Some driveability issues. - ZR-1 Net Registry Forums

VetteMed · 08-08-2011

I've been driving the Z a lot these past 2 weeks (just about to roll over 191K miles), and I've noticed some consistent issues, I'm hoping someone may have some idea of where to start looking.

My daily commute has been about 2 hours each way for the last 2 weeks -- when I get about 45-50 minutes in to the trip, the idle begins to hunt up and down, by 200-300 rpm. It acts like a vacuum leak, but I'd expect a vacuum leak to be worse when cold, and improve when warm, as the metal parts expand.

Another issue I've noticed, and this also seems to not be an issue until the engine is fully warmed up, 40-50 minutes in to the trip, is that I get a bog / hesitation when rolling on to the throttle in a corner. Gentle sweeping turns in the road are not an issue, but an actual corner, taken at 20-30 mph, while in gear (usually 3rd or 4th), results in a complete loss of engine power, a bogging/hestitation sensation. As soon as I straighten out after the corner, power returns to normal and it runs fine.

Background info:
1991, 191K miles
Mostly stock, except for Jeal Headers, no cats, FIC injectors, secondary throttle plates removed, Haibeck PROM, 93-95 Injector housings.
Power seems to be excellent, fuel mileage as well (21-23 mpg).

Thanks,
Andrew

lbszr · 08-08-2011

For the power loss in turns, could connect a fuel pressure guage and see if it drops off in the turns to see if there's an issure in the tank. There's a sump in the bottom of the tank to prevent fuel starvation.

Sounds like you need to detune it anyway, since the cops are eyeballing you

VetteMed · 08-08-2011

Quote:

Originally Posted by lbszr

For the power loss in turns, could connect a fuel pressure guage and see if it drops off in the turns to see if there's an issure in the tank. There's a sump in the bottom of the tank to prevent fuel starvation.

Sounds like you need to detune it anyway, since the cops are eyeballing you

I thought of the fuel pump issue too, but this has been happening even on a tank that's close to full, so starvation seems impossible in my mind. I don't know if my fuel pressure gauge can reach to the windshield while connected.. but I'll give it a try.

You're probably right on the cop issue

XfireZ51 · 08-08-2011

Quote:

Originally Posted by VetteMed

I thought of the fuel pump issue too, but this has been happening even on a tank that's close to full, so starvation seems impossible in my mind. I don't know if my fuel pressure gauge can reach to the windshield while connected.. but I'll give it a try.

You're probably right on the cop issue

You are starving fuel because of filter. Likely the sock filter on the pumps.

VetteMed · 08-08-2011

Quote:

Originally Posted by XfireZ51

You are starving fuel because of filter. Likely the sock filter on the pumps.

Why is it only appearing on turns? If there's enough fuel in the tank for the pumps to be completely submerged, why would it have good performance in s a straight line? I certainly don't mind pulling the pumps and inspecting/replacing the strainers, but it just seems odd.

XfireZ51 · 08-08-2011

The filter socks are what control the amount of fuel surrounding the fuel pump inlet. If the sock is clogged it let's in only
so much fuel at any time. In a turn the fuel may slosh to one side of the sock because there may not be enough to
completely fill the sock.

VetteMed · 08-08-2011

Quote:

Originally Posted by XfireZ51

The filter socks are what control the amount of fuel surrounding the fuel pump inlet. If the sock is clogged it let's in only
so much fuel at any time. In a turn the fuel may slosh to one side of the sock because there may not be enough to
completely fill the sock.

good enough for me.... I'll pull the pumps this weekend and swap out the strainers. Thanks Dom for the input.

Andrew

GOLDCYLON · 08-09-2011

Late to the party but Fuel pump would be my guess as well Andrew assuming you replaced the fuel filter as well. Not just the sock but the one on the rail side near the passenger door as well. Glad to hear about the fuel mileage im pulling the secondairies and blades as well. GC

VetteMed · 08-13-2011

Pulled the fuel pumps out today, and changed the strainers. There was honestly no sign of anything wrong with the ones that were on there.

VetteMed · 08-14-2011

I checked for codes this morning, had a stored low TPS code (22), I checked the voltage at closed throttle, it's within spec (0.53v), so I'm going to replace the TPS and see if that improves the driveability issue.

08-08-2011	#1
VetteMed Join Date: Mar 2009 Location: Orlando, FL Posts: 1,828	Some driveability issues. I've been driving the Z a lot these past 2 weeks (just about to roll over 191K miles), and I've noticed some consistent issues, I'm hoping someone may have some idea of where to start looking. My daily commute has been about 2 hours each way for the last 2 weeks -- when I get about 45-50 minutes in to the trip, the idle begins to hunt up and down, by 200-300 rpm. It acts like a vacuum leak, but I'd expect a vacuum leak to be worse when cold, and improve when warm, as the metal parts expand. Another issue I've noticed, and this also seems to not be an issue until the engine is fully warmed up, 40-50 minutes in to the trip, is that I get a bog / hesitation when rolling on to the throttle in a corner. Gentle sweeping turns in the road are not an issue, but an actual corner, taken at 20-30 mph, while in gear (usually 3rd or 4th), results in a complete loss of engine power, a bogging/hestitation sensation. As soon as I straighten out after the corner, power returns to normal and it runs fine. Background info: 1991, 191K miles Mostly stock, except for Jeal Headers, no cats, FIC injectors, secondary throttle plates removed, Haibeck PROM, 93-95 Injector housings. Power seems to be excellent, fuel mileage as well (21-23 mpg). Thanks, Andrew __________________ 2004 Z06/Z16 LeMans Commemorative Edition 1991 ZR-1 #302 White/Gray (sold) 1991 ZR-1 #1147 Red/Saddle (sold)

08-08-2011	#2
lbszr Join Date: Nov 2006 Location: dayton,ohio Posts: 425	Re: Some driveability issues. For the power loss in turns, could connect a fuel pressure guage and see if it drops off in the turns to see if there's an issure in the tank. There's a sump in the bottom of the tank to prevent fuel starvation. Sounds like you need to detune it anyway, since the cops are eyeballing you __________________ [FONT=Comic Sans MS][COLOR=red]"I wanna go fast!!"[/COLOR][/FONT] [FONT=Comic Sans MS][COLOR=#ff0000]-- Ricky Bobby[/COLOR][/FONT]

08-08-2011	#6
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,708	Re: Some driveability issues. The filter socks are what control the amount of fuel surrounding the fuel pump inlet. If the sock is clogged it let's in only so much fuel at any time. In a turn the fuel may slosh to one side of the sock because there may not be enough to completely fill the sock.

08-09-2011	#8
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,155	Re: Some driveability issues. Late to the party but Fuel pump would be my guess as well Andrew assuming you replaced the fuel filter as well. Not just the sock but the one on the rail side near the passenger door as well. Glad to hear about the fuel mileage im pulling the secondairies and blades as well. GC __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V Last edited by GOLDCYLON; 08-09-2011 at 10:23 AM.

08-13-2011	#9
VetteMed Join Date: Mar 2009 Location: Orlando, FL Posts: 1,828	Re: Some driveability issues. Pulled the fuel pumps out today, and changed the strainers. There was honestly no sign of anything wrong with the ones that were on there. __________________ 2004 Z06/Z16 LeMans Commemorative Edition 1991 ZR-1 #302 White/Gray (sold) 1991 ZR-1 #1147 Red/Saddle (sold)

08-14-2011	#10
VetteMed Join Date: Mar 2009 Location: Orlando, FL Posts: 1,828	Re: Some driveability issues. I checked for codes this morning, had a stored low TPS code (22), I checked the voltage at closed throttle, it's within spec (0.53v), so I'm going to replace the TPS and see if that improves the driveability issue. __________________ 2004 Z06/Z16 LeMans Commemorative Edition 1991 ZR-1 #302 White/Gray (sold) 1991 ZR-1 #1147 Red/Saddle (sold)

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