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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #1
ARGGGHH! It's back AGAIN. The problem I had with my 90 4.5, and earlier on my current 91 4.9. No codes, a 'putt....putt....putt.....putt' sound from the exhuast, sloppy idle, and that tell tale shuddering during light acceleration that tells you the engine is missing a cylinder. If I've experienced the exact same problem on two different year/engine/mileage cars, SOMEBODY SOMEWHERE has to know what sensor or electrical component is wacky to cause this. I'm | | that close to saying to hell with Cadillac, I'm buying a Lincoln. I've put TONS of sweat into this car, fixing the rad, changing the water pump, even swapping out and charging the A/C, only to have it all for naught as my perfectly running engine decide to run like garbage out of the blue. please help
 

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93 Sedan Deville 4.9L
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1,005 Posts
If the tune up items are all done (cap/plugs/wires) then it could possibly be leaky fuel injectors, not sure how to check them since I haven had to yet
 

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1993 Eldo 4.9 66K miles
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368 Posts
From the description it sounds as if it isn't firing on one or more cylinders. How old are the plugs, wires, cap, and rotor? Have you inspected the cap interior for carbon tracking which would indicate a crack? Have you misted the wires with a spray bottle of water in darkness in an attempt to observe arcing?
 

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'87 SDV
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1,296 Posts
First, don't panic. Stuff happens to old cars - that's part of the fun.

Starting with a few questions:
You mentioned you experienced this problem with this engine once before - what happened then? Did you do something or did it just go away? Does this happen regardless of engine temp, or is it worse when it's cold or warm? Is the miss constant through the power curve, or does it come and go? Does the exhaust smell rich? Is there smoke of any color? Does the car snap and start easily, or does it require more cranking?

Since you have no codes, all sensors and the distro signal are within range. I'll predict it's going to be something pretty simple.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #5
No, it isn't plugs/cap/rotor/wires, that is ALWAYS the first thing people ask. This problem happened before any time there was excessive moisture under the hood. Over night it would dry, and the car would run fine. (I had a leaky rad which sprayed on the exhaust and misted under the hood). Temperature isn't a factor, the miss is constant. It's something that shorts out when there's moisture under the hood. Once the rad was repaired, the miss problem disappeared. Until the other day when it came back and I can't figure out why, and it doesn't appear to be going away this time. There has GOT to be a sensor or electronic component that can do this. If I've had it happen on two cars, SOMEBODY has to have seen this before. Nothing different from the exhaust, nor any different starting. It fires right up, and then settles into a sloppy missing lope idle.
 

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'87 SDV
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1,296 Posts
You're on the right track. Fuel issues normally will give you some sign at the tailpipe.

Two possibilities, both in the same spot. The weatherpack connector on the distro, especially 4.5s and 4.9s, tend to get brittle. Some people report the wires actually crumbling to the touch. I think Delco still makes a pigtail to replace it. The other possiblity is the pickup coil. The coil will sometimes set a distributor signal code (E12 I think), but not always.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #7
hey now that's more like it, I've SEEN the E12 (Distributor Signal Interrupt). I just never knew what was being interrupted, and like you said it doesn't show up all the time. Ok, whereabouts is the pickup coil so I can a)replace it, or b)spray electrical contact cleaner on it? Is that the little electronic piece that has to be taken out to replace the distributor cap? (As the new cap doesn't come with it?)
 

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'87 SDV
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1,296 Posts
The external coil the on top of the distro is the primary coil.The pickup coil is inside, surrounding the shaft, and requires removal of the distro to replace it - but let's not get ahead of ourselves. Since you are getting an intermittent E12 it's better to diagnose it than just throw parts at it hoping something sticks.

First carefully check and clean the contacts of the weatherpack connector - the 4 wire connector that meets outside the distributor, and the primary coil connector at the top of the cap. Are there any brittle wires or burnt contact points?

If you have access to a voltmeter, disconnect the weatherpack connector and while cranking the engine, measure the voltage at terminal B (purple/white wire) on the distro side of the connector. Post back the results.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #9
Well, I've listened more closely to the car, and it's not a complete putt putt miss like it was before. More like the car had a fat cam stuffed in it. The miss is barely noticeable under acceleration, so I'm now thinking that it may not be the same issue as before. But even so, it sounds like hell. Is the bad gas theory plausible? Maybe this particular car just doesn't like 94 octane?
 

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'87 SDV
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1,296 Posts
Bad gas is possible. Try a jug of gas line antifreeze, sometimes called dry gas in warmer climates. If you got a bit of water it will clear it up almost immediately.

That E12 code still needs attention, though. If it keeps coming back something is going on with the distro.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #12
Well hopefully somebody can give me some more clues. The problem started after an approximate 60 mile drive at 75mph. I arrived in Windsor, didn't notice any problems until after I fueled up at a Sunoco, and started to drive away, my g/f asked 'why is the car shaking now', and it's been running like hell ever since. It starts fine, nothing from the tailpipe, just idles, drives with a noticeable miss. Could the fuel pump have failed during the trip? Crank sensor (does a 4.9 have one?) It is a sudden thing, so I'm not thinking an injector just suddenly plugged itself while on the highway, nor a camshaft being rounded off. Anybody else with any clues?
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #13
And the E12 hasn't come back since I fixed the rad leak. Still no codes. But still running like garbage despite multiple gas station stops. I don't get it.
 

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1996 Deville Concours
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805 Posts
Not to patronize or repeat, but have you checked the ignition coil itself? You can check the resistance with a multimeter. I don't know the specs for this one, but I'm sure someone does... I'm sure you've checked the battery terminal connections, but make sure to follow them and see that they're in ok shape, as well as engine grounds. I've had a few issues with those getting oil on them.

There is still the pickup coil...but I agree in exhausting everything before that. That's the one part of the ignition system that isn't replaced on a "tune-up" basis...because it's more expensive...and clearly more of a pain in the arse hehe.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #15
Where IS the ignition coil, I thought that on this engine it was solid state, is it that little pack on top of the resistor? Somebody else told me that possibly the gear on the bottom of the distributor could have skipped and that twisting my distributor might help, but I've messed with ignition timing before, and it never had this effect.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #16
Well, it seems that when I said there were 'no codes', I meant the S.E.S. light wasn't on. apparently there are codes that come up that don't cause the light to stay on. Just on a whim I checked the history and came up with E34, and E71. MAP Sensor, anyone? And the symptoms of a bad MAP sensor describe how my car is running to a T. Now, is there anybody who can tell me where it is?
 

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93 Sedan Deville 4.9L
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Well, it seems that when I said there were 'no codes', I meant the S.E.S. light wasn't on. apparently there are codes that come up that don't cause the light to stay on. Just on a whim I checked the history and came up with E34, and E71. MAP Sensor, anyone? And the symptoms of a bad MAP sensor describe how my car is running to a T. Now, is there anybody who can tell me where it is?
IIrc the map sensor is the little black box at the top of the engine compartment, On my 93 it is mounted toward the passenger side just under the crossbar that connects the strut towers.

Id guess its about 3.5 - 4 in long and about 1.5 inches wide.
 

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1996 Deville Concours
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805 Posts
Blah, sorry I took so long. The ignition coil is that little cylinder-shaped doodad that's right on/in the distributor cap. The MAP sensor is like behindbars said... If you're looking under the hood, towards the back, I believe the vacuum hose that goes from the throttle body to it is easily accessible, but given the kPa readings you indicated before, I wouldn't bet this as being the problem. If you take the vacuum hose off the MAP sensor, you should notice some obvious problems with the engine running.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #19
Beautiful. 80 bucks for a new MAP sensor that didn't do a damned thing. I don' t know what else to do with this car. How can it run like garbage without tossing out codes or smoking or smelling. It sounds like somebody put a fat cam in it. Just chugs.
 

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1991 Sedan deVille 4.9L/1994 Lincoln Town Car 4.6L
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258 Posts
Discussion Starter #20
Well here's a new twist, was on a trip, and had to stop at a highway gas station. They had only 87 octane available, so I filled up. The car is now running BETTER on the lower grade fuel. What gives? I'm starting to lean towards the EGR valve not working properly, but there is NO way I'm dumping cash on another expensive part unless there is a way to tell for sure that it's the problem. It still chugs at idle, and still lightly shudders under hard acceleration, but under light acceleration the shudder is almost imperceptible. I managed to pull a couple of plugs, and they are clean. I didn't pull them all because it was hot outside and so was the car. Any more ideas, folks?
 
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