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butterfly opens to within about 2mm of WOT, so that seems good over all. Good news, car fires right up, mixture is good and the idle is set correctly. Upon going into the dash I found the last owner had taken much apart bit did not put screws back in. The dash display for the computer and brake light etc I opened up and I found a missing bulb. I can't imagine these things are wired in series. Can a missing bulb make none of the bulbs not function? Please see the photos. I found a 10 amp fuse behind the panel bit it was good. I replaced it anyway. Anyway, more to follow as I get into this mess
The grey wire is most likely a panel illumination wire. You check this by seeing if if get 12v when you turn the lights on.
Other possibilities include the hatch or the door ajar switch wire.
Thanks for the diagrams, a grey wire does go to the instrument lights for the dash. I think if I find the home, the lights might come on. I have everything working on my dash except for the instrument lights, (check eng, parking brake, etc.) I am going to by a scanner as well. Inova 3123 OBD 1 is highly rated and not expensive. Thoughts?
I see two gray wires, and I found 2. One goes into the instrument cluster, and the other has a loose end with a connector the needs a Male end. I think I am in the right track. The diagram is very helpful.
I just had a look at the Inova 3123 OBD 1 code reader. Personally I don’t think it is worth purchasing. It looks like it only reads the codes and converts them to words. You can read the codes yourself with a paperclip and look on the internet or in your FSM for what the codes mean
Here is a list of the diagnostic codes I found with a quick google search, I’m sure there are more detailed explanations out there but you get the idea http://www.corvetteactioncenter.com/...codes-579.html
What you are looking for in a scanner is something that will show you not only the codes but the signal coming from the sensor. For example you have calibrated you TPS so a scanner would shown 0% throttle 0.55volts. If you opened the throttle the volts and percent would change until you got to 100% throttle and 4.3volts (in your case).
Also a good scanner can log all this information so you can go for a drive and come back home and analyze the results. WinALDL is free and can do these things.
Thanks for the diagrams, a grey wire does go to the instrument lights for the dash. I think if I find the home, the lights might come on. I have everything working on my dash except for the instrument lights, (check eng, parking brake, etc.) I am going to by a scanner as well. Inova 3123 OBD 1 is highly rated and not expensive. Thoughts?
You may want to double check on the scanner . Maybe more a code reader than scanner. Also when I was checking around for obd1 readers , none came with the obd1 cable. It was an option.
Do you get an engine light now on ?
The Contacts and light bulb holders can be impaired by corrosion. I frequently will use a rubber eraser on the end of a Pencil to clean the contacts. On C4 Corvettes you frequently run into corrosion as they have been in service for over 30 years. The corrosion on the post supplying the Fusible links was the worst on my 1988 C4. It caused a voltage drop of close to 2 volts dc. It made everything work poorly or slowly. After fixing the corrosion I was surprised to have everything working inside the Corvette again. Be sure to CLEAN every contact surface you come across and your Corvette will appreciate it and run better.
When ever I find corrosion on small areas I use something called DeOxIt and it removes all the corrosion and leaves a clean surface for good connections. DeOxIt is not inexpensive but it sure does work well. I wish I had this stuff 50 years ago!
On this forum there is a "For Sale" section and I bought a Snap On MT2500 from a fellow Corvette Forum member. This device is a life saver as it shows you what the ECM is seeing at that precise moment. I have yet learned all it can do but I have been very impressed so far. They even made a cartridge for the MT2500 that diagnoses problems with the Bosch ABS Systems. I bought this thing for under $300 and have been loving it ever since. They are fairly common on EBAY and the prices varies based on the accessories that come with it. The cartridges are still sold on EBAY and Amazon for the MT2500.
I am planning on upgrading to Tuner-Pro as I get the time and needs. For now the MT2500 tells me more than I need to know! As GregMartin has mentioned above the ability to "see" what your ECM is seeing is very valuable and will speed the repairs up a bit.
Somewhere someone mentioned "Chilton's" manuals. I strongly suggest that owners of C4 Corvettes buy the Factory Service Manual in some format convenient for you. Helms Publishing produces the FSM set and they are not cheap, BUT they are accurate and very informative and help diagnose problems more easily. I had a BAD experience with Chilton's many years ago and stay away from them. The FSM's are priceless in my opinion. I have two printed sets for my 1988 and a single set for my C3. If they are too expensive look online and you can frequently find the set on a DVD for a whole lot less. My Daughter has a 2011 Camaro and they wanted over $400 for the printed set for her Camaro. I went to EBAY and for less than $25 I bought a DVD. I made a Copy for myself and then put it in the Car with her along with an OBD2 Code reader. The disc from EBAY had several additional guides as well which really makes it worthwhile!
Mr. Mccloskey,
thanks for the great advice. Over time I plan to purchase a scanner. Innova makes some decent ones and the SnapOn scanner seems to be a great choice as well. I am going through and cleaning the connectors. Using radios in the Army in austere combat situations required cleaning electrical contacts frequently . The pencil eraser works very well, but the cleaning compound you mentioned I will look into. Just cleaning up the connector to the TPS made a big difference. I look at this process like being in school. My last project car was a 73 Gran Torino with a 351C and a 9" rear end. It was carborated so much simpler. With the vette I have moved up to college level studies. Anyway, I am going to buy the code detector for now since I cannot get the codes directly from the ECM without it. Once I get power to the center console then it won't be needed as much. Soon I will get a real scanner. Everyone here has been so helpful. I still have a gray wire with no home in the dash. Based on the diagrams I am in the right track for power to the console. More to follow my friends.
I didn’t suggest putting 12v on that wire! I suggested checking for 12v when the head lights are switched on.
Anyway good to know it’s not part or the illumination circuitry. I was thinking I was possibly a door or hatch ajar switch wire, but if you reckon it’s not required that’s even better.
And, in this case, I "don't rekon", I know. This wire has been discussed at least three times in the past 3-4 months. The conclusion is always the same: It is found in 86-89 that do not have C68 electronic HVAC controls. It is just loose.
People get so wound-up around here. It's just a forum. Talk about the cars, and help solve the problems. Don't talk about each other.
Mate I think you’ve got me confused with someone else. My post are only ever about offering help and suggestions. I don’t see any value in horn blowing or over inflated egos. I was concerned that my suggestion had been misunderstood (which wouldn’t be the first time). And as these forums become a bit of a reference it’s good to be clear.
i was hoping that someone would chime in and say “I know that wire it’s this” which is what happen so that’s a great outcome.
Where I’m from we tend to use the term “reckon” as a bit more of an assertion of fact rather than unproven theory, so I’m sorry if you thought I was suggesting that you didn’t know what you were talking about, because that’s simply not true.
On a brighter note it’s a 30 deg C beautiful autumn day here in Australia Land the overnight new cases of COVID-19 are dropping and there is a general sense of positively, so have a nice day, I know I will.
I was the one asking about the gray wire, thanks for the advice. Not sure why the center console lights are not working, anyway, the real issue with my car is the fact that the power fades at around 3900. My next move is to pull the code with a scan tool and then check fuel preasure consistency. This forum has been very supportive with green horn like me.
I was the one asking about the gray wire, thanks for the advice. Not sure why the center console lights are not working, anyway, the real issue with my car is the fact that the power fades at around 3900. My next move is to pull the code with a scan tool and then check fuel preasure consistency. This forum has been very supportive with green horn like me.
didn’t you say you are getting some is the tell tale panel lights to work? And one of them the check engine equivalent ?
