1988 GTU - Pineapple Large StreetPort - Stock otherwise - Two Issues

-: First :-

When the car is hot, well warm at operating temperature (it's not overheating)...when I go to park the idle will seem just a hair low. If I engage the parking brake and open the door, the idle drops. If I push the little door button back in, then idle rises back up.

-I've checked for vacuum leaks :: none
-13.95V at battery while running :: Alt good
-TPS @ 1kohm, smooth to 5kohm @ WOT :: fiddle up and down .2kohm, no effect on the issue, returned to normal setting.
-Timing @ 9º adv :: tried taking back to stock with no effect, returned it to 9ºadv (dial-back timing light, it feels peppy-er with the timing advanced)
-Gapped CAS ridiculously close :: no change
-Turned variable resistor to too lean or too rich :: no effect, returned it to its normal setting.
-Raised/lowered idle via screw on dynamic chamber :: no effect, returned the screw to its normal setting.
-Added 4ga ground cables from both the engine and battery to the body.

Any other ideas?


-: Second :-
Going to gas station with very little fuel in tank. Open cap and hisses for a few second (pushes air out, can feel it on fingers). Fill it with gas, go to leave and it doesn't start...for like an hour. I swear by Optima Red Top, that thing just keeps cranking away without fading, A+ battery in my book!

Anyway, it only happens when I get the long hiss when opening the cap, so I think this hiss is related to my no-start issue. If my tank isn't damn near empty, it doesn't hiss and starts just fine.

My first thought is to pull off all lines at the tank and start blowing through them. However, I dunno how the evap system works or if there's a single line or part I should focus on.

I've noticed that if I remove my fuel lines at the pump, then tap the starter so the pump squirts a tiny bit of fuel out, then reattach the lines, it fires up very shortly thereafter.

Where do I start with this one?


Other than these two issues, the car runs amazingly.

 

did you try changing the gas cap?

 

Yup.

I know the vent/purge system has some check valves and stuff, I don't know exactly what and where though. Is there a standard order for checking this system from most problematic part to least? I'll just go down that list and start eliminating things. I can't imagine it being too difficult or costly to troubleshoot a vent/purge system.

 

Doing more reading and searching, via Google. (Google search > vB search)

I found that in my case, the gas cap doesn't matter.

I'm getting a buildup of pressure in the tank, not vacuum. The gas cap seals against pressure, but lets in outside air under vacuum. Since I'm pressurized, and my cap passes smog, one can assume the cap is fine.

Also, smog clamps the line to the charcoal canister to pressurize the tank to check for leaks. Well, maybe my canister is plugged/clogged? I guess I gotta check that vent line. I'm gonna pull the line from the canister and blow through the canister to see if it's clogged or not. Then go to the tank area and blow through the tank vent with the canister still disconnected.

Any other input is still well-appreciated.

Also, anything on this idle issue when I open my door?

-Edit-
Ooh....I should have like 14v+ from the alternator, huh? *facepalm* I need to find my other alternator to test that out...

 

At idle with nothing electrical turned on, doors closed, just sitting at a fully warm idle...reading at battery is 13.96V.

Turned on radio, pulled parking brake, opened both doors, turned on high beams, heater to full (no a/c), rear defroster on ... 12.26V at battery. Engine off reads 12.68V.

So...new alt?

 

I unplugged the BAC, no change to idle. I had a spare BAC from an 87 NA so I swapped that in. Pulled the plug, still no change. Left that one on for now. Checked voltage on the plug, 9V; is that correct?

Put in other alt that was sitting on floor of garage. It's at a ~14.1V at idle with no load, then with everything on it's about 12.5V; engine off is same, ~12.68V.

I also went ahead and reset the CAS to stock. I had an injector issue that was running me stupid rich (don't ask), that's probably why it felt better with the advance. Since I fixed the injector issue, it seems to bog a little. We'll see in the morning if pulling the timing back to stock fixed that.

Overall, after changing the alternator and adjusting the CAS back down, I had to lower the idle a touch at the dynamic chamber and richened up the variable resister a hair as well. It idles very strong now, but tomorrows heat will tell if still drops and stutters when hot.

Then for the gas tank hissing, all hoses seemed to only flow one way, out. I could barely blow through the charcoal canister so I did what another member did some time ago, I drilled out that nipple with a 1/8" drill bit. Now it flows pretty freely. Not getting any hiss whatsoever from the tank, but we'll know more tomorrow after a hot drive.

 

A nine volt signal from the ECU is normal w/key to on or idling w/no load. Unless there is some load on the engine, pulling the plug off of the BAC won't amount to much change if any at all.

 

I may've misread one of the posts from my searches, I'm sure.

So it would be better to load the electrical system and then pull the plug?

What's a definitive test for the BAC besides replacing with a known good unit? In other words, how do you diagnose a known-good unit to be good, to replace a bad unit? lol

Thanks!

 

Yes, you would place load on the engine first and then pull the BAC plug. Placing a ground on one BAC terminal and battery voltage to the other terminal should cause the BAC to click. If it does not then it is either stuck or broken. Repeated touches to the proper terminals should result in repeated clicking. Removing the BAC and watching it move from inside would also give you some insight. The voltage from the ECU should drop w/load. At start the voltage should drop to about 2 volts or so. At idle 9 volts. Idling w/load less than 9 volts but more than 2 volts.

 

Ok, thanks Satch!

Morning's drive to work went nicely; engine responded well, idle'd great. Once I got to work, I pulled the gas cap, no hiss. Idle barely dropped (but didn't stutter like before) after turning on all loads I could.

I read your response after coming inside though, so I'll check that this afternoon.

 

So it's still doing the idle drop when I open the door when hot.

On a whim, I pulled out my idiot lights. While handling the unit, still connected with the car on, several lights were flashing and I was getting weird beep noises. After I got the unit disconnected, I could not replicate the bad idle, at all. Reconnected the unit, bad idle; disconnected, good idle.

So, anyone got some good idiot lights for an S4?

I checked both BACV's, they both click with battery voltage.

 

ive got a set of idiot lights in the garage,. never did what you are describing of an issue lol. the gas cap may be a problem with the fuel pump. next time it does that try this, turn key forward to run (not crank) for 5 seconds, turn key off, turn key forward again. do this 4-5 times and see if it will start when you do that. the other issue could be flooding. all the pressure thats in the tank will push into your fuel lines and if you have leaky injectors it will push that fuel into your engine.. causing it to flood (hence a no start). if the above method wont get the car started, open the hood and pull the 2 fuses closest to the engine (pink and green i think?). crank the car for 10 seconds with the gas pedal floored. put the fuses back in and see if it will start then

 

I knew the fuse trick, first thing I tried, no worky.

I didn't get any hiss at all from the tank today. I'm thinking that drilling the charcoal canister helped. We'll see more.

Before I offer to buy your idiot lights, I'm gonna toy with it over the next couple days to make sure. That is indeed it.

 

Without the idiot lights this morning, everything was fine. Got to work, popped the door, nothing...good.

As soon as I plugged in the idiot lights (left the door open), some beeping started, the door/brake/charge lights were on and my idle went to hell. I pushed on the plug (not the wires) and all lights went off, the clock came on and the beeping stopped. I pushed the plug another direction and the door light came on and the idle went to hell again, but no beeping.

Unplugged the unit, idle returned to normal. Fiddled with all the wires in the empty plug, nothing happened in the least.

Popped the gas tank lid, opened the cap, no hiss.

 

Same thing yesterday afternoon.

Drove home, car got plenty warmed up. No issues until I plugged in the idiot lights. Then upon unplugging, the issues disappeared.

Is it safe to say it's something in the idiot lights?

 

could be, theres also the possibility that its the "cpu" which is down in the drivers side kick panel by where your left foot sits. all that stuff i believe sort of goes together

 

So putting differing pressures in differing directions on the plug of the idiot lights, which causes numerous issues/lights/sounds, could be a symptom of the CPU?

Not trying to blow you off, or sound like I am, but seeing as I've never touched the CPU and the issues are only present at this particular plug, it only makes sense that it would be this particular plug or the object into which it is plugged in.

If I can get my hands on another S5 idiot light cluster, I'll check some more. Otherwise, the car runs perfect with that plug just dangling.

 

The CPU controls some functions of the warning light cluster, so they are linked. They both have the same cold solder joints that fail everywhere else in the car without human intervention. Could be a botched repair on either of them. You figured out the cluster is causing problems two days ago, try another one or stop worrying about it.

 

Seeing as when I have an issue, I find many many MANY threads without conclusions, I feel obligated to document everything I'm doing so that the next person doesn't have to fish through 25 threads to find all just fade into the forum with no conclusion as to what actually was the problem.

So... Can someone explain to me how the CPU can cause issues triggered by moving a plug on a component halfway across the car, without the other component itself being the issue?

Or maybe how to troubleshoot the CPU?

What does this CPU do?

I know the ECU is on the passenger side under the carpet, but I've not come across anything ever talking about a CPU on the driver side.

-and-

Still no gas tank hiss and no hot start issues after refueling. Not that anyone appears to care, but for someone searching the forum for a solution, opening the charcoal canister nipple with a 1/8" drill bit has so far worked for me.

^^ Fixed ^^