I want to do open loop
04-28-2018, 06:05 PM
#3
Re: I want to do open loop
i would like to. I have a 86 lb9 that. Was running fine when the engine was pulled for ls swap. My car is a 85 iroc. I see a o2 on driver's side that my harness didn't have connector for. That in the exhaust manifold right? So are there 2 of them. I'm going to look
04-28-2018, 06:17 PM
#5
Supreme Member
Re: I want to do open loop
Need to disconnect Electronic Spark Control too I would think.
O2 sensor drives the fuel side.
Spark control drives the timing side.
I think another way would be to use Tuner Pro to write your EPROM to run open loop until 600 degrees. Temp sensor never reads that high, so closed loop never kicks in.
But really, driving around in open loop is going to bite you in the *** eventually. I would expect continuous driving in open loop would clog your catalytic converter pretty quickly. Gas mileage would be atrocious too. Eventually intake valves would develop severe gunking, and whatever you think is "fine" now, won't be fine pretty soon.
You need to fix it right, or make plans for its demise. Is there ANY car to which this truth does not apply?
O2 sensor drives the fuel side.
Spark control drives the timing side.
I think another way would be to use Tuner Pro to write your EPROM to run open loop until 600 degrees. Temp sensor never reads that high, so closed loop never kicks in.
But really, driving around in open loop is going to bite you in the *** eventually. I would expect continuous driving in open loop would clog your catalytic converter pretty quickly. Gas mileage would be atrocious too. Eventually intake valves would develop severe gunking, and whatever you think is "fine" now, won't be fine pretty soon.
You need to fix it right, or make plans for its demise. Is there ANY car to which this truth does not apply?
04-28-2018, 06:26 PM
#6
Re: I want to do open loop
A o2 sensor becomes active at 5-600f , what would be the advantage of disconnecting timing retard control ?
Need to disconnect Electronic Spark Control too I would think.
O2 sensor drives the fuel side.
Spark control drives the timing side.
I think another way would be to use Tuner Pro to write your EPROM to run open loop until 600 degrees. Temp sensor never reads that high, so closed loop never kicks in.
But really, driving around in open loop is going to bite you in the *** eventually. I would expect continuous driving in open loop would clog your catalytic converter pretty quickly. Gas mileage would be atrocious too. Eventually intake valves would develop severe gunking, and whatever you think is "fine" now, won't be fine pretty soon.
You need to fix it right, or make plans for its demise. Is there ANY car to which this truth does not apply?
O2 sensor drives the fuel side.
Spark control drives the timing side.
I think another way would be to use Tuner Pro to write your EPROM to run open loop until 600 degrees. Temp sensor never reads that high, so closed loop never kicks in.
But really, driving around in open loop is going to bite you in the *** eventually. I would expect continuous driving in open loop would clog your catalytic converter pretty quickly. Gas mileage would be atrocious too. Eventually intake valves would develop severe gunking, and whatever you think is "fine" now, won't be fine pretty soon.
You need to fix it right, or make plans for its demise. Is there ANY car to which this truth does not apply?
04-28-2018, 06:42 PM
#7
Re: I want to do open loop
l found the connector that Po tucked out of the way. They had done a 350 carb motor swap to it and I put it back stock. Not easy!😁 I dropped the ECM down and it's got a Bosch box piggy back on the mounting bracket. I've got the ECM that came with the engine. Oh btw car ran same with o2 connected.
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04-28-2018, 06:50 PM
#9
Re: I want to do open loop
l found the connector that Po tucked out of the way. They had done a 350 carb motor swap to it and I put it back stock. Not easy!😁 I dropped the ECM down and it's got a Bosch box piggy back on the mounting bracket. I've got the ECM that came with the engine. Oh btw car ran same with o2 connected.
04-28-2018, 06:56 PM
#12
Re: I want to do open loop
If the engine has a aftermarket cam in it you can always increase fuel pressure with an adjustable fuel pressure regulator to see if this cures the problem. Sounds like it runs better cold than warmed up not a closed loop vs open loop.
04-28-2018, 07:20 PM
#14
Re: I want to do open loop
starts up and is sharp in throttle response. Idles good. After 20 to 30sec it changes and gets sluggish with throttle response. Idles looping like it's got a race cam. Wants to drop under 500rpm but stays running. I do have some sea foam in it. I pumped all the gas I could out and put 7 gallon's of fresh fuel. Gas in the tank with sea foam was over 6 months old.
04-28-2018, 07:28 PM
#17
Re: I want to do open loop
Sounds like it might be lean. Running good with additional fuel from the ninth injector on startup. The only other thing I can think of to try is to prop the throttle linkage open so you have a higher idle and start pulling the injector plugs to see if each one causes a cylinder drop. If no drop that injector is clogged or stuck shut.
04-28-2018, 08:20 PM
#19
Re: I want to do open loop
6 to 9 months maybe. The tank had fuel in it,about 7 gal. When the engine was pulled and I got roller body. I put seafoam and few fresh gal of gas when I drop the engine in. Sat mostly for 4 to 6 more months so I run all I could out with the fuel pump. Added fresh to what was left in bottom of the tank. Runs seafoam stinky still. Down under quarter tank. Trying to run some more out before it put more in.
04-28-2018, 08:58 PM
#20
Re: I want to do open loop
i don't get it. I start it up. Runs great for 20 seconds. Then sluggish. Shut off and restart runs great 20 seconds.4 times same thing. I did pinch off the return line and it ran worse. About died and had to fight to keep it running. Why good on startup for short time? Even engine warmed up.
04-28-2018, 09:26 PM
#21
Re: I want to do open loop
I hate to tell you throw parts at it. I wonder if it’s a bad ecm.
You can find 1226870 ecms on eBay for $65 shipped but you would have to swap over your prom.
https://m.ebay.com/itm/1985-Chevy-Co...0AAOSwvvBazRyr
Seems like your resetting something that’s why I’m leaning towards a bad ecm.
You could try tapping on the ecm case while it’s running to see if it changes how it runs or if it kills the engine.
You can find 1226870 ecms on eBay for $65 shipped but you would have to swap over your prom.
https://m.ebay.com/itm/1985-Chevy-Co...0AAOSwvvBazRyr
Seems like your resetting something that’s why I’m leaning towards a bad ecm.
You could try tapping on the ecm case while it’s running to see if it changes how it runs or if it kills the engine.
04-28-2018, 09:28 PM
#22
Re: I want to do open loop
Wonder if the return line is causing back pressure. If I run rpm up around 1200 and higher it does better than low rpm. That fuel pump for 350 wouldn't cause that unless return couldn't return the fuel fast enough.
04-29-2018, 07:38 AM
#24
Re: I want to do open loop
the sending unit had been cut when the Po hacked into it. If that line got bent enough to reduce the I.d. of the line it could cause back pressure and after shutdown or rpm increase relieve line pressure. Rev would only during Rev. Shutdown would on whole thing
04-29-2018, 08:05 AM
#25
04-29-2018, 08:26 AM
#26
Re: I want to do open loop
Consider also that most (if not all) TBI and TPI systems from the beginning employed a "closed-loop timer" for both cold and hot engine starts. You might also find this referred to as the "closed-loop delay timer" with parameters for both cold engine and warm engine. The temperature threshold for the "hot start" or "warm engine start" is typically around 158°F coolant temperature. Below that the closed-loop mode is delayed for 300-400 seconds depending on the engine, and above that the delay is commonly 20-40 seconds, again depending on the engine and original programming.
This closed-loop delay is potentially what you are experiencing, and once the ECM enters closed-loop mode the changes in timing, IAC steps, and fuel trims are making the engine run noticeably differently.
This closed-loop delay is potentially what you are experiencing, and once the ECM enters closed-loop mode the changes in timing, IAC steps, and fuel trims are making the engine run noticeably differently.
Last edited by Vader; 04-29-2018 at 08:30 AM.
04-29-2018, 08:46 AM
#27
Re: I want to do open loop
Before condemning the ECM it may be helpful to collect the operating data for the 20 seconds when it first starts, including RPM and timing, then compare that to the parameters after entering closed-loop. You may find that the system is attempting to run just as it should, but other factors are preventing that.
Tuned Perf has pointed out the base timing, and that needs to be checked.
Old fuel, especially fuel with water in it (a.k.a., Sea Foam) will also affect proper operation. Get all the fuel out of it and add nothing but fresh, LOW octane fuel to begin with. Low octane fuel is more volatile since it contains fewer additives. It can help dissolve contaminants. Tuned Perf alluded to that by asking if the fuel had sat in the rails for a long time. That can clog injector inlet screens, pintles, and nozzles, as well as affect the FPR operation.
Clean the throttle body and check the TPS voltage. Since the previous owner tinkered with everything else, it's a safe bet that the TB position and TPS were "tweaked" at some time. Setting the final minimum air and final TPS voltage may be useless until it is running properly, but it should be checked now in case the adjustment is way off.
It would seem that the IAC is at least functioning or there would be less of a noticeable change in idle RPM once the closed-loop timer is satisfied. However, it may eventually need to be cleaned and lubricated so it reacts as quickly as it should.
Tuned Perf has pointed out the base timing, and that needs to be checked.
Old fuel, especially fuel with water in it (a.k.a., Sea Foam) will also affect proper operation. Get all the fuel out of it and add nothing but fresh, LOW octane fuel to begin with. Low octane fuel is more volatile since it contains fewer additives. It can help dissolve contaminants. Tuned Perf alluded to that by asking if the fuel had sat in the rails for a long time. That can clog injector inlet screens, pintles, and nozzles, as well as affect the FPR operation.
Clean the throttle body and check the TPS voltage. Since the previous owner tinkered with everything else, it's a safe bet that the TB position and TPS were "tweaked" at some time. Setting the final minimum air and final TPS voltage may be useless until it is running properly, but it should be checked now in case the adjustment is way off.
It would seem that the IAC is at least functioning or there would be less of a noticeable change in idle RPM once the closed-loop timer is satisfied. However, it may eventually need to be cleaned and lubricated so it reacts as quickly as it should.
04-29-2018, 10:14 AM
#28
Re: I want to do open loop
Before condemning the ECM it may be helpful to collect the operating data for the 20 seconds when it first starts, including RPM and timing, then compare that to the parameters after entering closed-loop. You may find that the system is attempting to run just as it should, but other factors are preventing that.
Tuned Perf has pointed out the base timing, and that needs to be checked.
Old fuel, especially fuel with water in it (a.k.a., Sea Foam) will also affect proper operation. Get all the fuel out of it and add nothing but fresh, LOW octane fuel to begin with. Low octane fuel is more volatile since it contains fewer additives. It can help dissolve contaminants. Tuned Perf alluded to that by asking if the fuel had sat in the rails for a long time. That can clog injector inlet screens, pintles, and nozzles, as well as affect the FPR operation.
Clean the throttle body and check the TPS voltage. Since the previous owner tinkered with everything else, it's a safe bet that the TB position and TPS were "tweaked" at some time. Setting the final minimum air and final TPS voltage may be useless until it is running properly, but it should be checked now in case the adjustment is way off.
It would seem that the IAC is at least functioning or there would be less of a noticeable change in idle RPM once the closed-loop timer is satisfied. However, it may eventually need to be cleaned and lubricated so it reacts as quickly as it should.
Tuned Perf has pointed out the base timing, and that needs to be checked.
Old fuel, especially fuel with water in it (a.k.a., Sea Foam) will also affect proper operation. Get all the fuel out of it and add nothing but fresh, LOW octane fuel to begin with. Low octane fuel is more volatile since it contains fewer additives. It can help dissolve contaminants. Tuned Perf alluded to that by asking if the fuel had sat in the rails for a long time. That can clog injector inlet screens, pintles, and nozzles, as well as affect the FPR operation.
Clean the throttle body and check the TPS voltage. Since the previous owner tinkered with everything else, it's a safe bet that the TB position and TPS were "tweaked" at some time. Setting the final minimum air and final TPS voltage may be useless until it is running properly, but it should be checked now in case the adjustment is way off.
It would seem that the IAC is at least functioning or there would be less of a noticeable change in idle RPM once the closed-loop timer is satisfied. However, it may eventually need to be cleaned and lubricated so it reacts as quickly as it should.
04-30-2018, 07:33 AM
#29
Re: I want to do open loop
You might not want to fill the tank, but only replace the old fuel with about 5 gallons of fresh fuel. If you discover you have to change the fuel pump for whatever reason, that full tank is going to be a hassle.
05-27-2018, 07:41 AM
#30
Re: I want to do open loop
ok. Maybe not open loop. Can I get a prom for my 85 ECM? Gotta be easier than finding a 86 harness and changing it. Just figure it a stock 86 Camaro lb9. Only it has 85 harness and ECM. Can that be done cheaper and easier?
07-08-2018, 04:36 PM
#33
Re: I want to do open loop
I have tried alot of stuff since I last posted. Different ECM with different maf sensors. I even put a 87 engine harness and ECM with maf. Found out while I was switching harness that the 85 harness didn't have the egr connector hooked up. I've also found that the water line coming off the TB goes to the wrong side of the heater core. Therefore wrong line goes back to the radiator. The engine runs worse than before. Guess I will put the stock ECM and harness back in and fix the two things I found wrong and see how it goes. I suspect the maf sensor for the 85 setup isn't doing right. Does maf cleaner help any?😂
Last edited by Bobby Suth; 07-08-2018 at 08:31 PM. Reason: Spelling
07-08-2018, 06:08 PM
#35
Re: I want to do open loop
No codes of any kind. Engine seems to have warmed up extra fast. I can't see how it can run so good in open loop and be so bad in closed. Now with the wiring and ECM that are in it . It's hard to start and keep running till warmed up. But still only wants to idle good
Last edited by Bobby Suth; 07-08-2018 at 08:28 PM. Reason: Spelling
07-09-2018, 05:38 AM
#37
Re: I want to do open loop
I have tried alot of stuff since I last posted. Different ECM with different maf sensors. I even put a 87 engine harness and ECM with maf. Found out while I was switching harness that the 85 harness didn't have the egr connector hooked up. I've also found that the water line coming off the TB goes to the wrong side of the heater core. Therefore wrong line goes back to the radiator. The engine runs worse than before. Guess I will put the stock ECM and harness back in and fix the two things I found wrong and see how it goes. I suspect the maf sensor for the 85 setup isn't doing right. Does maf cleaner help any?😂
07-09-2018, 06:37 PM
#39
Re: I want to do open loop
o2 sensor was part of the stuff I got with the engine. It doesn't have a Cadillac converter and I just have the line corked off right now. I'm going to treat it like it never run good before I got it. Start from scratch!😎
07-10-2018, 08:38 AM
#40
Supreme Member
Re: I want to do open loop
My dad used to have a Cadillac but i dont think it was a converter.
07-29-2018, 03:59 PM
#41
Re: I want to do open loop
Update. I found a broken vacuum hose from PVC to intake while switching back to the stock harness. I don't know when it was broken but I fixed it and made sure the egr was connected this time. So far it seems to be running better. Only get few minutes to work on it. Going to add gas to it now and maybe start taping it off for paint. I will keep you posted.
11-04-2018, 01:43 PM
#42
Re: I want to do open loop
I got it running better. But still low on power. Shifts out of 1st at abut 2k and I did reset decent cable to tran. Backfires some through TB. I had to replace harmonic balancer. Still gotta check timing. I've read that heater control vacuum can be a problem.
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