Ok so I just bought this 86 iroc for 2200 bucks, and it needs some work. I hope I don't have to play musical sensors for this current problem:
Engine fires up great first of all, hot or cold. When it's cold it fires up and stays running well, rpm's are high until it warms up, and runs very smooth in general. No leaks, no oil burning (just a freakin exhaust header leak). I shut the motor down. Before the engine cools down I start it back up and it fires up, yet it just shuts right off after. I have to keep my foot on the gas very very slightly to keep it running the whole rest of the way home. Wierd!!! It probably needs a tune-up very badly, but with it running so decent at first, and then not running as well after I shut it off and restart it makes me think it's sensor related. Any ideas fellas? Thanks for any help!! I'm going to change the cap/rotor/wires/plugs/air filter/oil this weekend and see if it keeps playing games. Again I appreciate any help!!!! I hope to become an active participant in this forum before and after becoming knowledgable on this car; will that ever happen I don't know! haha

 

As part of the tune-up I strongly recommend you replace the CTS sensor, or coolant temperture sensor. Not the one for the gauge, but the one right under the thermostat housing. They tend to lose accuracy over time. It relates to your problem because is may be sending false info to your computer, and not opening up the IAC(under TPS) enough to idle after hot start. Everytime you stop and start your car, the computer repositions the IAC(idle air controller)(same as air screw on a carb) depending on the signal it gets from the coolant sensor, load on motor(ac on or off) etc... You would not believe what a diif replacing the coolant sensor can make(about $20). After you try that, start looking at the IAC valve it'self, it could be sticking, or not working in some way like it should. Even with all the help the computer can give you, there is still skill involved. Alot of the sensors can be out of spec, but still work, and work good enough that the problem I described above still won't set a trouble code. If you are serious about keeping this car you NEED to got to HelmInc.com and order the factory shop manual for your year and model. They are about $100, but are the best you can get, forget about chilton's, or haynes!! These books are so good, they will turn you into a Camaro rocket scientist. I know it sounds funning, but they are that good.

 

I'm on it. Yes I'm serious about keeping this car. My first car was a 1980 carmaro I drove for 4 excellent years. I blew the head gasket and sold the totally immaculate car for $450 three years ago. Ever since then I have been through **** cars (integra, rsx type s) and toyota trucks. I'm totally psyched to be involved back with my roots with the camaro. No it isn't an 80, thanks to those being sold now for like 1500 bucks as complete POS condition (if I only kept the car...) yet I drove it the other day and it freakin took off like that $23K rsx couldn't dream of...and it's out of tune! I love this car. Thanks for the book info, I'm on it like flies on @#$t.

 

ok so now the food item called **** is blocked. thats amazing.

 

After a good tune up, try checking the min air adjustment. If someones been messing with it, as soon as the iac closes, the engine will stall.

 

I tell ya what. It really sounds along those lines. Engine cold, starts and stays running stop and go for miles and miles. Shut it off, restart? Vroom! Dead.

 

I think that book will definitely be my best bet considering my MAIN goal is to get this iroc-z back to it's ORIGINAL condition, no more, no less. Factory stock baby.

 

I agree about min air screw, it fact forgot about it. Anyway, trust me on the book, you won't regret it.

 

This car is great! I just called advance auto to get prices on the CTS and IAC:
IAC in stock $28
CTS in stock $10
!! I thought I was going to get railed! Gotta love how prices drop on old american car parts

 

Sorry if I missed this, but how many miles are on the car? I wouldn't go replacing the IAC just yet, they tend to last pretty long. You should remove your throttle body and clean it. Take the IAC off and clean the passage out and reset it and the throttle position sensor. You can learn how in the tech article here: https://www.thirdgen.org/newdesign/tech/tpimod2.shtml

The CTS is a good thing to replace. Don't forget the oxygen sensor. If the car has over 100k miles both of these are probably dying. The oxygen sensor is very important in closed loop and it could cause the car to stall and run poorly when warm.

 

Win2,

Got your cut-and-paste setup or printer ready? Good...

Treat any newly acquired vehicle like you've resurrected it from the junk yard. You must assume that NO maintenance has been done. Start with all fluids and filters. Engine and transmission oils and filters ($40), differential oil and additive ($15), coolant ($15), fuel and air filters ($10), PCV valve (AC only!) EVAP filter (your '86 still uses one), vacuum hoses, compression or cylinder leakage test, etc.

Continue through the ignition system (NOT just spark plugs), and then the control system and adjustments, like IAC, TPS, timing, oxygen sensor, etc.

Once it's running right, continue with brakes, wheel bearings, steering and suspension, belts and hoses, exhaust, and body lubrication/adjustments.

Once you've performed all the required routine maintenance, you can assume that everything should be normal, then attack those things that are not. One of these steps should get you closer to solving the problem, and would cost you a total of less than $200 if you do the work yourself.

Unless you know the person from whom the car was purchased, and can trust that person implicitly, don't assume that any maintenance has been done. It's far too easy to falsify receipts and service records, or to forget when service was done and recall incorrect dates/mileages, etc.

Start from the top. All fluids, filters, routine service, ignition components, adjustments, etc. Everything from the differential oil to the front wheel bearing repack should be done. Once the car has been returned to a "normal" serviceable condition, any remaining problems are a lot easier to solve.

As a general hint, most idle problems on TPIs are due to IAC problems. While you're there doing all the adjustments and service, clean the IAC and air passages in the TB. Set the minimum air position and TPS voltage, and the problem should at least be better.

And before replacing any sensors, test them first. One of the most important and versatile tools you'll have is a digital multimeter. You can get a cheap one for less than $25 that will at least get you started. You'll need it for a variety of tests, adjustments, and general troubleshooting on almost any car, including your new acquisition.

If you suspect a temperature sensor is failing, test it first. The correct range of resistance of a temperature sensor at a presumed temperature is easy to check:




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Your on board computer can also be used to identify problems, even if the CHECK ENGINE lamp is not on.

First, you'll need to make a jumper wire from a piece of stripped copper wire, a special jumper device or test plug, or a simple paper clip bent into a 'U' shape.

With the engine and ignition turned off, locate the ALDL connector under the dash, just to the right of the steering wheel in the driver's foot well area on Firebirds, and to the left on Cmaoros. There should be a small rectangular cover over the access hole in the lower dash trim.



Insert a tool as described above (paper clip) into the 'A' and 'B' terminals on the ALDL connector:



WITHOUT STARTING the engine, turn the ignition to the "RUN" position. Watch the Malfunction Indicator Lamp (MIL) and it will begin to flash. This is also commonly called the "Service Engine Soon" or "SES" lamp. The first code will flash three times, and will usually be a code '12'. This is encoded by one flash of the lamp, a brief pause, then two successive flashes of the lamp. Each code will repeat three times, so you should see a "Code 12" flash three times. Any other error codes will follow in numerical order, and each code should flash three times. After all codes have been displayed three times, the "Code 12" will again flash three times, then all other codes will follow as described earlier. This cycle will continue until the jumper is removed or the ignition is turned off.

After you have made a note of all error codes, turn off the ignition and remove the jumper immediately. If you forget to remove the jumper and attempt to start the engine with it in place, you could damage the ECM. For this reason you should remove it immediately.

Once you have a note of all error codes, check this file for the decoding:

GM Error Codes.pdf.


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As for the adjustment of the TPS and minimum air position (commonly but erroneously called "IAC Adjustment"), you can follow this procedure AFTER cleaning the throttle body and air passages:

Throttle Minimum Air Position

Tools needed:
1. Torx driver # T-20
2. Paper Clip
3. Small Punch
4. Tachometer

GENERAL NOTE: The engine should be at normal operating temperature before performing any adjustments. Never rely on the dash mounted instruments for diagnostics and adjustments. The oil pressure and temperature gauges and the voltmeter and tachometer just aren't calibrated accurately enough for diagnosis, but are a relative indication for monitoring the vehicle while driving.

For this adjustment, the transmission will be in DRIVE while you're under the hood. You will need to securely set the parking brake and block the drive wheels. It would also be a good idea to have an assistant hold the service brake while you perform the adjustments.

In order to successfully complete the adjustment, the IAC air passages and pintle need to be clean. The throttle plates and bores need to be clean as well. If this is not the case, you'll need to remove the intake air bellows to gain access to the area to be cleaned. A spray-type carburetor cleaner works well for this. Cleaning the IAC passages on a TPI/MAF engine will set a DTC, but we'll be clearing that later. With the engine idling, direct the spray cleaner in to the IAC air passages and around the throttle plates. Shut off the engine and continue cleaning the throttle plates by opening the throttle manually. Once everything is satisfactorily cleaned, replace the air bellows on TPI engines. Many times, this alone can solve IAC/idle speed problems.

If this doesn't solve the problem, you may need to remove and clean the IAC stepper motor. If the IAC appears to be clean and functioning properly, continue with the adjustment procedure.

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Idle Air Control Cleaning

You can remove the IAC and service it. Remove the electrical connector from the IAC. Unscrew the IAC unit from the throttle body.

You can gently rock the pintle back and forth and allow the spring to extend it until it comes apart in your hands. Clean everything with lint-free cloths and a mild solvent. Harsh solvents can affect the insulation of the stepper motor coils. It's generally the dirt and buildup on this worm shaft that causes sluggish IAC operation.

When the worm gear on the pintle shaft is clean and dry, apply one drop of clean light oil to the shaft and work the pintle back into the rack gears of the motor by the same rocking motion. It takes a while to get the pintle back into the worm gears, but you'll get it. It is important to get the pintle fully retracted into the housing so that the pintle is not forced against the gears when reinstalling the IAC unit in the throttle body.

While the IAC is out, clean the air passages in the throttle body. The orifice in the TB where the IAC resides is the seat that the IAC valve closes against, and it can accumulate a lot of carbon, dirt, and debris. The easy way to do this is with carburetor cleaner and a small stiff brush.

When everything is clean and dry, replace the gasket if it is damaged, apply a little anti-seize to the threads, and torque the IAC to the proper specs. (13 ft/lb for '85-'89 , 30 in/lb for 1990-on.) Proceed with setting the TPS and minimum air position.

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Go back to the ALDL connector under your dash panel, and jumper the 'A' and 'B' sockets once again with the ignition OFF.

Turn on the ignition, but don't start the engine. This will again force the ECM into its diagnostic mode. Wait 30 seconds to allow the IAC pintle to fully extend. Under the hood, remove the electrical connector from the IAC, then turn off the ignition and remove the paper clip jumper from the ALDL. With the IAC pintle fully extended (closed) all idle air will be controlled by the position of the throttle plates. Some manuals indicate that the EST bypass connector should be disconnected for this procedure, while some make no mention of it. While timing is a factor in idle speed, the EST should only operate as a function of engine RPM, temperature, and detonation sensor inputs. To remove all doubt, disconnect the EST bypass connector is your car is so equipped. Some TBI and V-6 engines do not have this bypass connector, and therefore must be set with no regard to the EST system. The EST can be bypassed on some cars by grounding the diagnostic terminal at the ALDL and continuing with the procedure, but the fuel mixture will be skewed to the rich side, affecting idle speed as well. In any event, the minimum air position idle speed range is wide enough to allow for some variations. As always, it is best to consult your service manual for the exact procedure for your system.

Locate the Torx screw on the left side of the throttle body. It may be equipped with a protective metal cap from the factory. This was intended to discourage adjustment. If the cap is present, use a small punch to knock it out. Once the screw is accessible, start the engine and place the transmission in DRIVE. Adjust the throttle stop to obtain 400 RPM with the transmission in "DRIVE" on an automatic transmission car, 450 in neutral on a manual transmission car, rotating the Torx screw clockwise to raise speed and counter-clockwise to lower speed. Once the idle RPM is set, place the transmission in PARK and turn off the engine.

Re-connect the electrical connector onto the IAC. Start engine. Idle speed should be governed by the ECM at approximately 600-650 rpm in "DRIVE" (for unmodified cars). Idle speed in NEUTRAL or PARK is less significant, and will be higher.



Throttle Position Sensor (TPS) Adjustment

Tools needed:
1. Digital Volt-Ohm-Meter (VOM)
2. Breakout jumper wires or probes (make your own)
3. AutoXray, Diacom, or similar scanner will replace the VOM and jumper wires.

Turn on ignition, but don't start the engine.

With a diagnostic scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.07 VDC.

Connect the VOM to the TPS electrical connector terminals ‘A' and ‘B'.

With a breakout jumper: Disconnect the electrical connector from the TPS. Install the breakout in-line, between the TPS and wiring harness connector. Connect the meter probes to terminals 'A' and 'B' on the connector. (‘B' is the positive connection, ‘A' the signal ground, or negative.)

With probes: If you have very slender probes on your VOM, you can back-probe the TPS connector while it is attached to the TPS. If you have made probes of large dressmakers pins or a similar item, you can back-probe the connector as well. Connect the meter probes to terminals 'A' and 'B' on the connector.

Turn on the ignition to read the TPS output voltage at the idle position. The reading should be 0.54VDC +/- 0.07VDC. The ideal is the center of the range, 0.54VDC for a stock engine. To adjust the output voltage, loosen the two Torx screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, the TPS sensor may be failing and could be a cause of stumbling and driveability problems.

After achieving the desired setting, turn off the ignition switch. Remove all jumpers or the scanner and reconnect the TPS connector as required.

Reinitializing the ECM

If you set a DTC during the procedure, the SES light should be illuminated on the dash. This ECM retains DTC data for the previous 50 engine starts, so the codes will eventually be cleared. If you want more immediate results, after shutting down the engine disconnect the negative battery terminal for five minutes. This will clear the ECM of all diagnostic trouble codes. Clearing the ECM also clears any data learned about your engine, and clears the radio presets. If you have a Delco-Loc or Theft Loc II radio, make sure you follow the procedure to unlock the radio protection before disconnecting the battery. This five minutes is also just about long enough to clean both battery cables. Reconnect the battery. When you first start the engine after clearing the ECM, the engine will operate with base parameters programmed into the ECM PROM. These parameters may not be optimum for your engine, but the ECM will enter a Block Learn Mode soon after the engine is warm and enters Closed Loop Mode. The ECM will write new data tables specific to your engine and will eventually rely on those tables instead of the base tables of the factory program. You can expedite this process by driving the car for 20 minutes under varying conditions to allow the ECM to initialize. Or you can wait and drive the car normally at your convenience. The BLM tables are constantly being updated as sensor input ranges change, but the greatest change will occur within the first twenty minutes of Closed Loop operation.


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If you have any problems remaining after those steps, they are either going to require more in-depth analysis, or be more of a mechanical nature. I'm thinking that most of the issues should be solved by that point, or at least identified fairly clearly.

 

Wow! You win!

 

I can't argue with a guy from Milwaukee, even if it's spelled a little differently around here.

 

NOW thats a very helpful reply Vader thanks! i'll be gettin started tomorrow with the project...
Where would I be without the help? Getting cleaned out at a shop for probably less quality thatn doing it myself.

 

The throttle body was totally clogged with crap. The IAC was caked with tons of crap. Cleaned out the throttle body, changed the IAC (and CTS) and it runs awesome. Thanks for the help fellas!

 

So now everything's cool except this. I have the min. air screw turned all teh way out, not even touching the throttle lever anymore, and it still idles a bit too high. Adjust teh TPS now? How does it get air with the butterflies shut all the way after it is very well warmed up?