Topic: 1990 wrangler 2.5 weird electircal problems

[thecrew2999]

got a 90 jeep wrangler with a 2.5 TBI and yesterday it rained bad but didnt seem to be the problem it was fine up until i changed the master cyl because there was no brakes, anyways i didnt lose any brake fluid i sucked it all out and also put rags down to make sure if any came out it wouldnt make a mess.

since that happened the jeep wasent happy.

first it was fine i took it out for a drive then some sudden stops to make sure it was gonna stop properly.
it stalled out a few times but seemed ok other wise.

after the night was over after trying to install a new front wheel bearing and after i got it on and tire back on only to find out it was the wrong bearing since the tire didnt move then having to put the old beat bearing back on. the thing didnt run right kept stalling out under any type of driving but being that it was late and i wasent in the mood i tried to push it and it didnt wanna go.
i stopped several times, playing with wires, vacuum lines and anything i could find that might be a problem including the injector in the TBI setup which had the 2 tq screws loose... nothing seemed to change the way it acted.

finally got it happy enough to drive back after using 3/4 a tank for a 70 mile trip which it normally only uses at most 1/4 tank.
i knew it was running rich real rich the exhaust fumes burnt my eyes and there was fuel puddling inside the intake.

got up this morning got some things around to try and help the problem.

so far i cleaned every plug with electrical cleaner and then using dielectric grease in every plug.
removed checked and double checked every vacuum line none leaking or crushed shut.

removed the injector cleaned it out reinstalled.

the thing has almost everything replaced for normal upkeep.
wires plugs (had to change them again got fouled out from being so rich)
cap, etc
fuel filter, injector cleaner etc...
air filter as well...
all but the o2 i wanted to replace yet.
the coil looks like it was on the jeep from its birth.


anyways heres the funny part.
at first it seemed to stall from the brakes being used like the vacuum was causing the problem but during the drive last night it seemed to get back when you used the lights, switched the high beams on and off would cause it to hiccup.
today after cleaned checking and greasing all the wiring etc. it seemed to be ok idling on its on with a slight miss on and off nothing that bothered me enough as it did last night.
anyways when i took it out for the drive i had to use some throttle to start it which its always been a little rough to start from time to time which i figured out coil since that and o2 havent been replaced but when i had it out driving it seemed like it was ok until i turned the headlights on where it got a good miss then switching between high and low beams cause some issues nothing major until i went to switch from high to low beams and held the switch back to make both high and low come on at the same time... it stalled right away with no warning or anything until i left it go since i was still it gear it started running again. so i tried it again same thing each time.

i dont know if maybe someone went threw this before or something and might be able to chime in.

it seems to be power related so i also checked the voltage and its putting out 14v running and battery checks out fine but i didnt do a load test on the battery.
my guess right now it the coil might be getting weak is the only thing i came up with thus far.

like i said i cant get it to get upset by messing with wiring or vacuum lines etc, i could find any leaks intake or anything.
only time i can get it to really get upset it by holding the high/low headlight switch in which kills it right away.
none of this happened until i did the brake master cly.

thanks for the time

[sharpxmen]

might be a ground missing somewhere - not the engine since you wouldn't be able to crank it.

[chardrc]

i was thinking battery when reading your post until you said you said it tested ok.. might try a load test still. i also have a 1990 and have had electrical problems but the headlights are on a pretty much totally different circuit than the computer or anything else since i would have a totally dead jeep except for headlights... i do have some wiring diagram pdfs that i could send you if you think they would help.

[thecrew2999]

i was thinking battery when reading your post until you said you said it tested ok.. might try a load test still. i also have a 1990 and have had electrical problems but the headlights are on a pretty much totally different circuit than the computer or anything else since i would have a totally dead jeep except for headlights... i do have some wiring diagram pdfs that i could send you if you think they would help.

actually yeah that would be great if you could do that.
this poor jeep had a rough life and looks like at one point some of the past owners had wired everything they could find into the jeep

[sharpxmen]

did you find the problem?

[thecrew2999]

no i didnt find the problem but its sorta running a little better like maybe the computer is learning on its on best it can at least.

i removed half the dash and removed the computer cleaned the wires i could checked the computer connection and it looked pretty good so i used some dielectric grease in there and found there is a wire someone cut and added a wire in its place like maybe before it was shorting out.

the wire was a brown and white one that ran to the plug that goes on the intake manifold temp sensor (IAC im assuming) right next to the head near the firewall.
the wire wasent perfect but i believe it was enough to do the job even tho someone used a wire that belongs in a house hold lamp or something.

im gonna replace it in the future but my first goal is to find the problem.

like i said only did it when i changed the master cyl on a really rainy day, probley dropped 3 inchs of ran in a few hours.

i know i did remove the vacuum for the brake booster for ease on master cyl removal, it could have pushed on some wires in that area but like i said i checked them out didnt see any real problems.. if i dont get anything figured out soon im gonna opt for a new wiring harness, dash and underhood.

if i got the wiring diagram i might be able to track down all the possible wires that could cause this.

[sharpxmen]

the reason i said might be a ground is because i have seen this on another vehicle - like you said, when turning on the headlights would die, same when braking (and was not because of the brake boost drum but because it would turn on the stop lights). turns out the ground wire between the motor and the body was broken. Now i cannot say that it is 100% your case but given the similarities it is something to consider - you can check that easily with a multimeter between the body and the engine, then go to the negative terminal on the battery and also check the ground between the negative of the battery and all the ground wires on your ECU (use the 1KOhm scale on the multimeter, should read zero on all measurements).

[chardrc]

i am sending the wiring diagrams as i type this.. sent to your email..... hope they help.

[thecrew2999]

the reason i said might be a ground is because i have seen this on another vehicle - like you said, when turning on the headlights would die, same when braking (and was not because of the brake boost drum but because it would turn on the stop lights). turns out the ground wire between the motor and the body was broken. Now i cannot say that it is 100% your case but given the similarities it is something to consider - you can check that easily with a multimeter between the body and the engine, then go to the negative terminal on the battery and also check the ground between the negative of the battery and all the ground wires on your ECU (use the 1KOhm scale on the multimeter, should read zero on all measurements).

very useful ill have to give it a shot.
thanks

[thecrew2999]

update nothing fixed yet but it did get better because i repaired a lot of wires and connections.
found some toasty wires on the turn signal harness but they werent the problem and seems like that were that way for some time...

i think it might be easier to try and find a new harness somewhere for underhood and under dash someone really hacked this thing up.

[sharpxmen]

i think it might be easier to try and find a new harness somewhere for underhood and under dash someone really hacked this thing up.

that would probably be best if it was hacked and looks like you have some wiring problems, but keep in mind that if you're still having the same issue i would first find out what it is before spending money on the wiring harness - it could be that you end up with the same issue so make sure it will solve your problem first (for example if you move your harness around and the engine stops running then it could be that and it is likely that replacing the harness will solve your problem, but it could also be a bad connector or wire beyond the under-hood wiring harness that can cause the same issue and you end up at square zero again with a lot of work and money in it too). imho (and if I was in the same situation) i would find out the problem first, if you have a source for cheap parts to help you troubleshoot go ahead, if you don't it can get easily expensive if you start replacing one at a time. If you do end up buying the harness try to get everything on it including the distribution box and fuse box and even the battery terminal, and double check that there's nothing missing (connectors that have been cut).

[SDWE61988]

Another thing you could look at, is inspect the wiring itself for corrosion. I have had this happen on my jeep and another old car I owned.  I am not sure if you live in an area that gets snow, but the salt and other chemicals the cities and states use will tear up the wiring.  I have had two cases where the wire looks fine on the outside, but it had corroded to the point of being open inside, under the insulation. 

[Matt vs YJ]

I'm not sure about the electrical problems, but for the rich-running and fuel-puddling problem, I've been there. Check the fuel pressure regulator. The rubber valve in the regulator can get torn and leak gas straight into the throttle body through a small vent tube that is visible just above the throttle plate. Pull the intake tube off and and have someone else turn on the key (without starting it) until you hear the fuel pump kick on while you watch the throttle body for leaking gas.

[que89yj]

By your description the electrical problem can be narrowed down quick with a multimeter. Your question shouldn't be what is going on at the switch but what is losing voltage because of it. Mkae a reading at the coil, fuelpump relay, ignition relay, and PCM module to see which one is losing power. I will bet that you are going to find voltage dropping at one of them.

[chardrc]

if you want soem diagnostic info go to http://jeepgarage.free.fr/ownersmanual.html.. lots of good info there about the ol renix tbi systems...