92 Caprice L05 Hesitating.

305 TBI has a weird hesitation at light throttle along with a lack of power. For those of you who have driven carb equipped cars this has all the earmarks of a bad accelerator pump.
Car has 340k miles on it, but runs like a top except for this.
Idles super smooth.
Cap and rotor changed. Fuel filter changed. MAP sensor swapped with a known good one. Throttle body cleaned out. No obvious vaccuum leaks. Temp heater door on air cleaner is fine. O2 sensor replaced last year. Jumpering the EDL connector while driving shows it going nicely from lean to rich (when I nail the throttle) and it is obviously in closed loop.
It's really weird, if you step down lightly on the throttle it will hesitate, and cut out a little bit but not all the time. If you press further down it will run fine except on the hiway it feels "spongy" and sluggish. It's like there are sags in the acceleration or somthing.
I am thinking Cat convertor clogged? It's the original. Plugs/wires? Not that old. Knock sensor hosed causing timing to not increase correctly?
Any ideas?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
__________________________________________
"Sean" wrote:
305 TBI hesitates at light throttle similar to bad accelerator pump in carb-equipped car.
Idles super smooth. MAP sensor swapped with a known good one. No obvious vacuum leaks. Goes nicely from lean to rich when I nail the throttle. Cat convertor clogged? It's the original. Plugs/wires? Not that old. Knock sensor bad?
Any ideas?
__________________________________________
These are guesses of some items to investigate:
1.) Throttle position sensor worn/erratic near idle position. 2.) Idle Air Control actuator slow to respond or sticking. 3.) MAP sensor slow to respond. 4.) EGR valve defective.
Can't think of more. Good luck.
Wendy & John. ___________________________________________
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 26 Aug 2004 00:11:18 +0000, Wendy & John wrote:

Thanks Wendy and John! I'm looking into those things today and will post back the results!
Sean
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Thu, 26 Aug 2004 00:11:18 +0000, Wendy & John wrote:

I put new plugs and wires in and it didn't improve anything, but left me with a lot of scraped hands which is normal for working on this beast! GNM has a
You nailed it with #4....
I put a vacuum pump on the EGR valve and the diaphragm was leaking like a seive. It wouldn't hold any vaccum at all.
IOW I had a good old fashioned vaccuum leak!
Fortunately the pintel is seated down correctly (hence the stable idle) so I was able to disconnect and plug the hose until I get a new valve.
Thanks for your advice! Sean
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Be careful you do not get mislead on the EGR valve's not holding a vacuum. Some of these things need exhaust pressure to seat an internal port before they will hold vacuum.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.