Hi gang. Here comes a novel, I could sure use some help.
84 60 with a 2FE from an 88. For over a year now I've been getting an intermittent hesitation. When it comes, the more throttle I give it makes it hesitate more. If i back off, it responds as it should. If I keep driving, it will gradually hesitate at a lighter and lighter load until I turn it off and let it sit for a minute, which usually helps. When this happens on the freeway I can often just shut off the engine (and put the key back to on, of course) and coast for a little bit and get by that way. It used to be once in a while, but is steadily happening more frequently till I'm happy every time it doesn't do it. When it's not acting up, it pulls super strong and feels like a brand new engine.
I would normally suspect a vacuum leak, but it has no correlation with engine temperature or how long the drive is. For example, I usually don't feel it until I've been on the freeway for a while, but the other day I started it up cold and felt it BAD just coming out of the driveway. Felt like my AFM was unplugged (which it isn't). Limped to a gas station, topped off the tank, and it was fine for a trip in the mountains.
Details: I replaced the TPS, FPR, spark/cap/plugs, and o2 sensors when I did the conversion 4 years and 6,000 miles ago. It was fine for about half that time so I'm not sure those would be the culprits (though I think the fpr was aftermarket). The exhaust is only a few years old so I doubt anythings falling apart in there.
Other issues that might be related (these have been present since/before the conversion):
-code 51. No other codes present.
-I think I may have a charcoal canister issue as I get that whooosh when I open the gas cap on an empty tank. before anybody says it, this doesn't necessarily solve the problem.
-It idles about 1000rpm and never below.
-it seems to run a little cold; on a long, hot drive I might get the needle almost half way. Usually runs about 1/3 the way up. Air out the heater confirms accurate temp readings.
What I've done: Replaced the fuel pump and filters (stock tank with inline pump), cleaned the AFM with MAF cleaner, checked for vacuum leaks, and checked the EFI harness for solid ground and power connections. I've also tried another circuit opening relay.
Hypothesis and next steps: It seems to me that at times, the fuel rail isn't getting enough pressure. If i'm not asking a lot of power, no problem. But if I ask for more pressure than it can handle, then it lets me know. Perhaps something is intermittently clogging the fuel line. I plan to get one of those electronic fuel pressure gauges so that I can see what my fuel pressure looks like in real time when it starts acting up.
If the issue isn't that it can't make adequate fuel pressure, maybe the ECU/FPR thinks it needs less? Maybe there isn't enough voltage difference at the injectors for them to open enough? Does turning it off help because debris in the fuel line isn't sucked up against a filter or because the short term fuel level trims are reset?
I'd like to find information about how the EFI system works on a deep level. I want to learn when the ECU uses the AFM or 02 sensors or both at the same time. I want to learn when exactly the ECU goes in and out of closed loop, be certain I know the difference, and how to test if it's getting into closed loop. I want to know if the ECU grounds the 2 injector banks in a pulsing, 0v or 12v fashion or if it has a variable resistance that constantly is being applied to the injectors? I've been unsuccessful in finding this information on mud or otherwise.
Please lend me your thoughts.
Thanks,
Drew
84 60 with a 2FE from an 88. For over a year now I've been getting an intermittent hesitation. When it comes, the more throttle I give it makes it hesitate more. If i back off, it responds as it should. If I keep driving, it will gradually hesitate at a lighter and lighter load until I turn it off and let it sit for a minute, which usually helps. When this happens on the freeway I can often just shut off the engine (and put the key back to on, of course) and coast for a little bit and get by that way. It used to be once in a while, but is steadily happening more frequently till I'm happy every time it doesn't do it. When it's not acting up, it pulls super strong and feels like a brand new engine.
I would normally suspect a vacuum leak, but it has no correlation with engine temperature or how long the drive is. For example, I usually don't feel it until I've been on the freeway for a while, but the other day I started it up cold and felt it BAD just coming out of the driveway. Felt like my AFM was unplugged (which it isn't). Limped to a gas station, topped off the tank, and it was fine for a trip in the mountains.
Details: I replaced the TPS, FPR, spark/cap/plugs, and o2 sensors when I did the conversion 4 years and 6,000 miles ago. It was fine for about half that time so I'm not sure those would be the culprits (though I think the fpr was aftermarket). The exhaust is only a few years old so I doubt anythings falling apart in there.
Other issues that might be related (these have been present since/before the conversion):
-code 51. No other codes present.
-I think I may have a charcoal canister issue as I get that whooosh when I open the gas cap on an empty tank. before anybody says it, this doesn't necessarily solve the problem.
-It idles about 1000rpm and never below.
-it seems to run a little cold; on a long, hot drive I might get the needle almost half way. Usually runs about 1/3 the way up. Air out the heater confirms accurate temp readings.
What I've done: Replaced the fuel pump and filters (stock tank with inline pump), cleaned the AFM with MAF cleaner, checked for vacuum leaks, and checked the EFI harness for solid ground and power connections. I've also tried another circuit opening relay.
Hypothesis and next steps: It seems to me that at times, the fuel rail isn't getting enough pressure. If i'm not asking a lot of power, no problem. But if I ask for more pressure than it can handle, then it lets me know. Perhaps something is intermittently clogging the fuel line. I plan to get one of those electronic fuel pressure gauges so that I can see what my fuel pressure looks like in real time when it starts acting up.
If the issue isn't that it can't make adequate fuel pressure, maybe the ECU/FPR thinks it needs less? Maybe there isn't enough voltage difference at the injectors for them to open enough? Does turning it off help because debris in the fuel line isn't sucked up against a filter or because the short term fuel level trims are reset?
I'd like to find information about how the EFI system works on a deep level. I want to learn when the ECU uses the AFM or 02 sensors or both at the same time. I want to learn when exactly the ECU goes in and out of closed loop, be certain I know the difference, and how to test if it's getting into closed loop. I want to know if the ECU grounds the 2 injector banks in a pulsing, 0v or 12v fashion or if it has a variable resistance that constantly is being applied to the injectors? I've been unsuccessful in finding this information on mud or otherwise.
Please lend me your thoughts.
Thanks,
Drew
