donovan24

good day all just finished installing my 383 but it runs terribly. it misses on idle, it will stall with my foot off the throttle and misses/surges/no performance for a 383 all the way thru the power band. To make matters worse it will back fire thru the intake when i rev it up in park. I have a mini ram with no vaccum leaks ( checked with smoke machine), new 30lbs injectors,230/236 cam and yes i have a tune from PCMforless for all of it. I have checked the injectors and have 16.4ish ohms on all cold and 18ish when hot. fuel pressure is at 48lbs and will hold it and no fuel in the vacuum for the FPR. i also checked the injector pulse with a noid light all good there too. advance is set at 10 degrees with the EST unplugged. with it plugged in the advance jumps all over the place from 15 to 30 btc then to 0. I don't know if thats normal or not. So removed the distributor and noticed that i have a lot of play on the shaft ( up and down) and the shielding on the pickup coil is gone BUT the resistance is within specs at 850 ohms and it doesn't seem to have continuity to the body. any ideas or help would be appreciated

thx Chris

DanielRicany

The problem is, you need to get a real tune. Email order tunes with data logging revisions is the most practical. Or you can do it yourself.

syco_cop

I've had the same problems with a new engine to discover I misrouted a couple plug wires.

donovan24

it barely runs so not sure would get enough data for the data logger ( i have the moates connector ) can it be anything else?

donovan24

i have checked the wiring more than once and a local mechanic as well they are good

Cliff Harris

That's normal. When the engine is running the cam gear pushes the distributor gear up against the bottom of the distributor housing so the play goes to zero.

blackozvet

if the timing is jumping around when its controlled by the ECM then your computer is probably fritzed !
there is every chance that while you have been installing the engine etc, the ECM may have got a power spike.
the only way to really test is to put a good ECM in (beg, borrow, steal ?)

WW7

, timing should be a fairly steady movement as rpms change,not jumping around... Could the timing gears not be set up correctly?...Could the wires be switched? Or like mentioned above, it could be electical or computer related ....48 LBS is very high for fuel pressure, why did you go higher then 42-43 lbs?..If the car is backfiring ,it's very likely something timing related...As far as Alvin at "PCM for less" tuning your car, he's done alot of C4s so your startup chip should at least get the car running halfway decent.."BUT", you may want to check with Alvin so he can look at the tune on his end, because it's not unheard of for a tune to get corrupted while being made... WW

DanielRicany

Mine does the same. Not 100% steady. I always thought it was because of the cam.

coupeguy2001

If it back fires through the intake our intake valves are mis adjusted and one or more are hanging open.
Readjust your valves and the back firing should go away
My 383 will run with the stock 86 tune, so don't let anybody tell you that you need a tune to run it.
It is not a firehouse with the stock tune, but it runs pretty good up above 2000 RPM.
If the timing jumps around, it could be worn distributor bearings, but since these engines run below 2500 RPM most of the time, I would not think it is the distributor.
I would believe it might be a dirty plug on the distributor 4 pin plug, or a problem with the distributor module over by the heater. Unplug the module, and the engine will go into limp-home mode, and the engine will operate on look-up tables. If the engine smooths out, it might be worth while unplugging the battery, and let the computer sit for about 3 minutes with no power on it then plug it back in and try it again. or change the timing module that you unplugged.
But adjust those valves, no engine will run right with no compression on a couple of cylinders.
While you are at it, check the plugs. if any of them are black or smell like gas, you have a leaking injector in that cylinder.
Remember, all of the injectors made are mass produced, and you might have got a bad batch.

DanielRicany

Judging from your threads, you don't appear to have an aftermarket cam or a Miniram intake manifold, or at least I did not see you mention it. However, let me start by first saying that every combination will respond differently to a stock tune, and also, any time heads or cam are changed it most likely needs a tune to bring it back into the good driveability zone.

When I put a cam, miniram, and headers on my '85 Corvette with 350 engine, my tune was thrown off so bad that the thing barely wanted to run. I too had backfires out the intake which was solved by adding more acceleration enrichment fuel. Lean conditions can cause backfires out the intake, which was the case with mine.

I firmly believe that the tune is a good contender as being the problem.

Flywild

Hello. It does sound like like a timing issue. You might be off a tooth or 2 when you installed the distributor. That's about what a timing issue sounds like. Not sure about the ecm and how that would make it run. Try resetting the distributor back in the engine again. If that doesn't work try another distributor. Then look at ecm if all else fails.

gerardvg

Hi

what year is she?

the 85-89 have a Maf sensor, that needs to have a modification (sample tube) for the larger injectors. The tune my have taken care of it another way.

The main culprits.

Injector connectors, they can break internally if pulled by the wires.
Also inspect the connections for corrosion, you can easily replace bad injector connectors. they batch fire one side all together, then the other. There is no problem swapping them to test, for example you can swap cyl 2 an 4 or 6 and 8 or the other side 1 and 3 or 5 &7 for a test.

The valve lash, check compression if the valve last is too tight you will have a valve slightly open.

A simple check from my toolbox ...
when cold start the car and run for 10 or 20seconds, now feel the exhaust pipes at the head. if one or more are cold you know what cylinder is causing the problem.

I found my new 383 lifters only need 1/2 turn from zero lash, not the factory 1 turn. Had a few dead cylinders. was an easy valve lash re adjustment.

Running high fuel pressure did not affect my engine when stock, 45-48psi was fine on the standard injectors.
Good luck.

donovan24

Update so I put in a D.U.I distributor complete assembly at the same replaced the ECM with a rebuilt unit ( no PROM) and still the same fu.... problem. I haven't redone the valves but did do a compression check and have between 165 an 175. I have the fuel pressure at 48lbs because that what the instruction from Tpis say to do for the mini ram. Im getting a new chip from PCMforless ( spoke to them and they graciously will send me a new one ) hopefully that solves my problem.

donovan24

She is a 1986 btw

donovan24

whats next could the PROM have gone bad any tests i could do to the Distributor module?

donovan24

sorry not distributor module the ESC and found the test for it in the manual ( not sure its my problem though)

whalepirot

I like using, as an additional tool, the relatively cheap 'laser' sensors; point shoot and read, to ID problem cylinders via comparative exhaust temperatures.

Indeed; mechanical B4 software, which includes my antique and trusty vacuum gauge!

blackozvet

does the check engine light come on ?
are there any fault codes ?

donovan24

NO check engine is not on the only code that does come up is for the ESC wire