience, when their bad, they're dead.

My problems continue to be:
1) Poor idle and severe missing when cold... takes about 15-20 minutes before it smooths out.
2) Occasional missing when accelerating past 60mph.
3) Poor idle for a few minutes when you restart the engine while hot.

I'd hate to replace a good CPS. Any thoughts or suggestions would be appreciated!

 

[BrooklynBay]

Some electrical parts have a guarantee for a short period of time, so the CPS might still have a warranty. You could test it with a multimeter.

 

[robcarz]

One of my old Datsuns had a baffling misfire problem for a long time. Turned out to be a defective fusible link near the battery. Found it by accident when I wiggled the wire and the radio came on. Good luck hang in there.

 

[Aeroguy]

I checked on the CPS... over a year old and out of warranty.

Late last week I started checking wires one by one. I got through all the wires and found nothing, so I started the engine and started wiggling. One of the first things I grabbed was the coil pack connector. Now, the coil pack connector has a broken tab... found that out the first time I changed the spark plug wires, but I found it to be secure, so I never thought much more about it. When I replaced the coil pack, I took note of how far the connector went into the socket and made sure it was the same with the new one. It was, and again, seemed secure.

Now, while I was wiggling wires I got to the coil pack wire and immediately noticed a change in the way the engine ran. Every time I moved it the engine would improve or get worse. I pushed it backwards and caused the engine to stall. I popped the connector out and took it apart, cleaned the wire connectors (it was a bit dirty), and put it back together. The coil pack was new, so that end didn't need attention. I plugged it back in and started the engine... no change. I began moving the connector around a little and then tried pushing the connector further into the coil pack. When I did, I noticed a bit of a spring back, so I popped the connector out and looked closer at it. I noticed the seal in the connector was a bit folded, so I yanked the seal out and tried plugging it back in. I immediately noticed the plug snapped in a good 1/4" further then it was originally going in. I started the engine and noticed an immediate improvement.

It's been four days now and although I was a bit leery about getting happy too early, there has definitely been a huge improvement. All but one of the problems is gone... no more codes, no more missing while driving, and no more horrible idling. I'll be picking up a new connector this week to officially end the chance of this ever happening again. The only problem left is the original rough idle when cold, however it disappears within five minutes and the engine runs beautifully after that. I unplugged the air flow sensor, but there was no change. I tested the IAC and it shows it's within specs. I guess I'll continue the hunt, but at least the big problems are out of the way.

 

[FORDBOYpete]

Aeroguy,
I have found over time throttle bodies get "dirty" inside their bore, after or "behind" the throttle plate in the "throat" where it bolts to the upper intake plenum. Periodic cleaning of a throttle body can reduce this symptom if/when build up is severe enough. Cold Idle/ Low RPM transition (acceleration & de-acceleration) apparently is affected by build up in throttle body bore. Using a repair manual disconnect throttle body & related parts, like TPS, accelerator cable, snow shield, etc.

Use a good grade solvent type, carburetor cleaner, and a clean lint free rag or wiper to clean the black greasy fouled build up inside throttle body neck. For good measure you may want to clean duct tube running between MAFS @ filter box & throttle body itself. Most solvent type carb cleaners will not affect this tube.

If the throttle body to Plenum gasket was damaged in disassembly, replace it on reassembly. The source of black stuff is vacuum draw tube off your PCV. It is ecavuating crancase fumes. They cool & condense over time building up in Throttle Body , mostly after throttle plate. There will be some residue in duct tube too. I reccommend replacing Airfilter in your airfilter box at the same time.

I replace Ignition harness @ 100,000K miles on "GP". I run the Autolite Dbl platnum Spark plugs. Both help stop cold engine stumble & increase MPG Avg overall. I believe DBL Platnum plugs run better throughout out their lifetime.

There is a comment in this thread made back on 20 April that says & I quote:
" he said he replaced the coil pack"
I know what he said, sir. However symptoms & codes he got were ignition spark based problems. Just because a component is replaced does not make it "good" or functioning correctly. In this case coil pack did function correctly, however connection & wires apparently did not. Think in terms of "Systems", systems are made up of component parts all working together to accomplish a task. Any part & all connectors within a system can be suspect of malady or failure. DTC's allow us to stay on track & get to root of a problem there-by eliminating gueswork and all shadetree parts changing procedures & expense. etc. etc. etc.

CIAO
FBp