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383 Tbi probs *new problem*

yeah, what gauge are you using? My Summit gauge said I had 9 lbs but I put my snap-on tester on there and it was way higher!
 
Are you serious? That was a joke correct? 200 big ones for a guage? No thanks, but thanks.

I now have a problem with the TBI surging when it gets warm. I have all new sensors, except IAC and TPS which came on the used holley TB (except EGR which I had programmed out of the sytem), and I have the timing set at 10 degrees. Runs like a champ when its cold, but when it warms up, its like its trying to find a place to idle. It almost dies, revs up a bit, then does it again. When its warm and I give it gas, its stumbles or backfires then revs up.
 
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You friggin asked for a 30 lb'er, there it is... I didn't even look at a price... That is pretty nuts, but hey it's what you asked for... Next time I wont bother looking..... :mad:
 
Apparently 15's (which is what I run on my hood in Pro Comp form) are a standard gauge price of $30 to 50, but that extra 15lbs requires a gold-plated doohickey raising the price to $200... :wink1: :haha:


uh, wait, I figured it out I think.. Those are $200 because they are electric, thus needing the isolator, hence the big bucks..

Apparently the only one over 15 lbs in mechanical is the 100 lb Pro Comp at $50... not bad....

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neverendingproject said:
Are you serious? That was a joke correct? 200 big ones for a guage? No thanks, but thanks.

I now have a problem with the TBI surging when it gets warm. I have all new sensors, except IAC and TPS which came on the used holley TB (except EGR which I had programmed out of the sytem), and I have the timing set at 10 degrees. Runs like a champ when its cold, but when it warms up, its like its trying to find a place to idle. It almost dies, revs up a bit, then does it again. When its warm and I give it gas, its stumbles or backfires then revs up.
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Summit does have some cheap in-lines that I have always found close enough to diagnose a fuel presure problem, then just leave it in-line under the hood, you can run a longer line outside the hood to watch while you drive but don't run a fuel line inside the passenger compartment! There are electronic gauges for that, they have no fuel running inside just electronic signal.

Ramping idle like you have is almost always a vacuum leak. Just takes a small one to throw off EFI.
 
eagle mark said:
Ramping idle like you have is almost always a vacuum leak. Just takes a small one to throw off EFI.
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Thank you! I will look for the leak when I get back to the truck.

As far a guages go, I wanted a guage that will show me rough pressure, it doesnt have to be exact, but FPR is set to the max, which shoudl be running around 20psi and my 383 is running rich. (Leaving black marks on the wall and water/soot coming out the pipe) My guage says 7psi, so I know its way off, but I dont want to burn up my motor by running it too rich. When the truck runs cold, my A/F guage says im running just lean (im thinking ~14.3 but it does go up higher ~16 or more when it warms). I guess I would have to hook up ALDL to get a good reading.

Eagle mark. If I set the pressure lower, will the TBI adjust injector width to compensate for the lower pressure?
 
neverendingproject said:
Eagle mark. If I set the pressure lower, will the TBI adjust injector width to compensate for the lower pressure?
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The TBI won't adjust it just does what you tell it to. If you are up around 20 PSI I think you said, that is a huge increase over the stock about 13 psi. But without a gauge on there we are just guessing? I would get it back to 13 ish and record some data. Most guys run a vacuum regulator so they have 13 at idle and driving around but when you mash on the skinny pedal the vacuum drops and the regulator will raise pressure when needed.

And depends on what injectors are in your Holley TBI unit, usually they are to big to begin with, add to that more pressure and you'll be washing your cylinders with gas right into your oil...

Set the timing back to 0 with the wire disconnected, check for vacuum leaks which I would bet on, get pressure to 13 and record some data.

Cam specs @.050 ?

Have you checked for codes?
 
Its a 383 vortec with GMPP 383HT cam, im not sure of the specs, but I was told to run over 15psi at least with the 383 as it needs more fuel. I dont think I can get a vaccum FPR on the holley unit, as its not the same as stock. I know its running around 20psi cause thats the pump I have in there, and the FPR is at max. I have the delphi injectors and not holley ones, so im not worried about the pressure. Right now im not throwing any codes.

Edit: I just noticed I have the shortest scentences I could give. Efficient I guess.
 
Is this a new engine? Just wondering if it ran fine then started having problems. Or if you have been having problems with it all along.
If you dont have any vaccum leaks. You may need a new chip burned for your engine. The stock chip will barely handle a 383 Ht cam specs. Then throwing a big holley TB on to add more air flow changes things even more. 383 Hts are designed to be ran with a carb Your low RPM Vaccum may be to low. Many times a bad idle is a symptom of your chip not being up to the job. Uping the FP is really not the best way to tune a modified TBI engine. The proper chip tuned for your application is the best way to go
There are a number of chip burners that make chips for TBI that work good with the 383HT.
 
Yes, I spent the money and had the chip burned. I dont event think it would run on a stock system.

Edit: It seemed to run good one time, then I started messing with odds and ends in the enigne bay, so Im thinking the vacuum is the culprit
 
I think the problem might be the 383HT cam. I was looking at getting this motor for my truck and I believe the Lobe seperation on the cam is to small therefore not building enough vacuum to let the TBI run properly. I want to say that cam is only 108 deg and TBI needs 112 to 114 to run properly.

Ira
 
Well, they guy I had burn the chip has burned several with this cam and he is respectable, but I thought that the 383 cam was supposed to build good vacuum throughout the range.
 
I was told by turbocity that a 383ht cam would work fine for a modified tbi setup.
 
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