Open Loop Lope
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Just basic troubleshooting. When cold, a high idle speed can mask a bad cylinder or two. When the motor is idling at 700 it becomes noticeable. A compression test takes only a few minutes to run and can rule out mechanical issues, of course you knew that.
Last edited by 383vett; Nov 27, 2016 at 02:18 PM.
Thread Starter
Instructor
Joined: Feb 2016
Posts: 111
Likes: 10
Hello ddahlgren. Think maybe the Scanner I have is not much different than your ACTRON, problem is mostly that I just don't know how to use it....still studying. I have a CEN-TECH 60693, from Harbor Freight, and it says: OBDII & CAN scan tool, guess you can have it plugged in while you drive.
If I discover it is indeed "rich" in closed loop, how do I change it ??
Racer
Joined: Jan 2012
Posts: 275
Likes: 26
From: Austin TX
I didn't see where you said you have checked fuel pressure. Could be some junk in the pump filter, fuel filter or the return line(96 still return style?). Slow flow on either end if the fuel rails can cause a problem. Also pull the vacuum hose off of your fuel pressure regulator and check for fuel being sucked into the motor that way. The diaphragms have been known to rupture and leak fuel into the engine.
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
Hello ddahlgren. Think maybe the Scanner I have is not much different than your ACTRON, problem is mostly that I just don't know how to use it....still studying. I have a CEN-TECH 60693, from Harbor Freight, and it says: OBDII & CAN scan tool, guess you can have it plugged in while you drive.
If I discover it is indeed "rich" in closed loop, how do I change it ??
If I discover it is indeed "rich" in closed loop, how do I change it ??
Last edited by ddahlgren; Nov 27, 2016 at 08:16 PM.
Thread Starter
Instructor
Joined: Feb 2016
Posts: 111
Likes: 10
I didn't see where you said you have checked fuel pressure. Could be some junk in the pump filter, fuel filter or the return line(96 still return style?). Slow flow on either end if the fuel rails can cause a problem. Also pull the vacuum hose off of your fuel pressure regulator and check for fuel being sucked into the motor that way. The diaphragms have been known to rupture and leak fuel into the engine.
Hi Thurman. Appreciate you responding. The FPR is good, think the previous owner replaced it. Fuel pump and filter good, I replaced them just preventive, changed just about everything, been throwing parts at it for about a year, but even so, have encountered several "new" defective parts. Did change an o2 sensor (upstream bank 2), and seemed to make a difference. The PO, replaced the upstream 02 on bank 1, but who knows, may be bad. Thinking about replacing them all ?? Right now, trying to figure out how to "scan" with the tool that I have. May have to give up and take it to the dealer
Racer
Joined: Jan 2012
Posts: 275
Likes: 26
From: Austin TX
Hi Thurman. Appreciate you responding. The FPR is good, think the previous owner replaced it. Fuel pump and filter good, I replaced them just preventive, changed just about everything, been throwing parts at it for about a year, but even so, have encountered several "new" defective parts. Did change an o2 sensor (upstream bank 2), and seemed to make a difference. The PO, replaced the upstream 02 on bank 1, but who knows, may be bad. Thinking about replacing them all ?? Right now, trying to figure out how to "scan" with the tool that I have. May have to give up and take it to the dealer
I chased a rich condition in an rx7 I had until I found a partial clog in the return line, no one ever thinks to check the return line. Just like your car mine had been sitting for a couple of years before i got it.
Thread Starter
Instructor
Joined: Feb 2016
Posts: 111
Likes: 10
Not sure I understand ? My car is a 96 with LT1 engine, first year of OBD II ?? The scanner I have ( OBD II & CAN Scan Tool) seems to have several capabilities that I really don't know how to interpret, such as : "recording data" "freeze frame", etc. So maybe as I "screw" with it more, I may learn something "diagnostic"
Team Owner
Joined: Jul 2004
Posts: 28,502
Likes: 3,302
From: Hartford WI
What model do you have? IIRC, they bought out Auto X-ray. My old Auto-X-ray works for my 91 but the newer ones seem to have an issue a year or so ago when I borrowed them at O'Riley's and the tech support said my car wasn't supported which is why I can't read the data.
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Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
Not sure I understand ? My car is a 96 with LT1 engine, first year of OBD II ?? The scanner I have ( OBD II & CAN Scan Tool) seems to have several capabilities that I really don't know how to interpret, such as : "recording data" "freeze frame", etc. So maybe as I "screw" with it more, I may learn something "diagnostic"
Thread Starter
Instructor
Joined: Feb 2016
Posts: 111
Likes: 10
But have you checked the actual pressure in the fuel rails? Check both KOEO (key on engine off) pressure and pressure when the engine is idling, open and closed loop, and compare them.
I chased a rich condition in an rx7 I had until I found a partial clog in the return line, no one ever thinks to check the return line. Just like your car mine had been sitting for a couple of years before i got it.
I chased a rich condition in an rx7 I had until I found a partial clog in the return line, no one ever thinks to check the return line. Just like your car mine had been sitting for a couple of years before i got it.
Well, I haven't checked the pressure since I changed the pump and filter. It didn't make any difference in how it ran. Think I will go ahead and borrow the tester from Autozone and check it out. It does have a return line. How did you check your return line for obstruction ? Think I could just hook my airhose to it ??
Racer
Joined: Jan 2012
Posts: 275
Likes: 26
From: Austin TX
Well, I haven't checked the pressure since I changed the pump and filter. It didn't make any difference in how it ran. Think I will go ahead and borrow the tester from Autozone and check it out. It does have a return line. How did you check your return line for obstruction ? Think I could just hook my airhose to it ??
Thread Starter
Instructor
Joined: Feb 2016
Posts: 111
Likes: 10
Hi Dahlgren---appreciate you helping me. I have also been trying to resolve a P1351 code, and replaced my coil and ICM, as well as untaped/seperated wires to the ICM, and seems to run a lot different. Runs good at idle for about 2-3 minutes, then now starts loping. Haven't taken it on the hwy. yet, that might change things. Code P1351 went away. Anyway, got some "live data" on my scanner, loaded software and tried to print, but doesn't work. I wrote down some of the "data" maybe you can tell me what it means ???
Temp: 102
RPM : 752
SHRTFT1 (%) -0.8
LONGFT1 (%) 9.4
SHRTFT2 (%) 0.8
LONGFT2 (%) 11.7
Spark adv. -18.0
O2B1S1(V) 0.225
O2B1S2(V)0.435
O2B2S1(V)0.385
O2B2S2(V)0.805
MAF (lbs/s) 0.02
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 207
From: Orlando FL
Hi Dahlgren---appreciate you helping me. I have also been trying to resolve a P1351 code, and replaced my coil and ICM, as well as untaped/seperated wires to the ICM, and seems to run a lot different. Runs good at idle for about 2-3 minutes, then now starts loping. Haven't taken it on the hwy. yet, that might change things. Code P1351 went away. Anyway, got some "live data" on my scanner, loaded software and tried to print, but doesn't work. I wrote down some of the "data" maybe you can tell me what it means ???
Temp: 102
RPM : 752
SHRTFT1 (%) -0.8
LONGFT1 (%) 9.4
SHRTFT2 (%) 0.8
LONGFT2 (%) 11.7
Spark adv. -18.0
O2B1S1(V) 0.225
O2B1S2(V)0.435
O2B2S1(V)0.385
O2B2S2(V)0.805
MAF (lbs/s) 0.02
Temp: 102
RPM : 752
SHRTFT1 (%) -0.8
LONGFT1 (%) 9.4
SHRTFT2 (%) 0.8
LONGFT2 (%) 11.7
Spark adv. -18.0
O2B1S1(V) 0.225
O2B1S2(V)0.435
O2B2S1(V)0.385
O2B2S2(V)0.805
MAF (lbs/s) 0.02
The O2 numbers look steady (not swinging) and probably not moving yet because they might have not heated up enough so no real data there.
The long-term trim numbers are a little high which might indicate a lean condition however since the engine is not at operating temperature and not known if it's in closed loop yet, the trim numbers may not be totally valid.
I don't know if this data at this point is very helpful and don’t know how long engine was running before you took them.
In my post 32 I asked if you checked the vacuum line from the FPR to make sure there's no fuel in it.
You might try unplugging one injector at a time to see if you can localize it to a specific cylinder.
Thread Starter
Instructor
Joined: Feb 2016
Posts: 111
Likes: 10
It's only at 102 degrees in temperature and probably in open loop.
The O2 numbers look steady (not swinging) and probably not moving yet because they might have not heated up enough so no real data there.
The long-term trim numbers are a little high which might indicate a lean condition however since the engine is not at operating temperature and not known if it's in closed loop yet, the trim numbers may not be totally valid.
I don't know if this data at this point is very helpful and don’t know how long engine was running before you took them.
In my post 32 I asked if you checked the vacuum line from the FPR to make sure there's no fuel in it.
You might try unplugging one injector at a time to see if you can localize it to a specific cylinder.
The O2 numbers look steady (not swinging) and probably not moving yet because they might have not heated up enough so no real data there.
The long-term trim numbers are a little high which might indicate a lean condition however since the engine is not at operating temperature and not known if it's in closed loop yet, the trim numbers may not be totally valid.
I don't know if this data at this point is very helpful and don’t know how long engine was running before you took them.
In my post 32 I asked if you checked the vacuum line from the FPR to make sure there's no fuel in it.
You might try unplugging one injector at a time to see if you can localize it to a specific cylinder.
ok, thanks for your reply and help. I have been concentrating on correcting a code P1351, and have replaced the coil and ICM connectors, as well as tracing the coil and ICM wires and checking continuity, etc. At first it started kinda hard, like about 4 seconds of cranking, then would start ok after that, and seemed to run good. Last time I started it, it started right up, first crank, and ran just fine. I have been chasing this crappy idle in open loop for about a year, and then this Code started showing up, not sure about all these coincidences, but I guess I don't care as long as it keeps running ok, and the codes stay away...Thanks, Brownie
Thread Starter
Instructor
Joined: Feb 2016
Posts: 111
Likes: 10
ok, thanks for your reply and help. I have been concentrating on correcting a code P1351, and have replaced the coil and ICM connectors, as well as tracing the coil and ICM wires and checking continuity, etc. At first it started kinda hard, like about 4 seconds of cranking, then would start ok after that, and seemed to run good. Last time I started it, it started right up, first crank, and ran just fine. I have been chasing this crappy idle in open loop for about a year, and then this Code started showing up, not sure about all these coincidences, but I guess I don't care as long as it keeps running ok, and the codes stay away...Thanks, Brownie