I have had this problem with my truck for about a yr now, I will try to explain it the best i can so 1st off I have an 89 chevy silverado w/ 5.7 tbi 4x4 and a while ago I was getting a car wash then the undercarriage wash started (spraying the bottom side of my truck) and it dies and wont start so I tow it home figured cap and rotor got wet, so replaced them and nothing so I replaced the module under the cap and still nothing so I figured it was the computer behind the glove box and replaced that and nothing still, the only way I could/can get it to run is by unplugging the timing advancement wire I believe it's called just a male and female plug you can unplug when u do the timing on the vehicle, so it's unplugged still and the s.e.s. Light is on rough idle feels like all the power is not there just doesn't seem right, but when I plug the wire back together it backfires crackles blows black smoke will not start unless ur foots on the gas, I mean u cannot drive it like this at all I mean it sounds pretty bad, but u unplug it and it starts right up and idles but it rough like I stated above, but I'm wondering if anyone else has had this prob or if anyone can help me out!! Thanks a lot for looking, and ur time and if u have any questions feel free to ask!!

 

How long since you washed the undercarriage has this been going on? Also the ses light, was it on before? I'd suggest unplug all engine connections (if this just happened since you washed it) and with an electrical contact cleaner, spray the connections, then rehook them up.

 

Scan it that what light is for.But you probably brought the light on by disconnecting the timing bypass wire. Can check by jumping points a&b at scan port.. underdash at sterringwheel. Can jump with paper clip ,or a wire. Turn key on .. do not crank.
Will start flashing codes .. first will flash 1 time short pause then 2 flashes.
Will be 12.. means system is working. Then it will start flashing other codes .. example
3 flashes short pause 2 more flashes will be code for egr. You said you were washing it .. check for wires that may have got knocked loose. Need to check timing.

 

This happened about a year ago, also I forgot to mention after I got it home, after the whole wash thing when I would push the cap down with my hand it would run so I think the was broke one of the screw off on my cap and made it sit crooked so when I would push it flat it would run so then I started replacing things? Could it be my plugs or wires? And as far as the s.e.s. Light goes it was never on before the wash, I did try pluggin a snap on scanner into it but bein it's obi 1 it doesn't really tell me much but I did the a&b jump and after the 1 flash then 2 flashes it did that code 2 more times then it did 4 flashes then 2 flashes right after, it did that could a few times also, then it went back to the 1 then 2 flashes 2 more times then the 4 then 2 flashes so what does this mean? Thanks a lot for your guys help!!

 

Ok you brought on the ses light when you disconnected the timing bypass wire.
Try this plug timing bypass back. Crank truck.. then disconnect coolant temp sensor.
It is located beside thermostat housing .. 2 wires. See if this makes a difference.
If not try disconnecting tps / throttle position sensor .. on the passenger side of throttle body. Did you have distributor loose for any reason?

 

I did have the distrib. out I replaced something inside of it or something I can remember but I had to take it out to replace some electrical component, put it back in and I was 180 deg. off so I turned it and tighted it all back up

 

I did have the distrib. out I replaced something inside of it or something I can remember but I had to take it out to replace some electrical component, put it back in and I was 180 deg. off so I turned it and tighted it all back up

 

Did you time it at 0 degrees tdc? If not this is your problem. Must of replaced pickup coil.

 

Thats the only thing you would have to pull the distrubutor for, if thats what he did, I can't believe he would forget that experience.

 

Ok tried unplugging thermostat sensor with bypass connected and wouldn't start, unplugged tps with bypass connectected and would not start also, and yes pickup coil sounds right. And I was at tdc I lined up the harmonic balancer correctly and I think I did advance the timing to plus 3 or 4 nothing to crazy. But yea anymore clues? Or ideas? Thanks again for all the help