rough run with cold start


Old 06-20-03, 02:03 PM
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rough run with cold start

I have a 1994 Dodge Caravan SE, 3.3 liter, 6 banger with 169,000 miles. Engine Light came on and took it for computer diagnostic and indicated MAP Sensor, and Coolant Temp Sensor was bad. Replaced both. Just replaced Radiator fan and fuel pump, Oxygen sensor and EGR. When you start it when the engine is cold, acts like the old choke cars and the choke is not opening, and you smell gasoline like it is flooded. After several attempts it will turn over, but idles rough, with chugging and surging for first 3-5 minutes then it runs fine. Starts right up and runs fine all day as long as the engine does not cool down all the way. Someone told me might be a MAF Sensor, but Dodge Dealer Mechanics told me there's no MAF Sensor on these. Changed plugs and wires and ignition housing thinking it might be that. Diagnostic not showing any other codes. Any ideas what else it might be and what I might check next?
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Old 06-20-03, 02:22 PM
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Do you still have the same codes?Check the fuel pressure regulator and fuel pressure.Do you see any fuel leaks?Your fuel pressure regulator may have a ruptured diaphragm.
Old 06-20-03, 03:38 PM
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I agree.
Old 06-20-03, 08:52 PM
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I see where you replaced the temp sensor, but it sounds like either you got a bad one, or chenged the wrong one. There should be a sender for the gauge, and a sensor for the computer.
If the sensor for the computer is bad, it can very well cause these symptoms. Also, what's you coolant condition? Clean and proper mixture?
Old 06-21-03, 02:07 PM
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169,000 miles is a lot for anything, but by no means the end of your car, you certainly almost have the dartboard full of parts, not much left to replace until you hit the bullseye, look at all the money you saved by replacing everything 'yourself' except the one part that it's going to need to actually fix it.

first thing is to check engine's compression, if it's low or uneven, no matter how many times you tune it up it ain't gonna fix it, next, check you fuel pressure with a reliable guage, it should drop off very slowly with the key off, but not to zero in ten seconds, seeing as your fuel pump is new, that would indicate a leaking regulator (which i haven't seen yet on a dodge) or even a bad 'new' fuel pump(caused by junk in the tank)

one thing i've seen, but not very common, is a leaking fuel injector dripping fuel into the engine when the engine is off, this however will cause it to crank for about 7-10 seconds then run rough for 3-5 seconds, not 3-5 minutes as the extra fuel burns off, the easiest way to check this is to unbolt the upper intake manifold( a few bolts and vacuum hoses) and look at the injector tips with a flashlight, ANY fuel dripping is going to cause this problem, even as small as a small misty/foggy area in the intake.

another thing that it "might" be is heavy intake valve deposits, which my car has bad(184,000 miles) on a cold start up, the car obviously needs a little more fuel, the heavy deposits act like a sponge and absorb that small amount of fuel needed to make it run so smoothly, you should have looked at your original spark plugs for any ash deposits as worn valve stem seals will cause the deposits to build up fast(note--these seals cannot be checked by a compression test, it needs the eyeball test only)

if you saved 15 dollars by buying a non-original coolant temp or map sensor, the quality might be so low that it won't kick a fault code, but the calibration might be off by 40 degrees, telling the computer its 20 degrees out when it's really 60, this i've seen before and can be very easily checked with a thermometer vacuum guage and scan tool. ditto with aftermarket oxygen sensors. you definitely get what you pay for here. the coolant sensor you 'should' have replaced is under the coil(ignition) pack and has two wires, not the one in the cylinder head with one wire(you might not have this one).

another weird thing i've seen on high mileage 3.3s is the lower intake manifold bolts mysteriously snapping, but staying in the manifold, you can easily check all 8 of them(10MM) by poking them, if any move or spin with finger pressure, you could very easily have an intake leak, a little spraying of a flammable liquid near the 'lower' (V-shaped) gasket at idle will confirm this, be careful of fires with this, you only need a little spray for this (and to start a fire)

i guess by now you know how hard it is to diagose a computer 'system' without another computer to communicate with it. fault codes point you in a direction, they DO NOT condemn a sensor, it can range from the sensor, a connector, wiring(too close to an exhaust part or chewed through by mice which is very common) or even the computer itself, you will need a good voltmeter along with a scan tool and a good drivibility test(manual) to accurately diagnose any system

hope that helps
Old 06-21-03, 04:11 PM
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Everyone has given great advice here---one addition.

On some Chryslers, the fuel pressure regulator is built into the fuel pump module. If you bought a full in tank unit from the dealer or even the aftermarket, it should have had a new regulator with it.

If you bought a replacement pump kit, you likely still have the original regulator.

As a side note, recently, I changed the fuel pump on my friend's 1991 Dodge Shadown with 160k on the original pump. This is a 2.2 TBI engine, so the regulator is in the throttle body.

A pump kit from Pep Boys in Borg Warner was 150 bucks. I got him the whole Kem in tank unit for 127 bucks, and the Kem part turned out to be a Walbro part---same EXACT pump as the dealer quoted him at 250 bucks.

The part we installed dropped right in with 5 minutes labor after removing the tank and has been working great ever since .
Old 06-21-03, 07:47 PM
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yes, chrysler did start phasing in the 'returnless' fuel system in about 95(neons?)until about 96-97? as they redesigned vehicle lines, i think caravans were about the last to get them though, and i'm pretty sure his 94 doesn't have this setup, i don't know exact dates as this was something i didn't pay close attention to. if anybody else is curious about something like this, the easiest way to check is to look for one or two fuel lines to the rail.

excellent find on the fuel pumps, i'm about the biggest price shopper when it comes to 'my' money, i'll have to keep that in mind, that and my favorite which i've seen you boast about before, if i didn't work in a dealer, i probably would never buy from one, the price markup almost makes me sick, and i do feel bad for some customers, the only thing is that cutting corners (for them) will sometimes bite me back hard, so what do i do, CYA!
Old 06-21-03, 09:18 PM
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Yes, has excellent online cataloging and price lookup. I use that when I'm home. If I'm at work, I use the Triad (same computer the parts stores have)
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