Check power to the ECU, there are two pins that splice together into one wire that goes all the way to the junction block below C500 on an 85. There is a single pin connector inline at the junction so you can reset the ECU. This line went bad on me and caused all kinds of weird intermittent problems.
Wires 10 and 15 on the white connector provide power to the ECM from a fusible link (unswitched power). The 84 does not have the junction block by the battery. I don't remember where the fusible link is connected. In addition the C500 connector is located in front of the engine on the firewall not by the battery as in 85-88.
With the ECM connectors removed use a 12V test light to check wires 10 and 15 on the white connector. The bulb should light brightly. If it doesn't there is resistance in the power supply wiring to the ECM.
------------------ formerly known as sanderson 1984 Quad 4 1886 SE 2.8L 1988 4.9L Cadillac 1988 3800 Supercharged
A lot of issues going on here. Perhaps a common source is causing multiple issues totally unrelated to one another. To keep this short, how many ground connections have you tested? Body, engine, chassis, etc. This is where a factory service manual comes in handy.
I recently had an issue with a 2011 Cadillac. Started it one morning and drove 40 yards and check engine light came on along with Anti-Traction, etc resulting in limp home mode. I connected my scanner and nearly every code in the book popped up virtually over night. If I was to replace every component that was affected I would of spent a fortune and still have a problem. It turned out to be a damaged wire harness that some hungry mice chewed apart and some wires within the harness were chewed together causing cross voltage, etc.
In your case a high idle could be caused by a bad or weak ground causing unstable voltage. A probe may reveal 5 volts to the component, lets say a O2 sensor but without a dependable ground to regulate it all bets are off. I once solved a high idle (2500) rpm on my 2.8 Fiero by adding wide braided ground straps from battery (-) to frame to engine and body. Just my 2 cents, hope it helps.
Spoon
------------------ "Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut
Well here's what currently happening behind the scenes.
I have been driving the car using ALDLdroid on my radio headunit so I can always monitor the ECM. It is turning up all sorts of weird quirks that I am starting to think may be a ground issue.
The car gets really funky driving in the rain. Alternator will randomly kick on and off when wet. Watching voltage on the screen go from 14.8 to 12 to 11 then back to 14.8 for a while. The headlights dim aswell during the voltage drops. So that's not good, never happens dry.
BLM is all over the place. The more throttle the more BLM. At idle its 128/127 and just keeps increasing.
Car is flooding when cold. If I dont give it gas to start it wont. If I keep cranking without gas, I have to put my foot to the floor to start it.
New, random code 24s while not moving.
I am starting to think there has got to be some sort of ground issue. But at the same time, the high idle only began after I changed by TPS and my intake gasket. Which doesn't involve a ground. But who knows. I'm going to start grounding the snot out of everything and see if It alleviates some symptoms.
Yes I agree with your grounding plans, I just highly recommend also checking all power to the ECU with a test light as mentioned above to verify good power to the computer. If your alt is not working great in the rain, makes sure the alt itself is not bad. There is a wire going to the alt from the battery light on the dash, if that is not putting a drain on that pin in the alt, it will not create a field and therefore will not charge. Check continuity and connections. Your alt is clearly giving up if you are dropping down to batt voltage, and I doubt it is an issue on the output side, it is most likely either on the input side, or internal to the regulator.
Does not take much low voltage to get electronics to freak out. I have an open source tuning cable for my WRX and it would not work at first, it kept reporting back that system voltage was like 8volts when trying to flash a new ROM. I was puzzled as the battery was at like 12.8V. Since it was open source I found the schematic and looked up the data sheet for the 12V regulator in the cable, turns out its minimum voltage was 14V, and since I load a tune with the car not running the voltage regulator was breaking down and only outputting at about 8V. I bypassed it and have been fine since. But just an anecdotal story that slightly lower voltages can cause serious headaches in the performance of the sensors and ECU. These 80s electronics are especially sensitive to this.
[This message has been edited by zkhennings (edited 03-02-2023).]
BLM is all over the place. The more throttle the more BLM. At idle its 128/127 and just keeps increasing.
Car is flooding when cold. If I dont give it gas to start it wont. If I keep cranking without gas, I have to put my foot to the floor to start it.
New, random code 24s while not moving.
I am starting to think there has got to be some sort of ground issue. But at the same time, the high idle only began after I changed by TPS and my intake gasket. Which doesn't involve a ground. But who knows. I'm going to start grounding the snot out of everything and see if It alleviates some symptoms.
Seems like multiple problems:
High BLM with engine under load but not at idle could be a sign of fuel pressure decreasing as fuel demand goes up. This could be partially clogged screen on the fuel pump suction or a partially clogged fuel filter
According to the FSM a code 24 that is setting even though the speedometer is working could be caused by a faulty ECM connector or ECM
The TPS can be bench tested. You'll need a 5V power supply like three 1.5V battery taped together or a power supply from a computer. Also need a multimeter to check voltage on the sense wire as the TPS is stroked.
As I mentioned earlier start by checking the ground resisyance on the ECM plugs. These are critical.
[This message has been edited by sanderson231 (edited 03-02-2023).]
The TPS can be bench tested. You'll need a 5V power supply like three 1.5V battery taped together or a power supply from a computer. Also need a multimeter to check voltage on the sense wire as the TPS is stroked.
Try and hook it up to a scope if you have access, or use an analog multimeter so you can see if the needle dances at certain points, can be hard to pick that up with a digital one.
Originally posted by zkhennings: Try and hook it up to a scope if you have access, or use an analog multimeter so you can see if the needle dances at certain points, can be hard to pick that up with a digital one.
I agree with use of analog multimeter. I think they are also better for resistance checks. Digital ohm meters sometimes give ghost readings
------------------ formerly known as sanderson 1984 Quad 4 1886 SE 2.8L 1988 4.9L Cadillac 1988 3800 Supercharged
There are thirteen ground connections on the 1984 Fiero. However not all of them are pertinent to engine related problems. The ones to focus on are:
G501 - this is a size 19 wire that connect the negative battery post to the engine G502 - this is a size 3 wire that connects the negative battery post to the sidewall G502 - this is a braided strap that connects the location where G501 is on the engine to the trunk hinge G503 - several small wires connect to this ground. It is locate behind and just below the water neck. This is the ground for two ECM wires G504 - vertical stud driver's side of the engine just ahead of the valve cover. This is the ground for the other ECM wire G202 - under the console passenger side below the ECM
To clean ground connections I like to disconnect the wires and then polish the eyelets and contact surfaces with a wire brush on a Dremel.
I would also clean the connectors and the pins at the ECM with CRC QD electronics cleaner or a similar product. Then work the plug in and out a bunch to brighten up the connections
You can do a visual check on the spray pattern of the fuel injector by removing the hat. Should see a nice spray pattern if there are droplets that's an indication of partial plugging.
------------------ formerly known as sanderson 1984 Quad 4 1886 SE 2.8L 1988 4.9L Cadillac 1988 3800 Supercharged
I'm gonna have to keep working at it. A lot of what you said has already been done.
New FP with a spotless tank.
New fuel filter.
Only thing I haven't opened is the injector.
I will keep trying y'alls suggestions and keep you updated. Still moving into my new shop so I may be a bit spotty over the next few days.
I would still hook up a fuel pressure gauge and record it with a gopro while you drive, if nothing else to eliminate fueling prior to the injector being a cause. I have had the submersible fuel hose fail that couples the pump to the sender, you could have wiring/connector issues preventing enough current getting to the pump with higher fuel demands, etc.
I would still hook up a fuel pressure gauge and record it with a gopro while you drive, if nothing else to eliminate fueling prior to the injector being a cause. I have had the submersible fuel hose fail that couples the pump to the sender, you could have wiring/connector issues preventing enough current getting to the pump with higher fuel demands, etc.
I would echo this. I mentioned the same thing a few pages earlier... I've personally had that issue where the connecting hose would restrict flow under hard driving (I used normal fuel line, not the kind that's intended ot be submersed in fuel). But removing the tank is a bit time consuming. At this point, I would clean or replace the injector, and check all the grounds. If it still is giving you problems... then that's my guess.
I am going to go ahead and say that this will likely never be resolved. I did find the TPS was wrong and the cause of the high idle. Never found out what the misfire was.
I was driving home Friday night and noticed dropping oil pressure. With the idiot light coming on at idle. The top end was beginning to tick on and off. I hightailed it home and parked it for the night.
I rolled the motor over on the starter the other morning and heard a sound like a jar of yogurt getting pored on concrete. Shut the motor off and found 2-3 quarts of oil all over the driveway that was not there when I started cranking. It looked like it was coming from around the oil filter. I'm not sure what the heck I'm supposed to make of this. A new filter and fresh oil made no difference. It just pours out from what appears to be under the filter where the motor mount bolts to the block. I currently have the intake off trying to find where the oil is coming from.
Maybe a clogged oil galley? The engine was sludgy when I redid the lifter. Maybe the Lucas breaking additive released the sludge.
Just be know that there likely wont be an answer to what the misfire was if this engine died. But the high idle was verified to be the fault of the TPS and not a ground.
The motor is probably fine, did your oil pressure sensor back out? Could have lost an oil galley plug. Hopefully nothing in your block is cracked (would be very unusual).
But something in the pressurized oiling system has failed. Distributor seal? Don't think a leaking dizzy seal would drop oil pressure that much though. Hopefully an easy fix.
Was your misfire not solved by the TPS? I have found a bad TPS results in backfires as the fueling goes all wonky from the TPS input not matching the cells in the tables.
I am going to go ahead and say that this will likely never be resolved. I did find the TPS was wrong and the cause of the high idle. Never found out what the misfire was.
I was driving home Friday night and noticed dropping oil pressure. With the idiot light coming on at idle. The top end was beginning to tick on and off. I hightailed it home and parked it for the night.
I rolled the motor over on the starter the other morning and heard a sound like a jar of yogurt getting pored on concrete. Shut the motor off and found 2-3 quarts of oil all over the driveway that was not there when I started cranking. It looked like it was coming from around the oil filter. I'm not sure what the heck I'm supposed to make of this. A new filter and fresh oil made no difference. It just pours out from what appears to be under the filter where the motor mount bolts to the block. I currently have the intake off trying to find where the oil is coming from.
Maybe a clogged oil galley? The engine was sludgy when I redid the lifter. Maybe the Lucas breaking additive released the sludge.
Just be know that there likely wont be an answer to what the misfire was if this engine died. But the high idle was verified to be the fault of the TPS and not a ground.
Ah man, that sucks. If I was nearby, I'd come over and help. Just know, an engine for this car is really cheap. And at this point... you've basically built a new car already since you've replaced everything! (bad attempt at humor, sorry).
Its coming from around the oil filter. and it is ALOT of oil.
Basic question (checking the simplest things first)... what oil filter are you using?
I forget how it's designed, but... does the oil filter screw and tighten up directly against the block, or does it screw onto an assembly of sorts that is bolted onto the block? If it's the latter, any chance the assembly has somehow gotten loose and/or is leaking?
[This message has been edited by Patrick (edited 03-08-2023).]
It should be simple to find the leak, blast everything clean with brake clean, unplug the injector, get someone to crank the car over to build oil pressure while you look from underneath to see where it originates.
This is the duke's oil filter mount. Where do you believe the oil might be escaping from? The push rod gasket is right above the oil filter location. That would be my guess (if it's not from the valve cover gasket).
[This message has been edited by Patrick (edited 03-10-2023).]
Somewhere in this general vicinity. which leads me to believe its the oil filter. But what's causing the seal to blow out??? Its been soaking in diesel all week. Im going to refresh it today and see what happens.
Its just pouring so much oil. Its like theres a hole. (There isnt I checked.)
[This message has been edited by Dukesterpro (edited 03-13-2023).]
...which leads me to believe its the oil filter. But what's causing the seal to blow out???
You've been asked this before... but what was the condition of the seal on the two oil filters you've removed?
quote
Originally posted by PhatMax:
Pull the filter off and look at the gasket. Could be a split in the filter….or seam.?…?
A leaking oil filter could be one of three things... Screwed on too loose Screwed on too tight (and splitting the seal) Faulty filter(s)
I suspect both oil filters you've installed have been the same brand and type. Perhaps it would be worthwhile to try a different brand of filter and see what happens.
Sorry my communication has been spotty. I really appreciate the help you have provided. The issue has hopefully been fixed. I will explain. The condition of the oring seal was always a concern. Whenever I spun the filter off after a leak. It had what looked to be a hernia on the circle. The filter would be very tight regardless of how it was tightened down and that little hernia spot would appear. (Wasn't obvious till i took the intake off and look right down at the filter.
I soaked the crankcase in diesel last week. Spinning the engine over on the starter with no plug. I kept doing this till I saw diesel at the rockers.
Drained the diesel last night. Refilled with fresh oil and a Fram filter this time instead of a Delco. Reinstalled the intake and the duke fired up. No oil leak. Ran the engine up to operating temp. Drained the now shockingly dirty 15 minutes oil.
Will refill tonight with fresh oil and a new Fram ultra filter (I was using AC Delco previously) hopefully got this issue whipped.
New filter after diesel soak did not exhibit the bulge
Can't see any connection between between a diesel soak and no "bulge"... unless you're suggesting that an oil gallery was plugged so badly with gunk that the resulting oil pressure was forcing the bulge in the seal?
quote
Originally posted by Dukesterpro:
a new Fram ultra filter (I was using AC Delco previously)
Don't know if you still have both a Fram and an AC Delco oil filter off the car to check... but do the oil seals on the two brands of filters line up perfectly with each other, or is there a slight difference?
[This message has been edited by Patrick (edited 03-14-2023).]
You do lubricate your oil filter o-rings with fresh oil when installing correct? It seemed like oil filter o-ring was going to be the issue, just cuz a leak that big will be obvious where it is leaking from. And you kept indicating it was only visible around the filter.
Your 15 min oil change was probably dirty just due to the diesel loosening up a buncha gunk.
I am suggesting the oil gallery was plugged to high heaven. I cut open the original filter and found the filter media collapsed and cracked. Not to mention the filter was filled with sludge. Looks like the insides burst and let sludge past the filter and into the oil gallery. Plugged her up pretty good. Hence why the new filters O-Ring developed that bulge and let the oil run out. After the diesel soak, I am left with a duke that in the year I have owned has NEVER run so quiet, its like a completely different engine its not even funny. It doesn't even tick on startup anymore. 50 miles of running in so far and no more oil leak. Comparing my second ACDelco and First Fram the seals are identical. in outer diameter but the Fram seal is a little thinner both in height and width.
zkhennings,
Yes, I always give the O-Ring a generous rub of fresh oil when installing. I believe a clogged gallery was responsible for the blown O-Ring seals. The matter so far I believe to be resolved.
I did figure the oil was dirty due to the diesel flush, I was more trying emphasize just how dirty it was for only 15 minutes of running.
I drain my oil into a white tray 1 qt at a time. Zero metal particulates or shavings, just grimy and sludgy. Now back to that misfire. I will keep you guys posted as information develops. Thanks again for all the help!
I managed to fix my bouncing Tach. I found the tach filter way further back into the harness than I initially thought. For my 84, it was in the plastic shielding all the way back by the coolant fill neck. Low and behold, disconnected ground loop. After reconnecting the tach works perfect.
Im going to redo all of the ground on the motor to weed out that situation.
A more interesting discovery is that my TPS is not bad. The little tang that moves the TPS arm is actually holding the TPS at 1.2V and if I bend the tang to get it down to about .3 the engine continues to high idle and at full throttle the voltage is only about 3.8 so I'm guessing my throttle plate isn't fully closing.
The little tang that moves the TPS arm is actually holding the TPS at 1.2V and if I bend the tang to get it down to about .3 the engine continues to high idle and at full throttle the voltage is only about 3.8 so I'm guessing my throttle plate isn't fully closing.
With the presumption that your throttle is closed as far as it should be... try adjusting your TPS. No, don't bend the tang. Watch/listen to the way the fella in this video does it. He rotates the TPS. If your TPS isn't slotted, break out the Dremel...
Will straighten the tang back out and try your method.
Now that it's already bent I suggest you don't bend it back, as that will only further weaken (if not break) it. But if the TPS needs further adjustment, by all means rotate the TPS instead!
I have blown a head gasket. This car is cursed. Its the only explanation. I will get back with all of your after I repair the gasket and verify the head isn't cracked.
I have blown a head gasket. This car is cursed. Its the only explanation. I will get back with all of your after I repair the gasket and verify the head isn't cracked.
Somewhere in this general vicinity. which leads me to believe its the oil filter. But what's causing the seal to blow out??? Its been soaking in diesel all week. Im going to refresh it today and see what happens.
I suggest you don't bend it back, as that will only further weaken (if not break) it. But if the TPS needs further adjustment, by all means rotate the TPS instead!
