In general, the car idles rough, unburnt fuel explodes in the catalytic converter (and smells out the tailpipe)
Puff of gray smoke on startup and under throttle. Smokes slightly when running.
Service engine light comes on while driving and clears when I shut the car off. Can't figure out what code it is.
Alternator whine.
Static 'pops' through the speakers. New since I replaced plug wires, dist cap and rotor. Most pronounced under throttle. Undetectable while sitting at idle. Seems to match engine speed.

the rough idle is intermittent. Sometimes it surges slightly (repeating every three seconds or so) at a stop light, sometimes it seems pretty smooth with just an occasional stumble.
The smoke isn't as white as some I've seen but it's more white than black. Honestly appears different sometimes, sometimes darker than other times.
The service engine light comes on under pretty specific conditions. If I keep my speed under 30 or so and drive it easy, it never comes on. If I get over 45 or so and let off the throttle, it comes in. Sometimes it feels like the engine missed when the light comes on.


Then here's what's been done. Lower half replaced by shop. Pistons, rings, block. Upper half untouched. Fuel pump and filter replaced by shop. Alternator replaced by me. Oxygen sensor replaced by me. Dist. cap and rotor replaced by me. Plugs and wires replaced by me. Throttle body cleaned by me. MAF sensors replaced by me. ECT replaced by me.


Dist seems to have some rotational play. Perhaps 1/8th inch as measured around circumference. Is that okay?
Don't know how to check timing. Don't know if timing is okay.

No idea of the condition of the valves, valve seals, springs, lifters, camshaft, rockers, or fuel injectors.

Get some noise under full throttle if I use less than 93 octane. Knock? Not sure what you call that.

Car typically runs at 185 degrees. I interpret this to mean the prior owner installed an aftermarket t-stat. is that the 160 or the 180?
Does this mean he probably changed my chip too? I also found a cut airlid so he must've been performance minded. For all I know, he could have even changed out the camshaft. My vette is my only vette and it's never run quite right so I don't know if it's 'warmed over' or 'mostly stock'. I CAN say that the heads, mani, runners, plenum and throttle body look stock. Ported? I wouldn't know.


I know this is a lot of info but I'm not sure where to go next with this. A point in the right direction would be greatly appreciated.

86 A4 w/ aluminum heads

TIA

 

retrieve the stored code

 

I can pull codes but this one doesn't store. It shows no codes when I use the paper clip

 

Where do you start? What comes to mind is white smoke might mean water in cylinders. Do a compression check with radiator cap off to see if your pressureing the cooling sys. The ideal check to to have all plugs out, pressureize with compressed air (cap off also) with piston at TDC. See if the air is coming out somewhere else. You will get some blow by in the crankcase. I know, lots of effort.

For your speakers, run a search in C4 tech with word -bose- and look for my post and schematics by 4ever. If you can do electronics, this will fix you up with lots of information. Good luck!

 

Just a few things I'd check, the IAC, that's idle air control valve, they get full of carbon and do affect idle. Next I'd probably check the fuel pressure.I'd also pull the vac. line from the FP pressure regulator, if it's wet, time to replace it. I'd also check the timing, you need to disconnect the ESC wire, and your timing should be set at 6 degrees BTDC. All these things are easy to do-BUT, you need to get the FSM-that's factory service manuals, year specific, I bought mine off ebay, you can check there or go to HELMs which you can also find on the internet. Their full of diagnostics and trouble shooting flow charts-an absolute must for us guys who try repairing our vettes.

 

I have never had that happen. Definately makes things tougher.

 

Sounds like a intermittent code due to bad wires, "Definately makes things tougher". First try the suggestions Rick made. White smoke could be coolent in the exhaust. I would smell the exhaust too, could be burnt oil, but usually has a blue tint. To check timing you will need a timing light. The 1/8 inch play in distrubitor could present a problem if bolt is not tight enough. Disconnect the EST before trying to adjust timing (a one wire connection between dist. and brake booster), if not the ECM will default the set timing. Vacuum leaks will not show a code, usually found by listening for a hissing sound or smoke test. Key on, TPS should be 0.54v at closed butterfly position and 4.00v at WOT position. Mine was 0.42v and no code avaliable but ran rough. Let us know the #'s of the tests.

 

The idle air control valve acts like a choke... it could be causing the rich idle smioke and surging you are seeing...

Typically I would think if it were a blown head gasket you would be over heating.... To eliminate that there are some dyes you can add to the coolant to see if that is the case....

The puff of gray smoke at startup could be valve guide seals... which could indicate a valve job is a potential need...

As also suggested... I would maybe start with the simple things... plugs new wires and cap to start and see if things get beter.. there will be a touch of play in the distributor....

I would definately pull the IAC and check for carbon build up... as well...

Mo

 

Absolutely, 100%, false.
The IAC admits varying amounts of air to establish the idle speed the ECM wants for the conditions, at the time. The ECM, than adds or reduces the fuel to maintain the correct A/F mixture for the conditions. The IAC has NO control over the mixture.

RACE ON!!!

 

 

Yes I agree the IAC varies the amount of air into the Thottle body... and the ECM controls the AFR in closed loop the O2's handle that as well how deep does a suggestion need to be?

IT was an analogy

Shessh....

Mo

 

He's just waiting for me to reply I thought it was a good analogy
perhaps if you would have said-may cause symptoms like a choke
a simple gramatical error CFI-EFI, then adds, rather than "than adds".

 

 

And a **** poor one at that. Actually, it wasn't a poor analogy, it was a false, untrue, analogy. A choke valve CLOSES, restricting air flow, causing a rich A/F mixture. The IAC opens, when cold to admit MORE air to increase the idle speed. The IAC has NO affect on the A/F mixture, where the choke is all about the A/F mixture. If you want to compare the IAC with something on a carb, try the fast idle cam. The IAC is much more versatile and has other functions, but among other things it DOES admit (not block) additional air for the fast, cold idle. It doesn't matter what you choose to call it, an analogy, or whatever, this statement is 100% false.


No way! Not in the least.



Then you, too don't know much about either IACs or chokes, or possibly both.

RACE ON!!!

 

doh! fight in my troubleshooting thread! :p

lot's of things to respond to....

First off, I made this because I don't trust my ability to troubleshoot so much right now. I was CERTAIN that cleaning my throttle plates would solve the idle problem. Failing that I was CERTAIN that changing plugs and wires and cap and rotor would solve my idle problem, (and unburnt fuel problem as well)
Seems I don't know diddly.

So I really truly appreciate all the help going around in this thread. Thanks guys. Really thanks.

Now on to specifics...
not white smoke. gray... I've had varying opinions from 'car guys' that have seen the exhaust smoke that I had either valve seals, piston rings, or rich or lean fuel mixture. I don't understand why one guy thinks I'm rich and another guy thinks I'm lean.
I don't think it's the piston rings since that work was done only 2 years ago and I have no particular reason to doubt the quality of their work. That goes for the head gaskets too. Not that I'm discounting the possiblity but it doesn't seem most likely to me. I've observed no oil in the coolant nor coolant in the oil. I AM losing coolant level but I'm pretty sure it's coming out my loose radiator cap.
Compression was checked by me at 215# +/- 5 on all cylinders, but I must account for the possiblity of errors. Plugs pulled on all cylinders, engine turned over, highest reading recorded.

 

IAC. Okay looks like maybe I have to pull the throttle body off and clean it for real this time?
Is this voltage test in the service manual? I do have one I just have a hard time reading it.

I also see vacuum checks and fuel system checks in addition to the timing check. I need to get a special tool for these eh?
One thing at a time for me though. I'm going to work on IAC first.

 

i remember a loooooong looooong time ago, 7th grade gym class and health teacher, mr. rocky (yup that was his name). he was a very tough bird, but a fair man, but again super tough. he was exacting in his teachings, he taught us how to listen. he was hard, but ultimately fair. he taught us how to think, and how to be clear. sometimes of forget how to do that, but i'll never forget him. as hard as he was, i loved the man for it. he got my respect, and i listened. this didn't come across well with the girls in the class (they tended to cry), but many of the boys learned to understand.

 

what happens if the IAC is so carboned up-or simply fails so that it can't open? I don't mind being taught, what I do mind is sarcasm in the teaching-which is simply uncalled for! reminds me of the days they used to slap your hands with a ruler if you missed a key in piano class.

 

Then you are at the same conditions YOU create on purpose for making your minimum air adjustment. To set your minimum air, first you turn the key to on. Second, you jump the "A" and "B" terminals on the ALDL connector. You do this because that causes the pintle of the IAC to extend all the way and block the IAC passage. AFTER the IAC has closed, you remove the electrical connector, so the IAC won't receive a signal that might, allow or cause, the IAC to move. NOW with the IAC passage blocked, thoroughly, and on purpose, the only air that can reach the engine, is what can pass between the throttle butterfly and the TB bore. You then remove the "A" to "B" jumper and start the car. One then sets the "minimum air adjustment, adjusting the throttle stop screw for a specified, extremely slow engine speed. Some people mistakenly refer to this as the minimum idle speed adjustment. Due to the nature of the adjustment, that is a natural mistake. Does the engine choke up and run rich, blow black smoke, and stall during the minimum air adjustment? Not if everything else is up to snuff. And if it does, it isn't because the IAC passage is blocked. Short answer? If the IAC becomes plugged up, it won't be able to pass the amount of air that the ECM commands and the idle will be slower that it should be. And THAT is all.


Truly, what is uncalled for, here, is the proffering of totally, false, untrue advice. Posts like Mo_Bandy's give the observer a false impression of how things work, that is destined to be propagated. Worse, it sends an already befuddled Corvette owner chasing shadows in the night, trying to check or cure that what doesn't exist. It is one thing to not know, but to offer up advice out of ignorance does a disservice to all that may read it and any other postings it may cause to be written. To agree (as you did) only perpetuates the problem. Although is wasn't my intention, if you feel as though you have had a "slap your hands with a ruler", so much the better. Maybe you will have more consideration for your fellow Corvette owners, next time, before you help spread poisonous misinformation.

The sarcasm and abrupt mannerism wasn't because someone wasn't knowledgeable, but for the irresponsibility of passing along misinformation as fact.

RACE ON!!!

 

He used a simple analogy-look up the word! while you're at it-remember one of my very first posts "the main fan is controlled by the ECM" , twice-not once-but twice you-in your hollier than thou attitude admonished me-said I was wrong!-only to eventually come back and say-"I admitt I didn't check the entire wiring diagram" did I admonish you? NO! learn how to communicate with others and Get a life!