Could you help narrow this down???
Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Could you help narrow this down???
I have a engine miss when Im just cruising, not when Im accelerating. If I accelerate it runs smoothly, its only when Im either just running along at one speed , letting off the gas slowly,or at idle...I just replaced the egr and the O2 sensor,checked the fuel pressure and checked for vacuam leaks and it still does it..The plugs and wires are only a year old but tomorrow Im changing them hoping that fixes the problem. With it only doing it while going at a steady speed or at idle can you think of any other things it might be? Anything you can suggest as being the cause will be appreciated....WW
Last edited by WW7; Jul 30, 2009 at 06:51 PM.
Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
Had a similar problem on a 89 vert. Miss at cruise, full power at WOT. Had one injector that would not seat properly. Two cans of NAPA injection cleaner through the fuel rails solved the problem. This procedure requires specialized equipment.
Suggest reading the plugs when you remove them, if one or more show signs of running rich you may have a similar problem.
Suggest reading the plugs when you remove them, if one or more show signs of running rich you may have a similar problem.
Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Well I didn't get very many answers to my question but I figured out the problem anyway, (By myself)
..Anyhow I thought I would post what the problem ended up being so it may help someone with similar problems in the future..It turned out to be the coil, the wires in the coil somehow touched and burned each other causing a short that was only present at idle and when cruising, so I guess if you have a miss its a good idea to start at the plugs and work your way up to the distributor.I hooked it up to my Auto Xray 6000 and it showed no problems....WW
..Anyhow I thought I would post what the problem ended up being so it may help someone with similar problems in the future..It turned out to be the coil, the wires in the coil somehow touched and burned each other causing a short that was only present at idle and when cruising, so I guess if you have a miss its a good idea to start at the plugs and work your way up to the distributor.I hooked it up to my Auto Xray 6000 and it showed no problems....WW
Last edited by WW7; Jul 30, 2009 at 07:08 PM.
Racer
Joined: Jul 2005
Posts: 387
Likes: 3
From: Indian Trail, NC
i'm actually having a similar problem. i'm missing and sputtering and stalling at idle, but at WOT, i've got full power for the most part. occasionally under hard acceleration, it suddenly falls on its face and then the SES light comes on. any ideas?
Racer
Joined: Oct 2008
Posts: 299
Likes: 1
From: Ottawa Ontario
That sounds like a bad o2 sensor. I just had nearly the same problem. My understanding is that the o2 sensor isn't in the loop at WOT which is why it runs fine then. I just changed the one on the driver's side since it was giving me erratic and low (4mv) readings when I had a laptop hooked up to the car yesterday.
Racer
Joined: Jul 2005
Posts: 387
Likes: 3
From: Indian Trail, NC
That sounds like a bad o2 sensor. I just had nearly the same problem. My understanding is that the o2 sensor isn't in the loop at WOT which is why it runs fine then. I just changed the one on the driver's side since it was giving me erratic and low (4mv) readings when I had a laptop hooked up to the car yesterday.
and what program are you running with what cable?
Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Actually, I found 2 other problems while looking for the answer to this problem..I found I had a bad EGR, and a bad O2 sensor. Its amazing it was running at all..
...WW
...WW
Last edited by WW7; Jul 31, 2009 at 08:15 AM.
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Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
what's the O2 sensor supposed to read? i never thought about that. i thought it might be electrical or throttle body related. i already pulled the throttle body and cleaned it as well as changing the PCV valve, but to no avail...
and what program are you running with what cable?
and what program are you running with what cable?
Last edited by WW7; Jul 30, 2009 at 08:09 PM.
Racer
Joined: Jul 2005
Posts: 387
Likes: 3
From: Indian Trail, NC
and i didn't mean to hijack your thread... you were just having a similar problem that i am having... thanks!
Last edited by farscape1a; Jul 30, 2009 at 08:08 PM.
Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
No Problem, Yes it will cause it to fail, as a matter of fact most of the guys on here will tell you if you have emissions testing in your state not to delete your EGR. Also the O2 sensor that Tom was talking about can cause it to fail . I replaced my O2 sensor yesterday because I was reading a Lean condition ( Block Learn was at 148 ) and it was dumping a ton of gas into the engine making it run Rich..After the O2 was replaced the Block Learn was down to 128 which is normal. I just noticed you have a 94 vette, I believe you have 2 - O2 sensors in your car....WW
Last edited by WW7; Jul 30, 2009 at 08:28 PM.
Racer
Joined: Jul 2005
Posts: 387
Likes: 3
From: Indian Trail, NC
No Problem, Yes it will cause it to fail, as a matter of fact most of the guys on here will tell you if you have emissions testing in your state not to delete your EGR. Also the O2 sensor that Tom was talking about can cause it to fail . I replaced my O2 sensor yesterday because it was causing a Lean condition ( Block Learn was at 148 ) and it was dumping a ton of gas into the engine making it run Rich..After the O2 was replaced the Block Learn was down to 128 which is normal. I just noticed you have a 94 vette, I believe you have 2 O2 sensors in your car....WW
now what would cause the car to fall on its face under hard acceleration and then cause it to throw a code? i haven't pulled the code yet, so i can't give that info unfortunately...
Racer
Joined: Jul 2005
Posts: 387
Likes: 3
From: Indian Trail, NC
Racer
Joined: Oct 2008
Posts: 299
Likes: 1
From: Ottawa Ontario
Tom, On my scanner it shows the O2 sensor being used at all throttle openings. Farscape,It could be your EGR is stuck or sticking open,this is usually what goes bad on them..This will cause it to run bad at idle and midrange but at WOT the EGR cuts out and isn't used by the ECM...Just a guess....WW
My issue was that the car idled rough, ran rich and stumbled under normal driving but worked fine at WOT. I replaced the fuel filter and pcv valve to no avail. Then saw the weird readings from the driver's side o2 sensor and replaced it and all my issues seem to be resolved.
Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Yep it shows the o2 sensor working at all throttle openings because the o2 sensor never stops working but it's my understanding that it's not in the engine management loop at WOT. Thus you would see it working on any scanner but it's not being read. That's my understanding of it anyways and I could very well be wrong..
You may very well be right, your car is much newer then my 89 and there are many differences in the electrical systems...WW
Racer
Joined: Oct 2008
Posts: 299
Likes: 1
From: Ottawa Ontario
what's the O2 sensor supposed to read? i never thought about that. i thought it might be electrical or throttle body related. i already pulled the throttle body and cleaned it as well as changing the PCV valve, but to no avail...
and what program are you running with what cable?
and what program are you running with what cable?
http://www.ttspowersystems.com/DataMaster.html
and PCMComm from here:
http://carputing.tripod.com/9495LT1Edit.htm
as well as Tunercat from here:
http://www.tunercat.com/
Really for diagnostics PCMComm works perfectly well and is free. I only use Tunercat to reprogram the PCM.
I bought a USB to ALDL cable from somewhere online (I can't remember where) and hook that to the laptop. It's an awesome troubleshooting and diagnostics tool. The cable is only about 60.00 and the software is free so it's great to have. You can also do easy updates like removing the skip shift if you have a manual transmission, remove VATS if you have an issue with it, lower your temp for the fans to kick on, etc.
Thread Starter
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
Racer
Joined: Jul 2005
Posts: 387
Likes: 3
From: Indian Trail, NC
