Everytime it rains my car stumbles at idle and when accelerating, I'm thinking it's ignition but not sure, what would you guys suggest?
1989 camaro engine stumbles when it rains
wisemanz28
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Everytime it rains my car stumbles at idle and when accelerating, I'm thinking it's ignition but not sure, what would you guys suggest?
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I've changed the wires, I was leaning towards a cracked distributor.
Before replacing the distributor, check the cap and the wiring especially the 12V lead that goes into the drivers side bottom of the HEI module. I have seen a few case where a 12V lead with cracked insulation and when wet it starts to short until the engine rev's enough to overcome the added resistance.
another thought, on a dry day you could take a spray bottle of water and give the ignition components a light bath to see what shorts when it gets wet.
another thought, on a dry day you could take a spray bottle of water and give the ignition components a light bath to see what shorts when it gets wet.
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Make sure the rubber seal between the cowl and the hood is there. some people will remove it to get a "cowl induction" effect. Downside is when it rains it leaks on the distributor and causes problems like you have.
More info on the car would be nice. What engine? V6 or 350/305TPI or 305TBI? or has it been changed to a carb? Stock hood or aftermarket?
More info on the car would be nice. What engine? V6 or 350/305TPI or 305TBI? or has it been changed to a carb? Stock hood or aftermarket?
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The engine and car are all stock, 305 c.i.d. tbi with a automatic transmission. The hood is a stock flat hood.
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Anytime someone says they are having problems when it rains, i always think about the LT1 optispark system, and how you could drive through a puddle and it would short out. (Distributor was on the lower end of the motor) Different motor obviously but still. Definitely check all connections, see if you can find a bare or exposed wire. Maybe look to see if the cap is cracked, one easy way to check wires and cap is to run it at night in the dark. Just open the hood, and sometimes you can see a plug wire or even a cap arc to a manifold. If you do, it would explain your situation. You may try also to take your cap, spray some WD 40 inside, wipe it out good, then re-install. Most people think WD 40 is just a lubricant, but its called WD-40 for a reason. Stands for Water Displacer #40. Won't affect spark, but will help keep water out of the cap.
Question: Once it runs up to temp or for ten miles or so does it stop stumbling?
Reason I ask is because I'm not certain but think there might be two little screened vents on the bottom similar to others that have a problem with the screens getting clogged up so condensation can't dissipate. At least on some later models there's a TSB to just knock the screens out. My S10 used to do that on wet days and it would always clear up after a few miles. I'd usually just replace the cap and rotor since they're cheap (aluminum terminals and they'd always show white oxidation/corrosion inside). Finally used an air gun to blow out the vents and used a good brass cap and rotor.
Reason I ask is because I'm not certain but think there might be two little screened vents on the bottom similar to others that have a problem with the screens getting clogged up so condensation can't dissipate. At least on some later models there's a TSB to just knock the screens out. My S10 used to do that on wet days and it would always clear up after a few miles. I'd usually just replace the cap and rotor since they're cheap (aluminum terminals and they'd always show white oxidation/corrosion inside). Finally used an air gun to blow out the vents and used a good brass cap and rotor.
The first gen of the optispark was a nightmare. I eventually modified mine (93 Z28) to add the vaccuum like the newer ones had and it was much better. Caps and full new optispark distributors weren't readily available like they are now.
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The engine usually won't stop stumbling at all if it is raining, especially stinks when I'm at a stoplight.
Atmospheric pressure is changing between a sunny day - high pressure - and a rainy day - low pressure.
I suggest looking at both the MAP sensor, Manifold Absolute Pressure, approx 1 inch wide by 2 inches long by 3/8 inch thick black box, and its vacuum line and its connection at both ends.
Just a thought, as others have said, check distributor cap and if in doubt, replace it with a new cap having copper terminals, no alum.
I suggest looking at both the MAP sensor, Manifold Absolute Pressure, approx 1 inch wide by 2 inches long by 3/8 inch thick black box, and its vacuum line and its connection at both ends.
Just a thought, as others have said, check distributor cap and if in doubt, replace it with a new cap having copper terminals, no alum.
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Just got out from under the hood, turns out the vacuum line that goes from the MAP sensor to the rear of the TBI was broken , I spliced in a rubber line and will wait till it rains (Monday) , I hope this cures the problem.
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Just washed the car and took it for a drive , it hesitated again, opened the hood when I got home and there wasn't a drop of water anywhere, now I'm stumped.
TPS (Throttle Position Sensor), has three wires going to it.
Find the two wires connected to the sensor wiper as these two wires should show varying resistance continuously while slowly opening/closing the throttle.
Any interruption of the reading, bad sensor.
Also, get a Haynes manual and read up on setting base idle and base initial timing.
Start here first.
Find the two wires connected to the sensor wiper as these two wires should show varying resistance continuously while slowly opening/closing the throttle.
Any interruption of the reading, bad sensor.
Also, get a Haynes manual and read up on setting base idle and base initial timing.
Start here first.
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71 Posts
Just reinstalled my distributor in my car and after changing the pickup coil ,cap, rotor, ignition control module, blew out the screens in the baseplate, and changed the map sensor, it stills is stumbling when I spray water on the closed hood, I'm at a loss, can you guys suggest anything else?
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