symptoms:

- Bouncing idle when I have my headlights or lots of electrical load on (defroster, heater, wipers), but the idle will be rock solid with no electricals on. This only happens some times. About 50% of the time, the idle is fine even with a load on, and the other 50% of the time, it will bounce.
- Not sure if this is related, but my lights dim with electrical load, and I have no aftermarket electrical things installed, and I've got an FD alternator (I'm thinking grounding, I haven't gotten around to re-grounding yet)
- Not sure if this is related either, but my exhaust surges when I'm cruising, and I think I can feel it when I'm accelerating as well, but it is much more prominent when I'm cruising. I hear pops and my car stutters a bit when it surges -- this is only occasionally though, it doesn't happen too often.
- hesitation (not at 3800), when I mash the gas pedal, sometimes I do feel hesitation at various places on the tach under 4000RPM, usually around 3000RPM -- but this is pretty rare, it usually doesn't happen either.


What I've checked:
- set tps with the car warm using the LED method
- checked for VAC leaks with carb cleaner
- verified that the BAC is working and has the right resistance (However, I tried pulling the plug of the BAC while my car was on, like it says in the FSM, and the idle speed DID NOT drop, what exactly does that mean? Does that mean there is something wrong with the Wiring and the BAC isn't actually even on?)
- fuel filter replaced
- air filter not dirty
- primary fuel injectors replaced


Any ideas on what else to check?

 

I think your grounding suspicion is a big part of it.

If the revs remain constant when pulling the BAC plug, it just means the hard stop is high enough that the BAC was not adding more air to hold idle.

Maybe recheck the connector pins on the BAC plug for clean shinny bright contact.
Also check the plug wires. You may have high resistance in a leading plug wire.

 

Thanks, I'll take a look at the BAC plug and the plug wires, I didn't even think to look at that.

Regrounding should be next on my list, I've heard mixed opinions about what gauge wire to use though, would 12 gauge be enough, or should I go down to 8 or 4 gauge?

 

IF the idle is set with the rpms at over approx 750rpm, then there will be no change in rpms when the bac plug is pulled off.

Idle is set with the bac disabled i.e. the initial set coupler installed.

IF the idle was set below 750rpm previously, and you pull the bac plug off, then the rpms should drop. If the rpms don't drop a touch, then I'd suspect the BAC circuit. Everything from the transistor being kaput to one of the wires in the bac plug being pushed back in the plug not making contact.

It's real easy to see if the bac is working or not. Just remove it from its mount and turn the key to ON. The bac should be vibrating. Then go pull the small wire off the starter solenoid and HOLD the key to START. The BAC should go full open anytime the key is in START.

Normally if you just turn the key to ON, and listen at the bac, you'll hear/see it pulsing. If it pulses then the circuit is good.

It would also help if you set the TPS with a fully HOT engine .

 

When I checked, I was idling pretty low (~600RPM I believe), so I don't think it's cause the RPMS was set over 750 could be what cause.

When you say the transistor could be kaput, which transistor are you talking about? On the ecu?

Thanks

 

Just wanted to say I fixed the idle problem.

I cleaned the main ground, and what I think is the main ground for the ECU that goes near the Top manifold (although I've always been told it was underneath that manifold on top of the engine). But either way, I've had a steady idle with FULL electrical load for the past week.

I still have a surging problem though.

This ONLY happens when I have the heater on, and it gets more and more worse the more power I give to the heater.

When I'm decelerating, it backfires every couple of seconds. When I'm accelerating, it hesitates every couple of seconds at various RPM ranges (not just 3800, actually, it doesn't hesitate at 3800 at all).

What baffles me is why it would only do this when I have the heater on. I thought originally it had to do with the electrical load I put onto the car, but I've tried turning on my defroster, lights, wipers and fog lights and it won't do the same thing as if I have the heater on.

Any ideas?

 

can you double check and confirm that the surging only happens with the heater/blower and not anything else like the rear defrost, or brakes and headlights, or the steering being turned while parked (but engine running at idle).

 

when i was replacing my slave cylinder i had the car running for some reason and when i turned it off i heard this clicking comming from my UIM. i didn't know if it was and injector still firing, or my BAC acting, both of them need to be fixed, i have a shitty hot idle as well.

 

I'll confirm it later on today when I drive it. But I do remember testing that out and it seemed to only happen when my heater/blower was on.

I'm not sure how the steering being turned while parked would affect the surging.

I forgot to mention that the surging is only when I'm in gear. If i'm neutral, it's smooth

 

The BAC is activated during those load things I mentioned, trying to trace it down to a voltage issue or a BAC issue.

 

ahh, I see....well I checked, and yes, the surging and hesitation only seems to happen when I have the heater/blower motor on. I tried turning on the wipers, headlights, DRL, defroster, my aftermarket fog lights, and the car was very smooth, but as soon as I turn the heater/blower on, it'll surge.

Could it be that the power connection of the heater/blower motor isn't that good and it's taking more power to operate it thus putting a larger load on the electrical system?

If it helps at all, according to my dash, I'm charging at around 12-13V with full electrical load on. But the heater/blower doesn't drop the voltage that much, the biggest drop comes when I turn the defroster on (I know that's a pretty big electrical drain). So the voltage shown on the dash doesn't reflect my previous idea.

However, I know the dash voltage meter isn't the most reliable thing, I've checked at the battery with a multimeter, what it's charging at and it seems to be relatively accurate. I just find it wierd that with my FD alternator, I thought I'd be charging at a higher voltage.

 

Your car at idle with nothing on, should be at 14.4 volts. With a FD alternator you should be able to have every option on, and still be at 14.4 volts at 1500 RPM.

Anytime you are under 13.5 volts you are not charging the battery (you need .9 volts+ to charge).

If you are hitting 12.6 volts or under, then you are running on battery power.

Idle and ECU operation can be messed with on voltages less than 9 volts.

 

With nothing on, I'm at 14.4V, and if I'm at 1500rpm, I know it's higher than idle for sure. As soon as I step on the gas, the volt meter jumps up a little to a decent level. But at idle with a load on, it is pretty low.

Any ideas on what else to check for on this and the heater/blower motor situation? Thanks Icemark