having a problem

[sleepyalero]

So car was running great all night till I merged on the highway.

Basically I get on highway. Car runs fine. Wheel hub lights kick on. No biggie. Get closer to home. And get to a stop sign. Car is idleing at 1000 rpm. So I shut car off and attempt to restart. It hesitstes and I have to give it gas to keep it running/get it started. So I throw on the flasher for the rest of the drive home and run stop signs so the car doesnt die. At this point I just want to be home. Get home pull in the garage. Shut car off thinking water got into my intake (yes it was in the rain...) so I take apart the intake and inspect it for water. All dry in there. I took maf off anyway and cleaned it with maf cleaner. tb looks great so didnt mess with it. Looked inside the UIM Through the TB. all looks fine. No standing water or traces of water in it.

So get the intake back together and fire car back up. Here is what my car is doing/specs.

- no SVS/SES lights
- idleing at 500-575 rpm and stuttering every 8 seconds or so.
- volts is at 11-12V
- oil pressure is in the low 30's.
- a/f is fine until the car stutters then shoots up to 17.x afr.


Whats the issue? I drove the car easy all the way home then it just started acting up. No sensors unplugged under the hood or anything. Vacuum checks out. (Have a vac gauge under the hood)

Maybe a shot in the dark.. but could it be the alternator showing signs of going bad? I mean I know low idle can also drop the volts. But its a thought.... please help.


I am going to hook up HPT soon to see if I can find anything that may be hidden causing my issue. So I will report back on that..

[sleepyalero]

Okay scratch my alternator plan. I thought my alt was going out awhile back and was wondering if it was struggling and finally on its last limb but I think it's okay.


After doing a log on HPT for about 10 mins running through all things like TPS voltage, %, injector stuff. Evap and everything you could possibly choose to put in the table. Started the car... died on me 4 times during the log then finally I got it to hold its self up while I could watch all the numbers. Everything looked fine.

But then I came accross IAC position. Its stuck at a solid 255. Doesnt go up/down when giving the car gas. So im assuming I have a bad IAC. Am I correct?

Im pretty postive on it. Cause I know in previous logs it moved. Lol

[mfuller]

Check your fuel pressure. Your fuel pump may be dying.

[MAC the KNIFE]

when my IAC went bad, the idle would creep up to 3000rpm. i thought that was the common symptom of them going bad. but it could fail to open at all. but if that were the case, then you should only have a problem at idle.
if your's is sticking fully shut, then use the throttle to give your car some air at idle.
if you held the throttle slightly open, would the car start and run ok? (it would idle faster obviously because you're giving it gas)
if it still runs like sht with the throttle cracked open, then you know it's not an airflow problem being caused by a stuck IAC


been doing any work under the hood lately? didn't bump anything loose like a plug wire?

[sudden_impulse]

Pull a plug or two to check their condition, if you're getting a stutter you might be misfiring just enough to feel it, but not set codes.

[AaronGTR]

If the engine stumbles and afr shoots up that sounds like a fuel problem. Either sticking injector or pump going bad. Check the fuel pressure if you can. The IAC should fluctuate too though, so that might be an issue. Could be causing the starting problem. Idle should be around 575-600rpm. Voltage sounds low though too. It should get up in the low 13's.

[sleepyalero]

Car runs fine through all rpm BUT idle.

I dont really have a way of checking the FP. But it still primes before you start car. And fuel stuff looked ok in HPT I believe

[99Alero_Boy]

in before the new fuel pump gets put on upside down........

[sleepyalero]

Really..

[99Alero_Boy]

[MAC the KNIFE]

Originally Posted by 99Alero_Boy

in before the new fuel pump gets put on upside down........

[[ChaosweaveR]]

Maybe he'll shoot for the upsidedown car mod.

[TDavis]

11-12v WHILE running? Should only be around that when the key in on and the car is not car running.

My volts, lets use decent warmish weather as an example sits around 14.5 when the engine is cold, warms up to 13.7-14 while warm and running.

Oil pressure for me when the oil is fully warmed up(200-225F) is around 20 at idle, 30 when coasting and 35-40 when constantly on the gas at a constant mph.


BTW MAYBE its a fuel filter?

[sleepyalero]

Fuel filter fairly new.

Its low voltage because the idle is so low. Rev up the car it goes to 13.5

My oil is always low 30s when warm.

[TDavis]

When fully warmed up mine idles at around 600rpm and the volts are still what I stated.

[sleepyalero]

My car is supposed to idle at 750-850. Not 450-575

[H.O. Driver]

Originally Posted by [ChaosweaveR]

Maybe he'll shoot for the upsidedown car mod.

Too late...



I am leaning to IAC or fuel pump. If reving the fuel pump may request more voltage and over come its suction issue but when my IAC died on my car it ran fine for everything other than idle.

[TriumphoverU]

what reading are you getting for your MAF at idle?

[AaronGTR]

Originally Posted by TDavis

When fully warmed up mine idles at around 600rpm and the volts are still what I stated.

^This. Like I said earlier, stock idle is actually set in the 550-600 range, and voltage should be higher than that at that speed. You shouldn't have to rev it up to get the voltage to climb. It's possible, though not terribly likely, that low voltage at idle could reduce fuel pressure or make the injectors not fire properly, or even mess with the IAC operation. I'd think it would have to get down into more like the 11v range for that to happen though. But still, it should be higher than that so it might be something to look into.

Originally Posted by sleepyalero

My car is supposed to idle at 750-850. Not 450-575

There a reason you need it to idle that high? And are you sure it's been properly programmed to idle at that speed?

[sleepyalero]

Yeah its tuned for 750 ish idle.

Im getting an iac tonight and I will see what happens when I swap it out.

As for the Maf reading. Gosh I know a jist but not exact numbers. ...

It was like 2200 or 2700 hz at idle and 1-2 lb/min or whatever the reading is in hpt

Kerp in mind it was going to around 450-580 rpm