More ZR-woes... - ZR-1 Net Registry Forums

N8nSM · 03-06-2006

Well I got her back together last Friday afternoon after replacing the fuel pump (and fuse that blew) the fuel pressure regulator, and the battery. I drove it to the gas station and then back to work. When I left the gas station I felt a slight stumble in it at low RPM's but nothing major. So slight that I was wondering if I imagined it.

So after work on Friday I go to take her home and it starts missing and backfiring as I leave the driveway. Turned her around and brought her back to my work parking lot. I had too much to do this weekend to deal with it so I got back in it this afternoon.

What I have now is a misfire in low rpms (below 2000) only when I try to give it gas. It idles fine but give it a little gas and it starts missing. I'm thinking I may have clogged the fuel filter from when I ran the tank dry (and fried the fuel pump) but I'm not sure.

Any ideas where to start? I'm going to double check the fuse for the fuel pump to make sure I didn't blow that again. It's got 60K on the clock and the original plug wires. They look good but I'm probably going to change them out anyway. I'm not looking forward to taking the plenum off again... ARGH...

Thanks all,

-Nate

03-06-2006

Didn't you say you had the injector cleaner? I can't remember from the other threads.

Jim Jones · 03-06-2006

I had a stumble like that and I ended up replacing all the injectors, the coil packs, spark plugs, and plug wires. I just got her back together this weekend and it runs great. Don't know if this will help, but my problem was similar. My Z is also 1990 and has about 60k on the clock. Good Luck!!

Jim

Aurora40 · 03-06-2006

Just wondering, you changed the fuel pumps, the pressure regulator, but not the $5 filter? I'd change that if I were you, even if it's not the problem. It's cheap and easy.

How old are the plugs and wires? My car had 21k on it and it greatly smoothed out from changing them, and from changing the PCV valves (to my surprise).

I'd just say do the maintenance/tune-up stuff first since that ought to be done anyway, and then take it from there if it didn't help anything.

tomtom72 · 03-07-2006

Hi Nate,

Please don't take this the wrong way. You did check the screen on the fuel pick-up, it's not clogged? The MAP hose is on?
I apologize for the Q's!

I would do the F/Filter.

Could be a fluke failure of plug wire(s) &/or coil(s) &/or spark plug(s). Bad injectors seem remote to me, either shorted or leaking you would smell that.

Tom

N8nSM · 03-07-2006

I ran out of time to get to the filter while it was at the school. They were pressed for space so I was going to change out the filter last weekend at home.

63k on the original plug wires. I don't know if the plugs have been changed or not but I think you are all right. Time to do a tune up of this thing. New plugs, wires, fuel filter. I have access to an OHM meter at the school and I'll check the injectors. (GOD I HOPE IT ISN'T INJECTORS!!). I changed the PCV valves before I brought it home and had a couple injectors swapped out. I also noticed yesterday that my ECM has a remanufactured sticker on it. Must have been replaced at some point in time. Suprise! Original owner neglected to mention that.

Anyway, thanks for the advice all. Time to get to work on it...

Thanks,

-Nate

tomtom72 · 03-08-2006

Hi Nate,

Okay it's time to get the Helms Manual set for your 90...trust me they are the ones you need! The link is at the netregistry site, in the maintenance section. I think it's Helminc.com.

In the mean time I would suggest a minor parts swap out. Plugs, F/Filter, PCV's, A/Filter. The next thing I would do is a scan of the motor, KOEO to see any codes. Then start the motor and scan the "open loop" data and then watch the data in "closed loop" operation. The scan data will give you a direction to look in or it may tell you out right what's wrong.

The ECM may have been replaced because some one "guessed" wrong, possibly. I know that when my OEM injectors shorted the first "guess" diagnosis was "maybe the ECM quit". I will not say by whom, no one here, let's just say by a few "Techs". A scan of the motor in "closed loop" gave data that if read correctly leads you to the fuel injectors if you know how to read the data. The Helms manual has a page of what the data from a good system should look like & you take it from there.

Tom

N8nSM · 03-08-2006

Thank you all. I have the Helms manual on the way. I'll keep you posted.

-Nate

03-06-2006	#1
N8nSM Join Date: Feb 2006 Location: Santa Maria, CA Posts: 20	More ZR-woes... Well I got her back together last Friday afternoon after replacing the fuel pump (and fuse that blew) the fuel pressure regulator, and the battery. I drove it to the gas station and then back to work. When I left the gas station I felt a slight stumble in it at low RPM's but nothing major. So slight that I was wondering if I imagined it. So after work on Friday I go to take her home and it starts missing and backfiring as I leave the driveway. Turned her around and brought her back to my work parking lot. I had too much to do this weekend to deal with it so I got back in it this afternoon. What I have now is a misfire in low rpms (below 2000) only when I try to give it gas. It idles fine but give it a little gas and it starts missing. I'm thinking I may have clogged the fuel filter from when I ran the tank dry (and fried the fuel pump) but I'm not sure. Any ideas where to start? I'm going to double check the fuse for the fuel pump to make sure I didn't blow that again. It's got 60K on the clock and the original plug wires. They look good but I'm probably going to change them out anyway. I'm not looking forward to taking the plenum off again... ARGH... Thanks all, -Nate __________________ [FONT=Tahoma][COLOR=blue][B]Nate[/B][/COLOR][/FONT] [FONT=Tahoma][COLOR=blue][B]Santa Maria, CA[/B][/COLOR][/FONT] [FONT=Tahoma][COLOR=blue][B]1990 ZR-1 #224[/B][/COLOR][/FONT]

03-06-2006	#2
Jeffvette Guest Posts: n/a	Re: More ZR-woes... Didn't you say you had the injector cleaner? I can't remember from the other threads.

03-06-2006	#3
Jim Jones Join Date: Apr 2005 Location: I'm in a constant state of euphoria in the Z! Posts: 237	Re: More ZR-woes... I had a stumble like that and I ended up replacing all the injectors, the coil packs, spark plugs, and plug wires. I just got her back together this weekend and it runs great. Don't know if this will help, but my problem was similar. My Z is also 1990 and has about 60k on the clock. Good Luck!! Jim __________________ Life's too short to be unhappy! [IMG]http://i4.photobucket.com/albums/y128/koolaid117/Montage.gif[/IMG] Last edited by Jim Jones; 03-06-2006 at 09:26 PM.

03-06-2006	#4
Aurora40 Join Date: May 2005 Location: Leesburg, VA Posts: 2,713	Re: More ZR-woes... Just wondering, you changed the fuel pumps, the pressure regulator, but not the $5 filter? I'd change that if I were you, even if it's not the problem. It's cheap and easy. How old are the plugs and wires? My car had 21k on it and it greatly smoothed out from changing them, and from changing the PCV valves (to my surprise). I'd just say do the maintenance/tune-up stuff first since that ought to be done anyway, and then take it from there if it didn't help anything. __________________ Bob Saveland Former owner of #2517 [IMG]http://a.random-image.net/aurora40/vette.jpg[/img]

03-07-2006	#5
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,645	Re: More ZR-woes... Hi Nate, Please don't take this the wrong way. You did check the screen on the fuel pick-up, it's not clogged? The MAP hose is on? I apologize for the Q's! I would do the F/Filter. Could be a fluke failure of plug wire(s) &/or coil(s) &/or spark plug(s). Bad injectors seem remote to me, either shorted or leaking you would smell that. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member

03-07-2006	#6
N8nSM Join Date: Feb 2006 Location: Santa Maria, CA Posts: 20	Re: More ZR-woes... I ran out of time to get to the filter while it was at the school. They were pressed for space so I was going to change out the filter last weekend at home. 63k on the original plug wires. I don't know if the plugs have been changed or not but I think you are all right. Time to do a tune up of this thing. New plugs, wires, fuel filter. I have access to an OHM meter at the school and I'll check the injectors. (GOD I HOPE IT ISN'T INJECTORS!!). I changed the PCV valves before I brought it home and had a couple injectors swapped out. I also noticed yesterday that my ECM has a remanufactured sticker on it. Must have been replaced at some point in time. Suprise! Original owner neglected to mention that. Anyway, thanks for the advice all. Time to get to work on it... Thanks, -Nate __________________ [FONT=Tahoma][COLOR=blue][B]Nate[/B][/COLOR][/FONT] [FONT=Tahoma][COLOR=blue][B]Santa Maria, CA[/B][/COLOR][/FONT] [FONT=Tahoma][COLOR=blue][B]1990 ZR-1 #224[/B][/COLOR][/FONT]

03-08-2006	#7
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,645	Re: More ZR-woes... Hi Nate, Okay it's time to get the Helms Manual set for your 90...trust me they are the ones you need! The link is at the netregistry site, in the maintenance section. I think it's Helminc.com. In the mean time I would suggest a minor parts swap out. Plugs, F/Filter, PCV's, A/Filter. The next thing I would do is a scan of the motor, KOEO to see any codes. Then start the motor and scan the "open loop" data and then watch the data in "closed loop" operation. The scan data will give you a direction to look in or it may tell you out right what's wrong. The ECM may have been replaced because some one "guessed" wrong, possibly. I know that when my OEM injectors shorted the first "guess" diagnosis was "maybe the ECM quit". I will not say by whom, no one here, let's just say by a few "Techs". A scan of the motor in "closed loop" gave data that if read correctly leads you to the fuel injectors if you know how to read the data. The Helms manual has a page of what the data from a good system should look like & you take it from there. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member

03-08-2006	#8
N8nSM Join Date: Feb 2006 Location: Santa Maria, CA Posts: 20	Re: More ZR-woes... Thank you all. I have the Helms manual on the way. I'll keep you posted. -Nate __________________ [FONT=Tahoma][COLOR=blue][B]Nate[/B][/COLOR][/FONT] [FONT=Tahoma][COLOR=blue][B]Santa Maria, CA[/B][/COLOR][/FONT] [FONT=Tahoma][COLOR=blue][B]1990 ZR-1 #224[/B][/COLOR][/FONT]