If I rev the car up freely or under a load, I still get the same weird stumble at like 4700 rpms. It will go past it just fine, but when you hit that range the car stumbles hard.

Any ideas? Buddy of mine was thinking TPS sensor could be bad and giving false information about where the throttle is at and at that range is telling it the throttle is closed or something.

I am going to put a datalogger and a snap on scanner on it tomorrow to see if there is anything funny there.

Any ideas of what it could be or what to look for?

-James

Mods in sig (now with t56)

 

Could be a problem with your fuel pressure due to fuel pump. For example, your fuel is rated in pressure level, not volume. If the volume is inadequate, when you use more throttle it could be using most of the volume available causing a fuel pressure drop. Try putting a fuel pressure gauge on it and drive it around to see if you notice any slight-heavy drops in fuel pressure.

Hope you figure it out... I bet your engine builder is curious to see what it will do after the problem is corrected.

Lots of luck,
Brian

 

worst case...

bad optical section of the Opti-crap... this is what finally failed in mine when it first went; a little bit of rust develops in that section, and can sometimes clog/get in the way of the "holey" disc... thus causing a stumble...

 

Is it a "stumble", or is it one big "misfire" that feels like someone cut the fuel off for a second.... sort of like the stock rev limiter?

 

This is what I have, and can't figure out; the misfire where the whole thing shuts down for a second or so..

 

Unfortunately, this is not the first post I have seen complaining about this problem with the Delteq. Many years ago, I was running a setup called the Electromotive SDI/Opti-Eliminator on my LT1.... another setup using the 4-coil waste spark setup. As good as the system was, it had the problem of a sudden, random hiccup that actually shut the injectors off for an instant, feeling just like a rev limiter. I was never able to get any help from Electromotive, even though I had one of their first systems, and was providing them with photos and other info. I believe that the same person who worked on the SDI/O-E at E'motive is now involved with the Delteq stuff..... similarities? Who knows?

 

ehh...this is giving me some bad thoughts of putting on my delteq when it comes in

 

I am getting bad vibes about the Delteq too

 

I don't have the Delteq yet, I'm hoping it will solve this issue actually...

 

Same thing i'm hoping it will solve. If not then back to the drawing board.

 

A) Check spark plugs - no matter how 'new' they are, you want to be sure they're in there and they're tight - check the tips etc.

B) Check plug wires ******AND SPARK PLUG BOOTS****** plug wiring on LT1's is bad no matter what kind of headers/manifolds you have.

C) Check fuel pressure

D) Check various sensors (TPS, MAF, MAP, IAC ETC) get the codes scanned if necessary.


I have a delteq - I've had missing occur at a variety of RPM'S but i ABSOLUTELY make sure everything is seated/screwed in/plugged in properly before I do anything else. At very worst you'll just send the opti-box back to Delteq and get a core exchange