Engine missing one cyl. when accelerating and getting warm / DTC code reading

Guys, since some days my BRM startet to crank hard for the first second just as the battery is poor on voltage. It wasn´t at all, 12,8 Volts and 11,5 when cranking. But thats not the problem. After starting cold, the car is running well so far and after about 5 km, behaviour getting strange. With a speed of about 30 -40 mph it starts to shake when demanding for engine load and wouldn´t accelerate easily, only when pushing harder it starts to go on. In this situation , I feel one cyl. is missing. When idling warm and I put a short throttle opening, definitly one - maybe two -cylinders are missing. Back to idle, all cyl. are working. No MIL is burning.

Apart from your advices, I would perform an DTC check but don´t exactly know how to do. I know basically the procedure with the AC operation  panel and get it into mode by pressing the "temp up" and "off" buttons. Then it shows -00. After that I can press the "middle" button. From there on I don´t know how to go on, I see a set of numbers by clicking up and down but I don´t know how to show any DTCs IF there are any present. How do I see whats wrong if something is logged? I can see some temp data and can figure out if they are plausible, ok, but there are other numbers what I have little use for it as long as I don´t know whats the message.

Would be nice if someone could clear up this stuff, thanks a lot.

I have another question hoping anyone would response...
If I remove the post connector at the small fuse box close to the passenger side in the engine bay ( the post is covered with a plastic cap for jump-starting) and sand it for better connection, is the problem fixed or is there on the lower side of the post another connection point what might causes problems and increased restistance?

What year is your car?

Is the check engine light on? If so, you need to get the codes - See if the below link will help you...

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Hi, my car is a 94. I know this chart from your link, anyway thanks. The car puts no Trouble code. My question is: Is a trouble code only existing once the check engine light burns? or can a trouble code can be stored without check engine light?

To fix the problem i did the following attemps until now:
- Cleaned and sanded the battery post from the fuse box
- Found 2 broken air bypasses on the trottle body going to ventilation valve cover and to the tank vent canister, fixed it, no influence to the issue at all
- replaced all spark plugs and spark wires ( passenger side it´s not a pleasure), no influence
- checked the injector resistance, all 13 Ohm as it should be
- checked fuel pressure with vaccum tube stuck ( 2,5 bar and pulled off 2,9 bar, pressure is perfect

Next checks: Checking voltage at the water temp sensor / Air mass sensor / Throttle poti / Map sensor / air temp sensor, checking all ground connections. Eventually checking fuel pressure when cycling and the issue comes up. No more ideas at all.....

Start with the basics.....If you believe one cylinder is dead, pull the plugs, looking for one that is wet....Compression check all eight cylinders to find if one is lower compression than the others.... Could be something as simple as one bad plug wire or plug.......If compression and spark are good, next you'd look at injectors......
I have no experience with LT1s, but I suspect that you have a fuel pump beginning to fail, or a clogged filter and low fuel pressure is affecting one or two injectors more than the others, which could cause lean backfire.....I'd start with a fuel pressure check, a compression check (and read the spark plugs) before moving into the electronic realm because no engine light....

AzDon, if you´ve read my posting, I already did all things you would advice. I already checked the injectors, the fuel pressure, and I´ve fitted a brand new set of sparks and spark wires. So there shouldn´t be any issues with these parts. I did no compression test as yet because the car is running great as long as it´s cold. If compression is poor, it will run poor immediately after starting. It´s also good on power after 1-2 km on the road, no power loss, all cylinders are working. Even then, once the engine gets warmer, the issues are going to start. So basically there´s not to suppose any mechanical issues at the engine. Should be something what is influenced by the engine temp, maybe water temp sensor f.instance. If the issues are coming up and I slow back down to idle, the engine is running smooth on all cylinders. BTW: The old spark plugs are looking quite ok, no one is wet, burned or looks any different to the others.

You need to take a look at the items that actually occur at the time you are seeing the problem, but be aware you may need some hardware to see what is going on or hire it done.

The first one that comes to mind is the EGR system as it only comes on at warm and low loads. It also does things like advance timing and reduce fuel when active. For instance, if you are at low load warm conditions and then you step moderately on the throttle, if the computer says turn off the EGR or reduce it a bunch, the timing will go back, the fuel will go back in but the EGR could still be open and messing up the power if it is sticky or failed. Step harder and it releases or the throttle air gets big enough to mask it still being open a bit. The same types of things can happen with cannister purge sometimes. You would be able to see the timing and fuel changes on a higher end scanner and probably EGR operations.

You may want to disconnect at the vacuum source both the EGR vacuum lines and the purge vacuum lines and plug the source side of the connection and see what happens. If nothing changes, you likely don't have issues with those areas and are back where you are now with minimal cost. If it gets better you have likely closed in on it. If it gets worse, it could probably be either. The biggest problem with this method is that the fuel and timing issues with the EGR will still happen, so may get a bit of low load lean miss, but it will probably go away when you step on the throttle a little to where you have the issue now.

Booster, thanks a lot for your advices. TBH, I have cancelled the purge vaccum line since a long time because the steel tubes were rusted through and there´s no reason to keep it apart from regulations. I plugged the vacuum valve to make sure getting no bypass air into the inlet. Worked fine since years. So there´s only the EGR function left and to figure out if this is the culprit. Plugging the EGR vaccum lines is a good idea to see if there´s an influence, if yes, I´ve a new hot track.

An US garage close to me has the Tech 1 available, maybe he can read all values, I´m confident. Will see him tomorrow. I will report further how all is about.

To finish this thread I would like to solve the mystery after 4 months of searching. Luckily, here in Germany is a very skilled US shop close to me and he has a Tech 1 to read the deepest miracles of the ECU. He found the knock sensor sometimes no clear signals coming up, the outer steel jacket wasn´t grounded correctly soemtimes to the engine block. Furthermore, the air flow sensor was heavily wrong with showing twice the air masses what it should do, resulting in excessive fuelling do to the big faked air mass. After swapping these both items, the car ran as never before, but after about 10 km it started to stall again, misfiring and sometimes knocking slightly. This happend before I swapped knock and air mass sensor already after 4 km of riding. So the only part what couldn´t be left was the opti spark what I tried to swap last due to the supposed big work. I ordered a Cardone distributor from RA and installed it easily in 5 hours, wasn´t that big expense. Now the car is running like hell, no issues any more. Some guys wouldn´t believe that 3 reasons might be possible the same time, but it´s the truth. I saw by myself the figures what were faulty and after swapping each of them the car ran better. Now the car runs perfect, although now the seat belt buckle is brocken - I´ll going crazy next time....