[AT] Any Chevy TBI experts

[ken knierim]

On Sat, 2005-11-05 at 00:06, Cecil Bearden wrote:
> This is for my tractor hunting vehicle.....
> 
> I have an 89 chevy 4wd 3/4 auto w/ TBI..    at light load, either starting 
> out, or running at 30-40 mph the engine surges.  It drives me nuts.  Has 
> anyone had this problem or knows how to solve it.  I have looked at several 
> statements about this on the internet, and according to what I read, it 
> could be a 2 week chore testing everything that it could be.  I do have a 
> on-board tester for it, but I have never had any codes show up....
> 
> Cecil in OKla 
> 

Try the simple stuff first... cap, rotor, plugs, plug wires... that
seems to fix a lot of things. After that, the next most likely culprit
would be the throttle position sensor... those seem to fix all kinds of
troubles on my '88 Camaro 305 TBI.
    I also had a really freaky one with the electronic spark control on
my '86 Blazer. There was some noise in the driveline that would show up
coming off a light and it would get picked up by the knock sensor,
causing a huge stall and surge as it retarded and advanced the timing.
Replaced the knock sensor, went through about everything, finally ripped
out the knock sensor and went to an old-style distributor (thinking the
noise was rod noise). When I finally tore everything down and separated
the engine from the transmission, I found that the factory hadn't gotten
the flex plate bolts tight. It had come loose and was slotting the holes
in the flex plate. The mechanical noise was getting picked up by the
knock sensor and wreaking havoc on driveability, similar to your
description. It was carbureted but they may be running similar knock
sensors...

Oh, 1986 305 V8, Rochester 4 BBL, TH700R4, K-5 Blazer (4X4).

Ken in AZ