OK guys I need help............went to accel 36 lbs injecters,superram intake and comp cam nitruse grind........224/236..............all sensers are the same......same TB........engine idles like a pro gas dragster, up to 1600, down to 500 and then dies in closed loop or open loop.... all though its less in open loop.......then some times it will idle at 1100 or 1200 rpm with the idle screw screwed ALL the way in.............disconnected the iac and pluged a spare iac in the harness, thinking the iac was chasing the cam........no change...if it was a vacuum leak it would idle high right? it wouldn't surge.......tbi hasn't been changed from original sitting......tryed some propane for leak detection but its idling so fast just to keep it running I can't tell if theres and increase in rpm........what next?
Re: New 383 surging and then dies (lead foot 85 vet)
Can't say if it is the same problem in your car but mine had the same problem when I first assembled the motor. I started out with the base timing at a stock 6 degrees. The car would barely idle, very rough stalled often, everyone was telling me to not go over 8 degrees on my base because of the SC. Make a long story short I am now running 12 degrees on my base and 40 degrees advance total and the car idles great and has great throttle response compared to before.
Every setup is different so I would try that until you get the idle down.
beleave it or not I got it from the shop in this condition.............$1900.00 for the engine swap :mad anyway thats the first place I checked and advancing it was helping but as you said and I've heard 6 degrees............I'll try it............whats BTM? Thanks for the help.
Re: New 383 surging and then dies (lead foot 85 vet)
OK tried it and it likes 8 ,9 degrees smooth steady idle but as soon as I plug the esc back in it jumps from 950 to 1500 rpm and the timing mark is about a inch above the timing gadge...... also the surge starts again.............were on to something here.
I have an accel ecm.........but I wanted to put some time on the engine with the stock computer............any idea what the advance should be at 1500 rpm? also anybody out there piggy backing the accel ecm to the stock ecm ? tried the one and only accel distrubuter in the state of Utah and he didn't have a clue.
Re: New 383 surging and then dies (lead foot 85 vet)
I don't know anything about computers so can't help you there.
Do you plan on running a DFI with the Accel computer?
Yeah, mine wouldn't even idle with the EST unplugged at anything below 11 degrees on the base. I don't really know what the "correct timing" should be at 1500rpm but I believe mine was at 26-29 degrees.
Re: New 383 surging and then dies (lead foot 85 vet)
I had the same problem with my 383 at one time and the problem was my computer couldn't handle the idle through the IAC. I drilled a hole through the trottle body per instructions from another 383 corvette forum member. All was better! The IAC/computer could then handle all the air my engine was sucking at idle. Do a search in the scan and tune board for the procedure. The computer will still sense total air flow through the MAF so the AFR will still be accurate.
Re: New 383 surging and then dies (lead foot 85 vet)
Did this just start after you reassembled the motor? Could you have swapped the runners from side to side by accident. This would block the EGR line. I did this by mistake once and the car would not run for s__t. Ran fine after I swapped them back.
No I changed to a super ram from a stock tpi intake during the rebuild.........I just noticed that the EGR is getting vacuum from the plenum rather than under the TB........Hmmmm wouldn't that keep the EGR valve open during Idle? or does it need a signal from the ecu also?
Re: New 383 surging and then dies (lead foot 85 vet)
While I'm not a mechanic or even the least bit knowledgeable about these things, I thought I might share my 2 cents worth...
When my motor was professionally rebuilt, my mechanic told me not to race until after a "break-in" period, he also said it will take a little bit of time for the computer to "learn" or "re-learn" the fuel curves, ratios etc. I find that after every time I have had my battery disconected for any amount of time - the motor idles rough or stalls... but this only lasts a little while and always returns back to normal after normal driving. My thoughts would be just try driving it around for a little while, and see if the problem doesn't correct itself - that certainly would be a "cheap fix". I was just wondering if all of you "technical" people just over-looked a simple thing like that...
Check out the link in my signature and check out my 87 L98 N20 motor.
Good Luck with your project, hope you figure it out!
latest checks
disconnected maf..no change
drilled 7/32 hole in tb blade...no change(except I now have a hole in tb)
sprayed intake with ether.... no change
its got to be the bigger injectors, but why would that cause it to hunt, it should just be rich..........the only change that the conputer is seeing from the original motor is super ram, cam, and injectors. it doesn't have as much vacuum as it did, about 10 at Idle. Im running out of Ideas...Im getting the harness to install the accel computer but thats going to be another bag of worms.
Re: New 383 surging and then dies (lead foot 85 vet)
Installed the accel dfi.........problem solved
I still have a stumble at 1200 to 1500 rpm but after that hang on buddy this suckers a monster............now to learn tunning with this ecu...read read read.........Im happy now
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New 383 surging and then dies
