kopbet89c4

Do you have a camera? I'd like to see what that side looks like. I've always thought the TBs on TPIs were essentially similar. That big port I circled is where the EVAP canister purges its storage of gasoline vapors once your car is fully warmed up.


BTW, the port on mine was connected with a 90 degree elbow fitting. My guess is that it is harder to see and you were possibly mistaking it for a plug from the factory.

I'll try and take pics of mine after work.

davemack

Thanks again. I wanted to take a picture, but I had trouble uploading images before (I think they were to high res to be used). And, of course, my Dell computer has some photo software that expired and no longer allows me to change the resolution. Some guys have all the luck..

You know, one thing I wonder is, when the mechanic sent out my TB last year for a re-build, did he receive the correct TB back??? It looks the same, but that doesn't mean much. Man, the myriad possibilities drive me nuts.

Some new data; started the car this AM. Idled at 980-1000 rpm. Ran it until it reached about 120 degrees, still idling at around 1000 rpm. Drove it two blocks to a stop sign, at a stop it was running at about 1100 rpm. Drove it 3 more blocks to another stop sign - engine temp at about 145 degrees, idle up to 1400 rpm steady. Wouldn't kick down, no variance, just a straight 1400 rpm. Drove it another two blocks to the thrid stop sign, still idling art 1400 rpm. Drove it 3 more blocks - operating temp at 180 degrees - idle at 1100 rpm. After many attempts to tap the accelerator to slow the idle, it finally dropped to 850, then 750, then 700, but jumped to 850, down to 750, up to 900, down to 690, etc. etc. All over hell.

So, I reconnected the vacuum lines that feed into the fitting under the TB. Idle smoothed out a bit at 670-720 rpm. Another thing; after I parked at work, I was idling at about 640 rpm, still up and down, but much less dramatically. Turned on the AC and idle increased immediately to around 690-710 rpm and seemed to shake the car less. I can definitely feel it when it idles crappy. there's an abrupt change in degree of vibration and the engine lopes when it's idling poor; runs smooth as a baby's butt when it's idling like it should.

Will try the pic up load after work. Thanks again kopbet89c4 - your help is very much appreciated !!

jan-erik

Try start gas or propane first around the throttle body shaft bearings. then around the runners where they meet the plenum and intake and also check for vacuum leak around the intake/heads.
if this sounds good. then check the EGR valve. It may be stuck or the vacuum membrane leaks. Apply vacuum on the vacuum port of the EGR valve and see how long it takes before it drops significantly near 0. it should hold the vacuum for about 20secs. If it doesn't change the valve. I had a bad EGR valve. Chack also the PCV valve for proper operation. Then there is the EGR solenoid on the passenger side. Check for proper operation see the manual.
good luck

all show and more go

i had the same problem and found out the idle control plug was disconected

davemack

Jan-EriK, All Show and More Go,

Thanks for the advice. I have checked extensively for vac leaks, but will double back to the throttle shaft bushings. I'm not sure I can ever rule out a vac leak, so I'll keep spraying. If nothing else, I'll have one heck of a clean engine! Another CF member had that problem (Great White, I think). EGR valve has been checked by a mechanic and I'm told it held pressure as per spec.

Now, EGR solinoid might be a different matter. I plugged off the vacuum line, but it made little difference at first (op temp), then made it idle even more erratically when started and driven from cold with the vac line plugged. I restored the vacuum and it got a bit better (like back to the way it was originally, which is still pretty crummy).

I replaced the IAC a while back, but I won't rule out a bad plug. The top locking mechanism is broken, but it runs much worse with the plug removed (did this when re-setting idle speed and IAC).

Last item, I drove the car over lunch and ran the AC. It runs much better at idle with AC on than off. Still drifts a bit, but mostly stays between 690-720, with occasional rise to 750 and drop to 660, but only for a second or so.

What could that mean?

kopbet89c4

It has to be hosted on a website. Then you copy the url to the pic and use the img button from there.

kopbet89c4

photobucket.com

davemack

Thanks again.. navigating this site reminds me of troubleshooting my car.. not real intuitive

goldeneye_vet

You are missing the small pipe that sticks out of the TB on the passenger side directly under the large pipe for your breather tube that goes to the passenger side valve cover. Stick your finger over that hole as the vehicle is running. I bet your finger feels the vacumn pressure from that opening. Use that hole with a pipe if you can get something to fit in there for your EVAP canister from the driver side in front of the wheel.

jmrl98

Yep, he's is missing that tube. I'm not at home, but I thought that it connects part of the air pump system to the throttle body. I have my air pump deleted, but that part of it I left there to connect to the TB. This was years ago, and I'm not experiencing any idle porblems, let alone like he is, that's for sure.

want2drivemy85

Not sure if anyone brought this up, but 24# injectors are stock for the 85 model year. not the 22# that he has in.

kopbet89c4

No. That tube he's missing is connected to the EVAP system.

The AIR system you are talking about is connected to the headers and catalytic converter.

davemack

That's true, but I've read that the Bosch D9B's are rated at Ford FP, which I believe is around 30 psig, not the typical 38 psig in a vette (not positive about those FP numbers; there's a thread that can be found under searches that discusses Ford vs. GM FP and how it affects injectors). Bruce at Five-0 Motorsports suggested the D9B's. A lot of the CF guys like him.

Brian at HiTech Motorsports (one of Corvette Fever's 100 best shops, located in Ramsey, MN) mentioned he was concerned it was getting too much fuel. I guess he checked vacuum and FP via a computer diagnostic tool(?) I thought you needed gauges to do that correctly, but I'm no mechanic. I circled back with his partner, Bart, who tells me they did what was required to determine my car runs fine. We have very different versions of fine... Bart tells me he'll gladly go over it again, at $100 an hour.

Thanks for the advice - it is indeed worth looking into further.

davemack

I did try putting my finger over the hole - made no difference (other than it burnt my finger tip!) It's strange, but I can see for sure that there is no open hole. It looks to be plugged by cast aluminum - no rubber or plastic plug, nothing shoved in the hole. It really does look factory - like it came that way.

Is your car an 85? I'm really wondering if GM changed the TB design for later L98's vs. the first gen?

Thanks very much for your help in this. I've been going crazy trying all summer to get it figured out, and still nothing. I know you senior guys can take me to the promised land!

davemack

Do you still have a stock TB lying around? My guess is yours is no longer stock based on your mods list. I'm very curious if your TB has two vacuum lines on the TPS side of the TB?

I'm starting to wonder if the mechanic that did my TB rebuild either a) messed up all of the vacuum line locations or b) installed the wrong TB on my car. In his defense, he may have rec'd the wrong TB back from the vendor (he sent it out for the re-build).

On my TB, the EVAP vac line and what appears to be the EGR solinoid vac line share a T fitting that attaches to the bottom of the TB. Any stock 85 TB owners care to go out and give theirs a look and report back?

Thanks for the advice, and thanks in advance if you can look at your TB.

davemack

Okay guys, tomorrows Saturday, a good day for me to get some work done on the car. What do you say? Where do I begin? So far, it looks like

a - check FP
b - check vac draw
c - check TB bushings for vac leaks
d - check injectors for ohm resistance

Might consider replacing coolant temp sensor - I already own it.

I've already tried spraying MAF with MAF cleaner, as well as disconnecting MAF (to verify it works - it does). Maybe check alternator? Remember, it seems to run smoother with AC on than with it off at normal op temp (about 185-210, depending on speed and traffic conditions).

What else am I missing?

RRT vette

This is a situation where you would benifit from using a scan tool. You would be able to see all the sensor function. It would be nice if you had a spare ECM. Stock injectors for a 85 are 24# and you are using Ford 22# at stock pressure. You can also try Field Service Mode where you ground the ALDL after the engine is running. The SES will flash twice a second or on more than off if rich. It will flash once a second or off more than on if lean. It is a rough estimate of what the O2 sensor is sending to the ECM. I've read that someone told you it was running rich. Have you smelt the exhaust fumes? Have you pulled the spark plugs to look at there condition? I wouldn't worry about the cold start valve as it is only active at engine temps under 95* although it could leak without you knowing.

EECS

goldeneye_vet

I would spend a little money on some tuning parts if you can to get you started unless you already have some of these things and then you're in better shape. A fuel pressure gauge $35...has to be the kind for fuel injection that screws onto the scrhaeder valve, a mityvac if you can swing it $35 at Sears, and a voltmeter for around $25 for a digital and you're in business. You mentioned in an earlier post that it ran better with the AC on. According to some of them boys at www.thirdgen.org they like to set their IAC for 20-50 counts. Without a scan program such as TunerPro RT or WinALDL you won't have an opportunity to view that but you can try something to see if it works. We all know that the ECM controls the idle speed. The IAC is a controlled vacumn leak plain and simple. The idle rises because their is more air being allowed in the TB. The idle gets lower as its losing the air and so the IAC goes back and forth adjusting this. This is what I would do......I would adjust your TB blades with the ESC wire and IAC disconnected at around 450-550 rpm in drive (parking brake on of course). Experiment to see what works best. My reasoning for this is that the higher idle will have lower IAC counts and MAYBE will help keep your idle from swinging in such a wide motion. This whole procedure will take less than 5-7 minutes so you don't have anything to lose other than the time.

If you're certain that your timing is set correctly at 6 degrees BTDC, your IAC is correct, and your TPS is set at .54 volts than you are very very close to being there if not done already. Another suggestion is to use that mityvac if you happen to get or have one and buy some new vacumn line hose. Running new hose only takes a few minutes, costs $20 or less, and you will be 100% certain that you have no leaks. The reason I say to use the mityvac is with my own problems of surging I tested the new hose for vacumn prior to putting it on. I did find some problems and was fortunate enough that I had extra otherwise I would have returned it.

Another suggestion I have is to get a cable from www.moates.net for the purpose of running the programs I mentioned above. For the moates setup you can purchase the ALDU1 and CABL1 combo as that is an all in one good to go with either of the above programs. You can also go here http://winaldl.joby.se/ for the free WinALDL program by Joby with a link to build your own cable to use with a laptop to do realtime scanning on the cheap. The only difference between the two cables is the cheap one you make you need a 10k resistor whereas the moates setup is all one peice and the 10k resistor is a switch that is built into the box. With your cheap cable you need an external power source such as your cigarette lighter and you have to plug the wires in directly to the ALDL port plus this cable is serial only. You can try the serial to USB converter cable however some have lots of problems converting the signal and possible changes need to be made to your operating system to see the conversion so keep that in mind. The moates is a cable that plugs in to the ALDL port, you switch to the 10k resistor and plug it into your USB connected laptop. Either one is a great tool and will help to diagnose problems further. Don't pay the mechanics you mentioned a $100 just yet for an hour of their time. Use that money to get your diagnostic goods and you'll be one step ahead.

This forum is a great help but you have other sources that can help as well. www.thirdgen.org has TONS of info. Sign up and use the search function. Then their is the old standby although a pain in the azz to use is the factory service manual by Helm www.helminc.com. With my manual I have no dividers so finding things is considered by me to be a pain in the azz. You can not beat the troubleshooting aspects of the Helm as it is very detailed. You're almost there....dont' give up hope yet.

davemack

Thanks RRT Vette. I did have it scanned, both while at idle and while driven. About all the mechanic told me was he wondered if it was getting too much fuel. I wish he could have printed the screen so I could relay the data. By all accounts, he is a skilled mechanic. He's the owner and primary diagnostic technician at HiTech Performance. But, even the best miss one here or there.

I did recently buy the FSM. Full of data, but yes, not real easy to find what you need. Still, it's become my go-to whenever I have time to read.

Plugs and wires are new. The old plugs looked clean - kind of very light gray, but no deposits, oil, fuel or otherwise. I will check for rich or lean condition. To me, it smells rich at the exhaust at idle. My guess is it should be diagnosed in closed loop?

Will run the diagnostic in a few minutes (need to take a short drive) and get back.

Thanks again - you're advice is much appreciated.

davemack

Once again, superb advice. I will head to Sears for a shopping trip tomorrow. I see the need for the mityvac, FP guage and DMM for sure. Those tools show up in many threads. Will look into the moates cable as well. I've got a decent laptop, so this should work.

I'll aim for a 500 rpm TB blade setting, since mines a 4+3 trans, which is suggested to be set at 450 in neutral. This time, will be sure to disconnect EST. I didn't see that on the forum thread that describes the resetting TPS and IAC.

I also have wondered aboyt the ECM. I may post a WTB thread to see if anyone has one sitting around. I've seen them on eBay as well. Maybe I'll get lucky.

Another thing suggested by my friend Sami is a custom prom from TJ Wong. Sami runs one and says it really helped smooth out his idle, as well as provide more punch at WOT.

Thanks again for some great guidance. It is very much appreciated!