Stalls and Bucks

[dckingan]

Okay Tom,

Have added the MAP and MAP hose to my "to do list." Hopefully have good news to report mid-May.

Thanks for all your help,
Dennis

[XfireZ51]

Couple of things:

1. How long has it been since fuel filter replaced?
2. Check TPS voltage at ignition ON.

[secondchance]

Originally Posted by tomtom72

Dennis, no problem. If you get a chance look at the hose that connects the MAP sensor to it's vacuum source at the rear of the plenum. Something is giving the ECM fits and I suspect it is an "input" signal.

Okay, humor me and my 1/2 a$$ed mechanical non-existent diagnostic skills! LOL I'm thinking that some blow by oil got from the plenum into the MAP hose, or the hose is collapsing under high vacuum conditions ( like closed throttle coast down?). Look to see liquid oil in hose or even getting up into the sensor itself. Or that the hose has become soft from oil and is collapsing under high vacuum. Either one would throw off the Hg reading to the ECM and proly mess up the fueling? Does she do this miss thing at WOT way up in the 6k rpm range also? Okay this is the only other off the wall thing I can think to write down here. Otherwise, yea the TPS voltage and look to see that the TPS voltage is responding from 0% to full wot. Yes to the IAC, and I have to vote maybe on fuel pump performance, but check the pressure regulator hose for gas.

See you in the spring, unless I figure something out that is worth while typing here!


Tom

Symptom being described sounds very similar to what I had experienced 2 years ago.
MAP sensor hose between the sensor and the back of the plenum is a hard plastic piece w/ rubber fitting at both ends. Mine were replaced with a soft hose. With age this hose got softer and at high vacuum during decelleration the hose would collapse cutting off vacuum reading for the MAP sensor. Trying to accelerate at certain condition would make the car buck.
Check and make sure you have a hard plastic hose.

[XfireZ51]

Originally Posted by secondchance

...Trying to accelerate at certain condition would make the car buck.
...

Sounds like fuel pump starvation to me. Check sock filter on pump(s)

[tomtom72]

Originally Posted by XfireZ51

Couple of things:

1. How long has it been since fuel filter replaced?
2. Check TPS voltage at ignition ON.

No problem Dennis! You're welcome. Listen to what Dominic ( XfireZ51 ) and Yun ( secondchance ) said also as these guys have forgotten more than I know!

I have a bad habit of projecting my P/M program onto every "help, having issues" thread I answer so I leave a lot of stuff out of my responses because those things are parts I consider 'consumables' and get r&r'ed every yr on my Z. My bad!


Tom

[dckingan]

Tom, Dominic and Yun,

Hey Guys, hate to admit it but when Tom mentioned the MAP hose it struck a nerve. When I bought the car and was battling high idle I replaced all the vacuum hoses and in stalled clamps. Yes, the MAP hose was replaced with rubber hose because the rubber fittings on the ends of the hard plastic tube were deterioated and falling off. So I did the exactly the wrong thing as confirmed by Yun. I ordered a new correct hose from White Racing Products (not inexpensive). Can't wait to get that hose on and if it's not the final answer will proceed next to fuel starvation. I did change the fuel filter a couple years ago. With your guys help I will have the beast running like it should.

Thanks,
Dennis

[dckingan]

Hi Tom, Dominic and Yun,

You guys are awsome. With all the warm weather in the Buffalo area I couldn't wait until I got back from Florida to install the new MAP pipe. Guess what, it was the dreaded MAP vaccum hose that I incorrectly installed just as Yun said and Tom suspected. Wow, the Z is now a pleasure to drive without the threat of an idle stall and accelerates smoothly in any gear with no bucking. I will also check out the fuel pumps and codes when I get back home. I can't thank you guys enough. Stay tuned you are now my go to guys for any future problems.

Dennis

[tomtom72]

drinking to the return of Permagrin!

[secondchance]

Originally Posted by dckingan

Hi Tom, Dominic and Yun,

You guys are awsome. With all the warm weather in the Buffalo area I couldn't wait until I got back from Florida to install the new MAP pipe. Guess what, it was the dreaded MAP vaccum hose that I incorrectly installed just as Yun said and Tom suspected. Wow, the Z is now a pleasure to drive without the threat of an idle stall and accelerates smoothly in any gear with no bucking. I will also check out the fuel pumps and codes when I get back home. I can't thank you guys enough. Stay tuned you are now my go to guys for any future problems.

Dennis

Great! Now instead of dishing out $39.50, I went to Advance Auto Parts, bought a hard plastic hose (1/4" or 3/16") and a piece of corresponding rubber hose for connections. At the joint between the rubber hose (used as fittings) and hard plastic a dab of crazy glue to keep them together and you have a cheap MAP hose!