New TPS = No Start

[v8zcar]

My TB blades were sticking so I dis-assembled and cleaned and then re-installed. My TPS got fried during this process so I replaced it.

Readings are:
.48V@TPS 11%
4.89V@TPS83%
Changed the idle parameter settings for Max TPS at Idle to "12"

Can't get the car to start, opening the TB while cranking doesn't help and it backfires out the intake. Does this mean I need more
cranking fuel?

Thanks,
Owen

 

[KECHME]

I wonder if your IAC could be stuck , and thus causing it to be too rich to fire up. Just a suggestion, but maybe a possibility.

 

[bobc455]

Did you change the resting position of the blades? In other words, is the engine getting more air during cranking than it used to? Or, maybe it is getting less air since the blades aren't sticking?

What did your TPS used to read at idle?

-Bob Cunningham
bobc@gnttype.org

 

[v8zcar]

The TPS used to read 16, I don't know if the IAC is sticking. Can I just remove it from the TB and watch it move when I crank the engine?

I don't think I have a rich condition either, since I have tried holding open the TB blades while cranking as well. The blades weren't adjusted, but it seems to me that manually holding open
the blades negates that - I mean - IF the blades were adjusted closed, holding open the TB plates SHOULD get the engine started, right?

I'm gonna try more fuel tonight after I check the plugs, it was too late at night to do anymore last night.

Thanks,
Owen

 

[Craig Smith]

I can't imagine why it would start backfiring unless something got changed with the timing. Did the distributor get removed?

 

[v8zcar]

Nope, nothing else changed, that's what's got me confused...

Owen

 

[v8zcar]

MAP sensor wasn't working, unplugged it and plugged it back in and the car starts. Idle is too high though. Here's some details:

Idle
TPS = 11 = TB fully closed
IAC green line set to 10, blue line hovers there (Throttle Follower)
IAC target reads 10
Idle = 1040 or so

The IAC motor appears to be working.
I plug the IAC hole with my finger and the blue line moves to 180
Idle = 700 - 850 (where I want it)
Remove my finger and the blue line drops back to 10 (sometimes)

If I rev the engine, then the blue line drops to 10
Idle back to 1040

At IAC 10, there is the most suction at the IAC hole. When I plug it, at IAC 180 and the engine sometimes holds there, there is
virtually no suction. Currently the Idle Parameters is set at P=45 and D=9, changing these numbers doesn't do anything for me.

Is the IAC motor is wired right? 10 is max open (most suction) and 180 is min (least suction) open. Is the IAC supposed to be open more at lower RPMs?

And the TB blades still stick

Oh yeah, tried the instructions on this page,
http://www.turbobuick.com/forums/showthread.php?s=&threadid=62304
but increasing the TB opening only causes the engine to idle faster. Maybe I need a new IAC too...?
Owen

 

[bobc455]

IAC motor - 10 should be fully closed (minium suction), 180 should be wide open (most suction). Time for a wiring check...

I used to have a Holley TB that would stick, only solution was to deep-6 it and buy a better designed TB.

-Bob Cunningham
bobc@gnttype.org

 

[Craig Smith]

If it idles too high and the target IAC position is at 10, the blades need to be closed, not opened.

Close them down until the target is 25 or so. As Bob said, 10 is minimum open, 180 is max.

 

[Tony sy2356]

How is the IAC wired. I ran into a similar problem, turns out the GM wiring diagram I used was backwards compared to the way the iac worked. Reversed the wires and it worked fine.


Tony

 

[v8zcar]

Yeah, I saw another post on this when I did a search. Well, I switched the A Hi and A Lo but no dice. So I switched this, switched that...and finally got it to work!

In the end I had to switch the B Hi and B Lo wires. So what my
configuration ended up as is:

94 Z28 IAC
Pin - FAST wire color
A - Red (A Hi)
B - Blue (A Lo)
C - Black (Blo)
D - Yellow (B Hi)

Now I've got the minimal suction at IAC Target = 10 and it increases as the throttle blades open. Plus I can here the IAC closing as the target returns back to the closed position.

One thing, I wasn't able to do this until I also slotted the TPS mounting holes to get TPS=11 (.51V). This gave me the coveted IAC Target = 25 or so.

Thanks to everyone for their help! Sigh of relief...although the
TB blades are STILL sticking...I put on a different return spring (not the stock coiled up one mounted on the side of the LT1 style TBs) and it works so far. Still want to get it the way it's supposed to be though.

Owen