1990 exhaust manifold issue... - ZR-1 Net Registry Forums

bdw18_123 · 09-23-2011

Ok, guys, got a bit of an issue here. Kinda kickin myself in the azz for not catching this before reassembly, but what is done is done.

My Z had been driving great, but after a couple high speed runs, started getting a check engine light. The first time it came on, it took awhile for it to come on again the next time I drove it. But then after several more drives, it pretty much started coming on within 5 minutes or so of turning the car off, then on again to get the light to go out. If I disconnect the battery long enough, it takes awhile for the light to come on again on subsequent drives, presumably because doing that wipes the learning that the ECM recorded. Also, after the light comes on several times, I notice that the instant fuel mileage is worse than before the light comes on. I happened to be under the car and I noticed that the passenger side cat rings like a bell when hit with a wrench. Driver's side doesn't do that, is a dull thud sound. Obviously, the substrate is gone on the passenger side. Dammit!!

After pulling the codes several times, I keep getting codes 44 (left oxygen sensor circuit - lean exhaust indicated) and 55 (fuel lean monitor), which seems a bit odd since it's the right side that has the substrate missing. I figure these codes are most likely the result of having substrate in one cat and none in the other causing an imbalance, especially at higher rpm's. This is also most likely why the mileage starts to suffer, since the ECM is probably trying to compensate for the lean condition.

Being that the going rate for a full set of stock exhaust manifolds is around $300-$400 (depending on mileage), it doesn't make sense to get those. I can't afford it anyway. However, if I went with the $450 OBX headers (from what some here have reported, quality is pretty good for the price), I'd most likely have to change my whole exhaust system (putting headers with stock exhaust doesn't make sense either) and I REALLY can't afford that. I'm in Cali, so those are illegal anyway.

Question - Will it damage my engine to drive it like this? Since as I said, I can't afford $300+ for stock manifolds or the headers, but I want be able to drive the damn thing, I worked on it for over 2 years.

What say the ZR-1 experts?

09-23-2011	#1
bdw18_123 Join Date: Apr 2009 Location: Prather, CA Posts: 809	1990 exhaust manifold issue... Ok, guys, got a bit of an issue here. Kinda kickin myself in the azz for not catching this before reassembly, but what is done is done. My Z had been driving great, but after a couple high speed runs, started getting a check engine light. The first time it came on, it took awhile for it to come on again the next time I drove it. But then after several more drives, it pretty much started coming on within 5 minutes or so of turning the car off, then on again to get the light to go out. If I disconnect the battery long enough, it takes awhile for the light to come on again on subsequent drives, presumably because doing that wipes the learning that the ECM recorded. Also, after the light comes on several times, I notice that the instant fuel mileage is worse than before the light comes on. I happened to be under the car and I noticed that the passenger side cat rings like a bell when hit with a wrench. Driver's side doesn't do that, is a dull thud sound. Obviously, the substrate is gone on the passenger side. Dammit!! After pulling the codes several times, I keep getting codes 44 (left oxygen sensor circuit - lean exhaust indicated) and 55 (fuel lean monitor), which seems a bit odd since it's the right side that has the substrate missing. I figure these codes are most likely the result of having substrate in one cat and none in the other causing an imbalance, especially at higher rpm's. This is also most likely why the mileage starts to suffer, since the ECM is probably trying to compensate for the lean condition. Being that the going rate for a full set of stock exhaust manifolds is around $300-$400 (depending on mileage), it doesn't make sense to get those. I can't afford it anyway. However, if I went with the $450 OBX headers (from what some here have reported, quality is pretty good for the price), I'd most likely have to change my whole exhaust system (putting headers with stock exhaust doesn't make sense either) and I REALLY can't afford that. I'm in Cali, so those are illegal anyway. Question - Will it damage my engine to drive it like this? Since as I said, I can't afford $300+ for stock manifolds or the headers, but I want be able to drive the damn thing, I worked on it for over 2 years. What say the ZR-1 experts? __________________ [IMG]http://i13.photobucket.com/albums/a292/bdw18_123/_zr1netforumsigphoto.jpg[/IMG][B] 1990 Corvette ZR-1 [/B][I] White/Flame Red, #2299, mostly stock, 144K miles.[/I] -Cams timed to the '93-'95 405HP LT5 stock timing. -IAT sensor relocated to below front bumper. -Haibeck hoops installed in airduct. -OBX cat-back exhaust. [COLOR=DarkRed][B](SOLD - December 2012 [/B][/COLOR][COLOR=DarkRed][B]:hello:)[/B][/COLOR] 1993 Corvette Coupe Black/Black, 6-speed (SOLD - October 2009 :hello:) Last edited by bdw18_123; 09-23-2011 at 02:06 AM.