Won't run head scratcher.

I don't post much because usually all my information is found by that handy little search button and I love this forum for that. But it seems that the following wouldn't fit in the search bar. I drive a 1987 7mgte 5 speed with 131xxx miles. 100% stock. The car isn't in the best of shape (I'm working on that though). Here is my problem. I didn't drive the car for about 5 days, I get in it the other day, check fluid levels etc. Start driving it nice and easy, no boost. I get off the throttle 0% after warmed up and it starts bouncing between 1000rpm and 2000rpm itself. Okay no biggie some random vacuum leak. I was washing the car while running because I was on my way to pick up a new battery (I had assumed my random starting problem was due to the POS battery in it, when going to start I always gave it one quick turn, wouldn't start, and then another one a second later and it'd usually start almost like a race car with advanced timing ie:almost die then fire up fine).

Pulled out from the wash, went across the street to get gas shut her down put some 92 octane in it. Did the same usual start up and took off and boosted down the road, during so the coupler at the 3000 pipe to the throttle body must have come off and I then got a boost leak. At this point the temp. was reading that it was running very cold, and mine always warms up fast and will sit there all day. I pulled over and put the coupler back on and it still ran cold, and had the same 1000rpm to 2000rpm 0% throttle bounce BUT now it also would sit at 2500rpm until I blip the throttle then it would drop into the rpm bounce again. I'm heading home at this point in town. Take off from a light and she starts missing at 1800rpm then past that it smoothed out never shifting over 2500rpm (trying to take it easy). Well in 30mph traffic 1800rpm is pretty hard to avoid. After about 1minute she starts missing all over the place and shuts off and I coast her into a lot.

Now here's the head scratcher. Won't start so I, check all fuses and the ignition is blown and that's it. At this point that battery was thrown out and we picked up a new one. Throw it in. Head lights work ie: go up and down, high low but there is no cranking, doesn't do anything on trying to start it up. No interior lights, windows don't work mirrors, I can't hear the fuel pump come on (still have to jump the B+ and FP to see if a friend can hear it at the rail or at the pump). Checked the kick panel fuses, all are intact. The hazards do work too. Tried starting it quick with the new battery and for 1 single time it did a slowwww crank but that was it. Didn't do it again after that.

At this point my window was down we've wiggled and checked everything, it starting pouring rain out (IDK if its on the news how bad chicago and places around it have been getting hit but its been crazy rain and storms for like 3 days) and my friend and I gave up on it. She got towed back early today (yay liability, bodily injury and tow insurance). Here's my ideas and what people have possibly thought: The starters little brown wire is off or loose, ECU but its not throwing a code, some random relay, or that I drive a broken ass 7m.

I am on 4 hours of sleep so I don't know how much of that makes sense so I'm sleeping until noon and have to be to work at 2 so that gives me about 1 hour to read responses or answer any new questions until I go to work.

Thank you VERY much for any and all input.

Aaron
 

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Feb 10, 2006
10,730
1
38
Valley of the Sun
Check your 100 amp Alt fuse in the engine compartment. Also, the EFI fuse in the same box. Confirm the battery is hooked up correctly and connections are secure. Check the voltage on the new battery to confirm a full charge.

When you washed the engine, bet you got water in the spark plug wells...that will make it run like crap ;)
 

dbsupra90

toonar
Apr 1, 2005
2,374
0
0
indiucky
jdub said:
Check your 100 amp Alt fuse in the engine compartment.

exactly what i was going to say. its one of those fusible links, and often need to take it out to inspect it. mine looked fine, but had a hairline crack in it causing intermittent issues.

also to note, these do NOT pull straight out of the fuse block. you have to unbolt the fuse block, and remove the bottom cover. the alt fuse is bolted in from the bottom.
 
I inspected all those from the top (I checked and pulled almost every fuse I could). I'll have to unbolt it and really check I guess. It was just odd how it slowly died; I'd think with a fuse it'd just shut off. But then you said "but had a hairline crack in it causing intermittent issues." so it opens that door again. The valley was dry from initial inspection (I usually give it a look after I wash it because of so many problems with water sitting there and car issues). Thanks for the help I'll see how it goes.
 

silvergsx623

WIPLSH & HWY KNG
Oct 16, 2005
498
0
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39
Alabama
ATL88Supra said:
check your alt connections then start checking wires that fuse grounded out so that means there is a bad wire some where


Exactly, fuses only pop when something shorts out. So something happened to cause the ignition circuit to short.

Replace the fuse and see if it blows again.
 
Well it actually ended up being the alternator. Someone with a sr20 said they had the same symptoms and he was right. So I get that fixed, interior lights come on, YES! Turns over YES! come one catch and fire. Come one catch and fire! CATCH DAMN IT!!!!!!!!!!! Fuel pump isn't coming on/priming and there's zero spark. I used the volt meter on the coil pack (read .5 on the secondary which is in spec), ignition system etc. They all read like .003ish with is obviously way low. I tried to test the cps but I was having trouble with that. I jumped the Fp and B+ just to see about the fuel pump and had a friend stick his ear in the open gas cap and had another friend by the fuel rail. Nothing. Checked grounds and I think I got most of them if not all of them. Checked connections, seem fine. What's the best way to go about finding this gremlin??? There's obviously something wrong early in the system and its not the fuse. I am trying to explain this the best I can with the limited electrical knowledge I have (one place I've not had a bunch of time with due to the simplicity with other cars). If you need clarity on anything please ask.
 
Oct 11, 2005
3,816
16
38
Thousand Oaks, CA
Sounds like you have no power to the B+ circuit of the ECU.

Quick check, with ign on, measure the voltage to ground at the B+ terminal. Should be 12V. If it isn't then the whole ECU system will be dead.