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Discussion Starter #1
Seems to be common, and though to diagnose.

The car: 1994 sundance 2.5 n/a
-New HG
-New cap/rotor; plugs/wires
-TB gasket (the thick one)
-Intake gasket
-Ground straps check out (I'll double check tomorrow - I missed the intake ground)
-Vac lines all check out
-PCV new
-MAP new

Symptoms:
-Car revs high upon starting, then comes down to a normal idle
-Bogs coming to a stop, has stalled before (intermittent)
-Bogs on the low end, feels fine in the upper RPM (intermittent)


Possible causes:
-Trans speed sensor (often forgotten about)
-Coil pickup
-IAC (Mines the OLD type, metal end)
-Intake leak, vac leak
-Converter locking when it shouldn't (not likely)
-O2 sensor (not likely)
-injector, fuel pump (I need to check pressure)
-ECU connector (never cracked it and looked)


The hard part is, it's intermittent. Some days it's fine, some days not so much. It throws no codes or the CEL. Any tips on where to start? Car looks to not be equipped with an EGR setup, rules that out.

Also: Can someone explain the vac deal on the passengers side firewall? - The canister and valve.
 

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This is acting like a vacuum leak. There are several possibilities.

1) Small split in the brake booster vacuum hose. It can flex when the engine rocks and be intermittent, and not enough to affect braking.
2) Leak at either the intake gasket or TB gasket. I had a TB loosen up about 5 months after rebuilding, even when torqued to spec, and cause this.
3) Any of the many vacuum hoses and lines. Some are encased in that corrugated sleeving and are difficult to determine if cracked.
4) MAP sensor vacuum hose loose, or sensor slightly damaged.
5) PCV hose loose or a small split. It's difficult to get it back on at the manifold, it's a tight fit. Or the elbow could crack or walk off the valve cover.

Can't be the O2 sensor if it happens on a cold start.

The passenger side canister is the fuel vapor canister. It stores the fumes vented from the tank and fuel system, and the purge solenoid on the fenderwell activates to suck the vapors in to be burned, at the appropriate times. A break in the rigid tubing or hose can cause symptoms similar to what you report. The canister is not serviceable and should be fine, unless it was cracked in a crash or impact.
 

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Check the wiring harness behind the valve cover (from the middle over to the driver's side end). Is there heavy oil contamination? That bundle of wires contains the AIS motor wires and I have seen oil contamination deteriorate the AIS wire insulation to the point where they were shorting together or contacting the ground wire (intermittantly).

I had this exact problem on my 87 LeBaron. The AIS motor was intermittantly shorting out causing high idle and stumbling on slowdown to idle (i.e. AIS pintle was stuck open or stuck closed and not properly tracking the commands from the computer). Generally a shorted AIS will not throw a code, but an open connection will. An intermittant open may or may not throw a code. You could even have a bad AIS motor although that is rare. Clean the connector to the AIS motor while you are at it.
 

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I can never get the PCV elbows to last more than a couple of months, regardless of where I buy them from. They all seem to have the exact same part number on them whether they're from NAPA, Autozone, Advance, whatever. They're pretty cheap, so if you haven't replaced yours in a while, I would look there first. Hard plastic vac lines can be replaced with hose.
I doubt it's the transmission speed sensor. That should also give you speedometer issues, as it's also the pickup for that.
I also have my doubts about the MAP sensor unless you're also experiencing more fuel consumption. Any failure of the MAP lines will cause a reduced vac signal to the computer, which translates to a "increase" in engine fuel demand, and a persistent rich condition. Personally, I have never heard of a MAP failing lean, but I'm sure it could happen.
Unintentional converter lock would would not explain the flare on startup, and I agree with you that it's extremely unlikely.
 

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Discussion Starter #5
It's got to be vac related. It only seems to be a problem with lower vac levels (no throttle)


When updating the hoses the last time, the top of the evap canister top popped off. I suspect it finally went completely. I didnt replace the PCV elbow either, going to change that out.
 

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Go to the dealer for the PCV elbow, the one I have is 4 years old and still fine. Autozone and others have a harder, almost plastic one that cracks readily and doesn't seem to be oil-resistant. The dealer one is a softer rubber and lasts.
 

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Plug the vac lines to the evap canister and see if that changes it. IIRC they can be difficult to find and the price isn't nearly as trivial as the PCV elbow.
 

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Actually, you can buy both the rigid tubing and the rubber vacuum tubing at Autozone these days, as well as rubber fittings.
 

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Discussion Starter #9
Update:

It's been a combination of issues.

-Wire from coil to cap is toast. Replacing it with a proper mopar.
-Hard plastic vac lines. Cracked when looking at them the wrong way. Tossed.
-Plug wires: the "better" set from advanced auto, junk. One was just pulling out of the cap.
-Car consumes coolant, afr changes with water temp, no good.

In the process of limping the car home I fear I may have washed down the rings and plugged the cat. It hasn't been a good month for me. KEEP UP WITH NORMAL MAINTENANCE....
 

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If it is a bad headgasket, replacing that should resolve a lot of things. Use a Mopar Performance headgasket and it should last the life of the engine. Also replace the cylinder head bolts (any brand). It becomes a little bit of a project at this point, but on this engine it is usually worth it and it is a much easier job than on most modern engines. I doubt that you washed down the rings badly enough to cause damage. Many of us here on the board have had headgaskets go out in that fashion and I haven't heard of any cylinder problems. You may have poisoned the O2 sensor. You'll just have to see how the cat acts after you are done with the HG job.

If your timing belt is old, now would also be the time to do it. Brand name kits are usually cheap on E-Bay or from Rock Auto.

EDIT: I see the original post says the headgasket was replaced. What brand? Was it torqued properly? Was the head inspected for flatness? Something doesn't seem right here.
 

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It's pretty hard to hurt a 2.5, they're very durable engines. Maybe the torque method wasn't followed when the headgasket was installed? IIRC, the bolts have to be torqued in steps, and I know you have to follow the pattern. Overheating can also spell the end of a headgasket pretty quickly on a motor with a cast iron block and an aluminum head.
If you're getting the classic symptoms of a blown headgasket, like bubbles in the radiator or "chocolate milkshake" in the oil pan, it's certainly time for a headgasket. That being said, I have my doubts. These engines have a very stupid thermostat location that causes any bubbles in the system to congregate at the thermostat and cause very erratic cooling system behavior, like rapid swinging of the gauge, chronic overheating, etc. I would imagine any failure of the headgasket that would be enough to cause noticeable coolant loss would be dumping tons of air into the system from either compression or vacuum on cooldown, so you would be seeing those symptoms as well. Major headgasket leaks can lower compression enough to make the vehicle undriveable, and you would be lucky to get it to rev very much away from idle. I would do a compression test and an exhaust gas test on the coolant before I singled out the headgasket. It certainly could still be that, but I know I would not be a happy camper if I spent $150 on parts for a headgasket and spent a weekend replacing it only to have the car run not much better than before.
How did you get the data on the fuel ratio?
 

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Monomer said:
afr changes with water temp, no good.
Not sure how you discovered this, but air/fuel ratio is DESIGNED to change with coolant temperature. The Coolant Temperature Sensor's input is used to determine richness of the mixture - richer when cold, leaning out when warmed up. Is there something drastically wrong with this, what data tells you this?
 

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Discussion Starter #13
Bob Lincoln said:
Not sure how you discovered this, but air/fuel ratio is DESIGNED to change with coolant temperature. The Coolant Temperature Sensor's input is used to determine richness of the mixture - richer when cold, leaning out when warmed up. Is there something drastically wrong with this, what data tells you this?
I phrased it wrong, you are correct. But currently theirs all kinds of air in the system, would this not cause afr's to be all over the place? The sensors want to see load, not hot air.


When I did the head-gasket I used a cortco (sp?) gasket, similar to a mc-cord. Used new bolts (stretch type) and torqued in sequence/steps to what was called out, plus the degrees. Head checked flat to less than .004 I didn't think to use the copper spray, as the gasket is a Teflon/graphite/slick to begin with. I think it has something to do with the surface finish of the head; I should have had a couple thou taken off.

If the gasket failed, it failed into a cylinder. No oil in the coolant, or milkshake. I plan on doing a compression test asap, along with new plugs/wire/cap/rotor (these were replaced 2 years ago now, my how time flies.) Belt was done at the same time as the head.
 

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You say you have air in the system. Have you double checked all of your hose clamps? I had a loose clamp on a heater hose on my 94 Spirit that was sucking air and it just about drove me nuts until I found it. Tightened it up and never had that problem again.
 

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Discussion Starter #15
chuzz said:
You say you have air in the system. Have you double checked all of your hose clamps? I had a loose clamp on a heater hose on my 94 Spirit that was sucking air and it just about drove me nuts until I found it. Tightened it up and never had that problem again.
It burns coolant


The smell...
 

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Head gasket.
 

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Discussion Starter #17
Bob Lincoln said:
Head gasket.
Still an ignition issue and a vac leak.


I'm going to top her off and get another week out of it before I tear it apart. Any recommendations on which parts to get? I usually go with non-felpro stuff from rockauto.
 

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Monomer said:
Still an ignition issue and a vac leak.


I'm going to top her off and get another week out of it before I tear it apart. Any recommendations on which parts to get? I usually go with non-felpro stuff from rockauto.
Search online for a Mopar Performance headgasket. These were high temperature, heavy duty gaskets originally designed for racing. The problem with Victor and McCord is that if the bolts are over torqued at all, the fire ring around the cylinder will get squashed and cause the material between the cooling passageway and the cylinder ring to breakdown. This was very common with the original Fel Pro design too. I can't speak for the newer Felpro gaskets, but on some cars (like Subaru) they now have a great MLS gasket. It is not likely available for a 2.2 or 2.5.

Rock Auto does not carry the Mopar Performance gasket. You will have to search online for another company (usually an online Chrysler dealer, but not always).
 

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I would say the headgasket hinges on the compression test. You could have a coolant leak somewhere else, like the heated manifold, that's spraying coolant onto something hot and boiling it, giving you the smell. I would expect serious idling and driving problems with a badly blown headgasket. Obviously, I haven't seen the car and how it performs, so there might be something that fingers the headgasket that I haven't seen. I know that if I were you, I would want to make sure it was the headgasket before I committed to replacing it. Like I said, a compression test will be the determining factor, but I would definitely do that before anything else.
 

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My last coolant leak, I thought it was the heater core, since the windshield wouldn't defrost, and I smelled it inside. Turned out to be a cracked overflow jug.
 
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