RPM's fall

[Eric Stauch]

Hey guys got another problem, my 87 GN is mainly stock other than upgraded turbo and fuel pump ect. but what im concerned about is when driving right before it shifts in to the next gear especially overdrive if you let off the gas before it goes into the next gear the rpms fall fast! it drops so low the power steering gets hard for a second and the lights dim cause how low the engines running, but it immediately recovers and runs great. anyone else run into this?

 

[WSLN 6]

Sounds maybe like MAF dropout? What chip are your running?

 

[Eric Stauch]

stock chip stock MAF. got a new turbo tweak chip on the way just aint got it in yet and i have and LS1 maf but waiting on a translator

 

[johnnyttype]

could the TCC solenoid be sticking? locked converter + stock chip lock up of 35-40mph i think + overdrive = very low RPM's ? maybe, just throwin somethin out there! never experienced MAF dropout so dont know what thats like.

 

[Eric Stauch]

bare with me on tranny stuff. TCC solenoid? what and where?

 

[WSLN 6]

Look under the car on the drivers side and unplu the 4 wire plug on the side of the tranny close to the shift linkage. This will control lockup for your torque converter. Go for a drive and report back....

 

[Eric Stauch]

will do thanks for all the help guys!

 

[87TIGN]

Im sorry I really dont mean to threadjack here but I have may have an issue like this. My plug (for the tranny) is not hooked up its just hangin out in the engine bay and I just noticed this. It was like this when I bought the car I assume cause I sure didnt do it. Why would someone unplug this? What am I missing out on if it is unplugged? I just put in a 3000 stall would I benefit from it being plugged in. Thanks and sorry again I really dont mean to threadjack
-Andrew

 

[Eric Stauch]

unpluged it, didnt help. didnt change anything. what is that plug?

 

[WSLN 6]

Allows the ecm to control torque converter lockup as well as tell the ecm when the tranny is in 3rd or 4th gear.

 

[shook0002]

I had this same problem on my stock t, turbo tweak chip solved it.

 

[Eric Stauch]

ok so since i unpluged it and it didnt change anything does that mean its not working? tweak chip solved yours? i got one on the way i will see if that fixes her. thanks for all the help guys

 

[bmackinnon]

Eric,
not an expert, but to chime in here, do you have a higher than stock stall converter?? With a loose converter, when you let off the gas suddenly, the engine likes to try and stall... especially with the stock chip. Sounds like that's whats happening to you. If it doesn't stall, then it should recover, like it apparently is. Turbotweak's chip can address that, but he needs to know. TCC = torque converter clutch. If you have a high stall stall converter, it may be the non-locking type... thus, no difference when you unplug the connector (except the ecm doesn't know what gear u'r in, which it DOES like to know). Surely we can figure this out.... hey, where in Bama are you?? Guntersville here...
Brian

 

[Eric Stauch]

stock converter. but has been replaced. maybe they gave me the wrong one? im in Hartselle bout 15min south of decatur and bout 40min south of huntsville. let me know if you ever come my way we can unite the buicks and cruise haha

 

[Luke]

MAF / BLMs???

I had similar problems back when I had the stock 200-4R and converter but it wasn't due to the transmission\converter. It was due mostly to my kenne bell chip and a poor setup from the previous owner.

1.) I had the same problem when I let off the gas the RPMs dropped between 200 and 400 RPM and almost stalled out. (It actually DID stall out on two occasions) It'd usually sounded something like this:

rrrrrrrrr grug grug grrRRRrrrrrrr (Please mind the extremely advanced and technical description)

I got an extender chip from fullthrottlespeed.com that happened to fix this. I bought it because I didn't think it was burnt to match the 42.5lbs injectors and because the Kenne Bell was giving my 30 degrees of false KR even after dropping the boost to 10 and increasing the fuel to 50 psi. The extender chip only gives me a few degrees of KR on a shift.

2.) When I accelerated hard from an idle the engine would stumble then take off like a bat out of hell. It would do this so consistently I used open the exhaust cutout right after the stumble... This would give the other car just enough time to think "that old granny regal is just as beat as it looks" (it’s a rough looking turbo-T). The look on people’s faces was priceless as it began to spin the tires as I blew past them... I actually miss doing that. Later I found out that the cause was my ported LS1 MAF. It gave me high BLMs. I swapped it out with a standard LS1 MAF and never had the problem again.

If you can rule out your transmission/converter, make sure you have a decent chip that compliments your setup. I'd get a hold of a scanmaster and calibrate the TPS, IAC, check BLMs, and see if your MAF is bad.

I hope this helps
Good luck

 

[Eric Stauch]

yea thats what mine sounds like! ok so maybe the chip? its the stock one right now but i got a new turbo tweak one sitting here beside me but i had it made for 42 inj's and i've only got stock ones right now but as soon as i get those i will try them both and see if that cures her, also new LS1 MAF but have yet to get a translator so hopefully one out of all of those things will fix it. thanks everyone for all the great information! i will let you all know what happens with the new parts.