jseremba

Just one or two things.
I know that you timing is correct.
Have you checked for vacuum leaks.
I have an 84 with cross fire so I am not familiar with your system. But is there anyother throttle adjustments on the lingage? Oh an if youget a vacuum pump you might want to try the MAF sensor.

Wish I could do more. Good luck

SunCr

TPS voltage changes whenever the shaft it's connected to moves. You moved it when you diddled with the screw. But, you have an air leak because with the butterfly closed, there's no air and an engine doesn't run without air. That may be why you decided to make an adjustment it doesn't need. Use some propane and aim it at the throttle shaft (outside). If it speeds up, the bushings are gone. Check vacuum hoses. By the way, idle spec is +/- 100 rpms from Targeted in Park/Neutral. 50 rpms +/- from Targeted in Drive. So, if your Targeted Number in Drive is 575 rpms, your Actual should be 525 to 625 rpms. Hook up your Scanner and see what it is.

aklim

IAC counts or did you use a DVOM? To read IAC counts you need a scanner.

Also, do you have any idea if the chip was modified?

L72M21

I tried the propane torch all around the top of engine, EGR, brake booster, cruise control, evap system. No change in engine speed. Maybe I could eliminate the vac system for the AC in case there is a leak under the dash. There was a rodent issue with this vehicle. Could you suggest other areas to check?

L72M21

I used a DVOM. I've known the PO since B4 he got the Vette in May 88, If there were any mods they would have been made b4 he got the car. The window sticker shows CPC Engineering Center Warren Michigan and was delivered to a dealer in Mesa Arizona. So GM may have been using it for testing. To my knowledge the MEDCAL is the original, but the ECM had a REman. by GM sticker on it. I did change the ECM recently. I took a picture before installing the MEDCAL in the ECM. The MEDCAL is blue with 68767 8710, the numbers are kind of faint. The 8710 may be a date code?

aklim

Then your IAC readings are not good. So, can I ask how you know what RPM the car is running at? Without a tach that is on say your timing light or your scanner, I used to read 300 above what the ECM said it was doing.

I doubt it.

Don't care. I have a MEMCAL with a smiley face sticker on it and it was painted gold. I have another one that says AUJP but it has been flashed for the current program.

L72M21

I sense that you are getting frustrated with my lack of knowledge about this vehicle. I did purchase a sevice manual and other C4 literature, but am not learning quickly enough. This is such a completely different vehicle than a C-1, 2, or 3. I thought some numbers might help identify the MEDCAL. I was wrong! It's a 20k mile car that has set for ten years. I bought it on a whim, as a summer project, to have something to do for 3 months. Had I planned better I would have brought more tools with me. I'll be leaving it here when my vacation is over and will continue working on it next summer, with more tools & information. The PO put 13K on it in 25 years and did nothing but change oil, oil filter, air filter, & battery, maybe wipers, nothing else not even tires.

MrWillys

A smiley face

Panted gold and the cover is siliconed on?

MrWillys

What is the alpha code from the memcal? IE: ABTR

aklim

Not at all. I have been chasing an issue for longer than that till my trusted source said it wasn't good but live with it till you get a new motor.

I don't care about the numbers since they can be reflashed to do whatever the programmer can make it do so that tells me nothing.

My advice to you is to get a scanner. Not a code reader but a scanner. That will let you see whatever the ECM is seeing from the ALDL.

Where is "here"? There could be someone nearby with a scanner. That or maybe an "Autozone" or something with a scanner than can read OBD I cars?

Change tires NOW. I wouldn't drive it if it were me.

aklim

Yep. It was from Eileen and Jeremy Formato. Used to be Jim ran it and when he died it went to Eileen and Jeremy? Later on, Jeremy formed his own company or something.

They ALWAYS sent out a chip like that with some of the pins of the IC chip cut off so it would work but you couldn't read it or duplicate it.

L72M21

See, I'm not sure if you are asking me a straight question, or you guys short sheeted my bed in basic training, and I'm to stupid to know it!

MrWillys

Yeah, that's why I thought it was so funny. I bought one from TPIS, Formato's, and Jim's performance before i started programming myself. I remember the gold glued cap vividly.

SunCr

If you have a Vacuum Gage - what it does show? (hook it up to the PCV fitting). Loose Accordian at the MAF or a pinhole leak. Torn PCV hose or leaking PCV fitting on the Manifold. Busted Check valve on the driver's side header sucking air by the O2 which will swing it Lean and it'll add fuel speeding it up (and make it rich). You could use vacuum caps on everything but the Regulator and see what happens.

Air flow from the A/C will be Defrost only if there's a hole somewhere, but if you cap the source - next to the Regulator, that'll rule it out.

MrWillys

Look, you have a vast knowledge base here. There's a silver sticker on the memcal when you look through one of the windows on the blue cover. This will identify the broadcast code (bcc). Sticker will be gone if it's been reprogrammed.

Without going back through. Is base timing now 6degrees? These systems are really simple, and either a device is adjusted improperly, broken, or ecm, and or memcal is bad.

vetteoz

L72M21

Can you recommend a scanner, I see them fron $25 to $150, online. I assume for $150, that would be an OBD I or II plus a scanner.

I'm in the Detroit area about a mile from Woodward. Dream Cruise time in a few weeks. The first little bit of frost in the air and I'm out of here, back to Florida to work on C2's, something I understand!
Regarding tires, Haven't been over 50 mph and no freeways. I would like to get rid of the salad shooters and get some 17" saw blades with adapters b-4 getting tires. Im looking at a set of SB's off of a 92. Any suggestions.

L72M21

The picture of the MEDCAL that I took before reinstalling it, looks exactly like the one in your picture including the little white sticker in the right side opening. There are 3 rows of black lettering on the white sticker, but I would have to pull the ECM back out to read the numbers on the MEDCAL.

L72M21

I'll have to get another timing light and a scanner, I don't have a scanner now so it won't be a duplicate. As mentioned earlier I only brought a few tools, oddly enough I did bring my Mightyvac to track and fix a vacuum leak on my truck.

L72M21

I have a Mighty vac gage, and was able to pull 27hg on the EGR valve and it would hold, but not when running. With engine running at idle I can pull a steady 10hg on the line to the EGR valve, straight on not with a Tee. Please clarify the "Busted Check Valve" I don't see it on the component location chart 6E3-A-2. No vacuum line to it I assume.
Getting late now, I will follow up on your suggestions tomorrow. Thanks. PS: I just got through fixing a defrost default vacuum leak on my truck.