strange surge

[mgbrv8]

When coasting fron 30mph to around 5mph in neutral either with clutch in or out the engine surges until you slow to around 5mph and then it smooths out. Now i just replaced all the injectors with new delphis, rebuild the entire secondary vacum system, replaced the map sensor and anything else I could think of under the plenum. Now the car did this before I did all the work but it was more prone to dieing when it was surging and the surging was more erratic then. Dose anyone have any idea what it might be.

Here is the video of the surge

https://www.facebook.com/photo.php?v=10201831228569270&l=8320842547347021421

And here are the pictures of all the work I have done so far

https://www.facebook.com/media/set/?set=a.10201021415884459.2217036.1439230280&type=1&l=bf12a0aa41

Dave

[mgbrv8]

I was thinking new O2 sensors maybe??

Dave

[-=Jeff=-]

What PROM (MEMCAL) is in the the car?

[mgbrv8]

What ever came from the factory.

Dave

[-=Jeff=-]

I think it was an issue in the OEM memcal and there was an updated MEMCAL to fix that specific issue

[Hammer]

It's not the chip. The engine would idle high for a bit and then settle down to normal, not surge like your's is doing. The later chip fixed that and Haibeck's chip does too. Call Corey or Marc and run it by them unless someone else has a fix, I don't.

TPS maybe??

[scottfab]

Surges? Try simple stuff first.
Clean the IAC and the pathway into and out of it on the TB.

[mgbrv8]

I dissasembled and cleaned the throttle body completely and the IAC. now I did order a new IAC and o2s it's on it's way we will see what that dose. Oh one thing this car has headers and O2 extensions


Dave

Surges? Try simple stuff first.
Clean the IAC and the pathway into and out of it on the TB.

[tf95ZR1]

I dissasembled and cleaned the throttle body completely
Dave

I remember reading that many people un-knowingly clean off some goop
from the throttle body butterfly shafts. This is supposed to be there (Dap?)
as a vacuum seal, else a leak.

[-=Jeff=-]

It's not the chip. The engine would idle high for a bit and then settle down to normal, not surge like your's is doing. The later chip fixed that and Haibeck's chip does too. Call Corey or Marc and run it by them unless someone else has a fix, I don't.

TPS maybe??



thanks I could not remember what issue the chip fixed.. that is why I stated I Think.. since I was not sure

[mgbrv8]

I did clean the throttle body Thoroughly but the thing that bothers me is that it did this before I did anything in fact it was worst.

Dave

[XfireZ51]

Did you remove TB when you cleaned it? If you have a scantool, check the TPS v
with Ignition ON. Surging of the LT-5 is common when idling down in neutral and slowing down. This can be mitigated by flattening the Spark and VE tables in the
"Idling zone". I also change the IAC setting so the idle stays a bit high until it reaches Idle MPH. First thing is to determine there are no technical issues. I would look at the IAC counts at idle. Maybe MIN AIR needs adjusting.

[Dynomite]

It's not the chip. The engine would idle high for a bit and then settle down to normal, not surge like your's is doing. The later chip fixed that and Haibeck's chip does too. Call Corey or Marc and run it by them unless someone else has a fix, I don't.

TPS maybe??

Exactly as my 90' functions...I kind of liked that as it would idle high for a bit (about 5 - 10 seconds) right after starting and then settle right down to 750 more or less. Same when letting off throttle in neutral. It would take a few seconds to settle down to normal idle :thumbsup:

But Marc sent me a new 90' chip so I expect now a normal and immediate idle under all conditions :p

[mgbrv8]

Yes I did.

Dave

Did you remove TB when you cleaned it? If you have a scantool, check the TPS v
with Ignition ON. Surging of the LT-5 is common when idling down in neutral and slowing down. This can be mitigated by flattening the Spark and VE tables in the
"Idling zone". I also change the IAC setting so the idle stays a bit high until it reaches Idle MPH. First thing is to determine there are no technical issues. I would look at the IAC counts at idle. Maybe MIN AIR needs adjusting.