98blacknchrome

Hello,

I have an 87 Iroc-z with a 305 tpi and a 5 speed. In just about any gear if there is no load on the motor and I am just trying to cruise near 2k rpm, there is a stumble. The needle dances down to 1600 rpm and flashes the shift light even in 5th. If im cruising in 5th at 2k rmp and 65 mph it will start to miss/stumble but if i get into it and go 75 at 2600 rpm it will never miss/stumble. If I give it a bit more gas it goes right away.


The car starts, idles , and for the most part runs and drives excellent when Im into it a little bit.

Found alot on low rpm stumble with ls1s but not too much for tpi, If i missed it I am sorry Im new here. Any help is appreciated.

mstacy1

I found this post from a year ago but it is exactly the same condition I'm experiencing with my 91 305 tpi. Anyone else have this issue. 98blacknchrome.......did you get this resolved? Thanks!

PDX88IROC

Are you getting any SES (check engine light) indicators/codes? My '88 with 305 tpi was having a similar issue and would intermittently give codes 33 and/or 34 which are MAF hi/low codes. So I changed both the MAF relays and the codes went away for a while, but 34 came back so had to change the MAF and all has been good since. Also, one time (on my way to band camp) my alternator's connector was bad and was not receiving the voltage from the starter solenoid to the field and the battery was not charging. When the cooling fans kicked on the volt meter started dropping faster that my gas gauge normally does and I could hear my fuel pump slowing down (yes I can hear my fuel pump but thats another story) and it started acting like it was running out of gas or "stumbling". So of course I started pumping on the gas and managed to rev it up and it started charging! Hmmm? It seems that the alternator will "self activate" at over 2500 rpms! So the point of that story is how are your volts too?

mstacy1

I pulled the TB and cleaned the IAC which was not seating well and also cleaned the throttle plates and blew out the bleed holes. Made a big difference in part throttle smoothness and idle quality. Not getting any codes but it still takes a few seconds to idle down when the clutch is in at a stop.