I can do that. Send credit card information.

I wasn't there but if they didn't disconnect the tan wire, they are morons. Run away and spend the money on hooked before you go back.

If they hook it up to a chassis dynamic they can tell what needs to be done.

Meaningless. All you hear is clicking. I send mine out every 3 years to be tested and they can see spray pattern and volume check. Your ear is only about to hear clicking.

Maybe but if the settings are wrong, even a new ECM and EPROM will NOT help.

I don't know who can test it. NAPA sends it out for rebuild as does GM. It will be better if you get some with a chassis dyno or does tuning using datalogs you gather as opposed to guessing.

 

EPROM. Erasable Programmable Read Only Memory. No. This is beyond a mechanic. A tuning place like Hitech, Lingenfelter, etc.

It did do anything YOU can see but the ECM knows.

Check fuel pressure and timing first. Engine running, hose off, check fuel pressure. Put hose back, tape gauge to windshield, do a short WOT run and report the pressure drop. Shut down and see how much bleed off. Then check timing, use scanner to do minimum air and TPS.

 

I'm not a TPI guy, but this sounds like a red flag! 26 or 29? Too much? Crap hits the fan (not literal, I presume)?

Do you still have your original injectors? You might try putting them back in. Or get them tested and/or cleaned.

 

I'd check fuel pressure first before I go anywhere. After that, look at the ACCEL specific ratings. Better yet, give Jon at FIC a call and ask what the specs are. Also ask if the original ones are Multec units. If so, toss them.

 

I bought 5 from a vendor on eBay. He turned out to be about 10 miles from where I live.

 

Hey man, I have a 1986 and when its cold I have the same problem you explained. At 145f it idles normal and runs ****!!!

After reading your conversation, I don’t think your problem is the new injectors. I have done most of the things you have and here is what i noticed from experience...

If the IAC was the issue, it would do it all the time, same with the TPS and MAF. I have always suspected the cold start injector with i believe was in 85-89 L98’s. The other suspect is the ECM. Like you I don’t have a fancy scanner to monitor data like that. Let me know if you still have this problem...

 

The cold start injector only works while the engine is cranking and the coolant is below 95°F. It was used in '85 through '88.

 

Sorry it's taken me a while to respond. I went back and checked everything and all the parts i out in and the injectors are actually 24lb so they should be fine.

Timing has been set and fuel pressure is holding (a little low) but holding well. Checked all the grounds and fixed a couple connectors and still having the problem.

 

So you must be driving yourself crazy like me. I have almost rebuilt the damn car a this point.

Soooo, I found a guy that races corvettes and mods them near me and he is working on it now. He his totally stumped and believes it is all a computer/electrical issue. He is putting in a new computer today and a hypertech EPROM to see if that fixes it. He thinks the EPROM is sending the wrong data for air to fuel ratio on the start up but as soon as gas and everything is flowing the computer at that point knows what's going on and re adjusts.

As soon as I hear something I will let you know. But he didn't think it was the IAC for two reasons. One, it tested fine and was working and two, the idle is smooth and not but and car is stable when it reaches that temp point.

I will send you an update later today.

 

From what I heard, the HyperJUNK is basically stock with the fans turning on earlier.

 

1. 125 degrees is where the temp sender signal makes the ECM happy, and your ECM goes from open loop to closed loop. In open loop, the computer assumes that everything is normal, and is preprogrammed for cold operation, and cannot compensate for abnormalities. That's why it runs better after 125 degrees. The oxygen sensor is shut out till closed loop.
2. If your running injectors any higher than 24lbs, in open loop, the engine will be running rich and will definitely need your foot on the throttle to keep it running.
3. In 85, Chevrolet programmed the ECM for 24 lb injectors, and with the new computers that were installed in 86 and up, the injectors were cut back to 22 because the new computers were more efficient..
The 86 and up ECM's have more memory and can respond faster, triggering the injectors as required.
4. If your car is running badly in open loop, you need to check the basic engine parameters.
A. timing with the connector disconnected
B. pull all the plugs again and "read" them.
they should be black and sooty with 29 lb injectors. Confirmation that your injectors are too large for your engine Sorry, but that's just physics. If oily, you might be getting oil past the intake valve seals or the rings causing driveability problems.
C.Then check engine grounds
D.Then double check that your plug wires are actually all the way in the terminals on the distributor cap and all the way on the plugs. gaps equal more resistance.
E. Then check to see that your harmonic balancer outer ring has not moved, and is still vulcanized to the hub. Sometimes with starting and stopping the engine, this ring loses it's original location, and even though you use a timing light, you timing will never be right because the reference line is in the wrong place.
F. Check the little three way vacuum diverter valve at the back of the engine that goes to the cruise control vacuum. Sometimes these crack or fall apart, and you have a vacuum leak.
G. Check your gas cap. you fuel system is supposed to run on tank pressure, and if the cap leaks, it won't run quite right. It is for the canister.
H. Unplug the ignition module that is on the right side of the car next to the heaterwhile it is running. If it smoothes out, it is failed... Sometimes this thing can fail, ruining your spark events. Sometimes it does not throw a code.
J. After all this, make sure that you have 40 PSI cold. If yours is higher or lower, with 29 lb injectors, it becomes critical.
Check all of the intake manifold gaskets. squirt a little gas on the intake when the engine is running when it is cold.
you will have to be quick, and sop up any gas puddles before the engine gets hot.
If you have a vacuum leak, the engine idle or RPM will falter or speed up.
K. Check that the plastic tubing under the plenum is still intact. The plastic tubing becomes brittle over time, and has a tendency to become a vacuum leak source.
L. Check your EGR valve. If it is sticking open, and needs cleaning, you have a massive vacuum leak that when in closed loop, the computer compensates for, but in open loop, is a vacuum leak and will throw in exhaust in too large of quantities that the open loop programming cannot regulate for.
M. After all that, Then check your cold start injector to see that it is not failed in the open position. If it is, it will add extra fuel.

 

Problem solved!!!

Sooooo... Here is what was going on. Come to find out the ECM and PROM went bad. I had wires shorting out that were going to the EMC and I found some wiring issues along the passenger side that were going to the IAC. On top of that we found a few vacuum leaks around the manifold. So, new ECM, new PROM and new gaskets solved the problem and it fired right and ran smooth.

Thank you to everyone for all your help in solving this. Now time to obsess on looks and get this thing looking brand new again!

 

Congrats!! How much did that ECM cost you?