Engine Miss At Cruise

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Old-Fart-Al

Registered
Guys, I'm in a situation of trying to figure out this problem without any codes. Scoped it with a cheepy OBDII scanner and it came up fine. The car runs great except when at cruise. About every five to ten seconds, mostly at highway speeds, under no-load at all (cruise, w or w/o cruise control), it has an inconsistant miss. Changed the plugs, new OEM Ford Boots, Jmod with Mercon V and actuator changes, and checked extensivly for a vacume leaks to no avail. Have an appointment next week to have it looked at but was informed since it isn't showing any codes, it could get pricy figuring it out. The miss is VERY noticable and I can't understand why it isn't showing any codes or warning messages. Any input as to why this might be happening is greatly appreciated. The car is a 97 Base with 75,000 original on it. Thanks in advance for your help in this matter.

Al
 
What plugs did you put in it...ummm, nice low milage. It doesn't miss at idle? That's tough. Without it giving up a cide, it'll be difficult (read expensive) for the dealer to figure out. It's bound to give a code sooner or later...you could just keep on running it until it does.
You running hi-test or 87 gas?
 
budpytko said:
What plugs did you put in it...ummm, nice low milage. It doesn't miss at idle? That's tough. Without it giving up a cide, it'll be difficult (read expensive) for the dealer to figure out. It's bound to give a code sooner or later...you could just keep on running it until it does.
You running hi-test or 87 gas?
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Hey bud thanks for the reply.
I put in the Motorcraft 768 or whatever the number is. They're the stock replacement plugs. Pulled one of the plugs the other day just to see what they looked like and it was a dark red. Figured it was because of all the fuel injector cleaner I ran through it on a trip I made recently, but that was five months ago. Shouldn't they be more of a cream color by now?
No it doesn't miss at an idle but it does idle slightly rough compared to what others have said their's idle like. I can barely feel it idling in and out of gear. Some say they can't feel their's running at all when idling.
Yes, I run premium EVERY time I fill up. Went on a 4,000 mile trip recently and ran abunch of fuel injection cleaner through it (every other fill-up). Ran fine the entire trip, the miss has appeared in the last couple of months.
The car hasn't ever gotten any better than 26 MPG except once during the trip when it got 31.2 MPG (?).
Hoping it's something I can trouble-shoot before taking it to the shop.
An injector maybe? Some sort of a sensor going bad? Exhaust restriction (no rotten egg smell)? Something dirty internally that needs cleaned? Got no idea. Got to be a reason for it. Any other ideas are definatly welcome. Thanks.

Al

PS; Got to go to work so I won't be able to get back with you guys for 2, 3, or as much as 4 days (I drive a semi for a living). I'll check back with you all as soon as I can. Thanks.
 
Roadboss said:
u said cheapy reader ? If you go to Advance or AZ theu will scan for free.
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I bought a Harbor Freight Super Dooper job (their Best) that wouldn't even connect to the system when pluged in. Took the car to AutoZone and had them scan it and it came up clean (PASS).
Cheepy, cheapy, however it's spelled it translates as less than a quality unit and in some instances, JUNK!
 
I know this is really simplistic, but it sounds a lot like what my car did when I had a bad plug wire.

Oh wait, you are gen 2... no wires... sorry :)
 
Did you have any oil on the outside plugs and inside the spark plug hole??

My Crown Vic was doing the exact same thing when I had some coolant in the spark plug hole...

Since you have a 97 it is very easy to pull all the coils and check the boots...
 
budpytko said:
...and you might run a can of SeaFoam thru it.....
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Think we'll have it figured out by the time he gets back? :D

I said a cracked coil and then re-read the initial post where he said he bought new coil boots.

In all seriousness.... intermittent drivability problems are best solved by datalogging in real time. At least it's an OBD-II and there are datalogging solutions out there to us.

It sure sounds like an ignition miss though. And if it is, there should be stored codes. Maybe AutoZone's code reader didn't read stored codes(only current codes)?
 
My Crown vic would not throw codes even if I disconnected an entire ignition coil... so OBD II is not as smart as you might think... I would narrow it down to the correct coil first by disconnecting them 1 by 1... the ones that doesn't make the idle worse once disconnected is the one with the problem.
 
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Could it be related to the A/C? I just remember that when I had a bad connection or fan or something (who knows, Eli looked at it for me), it would sometimes run funny which could perhaps be interpreted as a miss?
 
"The car hasn't ever gotten any better than 26 MPG except once during the trip when it got 31.2 MPG (?)."

I'll take the 26MPG with a slight miss!!! My '97 gets 25 (if I keep my foot out of it) running to Albany from Baltimore!! I can't keep my foot out of it on the NYS Thruway...I'd get run over!
 
When my Mark VIII (94 OBD I) had a miss during cruising on the expressway, it was the O2 sensors. The fuel mileage suffered also. It ran great around town and at idle.

I did get a check engine light and error codes stored though.
 
Thanks guys for all the input on this. I just got back and checked out what you all thought. After pondering this for some time I don't think it's a coil or it would be doing all the time (hot-rodding, cruise, idle, ect). I'm leaning more to what billcu was thinking, a bad 02 sensor. The only other possibility that I can come up with is a weak injector, spraying a bad pattern at a low flow or lean condition. But shouldn't any of these throw a code and display warning messages?
By the way, did the Sea Foam a couple of times awhile back, and there isn't any liqiud of any kind in the holes around the plugs.
 
Sounds like a bad/stuck EGR Valve to me...... The EGR only opens at cruising speed(translated as steady/normal/consistant throttle) and if its messed up, you might have a lean miss issue, but the only way this could be is if it was a mechanical failure of sorts, because anything else would be picked up by the ECU and a code would be thrown.

Tell us this Al, is it a "dead miss" like its only 1 cylinder, or does it just feel rough?
 
J said:
Sounds like a bad/stuck EGR Valve to me...... The EGR only opens at cruising speed(translated as steady/normal/consistant throttle) and if its messed up, you might have a lean miss issue, but the only way this could be is if it was a mechanical failure of sorts, because anything else would be picked up by the ECU and a code would be thrown.

Tell us this Al, is it a "dead miss" like its only 1 cylinder, or does it just feel rough?
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Hey Jesse, good to here you chimming in on this.
I hooked a vacume pump up to the EGR when it was running and began pumping on it to see if the EGR was defective. The engine stumbled and died, so I assume it's working. Whether or not it has a good seal when closed is not known.
It's not a "dead miss". It is completely erratic and inconsistant. Anywhere from 3 to 10 seconds it has either a single or multiple misses. If it was a dead miss we could isolate the cylander and troublshoot from there.
 
Good job Al...that was going to be my next suggestion. An erratic miss is a pita to diagnose, the best thing at this point would be to get a scanner to watch the a/f ratios and data log as suggested above.

Have you cleaned off the MAF sensor yet? It may have a ton of crud build up on it causing a bad reading when cruising?
 
Forgive my ignoance on this but I'm a carb guy. I love the new fuel injections that have been out for awhile but I just don't know that much about them. If the MAF is the sensor in the tube from the air cleaner filter box to the throttle body, then yes, I looked at it and it looks fine. If it isn't, would someone please give me an idea where it is, how to remove it, and how to clean it without destroying it? Got LOTS of carb spray here but don't want to use the stuff if it will harm the dang thing.
Anybody know if I can clean the 02 sensors without destroying them or should I just replace them all? Are all the 02 sensors the same or are the fronts and rears different?
Thanks again in advance for all the help.

PS; Got a full set of Ford Shop Manuals here and have had no luck using them so far simply because I usually can't find what I'm looking for. Three manuals about 4 inches thick each! Never found the number of each cyl for example. Had to call Ford to find out.
 
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