DallasZR-1
03-10-2022, 06:10 PM
I ran this by Marc but I don't want to keep monopolizing his time.
[I've got a '94 ZR-1 that recently started acting up. When I first bought it about 5 years ago it had some stumbling and stalling issues that were sorted out by replacing the spark plugs. Since then it's run wonderfully until very recently. About thirty minutes into a drive in temperate conditions, (maybe 60 degrees out) it suddenly started exhibiting very disconcerting, lurching losses of power. All gauges were normal. No engine lights. I couldn't figure out exactly what would cause the lurches. It would happen when I accelerated from low rpms at highway speed. It would happen at high rpms. I tried leaving the car in uncomfortably low gears at highway speed, keeping the rpms relatively high. I tried just cruising at a normal rpm with no acceleration and the stumble would happen then too. The occasional and seemingly unpredictable power losses would still happen no matter the driving condition. It felt like half a stall and very frightening at highway speed. I tried power key both on and off. It happened in both conditions. I've felt something similar briefly once before when I'm pretty sure the A/C system was malfunctioning and the belt was dragging (saw smoke that time and it was clearly associated with turning the a/c on. It never happened like that again.) This same power loss happened with a/c on and with the a/c system off. It also started stalling when idling. It's never had this problem before.]
After I emailed Marc the above in brackets, I took a look under the hood again and realized the airduct had slipped off by just a little bit. Putting it back in place and tightening it fixed almost all the issues except that engine would still stumble if I tried to accelerate from low RPMs (often right about 1750rpms in first or second.) It idled fine. The stumbling wasn't nearly as dramatic and the car was driveable.
I figured the air duct had become weak and was collapsing so I replaced it with a silicone one from Jerry's Gaskets. Drove it for thirty minutes and she was an absolute monster. Didn't seem to matter how I put the gas down she pulled hard. I parked it for about 10 minutes, got back in, and the stumbling returned. It seems to happen reliably around 1500-2000 RPMs primarily when accelerating in first or second. It's a sudden dramatic loss of power which can usually be overcome by giving it a TON of gas. It's driveable, but unnerving.
Any thoughts? Marc suggested the MAP sensor before I discovered the air duct issue. Thanks in advance to this incredible community.
[I've got a '94 ZR-1 that recently started acting up. When I first bought it about 5 years ago it had some stumbling and stalling issues that were sorted out by replacing the spark plugs. Since then it's run wonderfully until very recently. About thirty minutes into a drive in temperate conditions, (maybe 60 degrees out) it suddenly started exhibiting very disconcerting, lurching losses of power. All gauges were normal. No engine lights. I couldn't figure out exactly what would cause the lurches. It would happen when I accelerated from low rpms at highway speed. It would happen at high rpms. I tried leaving the car in uncomfortably low gears at highway speed, keeping the rpms relatively high. I tried just cruising at a normal rpm with no acceleration and the stumble would happen then too. The occasional and seemingly unpredictable power losses would still happen no matter the driving condition. It felt like half a stall and very frightening at highway speed. I tried power key both on and off. It happened in both conditions. I've felt something similar briefly once before when I'm pretty sure the A/C system was malfunctioning and the belt was dragging (saw smoke that time and it was clearly associated with turning the a/c on. It never happened like that again.) This same power loss happened with a/c on and with the a/c system off. It also started stalling when idling. It's never had this problem before.]
After I emailed Marc the above in brackets, I took a look under the hood again and realized the airduct had slipped off by just a little bit. Putting it back in place and tightening it fixed almost all the issues except that engine would still stumble if I tried to accelerate from low RPMs (often right about 1750rpms in first or second.) It idled fine. The stumbling wasn't nearly as dramatic and the car was driveable.
I figured the air duct had become weak and was collapsing so I replaced it with a silicone one from Jerry's Gaskets. Drove it for thirty minutes and she was an absolute monster. Didn't seem to matter how I put the gas down she pulled hard. I parked it for about 10 minutes, got back in, and the stumbling returned. It seems to happen reliably around 1500-2000 RPMs primarily when accelerating in first or second. It's a sudden dramatic loss of power which can usually be overcome by giving it a TON of gas. It's driveable, but unnerving.
Any thoughts? Marc suggested the MAP sensor before I discovered the air duct issue. Thanks in advance to this incredible community.