...I'm ready to give up. The flatbed is coming Monday?
1989 Stock - Corvette coupe - Red on Red w/L98
I'm open to any guesses...

I connected the A and the B terminal the ALDL
(Assembly Line Diagnostic Link) connector and the car did not like that at all. The radiator fan turned on; the dash went dim, some other thing going on, however it did flash 12.

Now it won't crank right at all. (Was just before cranking strong and staring). Next, (finally), I actually hooked up a good scanner and pulled down eight pages of codes but the PCM I'm thinking might be my problem.

I believe the car has an aftermarket prom in it. I believe I have the original prom in hand in a box.

The car was running perfectly. I replaced the intake manifold gasket. Everything went well until the comedy of errors began... I don't need to discuss the initial timing or distributor placement. I think that's definitely not the problem. (@TDC compression stroke, Rotor pointing to #1 distributor post. (rotor only goes around once, while # 1 piston comes up twice. obviously...))

At one point I actually tried starting the engine without the rotor in it which was a mistake! I since tested pickup coil. It is between the 500 and 1500 ohms. The ignition control module tests out okay.

However I think that might have a credible issue with the PCM.?

During the replacement of the intake manifold gasket I did not remove the idle air control valve, or the idle position sensor; nor the ERG on the intake manifold; while I was cleaning things up… I am still concerned about the ERG that I might have got some sort of liquid in there? however I've replaced the idle air control valve. I've replaced the throttle position sensor which I probably don't have that calibrated right (likely a BIG problem now and should be adjusted. When and how?)… I've tested the harness on the idle air control valve. of course you'll get a ground to harness test light with key on at two terminals. I assume the continuity to ground should be on the other two wires to complete the circuit.
The car was starting and running very poorly.

I very much expected the engine to start and run first time around.
Before I connected the A and B terminals I was actually getting “node?” light pulses at the injectors.
(car dash does not look right - dim, lack of current?)

At one point I was trying to use the timing light but had forgotten to disconnect the wire by the brake booster. (yet, still I would have expected the car to run Much better.? )

I'm tempted to buy a rebuilt PCM and put the original prom in at this point. (Not supper easy to find PCM. Any “best choose for source? Toledo core supple has them for $250) I believe it would be a miracle if that actually worked.? From a parts changer mentality; just wondering if it is a crazy idea? or am I going to continue to make things worse and possibly damage my dashboard and everything else with stray voltages? ( I still do not want to believe I have a short to ground from moving the wire harnesses around?) what else could it actually be?

I think I've created quite a mess. My Dealer GM certified mechanic is not going to be happy to work on this but he is near the end of his career and likely has worked on many ignition systems like this car before...

I have the thousand page manual from FSM. I'm not overly impressed how it's written.


The car likely has 55,000 miles on it. It has been garage kept. It was in pristine condition.
I did a J55 brake upgrade myself. (I better stick to oil changes and brake$ from now on! Ha!)

I have checked on the form quite a bit. I've actually exhausted my mental effort. I'm 62 years old and I've been a DIY turning a wrench since I was 14.
Any simple thoughts or encouragement would be highly appreciated.

I was helpful on a Chevy Malibu forum, 8th generation but this car is much more difficult.

Thanks Much.

 

in the FSM after every wiggle this use volt meddler here there and it says if can’t figure it out plug in your Tech 1 GM made that way they knew could not figure them out with out one that’s the way they were made

made people have forgotten that part they are not a 57 Chevy got to have high tech stuff to figure them out that’s why people get flustered trying to work on them I worked two weeks trying to figure out why my 93 would not fired found a guy with a tech 1 5 min yep 5-min found it bad plug going the the coil just saying

 

When you say it won't crank now do you mean it turns over but won't fire? If it won't even turn over then you got something wrong in the starting circuit. Check fuses and all your connections. If it cranks but won't start I'd double check your timing. There's a procedure to remove some wire and that is in the fsm. Double check all your work and use the diagrams in the fsm. Good luck hunting for them as the 89 fsm put diagrams on random pages no where near the procedure.

 

Before I connected the A and b terminal it was cranking strong and starting.
All along I've been conscious about wearing out the starter.

After The strange event of connecting the A and b terminal in the dashboard dimming and acting's real strange with the radiator fan turning on when I tried to crank it at first nothing and then it did try somewhat to crank but it did sound like the cranking circuit at that moment possibly the solenoid or something but the last try was a very weak attempt by the starter I still have a hard time believing the starter would go from working strong and hard to nothing at all.

I really did not have any reason to suspect ground straps or battery cables or battery I've been checking the battery and keeping it strong.
Thanks for the reply.

 

I would check all those connections. Take them apart and clean them. Your miles are low, but the age takes its toll. It might have just caused the contacts to get too oxidized.

 

The radiator fans turn on when you enter diagnostic mode. That is normal behavior. No worries there.
Did the dash dim and act flaky when you shorted the pins or not until you hit the starter? Sounds like you have an issue with the B+ power.
Put a volt meter at the the battery terminals and paperclip the A and B pins on the ALDL. Did the fans come on? Did the dash dim? Did the battery voltage drop below 9V? If it dropped low suspect the battery.
Try this again checking between ground and a 12v B+ line. The cigarette light socket works just be careful not short it out with the probes. Try it again. Does the voltage drop now? if yes suspect bad grounds or battery cables/ connections.
If the dash only dims and the voltage drops during cranking again suspect grounds and cables. Does the engine turn over? No, do you hear a clunk from the starter solenoid? Yes, but the starter doesn't turn suspect the starter. Yes, but the engine only turns a little and stops and the dash goes screwy, time to disconnect the battery, pull plugs, and see if the engine turns freely.
No clunk no crank? Check voltage at the starter solenoid terminal to see if it is getting power in start. No power to terminal, suspect the security system.
Yes it cranks ok but doesn't start. Do you here the fuel pump run for a few seconds when you turn the key to run but not to start? Yes, disconnect the battery walk away, have a beverage, watch an episode of Forged in Fire, come back reconnect the battery. Turn to run wait 1 minute, try it again.

 

Be patient, more great posts like these to come. Some real sharp guys on this forum who know this stuff real well.
Sorry I cant help...problem vette and 7 kids shoot man you deserve a paid vacation
It will be worth it once ironed out sounds like a nice car . Nothing these guys cant figure out for ya..bet you know its usually something simple you missed.

 

Thank You very very very much to everyone. For the detailed narratives.
Stock – 1989 Corvette Coupe – Red on Red – Targa Top
I still should / need to adjust the throttle position sensor. (FSM says that's one of them most important inputs to the PCM.) Can I just use the center pin (little piece of wire trick) to ground to find / adjust the TPS to 0.54 Volts +/- 0.08 volts.???

The battery tested Bad tonight it O'Reilly's. Unbelievable (embarrassing) to me. (Simple). it's a 2-year-old extreme battery. (Unfortunately, I did not purchase the battery. It was within the 3-year replacement.)

Very strange coincidence that it shows up right as I was connecting the A and B terminal (@ ALDL (Assembly Line Diagnostic Link) connector)). Had been cranking strong and starting.

Tomorrow will be the new battery.
With luck I'm back to square one on setting initial timing.

I will adjust the throttle position sensor.

I will disconnect the brown wire by the brake booster, while using the timing light looking for 6 degrees before TDC.

I may not have gotten everything in the exactly right order? (TPS - throttle position sensor) Unbelievable at my procedural memory going. short-term and long-term memory already gone.

I really believe the first time I put the distributor back in I got it back in perfect. I had many pictures coming up and out. I have never turned the engine over without the distributor in. ( I did at one point try one tooth forward and one tooth back. Now seems totally pointless. The rotor must to point to the number one post on the distributor @ TDC (comprestion stroke, the rotor only goes around once). Correct?. so basic, sorry. (Before removal, I marked the distributor housing with a center punch and marked the manifold)

Yeah the dash went dim at the exact moment I connected the A and B terminal (ALDL
(Assembly Line Diagnostic Link) connector). At first nothing. I put a battery booster on, tried to crank and I did finally get the classic dead battery solenoid sound. I was surprised by it and apparently didn't recognize that right away.

One other crazy item.

The first time I tried to validate top dead center. I actually did have a wrench on the crankshaft bolt. (I realize that is a big no-no now especially with only one plug out). So I was turning the crankshaft bolt the rotor was turning as I was approaching the full compression top dead center the rotor stop moving and it felt like the wrench was still turning.
Later I thought oh no! I stripped or broke my bolt; then later I thought maybe it was just a wrench turning off of the bolt / slipping off but when I think about it, it didn't seem like that was what was happening.

However, with my finger in the number one cylinder; starter cranking, it still seemed like it was popping and coming back to top dead center so, I don't think that that harmonic balancer can really slip on the crank or can it? Now I see / Looks like there is a keyway so it is fixed on the crank correct? Sorry for all the simple silly questions.

Thank You very very much to everyone.
I still have time to cancel the flat bed scheduled for Monday.
(It was running perfect before I did intake gasket.)
Stock – 1989 Corvette Coupe – Red on Red – Targa Top
I posted a "funny? poll

 

Sometimes it’s better to step away and collect your thoughts. Don’t overthink it. The chances of an obscure problem are slim. Sometimes you get lucky and the answer is right in front of you.

 

Since you asked for opinions -

You certainly can pay for the roll-on and pay for a mechanic to do the work. The plus side is he'll probably get it figured out and running, saving you time and anxiety. The down side is 1) you will be shelling out a lot of $$$ and 2) you really have not learned anything. Next time there is a problem you ill be stuck again.

No one person here knows it all, but collectively we pretty much do. You sound like you DO have a basic knowledge of mechanical and electric repair so my suggestion is use logic, patience and the forum to walk through it. You have several helpful posts - for example "talfryyn" in Post #6 has a nice progression of things to work your way down

Start out by taking a deep breath, then give it some time and effort, reporting back here to keep us in the loop. Even if long term you have to call for a truck, you will have learned a lot in the meantime. Good luck, you can do this!

 

It sounds like you are doing fine.
The reason the weirdness started when you shorted the ALDL pins is because of the fan test. When the fans turn on they have a substantial inrush current. If you have a weak or bad battery or bad connections the voltage will drop. The LED digital dash is power hungry compared to more modern electronics and can only take low voltage for a fraction of a second before the microprocessors have there memory scrambled. So the dash dims and the display is weird. No harm is done, it just needs to be turned off and it will re-boot the next time the switch is put into run.
No worries on the wrench movement at piston TDC either. TDC is where you get the least piston movement for the most crank rotation. When the piston reverses from going up to going down any bearing and bushing clearances reverse (remember there is no oil pressure when you are doing this) and the piston rings reverse and take up clearance in the ring lands. So if you are feeling the piston movement while you turn the crankshaft it feels like the crank is turning for a few degrees but the piston isn't moving you are right at TDC.

 

The battery is in
my dash is backAs you predicted.
Before I crank it I'm going to set the idle position sensor now 0.54 volts plus or minus 0.08 volts.
I am moving slow today.

 

0.539 volts

 

If car still does not run well and you think it's the ECM, I have an extra one from my 89 Corvette automatic. My original ECM problem was that it was not reading the coolant temp sensor. It would set off my check engine light with the code for high reading temp sensor (I think code 14). The ECM must have been reading the temp always as 232 degrees or higher because the cooling fan was constantly on even when first started and it gave me a hard start when first started in the morning. Would take about 5-7 times for car to start when cold. Once car started, engine ran perfect. I put the used ECM I bought from local Corvette specialist and now cooling fan turns on at 232 and fires off first try on first start of the day. Before you buy a used or new ECM, I will let you borrow my original one if you want. It even has the Prom. I put my original Prom in the replacement ECM because the replacement Prom was from a manual transmission. The upshift light would come on once in a while.

 

If it’s running that poorly, you would hope it sets off a code on computer. I would go to an Auto Zone and get a free loaner fuel pressure tester and see what you got. Did you trying spraying carb cleaner to check for vacuum leaks. Don’t give up.

 

If it’s running that poorly, you would hope it sets off a code on computer. I would go to an Auto Zone and get a free loaner fuel pressure tester and see what you got. Did you trying spraying carb cleaner to check for vacuum leaks. Don’t give up.

 

Sorry, looks like I hit submit reply twice.

 

Don't hit the panic button yet. You have at least eliminated the battery from here forward (unless you happened to get a bum one off the shelf ). You still have a lot of items to try, the more things you eliminate the easier to figure what's left.

 

Set the distributor to the base timing in the book. If you pulled any spark plug wires off of the distributor or plugs double and triple check they go to the right places.
Check every vacuum line, both ends, to see if they are connected right and not cracked. Check every connector in the wire harness to see if it is fully seated. Make sure the coolant temp sensor wire is connected.
Pull a spark plug and see if it looks wet. If it does do a clear flood procedure. That's turn the key to run. Press accelerator pedal all the way to the floor and hold it there. Crank it over until it pops and wheezes and clears out the extra gas. Stop cranking, take foot off the pedal and start as normal.
Basics first. You know the engine does run.
If you get codes please list them here first. Sometimes you get codes because the engine is running poorly not because they are the cause.