puntank4200

iTrader: (1)

My car is running horrible. It idles really rough, when I pull up to a stop sign it starts chugging and will stall if I don't drop it into neutral and rev the engine. I had a error code for O2 sensor so I replaced it. Got a code one time for low TPS voltage, I checked it like the tech article said and it looks fine. I have all the documentation for past work done and there is no mention of ever replacing the timing chain. Will a tune-up help my situation? I've had the car for 6 years and have never replaced the coil, cap or rotor. It has a clean k&n on it the oil changed every 3000. What's the deal, my timing is set to 13 will this cause any problems? Help me, its embarrassing to have my car die 3 times when I'm trying to parallel park.

2_point8_boy

It's very possible that a tune up might help, but it might also be something else. The 2 things that you have to be 100% sure on is that you're getting a good spark and the correct fuel pressure. either one of those missing and you'll have issues.

After you're sure about that, you have to start looking at the computerized controls on the engine. IAC, TPS, MAF, etc. If it idles really low and erratically, ten you might have a problem with a cloged/stuck IAC motor that might need just a simple cleaning or a clening of the bore and replacment of the motor itself.

Start with the tune-up stuff, that's always a good place to start just vbecause people neglect it, no on purpose, but it's not something you think of until you have an issue. If that doesn't help then the worst case about it is that you replaced things that were probably in need of replacment anyway.

puntank4200

iTrader: (1)

How do I check the fuel pressure? How do I go about checking the computerized controls on the engine IAC, MAF, etc? What does IAC stand for? I have already checked the TPS, should I start looking at vacuum lines?

Dale

iTrader: (12)

You've had it 6 years and not replaced the cap/rotor How much do you drive it? About 1000 miles a year?

I seem to replace my cap/rotor about every other oil change. Coil only needs changed if its bad. But being 15+ years old, it'd be your best intrest to replace it.

bobdole369

You really sound like your missing on one or more.

Timing chain could be it, maybe maybe not.

To check the timing chain:
Set your engine to #1 TDC on the compression stroke, then remove the distributor cap. If the rotor isn't pointing exactly to #1, then your timing chain is off by a tooth or two.

If the timing chain breaks the car won't start at all.
Typically if the timing chain has stretched badly - it continues to skip teeth leading to stretches of where it runs perfectly then for no reason it runs badly, then it won't start at all, then it starts up, then it runs OK, then perfect, etc. Not sure if thats it, but if you feel comfortable pulling the water pump, power steering pump (bracket), crank pulley, harmonic balancer, timing chain cover, maybe the oil pan, then you can get at the timing chain. Most over 70k miles need to be changed...

IAC = Idle Air Control. On most of our motors there is a small stepper type motor on the passenger side of the intake. If you remove the rubber intake boot you can see the Idle Air Control passages on the left and right side of the butterfly-type throttle valve. they are a squarish shape and function to control the idle. The IAC motor controls a pintle which allows more or less air to flow through the IAC passages. The IAC passages allow air to flow around the edge of the butterfly-throttle valve. This is because the throttle is normally 100% closed at idle. The IAC systems purpose is to allow idle.
Sometimes you get built up gunk all through the IAC system and this can gum up the works, thus not allowing the engines computer to control idle. the computer will tell the IAC to adjust to a particular position, it will try, and not be able to do so (because of the gunk), the computer thinks something is wrong and tries to compensate, at this point your idling funny stalling, misfiring, etc. Now the IAC may break free and overadjust from time to time causing whats called a "rolling idle". It goes up and down rhythmically.

Any idle problem should look to the IAC first for cleanliness.

MAF is "Mass Air Flow". This is a device that sits inline with the intake. On my 2.8L firebird its a 6 inch tube about 3" in diameter. It has a screen a circuit board and an electrical connector (connector on the outside). It's purpose is to tell the computer how much air is moving through the intake. Any air leak "beyond" the MAF will result in TERRIBLE idle and acceleration, since the computer is expecting a different amount of air than what is entering the motor.

CTS = Coolant Temperature Sensor. You probably have 2, one for the gauge in the car, and one for the ECM/fans. This tells the computer what temperature the coolant is at. When this is off, it throws the ECM off as it uses coolant temp to figure fuel metering, IAC operation, etc. CTS is a BIG factor in idle and you should check your sensor... Or better yet, just replace it, its rather cheap.

EGR - while not a sensor is important to idle. Engine vacuum controls a diaphraghm on the passenger side of the throttle body that opens in high vacuum condition (idle). This lets a portion of exhaust gasses back into the intake. This helps with emissions.

TPS - This is a simple variable resistor again on the passenger side of the throttle body that tells the ECM what position the throttle is in. Very important to idle. I'm not sure if the guide had you run the TPS through its range to verify that the voltage changes smoothly and there are no "rough spots". It's very easy to have a broken connector here cause all kinds of headaches. If you broke it during the test you should replace the connector.

IACT - Intake Air Charge Temperature sensor. This is a small sensor very near the air filter that senses the temperature of the air entering the motor. Very important for idle.

Are you running in Closed loop when the idle problem happens? You can tell by shorting the same two diagnostic terminals on the ALDL when the engine is already running. DO NOT START THE CAR with the ALDL diagnostic terminals shorted. Only connect the wire after the motor has started. A fast blink is open loop (i.e. the O2 sensor and CTS haven't heated up enough, the car is still cold) low blink is closed loop (i.e. O2 sensor and CTS agree that the engine has warmed up enough to listen to the sensors).

I'm pretty sure I laid out all the EFI sensors on our motors. Did I miss any?
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Vacuum lines never hurt to check. Look for cracks or missing plugs.... use carb cleaner to find the leaks.

13 degree timing - *shouldn't* be too far advanced to idle well. You ARE using 92+ octane with that timing right? Using 87 with 3 degree advanced base timing will eat holes in your pistons from the detonation.

However the fact that you got an O2 sensor code (which was it btw, O2 sensor reads lean or O2 sensor reads rich?) Just having an O2 sensor code doesn't mean there is something wrong with the sensor, it certainly didn't merit replacing it. It's trying to TELL you something that it read too lean or too rich!!!!!! Fix the problem that caused the lean or rich condition!!! Thats like replacing the coolant sensor because your car overheated.

I'm willing to bet it was a rich condition...

Short answer - YES a tuneup will not hurt anything, and is well worth the trouble. You might fix it, you might not...

drdave88

iTrader: (3)

im running mine at 13 degrees advance and have no spark knock at all on 87 octane. definetly doing a TomP tune up is a good thing. thats the first place to start. that way everything will have full advantage to run right. you may have a domino effect all stemming from lack of tune up. if you havent replaced any of that stuff, id start there. then see how it goes. and a timing chain may not be out of the question, especially with high mileage, but id start w/ a tune up and checking to see where timing is at. i believe somewhere in toms tune up it mentions some sort of an intake cleaning, that will burn the carbon out of the intake and heads and pistons.

Xophertony

one more vote for tuneup. trying to fix a problem like this on a poorly tuned car is like trying tore-align a door frame in a house with a sinking foundation... first fix the foundation, then try and get the door to hang right... more then likley it allready does.

TomP

agree with Xopher... imagine going crazy on everything when the last thing you check is the ignition timing ($20 timing light from Sears).

Sort-of similar problem happened to me; when the first fuel pump died, I had the gauge on there- it was only around 20 psi so I changed the pump out. When I was all finished, I started the car- and it ran like crap.

I almost started to drop the tank again- but then I checked over the normal tuneup stuff. Found the #1 plug was missing the center electrode and that my timing was WAY advanced. Once those two were "fixed" I was all set again and the car ran great.

Apparently the dist hold down bolt had gotten loose and overadvanced the timing so far that the #1 plug blew to pieces because of detonation. And to this day, that #1 cylinder has the lowest compression out of all the cylinders.

SO long story short, check all the tuneup stuff (if in doubt, replace!) including the timing. But 6 years on old parts... I'd vote to replace it all. You "can" check plug wires with a multimeter; if they're stock wires, they should be 15,000 ohms/foot. And you "could" scrape corrosion off of the cap/rotor terminals. And you "could" clean and regap spark plugs. You "can" try cleaning the PCV valve with carb cleaner. But geez... 6 years...

Other thoughts; MAF may be bad, with the car off, try unplugging it and starting the car- the engine will stall at first, then will start up- if it runs great, your MAF is bad. Feel underneath your EGR valve (see bobdole's message), it's the black valve on top of the passenger side exhaust- there's a hole underneath, and the EGR diaphragm should be about 1/4 inch above the hole inside. If the EGR valve has rusted/clogged, the diapragm might be sticking open and it'll stall the car. (Had that happen to me, new EGR valve from the dealer fixed it.)

But check the ignition timing... lights are $20 or so from Sears, may be cheaper elsewhere... not sure if Walmart sells things like that, but partsamerica.com stores should.

puntank4200

iTrader: (1)

So if i unplug the MAF and the car starts and runs, then its a bad thing? I've had the car for 6 year and been away at school so i've only driven for about two years now off and on, so its about time i treat it right. I've swapped out the plugs and got new wires six months ago. I have a timing light, and its been locked in at 13 degrees.

Is getting an ICM worth it?

bobdole369

Yes and no on the MAF... it's tricky... Y'see if the ECM doesn't have a signal from the MAF it simply uses "default" values and relies more heavily on the other sensors. So if you unplug it and the car works fine, then you've found at least part of your trouble. There may or may not be some relays involved. I've got a 2.8 bird which has a MAF power relay, and a MAF burn-off relay up near the brake booster. Not sure on the camaro.

However, just because it still doesn't work right when you unplug it, doesn't mean it's good either. Nor is the unplug MAF test 100%. WIth the MAF unplugged the car is forced into "open loop", which means it isn't listening to everything. The ECM operates differently in this situation. Good news is that open/closed loop doesn't come into play until the car is warm.

puntank4200

iTrader: (1)

Does anyone the part number for a MSD ICM that will work with these cars? Having trouble find it.

I see a package on summit, Crane HI-6S CD Ignition and Coil Kit. Is this kit any good?

TomP

I'm still not sure why you guys call it an Ignition Control Module. It's just "igniton module", there's no "control" in the name.

Unless everyone confused it with ECM and came up with ICM??

Anyway- just look for an igntion module used for a "remote coil v8 HEI ignition"; if they go by pin count, you need a 8 pin module. (2 internal to pickup coil, 2 external to spark coil, 4 external to computer)

Don't put an ignition box/coil kit on your car until you spend the $$ to fix whatever's wrong first. But as far as MSD/Crane/Mallory/etc, it's just what brand you like- and honestly, an aftermarket spark box won't do much more than an aftermarket coil by itself.

Back to the MAF, If a relay was bad on your MAF circuitry, you should be getting a code 34. The MAF can be bad and /not/ throw a code 34- and that's what unplugging the MAF checks for. But if you wanted to run thru the code 34 chart to check all the wires anyway (which isn't a bad idea, and it's free to do), then look at my old post here: https://www.thirdgen.org/forums/v6/1...af-sensor.html That's a retype from the GM Service Manual at http://www.helminc.com - and that GM service manual has many more diag charts and diagrams, well worth the cost.

Xophertony

i did somthing similar to what tom was talking about above (about the fuel pump). i thought i needed new engine mounts one time on my GTA because it was shaking real bad, but the engine seemed to run fine. turns out i had a dead spark plug... (dead cylinders are not as apperent on a car with 8 of them). had i been keeping up with my tuneups it would not have been an issue..

another good one:
so my car was dying at idle and the idle was going up and down slowley when it would idle on my 2.8. the car would also lurch like it was out of gas at mid throttle. i figured i had a bad injector... but being the smart guy i am i decided to check a few sensors first... turns out my TPS had a flat spot (about 1/2 way through) and my IAC was dirty... alot cheaper then new injectors.

anyway, yeah. tuneups rule. it's like spring cleaning for your car. everytime the weather gets nice (like today in portland) i start slowley tuneing up my ride. do a search for TOMPs complete tuneup. it's the Bible of tuneups.