Catalytic converters? - ZR-1 Net Registry Forums

fletchusmc · 12-26-2014

Been enjoying my ZR-1 and driving as often as I can, but now having some running issues.

1995, stock with Corsa catback, Screamin Demon coils, and Livewires spark plug wires. 68,xxx miles.

Drove it to work Friday morning, seemed fine. About a 50 mile commute one way. Left work to come home and started running a little rough, loss of power, no difference with power key on or off. Felt like maybe some bad gas. Drove it a lot over the weekend to burn off some fuel. Put in a can of Seafoam and filled up with fresh gas. Drove it to work Monday and same thing. Tuesday morning was the same thing but coming home Tuesday it got worse. Didn't want to hardly rev. Idle so bad at stop light that dual mass was making noises.

Pulled plugs, all looked the same and replaced about 8,000 miles ago.
Checked ohms through wires and coils:
1-6 9.03k
2-3 9.3k
4-7 9.07k
5-8 9.00k

Didn't drive it the rest of the week. Saturday took it out a bit and not as bad, felt like something "freed up" a bit like it could breath easier. Rev'd easier, idle not as bad, still not perfect and still low on power. Got on it and got a exhaust smell, took a lot longer to get up in RPM's but it would.

Decided to go ahead and pull the converters to check them out as it seemed like an easy thing to do. After being under there maybe not so much. Looks like possibly 3 bolts won't be so bad but one doesn't seem to have any room at all.

So, does it sound like I'm on the right track or should I be focusing elsewhere? Can't see any messed up vacuum lines, don't hear any vacuum leaks. MAP and fuel pressure regulator lines are good. Went ahead and replaced fuel filter as well and no change.

dredgeguy · 12-26-2014

Have you changed out the injectors? Your issues are very similar to what I had when I purchased the car. Changing to stainless steel injectors took care of it. Found out 7 were bad and lucky I made it from CT to MD. You might also change the fuel filter.
Good luck and keep us posted.

dredgeguy · 12-26-2014

Sorry, you took care of the fuel filter..........now if the injectors are stock, you know where the problem is.

We Gone · 12-26-2014

Did you check the fuel pressure?

fletchusmc · 12-26-2014

Thought about fuel pressure, will go pick up a gage tomorrow and check that. I know injectors were a common problem on the earlier ZR-1's, but didn't think the later ones really had any problems with injectors?

fletchusmc · 12-28-2014

Got in the garage this morning and this is where I'm at.

Fuel pressure, cold, key on engine off 48 psi.
Idle 44 psi, stayed there as it warmed up.
Remove regulator vacuum line 53 psi.
2000 RPM 43 psi.

After shut down stayed at 48 for 10 minutes, disconnected pressure gage after that.

Took some catalytic temp readings

Driver's side
Front of cat 380F
Rear of cat 650F

Passenger side
Front 350F
Rear 460

Still making me think a problem with the cats. OR is it running way too rich on the driver's side and causing the cat to work harder and causing the higher temps?

A26B · 12-28-2014

I think you need to isolate the primary fuel pump by removing the fuse for the secondary fuel pump. The cold readings you observed would be the results for both primary & secondary pumps operating together.

The secondary pump will shut down after coolant temp reaches about 170F ( I forgot the actual number). You did state "stayed there as it warmed up." but actual temp is unknown so the secondary pump may still have been running.

Good news is there is not a significant injector leak.

I have no input on the converter temp, just the fuel pressure test.

I'm sure you will get it resolved.

Marc Haibeck · 12-30-2014

If it is still idling poorly I would approach it from that angle. It's easy to work with in the garage. You have good fuel pressure at idle. A clogged catalyst usually won't effect the idle. The faces of the catalyst substrates can be viewed through the oxygen sensor hole.

Do a spark test. The spark should be at least 1/4" long, blue and make a nice snapping sound.

fletchusmc · 12-31-2014

I appreciate the help so far. Life, work, and the holidays have kept me out of the garage lately. However, the Marine Corps is sending my girlfriend on an expense paid trip to Quantico for a week so I'm looking forward to plenty of garage time and will keep all of you up to speed on what I'm finding out.

8cam · 12-31-2014

Check the simple things first. With it idling, start pulling plug wires. If you find one where the idle doesn't change, you found your culprit. Check the spark on each plug wire too, but if you have a bad coil or wire it should be pretty obvious as soon as you pull the wire. I've read about Screamin Demon coils failing, and going suddenly.

12-26-2014	#1
fletchusmc Join Date: Nov 2013 Location: Jacksonville, NC Posts: 48	Catalytic converters? Been enjoying my ZR-1 and driving as often as I can, but now having some running issues. 1995, stock with Corsa catback, Screamin Demon coils, and Livewires spark plug wires. 68,xxx miles. Drove it to work Friday morning, seemed fine. About a 50 mile commute one way. Left work to come home and started running a little rough, loss of power, no difference with power key on or off. Felt like maybe some bad gas. Drove it a lot over the weekend to burn off some fuel. Put in a can of Seafoam and filled up with fresh gas. Drove it to work Monday and same thing. Tuesday morning was the same thing but coming home Tuesday it got worse. Didn't want to hardly rev. Idle so bad at stop light that dual mass was making noises. Pulled plugs, all looked the same and replaced about 8,000 miles ago. Checked ohms through wires and coils: 1-6 9.03k 2-3 9.3k 4-7 9.07k 5-8 9.00k Didn't drive it the rest of the week. Saturday took it out a bit and not as bad, felt like something "freed up" a bit like it could breath easier. Rev'd easier, idle not as bad, still not perfect and still low on power. Got on it and got a exhaust smell, took a lot longer to get up in RPM's but it would. Decided to go ahead and pull the converters to check them out as it seemed like an easy thing to do. After being under there maybe not so much. Looks like possibly 3 bolts won't be so bad but one doesn't seem to have any room at all. So, does it sound like I'm on the right track or should I be focusing elsewhere? Can't see any messed up vacuum lines, don't hear any vacuum leaks. MAP and fuel pressure regulator lines are good. Went ahead and replaced fuel filter as well and no change.

12-26-2014	#2
dredgeguy Join Date: Aug 2012 Location: Ellicott City, MD Posts: 1,719	Re: Catalytic converters? Have you changed out the injectors? Your issues are very similar to what I had when I purchased the car. Changing to stainless steel injectors took care of it. Found out 7 were bad and lucky I made it from CT to MD. You might also change the fuel filter. Good luck and keep us posted. __________________ Charlie __________ Dredgeguy WAZOO Member 1992 Bright Red/Black ZR1 #246 Dana 4:10 gears Polished LT5 by Haibeck Polished Fikse FM5's with Michelin Pilot Sport 2 Stainless Works headers and cats with Corsa

12-26-2014	#3
dredgeguy Join Date: Aug 2012 Location: Ellicott City, MD Posts: 1,719	Re: Catalytic converters? Sorry, you took care of the fuel filter..........now if the injectors are stock, you know where the problem is. __________________ Charlie __________ Dredgeguy WAZOO Member 1992 Bright Red/Black ZR1 #246 Dana 4:10 gears Polished LT5 by Haibeck Polished Fikse FM5's with Michelin Pilot Sport 2 Stainless Works headers and cats with Corsa

12-26-2014	#4
We Gone Join Date: Apr 2004 Location: Atlanta, GA Posts: 2,170	Re: Catalytic converters? Did you check the fuel pressure? __________________ Steve 1990 Steel Blue/Black #2355 1990 Red/Red #1473 1991 Quasar /Black #118 Sold 1991 Turquoise/Black #766 Parted Out 1993 Yellow/White #179 Sold 1990 Black/Gray #1361 Headers/4:10s Sold

12-26-2014	#5
fletchusmc Join Date: Nov 2013 Location: Jacksonville, NC Posts: 48	Re: Catalytic converters? Thought about fuel pressure, will go pick up a gage tomorrow and check that. I know injectors were a common problem on the earlier ZR-1's, but didn't think the later ones really had any problems with injectors?

12-28-2014	#6
fletchusmc Join Date: Nov 2013 Location: Jacksonville, NC Posts: 48	Re: Catalytic converters? Got in the garage this morning and this is where I'm at. Fuel pressure, cold, key on engine off 48 psi. Idle 44 psi, stayed there as it warmed up. Remove regulator vacuum line 53 psi. 2000 RPM 43 psi. After shut down stayed at 48 for 10 minutes, disconnected pressure gage after that. Took some catalytic temp readings Driver's side Front of cat 380F Rear of cat 650F Passenger side Front 350F Rear 460 Still making me think a problem with the cats. OR is it running way too rich on the driver's side and causing the cat to work harder and causing the higher temps? Last edited by fletchusmc; 12-28-2014 at 09:51 AM. Reason: Added last sentence

12-28-2014	#7
A26B Join Date: Dec 2003 Location: Arcadia, OK Posts: 3,400	Re: Catalytic converters? I think you need to isolate the primary fuel pump by removing the fuse for the secondary fuel pump. The cold readings you observed would be the results for both primary & secondary pumps operating together. The secondary pump will shut down after coolant temp reaches about 170F ( I forgot the actual number). You did state "stayed there as it warmed up." but actual temp is unknown so the secondary pump may still have been running. Good news is there is not a significant injector leak. I have no input on the converter temp, just the fuel pressure test. I'm sure you will get it resolved. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1*, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed.

12-30-2014	#8
Marc Haibeck Join Date: May 2007 Location: Addison IL Posts: 253	Re: Catalytic converters? If it is still idling poorly I would approach it from that angle. It's easy to work with in the garage. You have good fuel pressure at idle. A clogged catalyst usually won't effect the idle. The faces of the catalyst substrates can be viewed through the oxygen sensor hole. Do a spark test. The spark should be at least 1/4" long, blue and make a nice snapping sound.

12-31-2014	#9
fletchusmc Join Date: Nov 2013 Location: Jacksonville, NC Posts: 48	Re: Catalytic converters? I appreciate the help so far. Life, work, and the holidays have kept me out of the garage lately. However, the Marine Corps is sending my girlfriend on an expense paid trip to Quantico for a week so I'm looking forward to plenty of garage time and will keep all of you up to speed on what I'm finding out.

12-31-2014	#10
8cam Join Date: Jul 2013 Location: Atlanta Posts: 450	Re: Catalytic converters? Check the simple things first. With it idling, start pulling plug wires. If you find one where the idle doesn't change, you found your culprit. Check the spark on each plug wire too, but if you have a bad coil or wire it should be pretty obvious as soon as you pull the wire. I've read about Screamin Demon coils failing, and going suddenly.