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Troubleshooting 90 l98

Old 09-19-2018, 08:23 AM
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rbates74
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Default Troubleshooting 90 l98

I did a stealth ram swap. Red top injectors, accelle 300+ blaster coil, small cap distributor kirban regulator. Pcmforless tune.

It starts up every time. Fuel presure holds steady at 42. But it shuts down 10 seconds later. It will however stay running with a steady spray of starting fluid.

i am useing both aldlscan and aldlDroid for diagnostics.
Only trouble code has been for the MAP, disconnect the map and the code goes away with no change.

New fuel filter and walboro pump 5k miles ago.
Found and cleaned all the grounds under the hood.
Used the "screwdriver stethoscope" trick to confirm injector pulse. Trying to borrow a noid light to be positive but at this point i dont think its an injector pulse problem.
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Old 09-19-2018, 09:28 AM
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Lets try this. Go to Autozone and borrow their noid light. While you are there, have them test your ignition module.
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Old 09-19-2018, 10:10 AM
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rbates74
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Would it still run on an alternative fuel source if the ignition module is bad?
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Old 09-19-2018, 10:12 AM
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Originally Posted by rbates74 View Post
Would it still run on an alternative fuel source if the ignition module is bad?
No but I'm already there at the Zone so why not make sure? I had an ignition module that was bad when hot and I want to rule out things it doesn't take the world to get at it.
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Old 09-19-2018, 10:19 AM
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If you have ignition and fuel pressure throughout, the noid light will tell us if you are getting pulsing. If you are, I'd look at the injectors. If no pulse, I'd look at wiring or ECM. Since you are getting pulse at startup, I would suspect ECM. Give the ECM a couple sharp knocks and see if that helps
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Old 09-19-2018, 10:52 AM
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Yes, noid light. It pointed to a failure in the ECM drivers in my case. This should eliminate a fueling issue at least.

Last edited by vader86; 09-19-2018 at 10:52 AM.
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Old 09-19-2018, 12:40 PM
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ctmccloskey
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This sounds more like it is a "Fuel related" issue here.
Since we know it runs after shutdown using the starting fluid and you did change the intake systems is it possible that the oil pressure switches were disconnected or connected in reverse? I have had problems where my pump would not energize and it was a bad connection at the oil pressure switch. Then while looking I also found a bad crimp going into the fuel pump relay. On my 1988 C4 I found two oil pressure switches, one for the gauge and the other for the ECM. When you changed the distributor does it have the same connections that the original had? You said the car "runs for 10 seconds and then shuts off unless you are spraying Starter Fluid into the engine. What happens when the MAP sensor is plugged in while you try to start it? Does it still run for 10 seconds. How precise is the 10 seconds?

I read in the FSM that the one of the signs of an ECM failure is when you turn the power on the cooling fans start up immediately regardless of the position of interior switches like A/C. You can try the Noid lights but I have a gut feeling that is not the right direction to be going in.

You have done so much to your car with the intake swap and without knowing the intricacies of those systems I would start from the beginning and be sure that everything is plugged in properly and you have no "Extra connections". Maybe the car starts but fails to see something important required to run in the "Open Loop Mode". One simple thing to do is to be sure that your Engine Block is grounded properly or for that matter that your whole car is grounded properly. The ground straps they used are junk or should I say "Were Junk" on my C4. They make a huge difference in how things work or don't work in our Corvettes. The Fuel pump has a dedicated ground wire going to it but you still want to ground the tank to make the fuel systems work properly.

I don't know if I have been much help, I hope that you stumble upon something simple that is causing your woes! Good Luck getting that Corvette back on the road again!
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Old 09-19-2018, 01:18 PM
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I can check again but I think my 91 started and ran with 0 psi oil pressure. I had disconnected the oil pressure sensor wire to check
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Old 09-20-2018, 08:38 PM
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Injectors checked out. Fuel pump lines and filter checked out. Grounds cleaned, no trouble codes map tps and iac all function properly. Ignition module and coil working and giving off a quality spark. Temperature sensors sensing temperatures accurately.

That only leaves one thing. After over a month of chasing ghosts, it appears to be ab ecm issue.

But wait! It ran just fine before the intake swap why would an intake swap mess up the ecm? That makes no sence... Unless you put a new chip from PCMforless in to match the intake? And of the chip was bad. Then all you would have to do is take the new chip out and it will idle!
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Old 09-20-2018, 08:52 PM
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Unless you put in the chip backwards. That will fry the ECM in a heart beat.
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Old 09-20-2018, 09:28 PM
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Originally Posted by rbates74 View Post
Injectors checked out. Fuel pump lines and filter checked out. Grounds cleaned, no trouble codes map tps and iac all function properly. Ignition module and coil working and giving off a quality spark. Temperature sensors sensing temperatures accurately.

That only leaves one thing. After over a month of chasing ghosts, it appears to be ab ecm issue.

But wait! It ran just fine before the intake swap why would an intake swap mess up the ecm? That makes no sence... Unless you put a new chip from PCMforless in to match the intake? And of the chip was bad. Then all you would have to do is take the new chip out and it will idle!
How did you determine all of this?

Maybe. Assuming all the above was tested properly

Assuming all of the above, sure. Test it
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Old 09-20-2018, 09:29 PM
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Originally Posted by vader86 View Post
Unless you put in the chip backwards. That will fry the ECM in a heart beat.
How would you do that? Doesn't it have a "key" to prevent this? That is, unless you force the thing in.
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Old 09-21-2018, 07:45 AM
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I did not put it in backwards.
I've spent the last month troubleshooting and have checked all the things mentioned. Along with fixing a few things that came up along the way.

During that time it has either idled like total crap and only at 2500 rpms or so, or it wouldn't idle at all.

Yesterday i was pulling the ecm. And decided to take the tune out of it and try it.
It idles perfect at about 600 rpm.

Now i am not absolutely saying that the chip is defective or that the tune is bad and even if they are im not trying to give pcmforless a black eye. **** happens.

I would like them to help me figure out why it won't idle and i am sure they will.

Sunday i will do some datalogging without the new chip, and then i will put the new chip back in and try again after making sure all the conections are clean.

Last edited by rbates74; 09-21-2018 at 07:49 AM.
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Old 09-22-2018, 03:59 PM
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Originally Posted by rbates74 View Post
I did not put it in backwards.
I've spent the last month troubleshooting and have checked all the things mentioned. Along with fixing a few things that came up along the way.

During that time it has either idled like total crap and only at 2500 rpms or so, or it wouldn't idle at all.

Yesterday i was pulling the ecm. And decided to take the tune out of it and try it.
It idles perfect at about 600 rpm.

Now i am not absolutely saying that the chip is defective or that the tune is bad and even if they are im not trying to give pcmforless a black eye. **** happens.

I would like them to help me figure out why it won't idle and i am sure they will.

Sunday i will do some datalogging without the new chip, and then i will put the new chip back in and try again after making sure all the conections are clean.
Use the factory chip or you'll be chasing your tail for another month.I got a PCMforeless and it would not work for me.
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Old 09-22-2018, 05:16 PM
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Originally Posted by steven mack View Post
Use the factory chip or you'll be chasing your tail for another month.I got a PCMforeless and it would not work for me.
I have used several different non factory chips but they are not from some guess a tune operator so....
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Old 09-22-2018, 11:07 PM
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rbates74
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I had a pcmforless chip before i did the intake swap (stroker valve upgrade and cam) had a new tune done for the new intake and injectors. Not sure how well the red tops will do with the stock tune, but i guess i am going to find out.

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Old 09-23-2018, 12:40 AM
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Originally Posted by rbates74 View Post
I had a pcmforless chip before i did the intake swap (stroker valve upgrade and cam) had a new tune done for the new intake and injectors. Not sure how well the red tops will do with the stock tune, but i guess i am going to find out.
I had 30 pph injectors (red top) I think on my 383 with TFS heads, 74219 cam and Superram intake. All out of the box so no porting. It ran like crap on an optimized tune for the 350 using the SR intake and LT headers. I'm guessing that the ECM thinks it is pushing 24pph injectors when it is pushing 30pph which is a 25% increase.
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Old 09-23-2018, 08:09 AM
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I think (scary words) that with some data logging i can bring down the fuel pressure to compensate for the bigger injectors, have to try anyhow.
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Old 09-23-2018, 08:54 AM
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Originally Posted by rbates74 View Post
I think (scary words) that with some data logging i can bring down the fuel pressure to compensate for the bigger injectors, have to try anyhow.
That may cut down on the atomization. I think a tune is needed at this point
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Old 09-23-2018, 10:09 AM
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rbates74
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A tune is definitely needed. I have always planned and still will if i can, do several datta logging sesions and use the info to improve the mail order tune.
its a lot cheaper than a dyno tune, and gets you a lot closer than the guess a tune approach.
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