1991 Zr1 bogging/jerking bad under acceleration - ZR-1 Net Registry Forums

Johnny5 · 12-10-2021

I just received my 1991 ZR1 and fuel gauge was at 1/2 tank when shipped, I received it with same mileage but tank read 1 or 2 bars. Also i filled up put seafoam and drove a little but my Range still says 19 miles with a full tank. Is this a sign of bad fuel sender? Also
My car is bogging, jerking very bad.
The injectors were replaced but that is it.
Would stuck fuel sender cause this as well?

If I pull the plenum I will do coil packs, plugs, and wires as well but I want try to diagnose why the car os bogging bad and not getting any power. It does it in full power mode and normal. Vacuum pump seems to stop and not run constant.
Anyone experience this and know where to start without pulling the plenum?

DRM500RUBYZR-1 · 12-10-2021

Normally, I would suggest a test of fuel pressure first, which is still a good idea.
However, based on your statement that the gauge registered half and with no miles added, after delivery it is down to 2 bars, there are two possible explanations.
The car was started and run a lot between those two times. Doubtful.
Or, the more likely answer, while bouncing around in the transport, the sender arm freed itself and dropped to the lower level.
The metal frame of the assembly tends to rust badly over time.
I would investigate this, as it would explain the bad gauge info and would cause contamination of the inlet sock on the pump pickup.
See if you can find out which injectors were installed.
Perhaps they were not replaced, maybe just cleaned and re-installed.
Pre 93 are not alcohol tolerant, so must be replaced at some point.
No matter, start at the source and confirm tank is clean, sock and pumps are good frame and sender are ok.
Change fuel filter, then measure pressure and let us know what you find.

Marty

Johnny5 · 12-10-2021

FIC stainless delphi with jerrys o rings/ gaskets were installed. I have receipts. Thank you for response.

Johnny5 · 12-11-2021

After checking the fuel
Pumps amps thanks to Marcs write up, ohming the spark plug wires to check coil packs, voltage test alternator, vacuum fittings etc. I found the rubber coupling that goes to the map sensor was loose. Once i put a new fitting on it stopped falling on it?s face/or engine dying. At full throttle now the secondaries open and run good but at normal driving/accelerating etc it still
Jerks but not as bad. I will pull the plenum and do a complete tune up along with all
New rubber for the vacuum lines etc. i have a feeling i have another small
Leaks.

A26B · 12-11-2021

Quote:

Originally Posted by Johnny5

After checking the fuel
Pumps amps thanks to Marcs write up, ohming the spark plug wires to check coil packs, voltage test alternator, vacuum fittings etc. I found the rubber coupling that goes to the map sensor was loose. Once i put a new fitting on it stopped falling on it?s face/or engine dying. At full throttle now the secondaries open and run good but at normal driving/accelerating etc it still
Jerks but not as bad. I will pull the plenum and do a complete tune up along with all
New rubber for the vacuum lines etc. i have a feeling i have another small
Leaks.

Check all of your PCV system rubber parts for vacuum leaks while you are at it & the plenum is off.

(1) The Crankcase Ventilation Hoses under the plenum can get as hard as a rock. Mine were so hard, I pulled the aluminum tube completely out of the housing.
https://www.jerrysgaskets.com/hose-s...new-90-95-3b1/

(2) PCV Pipe Elbow Grommets.
https://www.jerrysgaskets.com/gromme...new-90-95-7e3/

(3) Dual PCV Valve Lower Hose & top Connector. Offered as a set for lower cost, if you need both.
My lower hose was rotted on the side facing the engine & hard on the firewall side. So bad it pulled completely in two when I removed it. Top Connector gets soft & no longer seals effectively on PCV Valves.
https://www.jerrysgaskets.com/hose-s...ew-90-95-13d3/

(4) For 1990 Models only, this part typically gets soft, swells & no longer seals effectively. Zip Ties don't work well on oval shaped, dual connectors. Before these were available, the fix was bending the pipes further apart & using 2 pieces of hose. No longer necessary to bend pipes, since this became available.
https://www.jerrysgaskets.com/connec...new-1990-13d4/

Jerrys Gaskets has manufactured all of these parts and are identical to the originals.

Johnny5 · 12-11-2021

Yes thank you. I will give Jerry a call, order a full tune up besides injectors since i have FIC already & get rubber connectors + PCV valve rubbers.

12-10-2021	#1
Johnny5 Join Date: Nov 2014 Location: New Jersey Posts: 363	1991 Zr1 bogging/jerking bad under acceleration I just received my 1991 ZR1 and fuel gauge was at 1/2 tank when shipped, I received it with same mileage but tank read 1 or 2 bars. Also i filled up put seafoam and drove a little but my Range still says 19 miles with a full tank. Is this a sign of bad fuel sender? Also My car is bogging, jerking very bad. The injectors were replaced but that is it. Would stuck fuel sender cause this as well? If I pull the plenum I will do coil packs, plugs, and wires as well but I want try to diagnose why the car os bogging bad and not getting any power. It does it in full power mode and normal. Vacuum pump seems to stop and not run constant. Anyone experience this and know where to start without pulling the plenum?

12-10-2021	#2
DRM500RUBYZR-1 Join Date: Sep 2008 Location: Mullica Hill, New Jersey Posts: 2,593	Re: 1991 Zr1 bogging/jerking bad under acceleration Normally, I would suggest a test of fuel pressure first, which is still a good idea. However, based on your statement that the gauge registered half and with no miles added, after delivery it is down to 2 bars, there are two possible explanations. The car was started and run a lot between those two times. Doubtful. Or, the more likely answer, while bouncing around in the transport, the sender arm freed itself and dropped to the lower level. The metal frame of the assembly tends to rust badly over time. I would investigate this, as it would explain the bad gauge info and would cause contamination of the inlet sock on the pump pickup. See if you can find out which injectors were installed. Perhaps they were not replaced, maybe just cleaned and re-installed. Pre 93 are not alcohol tolerant, so must be replaced at some point. No matter, start at the source and confirm tank is clean, sock and pumps are good frame and sender are ok. Change fuel filter, then measure pressure and let us know what you find. Marty

12-10-2021	#3
Johnny5 Join Date: Nov 2014 Location: New Jersey Posts: 363	Re: 1991 Zr1 bogging/jerking bad under acceleration FIC stainless delphi with jerrys o rings/ gaskets were installed. I have receipts. Thank you for response.

12-11-2021	#4
Johnny5 Join Date: Nov 2014 Location: New Jersey Posts: 363	Re: 1991 Zr1 bogging/jerking bad under acceleration After checking the fuel Pumps amps thanks to Marcs write up, ohming the spark plug wires to check coil packs, voltage test alternator, vacuum fittings etc. I found the rubber coupling that goes to the map sensor was loose. Once i put a new fitting on it stopped falling on it?s face/or engine dying. At full throttle now the secondaries open and run good but at normal driving/accelerating etc it still Jerks but not as bad. I will pull the plenum and do a complete tune up along with all New rubber for the vacuum lines etc. i have a feeling i have another small Leaks.

12-11-2021	#6
Johnny5 Join Date: Nov 2014 Location: New Jersey Posts: 363	Re: 1991 Zr1 bogging/jerking bad under acceleration Yes thank you. I will give Jerry a call, order a full tune up besides injectors since i have FIC already & get rubber connectors + PCV valve rubbers.