My vette has a dead spot in the throttle. It doesn't do it all the time, and seems to only do it in closed loop. I don't recall it doing it when the car is cold, and it doesn't do it at WOT. It also doesn't do it at light throttle. But... when I accelerate between around 1/4 to 3/4 throttle, the car bogs hard, sometimes goes as far as to sputter. Keep your foot in the same spot, and eventually it'll recover and accerate normally. Or if you floor it, it'll accelerate normally.

My first thought was the TPS, but my scan tool shows that it's working fine. There doesn't seem to be anything else out of the ordinary on my scan tool either.

I'm kind of at a loss here. I'm thinking that maybe it's the o2 sensor. Anybody have any opinions or advice here?

 

O2 sensor, injector with a bad spray pattern, plug wire with high impedance....

 

I've got the same problem but mine doesn't sound as bad as yours..I'm starting think it might be the egr,or a leaky injector..The search goes on..

 

I have a similar problem that just started recently. Only occasionally on light acceleration the car will almost stall for a split second as if the fuel or spark was cut then it will surge real quickly and run fine. For the first time today it did it for almost five full seconds under moderate acceleration. I hit about 30MPH in 1st and all of a sudden it felt like I took my foot of the gas and started to coast. 5 seconds later it started running again (before I came to a stop). I hope it's not my fuel pump going out

 

I thought about the possiblity of an injector problem (It seems common on the 91 L98s). I'm just not sure why that would only show up at part throttle, and not at lower & higher throttle... same with the plug wire. I've had plug wire issues and generally they have not been RPM dependant, although I suppose anything is possible.

 

Sounds like a spark plug or two may be fouled. Some brands of gasoline can leave deposits on the plugs that on cause problems under certain load conditions.

 

Sound like EGR to me.

 

DannyT - Take a look at your pick up module and your rotor button. I had the same problem and thats what it turned out to be the pick up module and the ECM ground wire from the distributer was completely corroded away.

 

Thanks for the tip
err..rotor button? What's that?

 

?

 

Sometimes us southern folk call things different names. My bad. I just meant the rotor...

 

How do I check this without ripping the plenum & runners out to get to the EGR valve?

 

With a vacuum pump (mityvac) and an inspection mirror. and bright flashlight (minimag).

 

Yeah, thats about the only way to check it. *** forbid you have to replace it, you have to take off everything to get to that back bolt on the valve. A huge PITA.

 

Actually... I can get my EGR valve on and off just by pulling the plenum. I bent up a cheap 10mm wrench in a vice a number of years ago when I had to remove the EGR valve from my IROC. It's always nice to have a set of cheap tools around for when you need to "modify" one.

 

Just curious how an EGR could cause this trouble?
When I reinstalled my SuperRam I forgot to reconnect the vacuum hose that connects to the EGR valve. The trouble I'm having is intermittent but could that be the cause of it? It did not start immediately after the install and has only done it about 4 times since.

 

I simply removed the vac line going to the EGR. Once I did that, it ran perfectly fine with no sputtering or dead spots.

 

Jim85IROC - Yeah, iw would be nice to have some tools that fit where you needed them too. Not a bad idea though, I've got a bunch of old Wal-Mart tolls laying around, maybe I ought to "fashion" some custom tools.

DannyT - There's a way to explain it, but I'm not the guy for that. I've been battling my EGR for months now and I can;t get it straight. It seems every car has different problems and different remedies for the EGR system. I've had friends with problems just like mine and what works for them made mine worse and vice-versa...best of luck..lol.

 

I did the same as Steve... I unplugged the vacuum line from the EGR valve and plugged it. It seemed to fix my problem. Next time I need to take the plenum off for whatever reason, I'll either clean or replace the EGR valve, but until then I'll just leave it unplugged. We'll see if I throw a code when I hit the highway next week!

 

Hmm, I thnk I'll try that too..couldn;t hurt.