5.7 TBI runs like crap in the rain.

[CRF450R]

Oka so my 1994 5.7 TBI runs like crap in the rain. I have replaced the cap plugs and wires 30 000km ago. Problem started last fall so I pulled the cap off put electric grease on the points and thought that would help it kinda did but still runs like crap so I then just put a new coil in in May thinking that'll fix the problem but first rain storm said other wise. I'm stumped I've crawled all over that engine and around the distributor and can't see anything wrong.

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[df2x4]

I'd bet money that it's either the distributor cap or plug wires again. My red truck once had the same problem and a new AC Delco distributor cap fixed it right up.

 

[leegrady]

Are you running a distributor cap with a vent?

Ah...grease the points? On a '94?

CEL "0n"?

Here's a quick run down on how the ignition system works...

The crankshaft position sensor sends a CKP Signal to the PCM. Upon getting the crank signal the PCM sends a Triggering Signal to the ignition control module, ICM. The ICM then sends a Switching Signal/Ignition Control Signal to the coil.

Water moister in any of these components/connectors/wires may cause miss-fire.
Keep this in mind should all other simple solutions be exhausted.

Each of these components can be tested. However, duplicating such a complaint that occurs only when it rains is a tough one. A suppose one could do it the rain... (Hay, that reminds me of a song, lol) I mean if the miss-fire is consistent when it is raining then perform the tests at that time.

First tho', before performing any probe testing, I would individually spray each component/connector/wires with a water displacement spray, (Not WD-40. Too oily) Spray each thing one at a time, and see if the miss-fire disappears when that particular area is bone dry. Don't spray while the truck is running. A spark from say a faulty plug wire may cause a fire. Dry it then start the truck and see how it runs.

I cannot emphasize enough that these components can be tested before they are condemned fubar. In fact every single component on a vehicle can be tested. One does not have to throw parts at a problem.

Keep us posted. This is a real challenging one... Really like to know the outcome.

Rockin' on
-lee

 

[CRF450R]

I wonder if it's the crankshaft position sensor. Iv bin through the ingition system with all new parts within last year including a brand new coil and in May and still runs like crap when it rains runs like a champ on a nice day. Were is this crankshaft position sensor? Also the entire ignition system was replaced with AC DELCO but I've noticed acdelco parts have really bin going down hill. I'm getting very fusterated I hope this crankshaft sensor fixes this problem I'm about to walk away from this truck.

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[CRF450R]

I'd bet money that it's either the distributor cap or plug wires again. My red truck once had the same problem and a new AC Delco distributor cap fixed it right up.

I'm going to try this crankshaft position sensor if that doesn't fix it I'm going to completely redo the entire ignition system again if that doesn't fix it I'm lighting a match and going to walk away.

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[sntrym]

94 shouldn't have a crank position sensor. Those came on the Vortecs, not the TBI motors. TBI engines use the distributor to fire the coil. There are a couple components of the dizzy that can cause this.

The ignition control module - Located under the bottom plate. This is where the electrical wires from the coil and harness hook up to. Common failure point.
Pickup module - located on the top shaft of the dizzy.
Cap and rotor - I think you know this one.
Ignition coil - same as above.

Pull all the connections and check for moisture. Dry them out like @leegrady suggested.

 

[Bob L]

I would wait till it is dry and running fine then take a trigger bottle with water and spray each componet until you find what causes the problem.

 

[leegrady]

94 shouldn't have a crank position sensor. Those came on the Vortecs, not the TBI motors. TBI engines use the distributor to fire the coil.

Dang. That's right. Thank you for correcting my error.

It's just a engine speed sensor inside the dizzy. It sends a signal to the PCM once engine rpm reach 400 rpm's.

-I just put salt in my coffee,
lee

 

[Goose 3406]

I had the same issue on my 95 c1500, replaced a few parts but i never did figure it out. All i can tell ya is if it was rainin i had to gun the motor to get it to run smooth again.

 

[CRF450R]

94 shouldn't have a crank position sensor. Those came on the Vortecs, not the TBI motors. TBI engines use the distributor to fire the coil. There are a couple components of the dizzy that can cause this.

The ignition control module - Located under the bottom plate. This is where the electrical wires from the coil and harness hook up to. Common failure point.
Pickup module - located on the top shaft of the dizzy.
Cap and rotor - I think you know this one.
Ignition coil - same as above.

Pull all the connections and check for moisture. Dry them out like @leegrady suggested.

Oka I'll give that a try and see what happens hopefully that'll solve it.

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