'93 Sunbird, cold start=hi rpm's

[tomrhere]

'93 Pontiac Sunbird, 3.1MPFI, auto, Wife's car, just started doing this since the weather decided to go way cold here. On 1st start, whether overnight or when she leaves work, it'll start up just fine, But, it wants to do it's idle around 2500 to 3000 rpms. If you stand on the brake pedal and drop it into gear, it'll drop down to normal rpms. After it warms up, it's back to it's normal everyday self when you re-start engine. It's just the 1st time it's "cold" started that it does this, and no whacko idle speeds any other time.

Thinking it's the Coolant Temp Sensor, but not sure. Not real up on fuel injection systems and how things "talk" to each other. Need some input here.

[crank.it]

hey tom....think your on the right track with the temp sensor...i would check the iac valve first and clean the carbon of if its possible on that model....crank.it

[tomrhere]

Thanks, I'll try that.

[tomrhere]

It be fixed....

After a, "kick my butt" cold, and a bout with food poisoning, this month,,,,, I managed to fix it today..

Seems the idle air controller was the culprit. I did swap the CTS, but no help there. Pulled IAC, and boy,,,, was it ucky. Bought a new one and slapped it on. Nice smooth idle, at proper speeds mind you.

I did washout the bore on the throttle body with some FI system cleaner before installing new unit. She didn't wan't to fire off at 1st, but she caught and did the "normal" warm-up/drop down to easy idle speed thing. So it looks good to go now........

[tomrhere]

Acting up again.

Was good from last Sunday until Thursday, now it's doing it again. When I replaced the CTS, I took a good look at the connector, didn't see any corrosion, same with IAC connector. So I don't think that corrosion is culprit, but I could be wrong...

What's next???

[jgate]

Pull the IAC, check to see if it might of picked up some carbon , Spray it out with brake clean.

[tomrhere]

Pulled the IAC again, it be clean, same with the bore in the TB housing.

Checked for the throttle resting against it's stop, yep... Cable(s) have some slack in them so I can rule out that....

Got to thinking of a carbed engine; choke set, fast idle cam set, but a vac line is leaking somewhere. I know that'll do some way wacko idle speeds.

Anyways, got the can of carb cleaner out and started spraying around vac hoses and what not. Found one hose that "may" have been iffy. Replaced that hose, re-started engine, still goes bezerk on idle speed. Grrrr..... Killed engine......................

Replaced every single soft rubber vac line I could find.... Still no joy here......

Thought of maybe vac booster for brakes be leaking a bit, plugged port off of intake, no help.

I only get one day a week to actually work on any of my vehicles, and I really don't want to tear into this then have to wait a week to put it back together. Wife is having a coniption as it is............

I'm ready to break out the Howitzer....................................

[jgate]

The PCM controls engine idle speed by adjusting the position of the IAC motor pintle. The IAC is a
bi-directional motor driven by two coils. The PCM applies current to the IAC coils in steps
(counts) to extend the IAC pintle into a passage in the throttle body to decrease air flow. The PCM reverses
the current to retract the pintle, increasing air flow.
This allows control of idle speed and quick response to changes in engine load. If the
PCM detects a condition where too high of an idle speed is present and the PCM is unable to adjust idle
speed by decreasing the IAC counts, DTAC P0507 will set indicating a problem with the idle control system.

Do you have any active or history DTAC.That would relate to:
nonactive EVAP, EGR, TP sensor, ECT sensor,MAP sensor, IAT sensor,Fuel Trim, injector circuit, CKP sensor,
MAF sensor DTAC active. System voltage is not between 9-14 volts. Intake Air Temperature below 0°F.
BARO not above 65 kPa.

Check for:
Poor connection at PCM or IAC motor. Inspect harness connectors for backed out terminals, improper mating, improperly formed or damaged terminals, and poor terminal to wire connection. Damaged harness. Inspect the wiring harness for damage. Vacuum leak. Check for a condition that causes a vacuum leak, such as disconnected or damaged hoses,
leaks at EGR valve and EGR pipe to intake manifold, leaks at throttle body, faulty or incorrectly installed POSITIVE CRANKCASE VENTILATION valve, leaks at intake manifold, Throttle body. Check for a sticking throttle plate, when cold.

[tomrhere]

Hmmm...

No "Check Engine Light" other than when key is "on" engine not running. This is an OBD I system, my Haynes manual for it says I have to jumper 2 pins in the ADL connector to read codes. Trouble there is, the 2nd pin isn't there, period. This vehicle is the 3rd one I've owned that,, that wire is not in the ADL connector. ???!!???

The code given in the previous post, sounds like an OBD II code. On this car, you count the flashes of the CEL for code number(s).

I haven't actually driven the car in about 2 months, so I have to go by what she tells me it does. No missing, sputtering issues. Floor it, and it will take off from a dead stop with no hesitation and set you back in the seat doing so.

Fresh plugs, wires, air filter, PCV valve, fuel filter, oil/filter change as of Thanksgiving weekend. Been running good with no issues until this last month or so. Just since outside air temps have been in the low teens, single didgits.

I do know that when it does the "high idle",, you can drop it into drive, move it about 20-30 feet, and it will then do a "normal" idle speed, even if it's still "over-night" cold. What moving it has to do with idle speed is beyond me.

Have seen the tach bounce around during idle, say anything from 1000 to 2500 RPMs, even though you don't hear the engine change idle speed at all. This is when it's warmed up mind you. When it's cold and doing the whacko idle speed, you definetly hear the engine screaming at the indicated RPMs on the tach.

[driver540]

Just for kicks. Try sprayin some carb cleaner around base of upper and lower intakes to see if any change in engine.

[tomrhere]

driver540 Wrote:Just for kicks. Try sprayin some carb cleaner around base of upper and lower intakes to see if any change in engine.

I've done that. Did get engine to increase speed when I sprayed the rear area of it. Found a rubber vac hose that was a bit flaky, (left black stuff on my fingers). Swapped out that and all other rubber lines I could find.

I don't have to work this Saturday, so I have one more day to work on this.

If,,, it is an intake gasket leak. What are we talking about time wise to pull everything and replace gaskets, re-assemble? I have not been that far into one of these engines.

[tomrhere]

The previous post from me was before I left for work yesterday, Wife leaves after I do.

Anyways,,,, seems that when she started it yesterday morning, it did the "normal" fast idle warm-up drop down to idle speed. Same when she left work heading for home.

She just went out to warm it up, and again, "normal" warm-up function.

???!!!???!!!!????!!!!!!

I know things don't "fix themselves", so what the hey is going on here???

[tomrhere]

Here's the latest update;

After the Wife got back from hitting the meat sale at the local market this morning, I took the car for the weekly beer/smokes run. I noticed it wanting to hesitate some with throttle input, regardless of speed driving down the road. I'm guessing that calling it a flat spot would be the best way of describing it. No backfire or missing, just a delay in engine response to pedal input. Seeing as I had the "card" on me, I stopped and got a new TPS. $30.00 or so..

Installed TPS, fun job there. NOT..
Started engine and noted a difference in idle quality right off the bat, smoother than ever. I've always thought it idled good, but I guess I didn't know how good it could idle. I pulled car out of garage, turned it around in the drive and shut it off. Del comes out and asks if she can drive it, told her to go for it.

She comes back about an hour later and says car has "never" ran better. Apparently, she hasn't given me the full story on how it's been acting all the time. But she reports no weird idling at stop lights and no wanting to stall either like it has been doing. (I didn't know all of that, nor did I notice any weird idle issues at the few stop signs I hit).

Hopefully, this was $30.00 well spent....


Now, time to fix the exhaust system.
Seems she wacked a piece of frozen fenderwell slush laying in the road, broke the exhaust pipe where it meets the converter. YEA!! Get to lay under a car with salty water dripping on me... Will the "FUN" ever end?????

Time for a beer or 8

[tomrhere]

Been 2 weeks now, and she seems to be running properly. Wife reports no issues with it.

[re-tired]

THanks for the feedback. Glad we gotter fixed for you. :roll: Good work , its often system of elemination and it helps by main driver telling zackly whats it doin. Again good work. [smilie=pdt_alc.gif]