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I got my car running recently due to a number of issues but that isn't important for what is going on right now. I'll describe the symptoms, explain what I have done to diagnose the issue at the moment and will see what advice y'all might have.
Short Story:
Car will suddenly decide to run rough or smooth at random and I'll often get it running smooth for a while, decide to give it WOT and it will hesitate and abruptly stop increasing rpms for a second sort of like a glitch. It will do this multiple times so long as I am using the throttle (or not in some cases).
Long Story:
The car must idle with my foot on the pedal for some time to warm up but sometimes now I'll go for a cold start and it will rev and die instantly or rev not smooth and it sounds like **** when it's acting like this. When it is "acting up" as I put it, it grunts / farts instead of making a smooth noise but it's not the noise you'd hear from having a blown seal or one rotor making significantly less compression than another. The other issue is that it's not an engine health problem, because sometimes it will just run smoothly and be nice. At any point when I'm driving it will start "acting up" as I call it. When it does this, if I let it idle it will drop to 500rpms or lower and act like it died, then brap to life for a second and go back to 250 rpms or so and then die and stay there like that until it eventually actually does die out or picks up again and decides to run smoothly again. When running smooth it will idle between 700 and 1000 rpms. It's been acting like this at random, sometimes I can go an hour or two without it "acting up" and other times it will act up for a split second and then run smooth for 3-4 seconds and then act up again which becomes very annoying.
"Acting up" means my motor is running like ****, will provide little to no power, and can be revved damn near to redline without actually moving the car above 15mph! It's not a clutch / pressure plate or transmission related issue. It seems to act like it's misfiring or something or not getting enough fuel, I'm not sure. It will idle rough when acting up, hesitate, then surge, or do other random things that make it difficult to explain. I have not found anything that causes it to act this way when idling in the parking lot, but without using WOT it will barely increase RPM when acting up. I thought I heard my new fuel pump making weird noises one time when it was acting up, but I don't know if it was another car near me or not because mine is so loud it's hard to tell if it's making weird noises.
Known issues:
-Diagnostics give me the code for a bad water thermo sensor. Seems to be stuck open right now but in the El Paso sun, and driving to work and around town it doesn't overheat so I haven't gotten around to replacing the thermostat yet but if it's the culprit of the problem I'll go ahead and get right on it. Nothing's stopping me from fixing it but my work schedule at the moment really, maybe this weekend will be fruitful.
-Coolant has always been a murky-ish brown but the motor doesn't smoke without premix (no signs of a broken coolant seal), I ran it without the OMP connected and with zero premix to see if it smoked a tiny bit and it doesn't, not even a little until I add cheap premix.
(I usually run it without the OMP connected because it seems to want to leak oil when running and I premix anyway so I just add more 2 stroke and run synthetic 15w40 in my car).
Things I've tested so far:
-Went to test TPS sensor but my multimeter doesn't seem to want to show resistance right now and isn't working so I'll have to see what's wrong with that. Voltage is reaching the sensor, but it can't measure resistance right now for some reason.
-I checked my fuel tank, it was free of rust and looked clean. The fuel sock was clean. I rechecked my fuel filter and it still looks brand new.
-I went over all my grounds that I sanded down and re-grounded well the other day and none of them were showing any issues, none came loose, and they were all secure.
Any help would be appreciated, I'm gonna check out the FSM while I'm at it and start more diagnostics where it suggests I look.
the S4 (which you have) doesn’t have a limp mode. What could be happening is you could have an intermittent failure of the water thermo sensor? The ECU defaults to a value of 80C failsafe when it detects a fault on the sensor. The map is of course manipulated based on the water temp. If it starts reading sporadic signals maybe it could cause strange symptoms like you’re describing.
What I would do is pull the sensor and test the resistance curve vs the target curve in the FSM over temperature. This will at least confirm (or deny) the sensor itself is bad. If the sensor tests good, then perhaps you need to inspect the harness/ECU pins, or even the ECU itself.
the S4 (which you have) doesn’t have a limp mode. What could be happening is you could have an intermittent failure of the water thermo sensor? The ECU defaults to a value of 80C failsafe when it detects a fault on the sensor. The map is of course manipulated based on the water temp. If it starts reading sporadic signals maybe it could cause strange symptoms like you’re describing.
What I would do is pull the sensor and test the resistance curve vs the target curve in the FSM over temperature. This will at least confirm (or deny) the sensor itself is bad. If the sensor tests good, then perhaps you need to inspect the harness/ECU pins, or even the ECU itself.
Turn your kitchen into a laboratory
I can't get my multimeter to read ohms right now! I think it's faulty. On the flipside, I am glad to have found a leak in the return line right where it goes into the pump housing. I moved the line further onto the nipple and then clamped it behind the tear so that it doesn't leak. I took the fuel pump out prior to this and looked it over, everything was still connected right and it was functioning. I jumped the green two prong switch to have it running all the time and it sounds strong. I noticed a noise from the injectors area, I couldn't pinpoint it exactly so I recorded it or at least tried to and I'll upload that soon and see what you guys think. It also vibrated a bit when I put my hand on the rail. (This is just when the key is in the "on" position, not while running.
I went for start, it's been sitting there parked for like 4 hours and so it was relatively cold, it would rev and then die and then rev a bit more but if I didn't hold the throttle it would just die after revving for a second or two. It's not like before when I couldn't get it to start at all, this time it is starting and I can keep it alive but it's dying and picking back up randomly.
Hopefully I don't work tomorrow and I can go pick up a new multimeter or get mine replaced for free, we'll see.
Given the issue you had with the pump from the previous thread, the noisy injector(s), and the damaged fuel line, are you sure your FPR (fuel pressure regulator) is functioning correctly? Did you ever rent that fuel system pressure tester?
what pump was in there before and what pump did you replace with (OE equivalent for your model)? An “upgraded” pump overpowers the stock FPR quite easily. Not saying that’s what happened, but it’s worth asking.
Given the issue you had with the pump from the previous thread, the noisy injector(s), and the damaged fuel line, are you sure your FPR (fuel pressure regulator) is functioning correctly? Did you ever rent that fuel system pressure tester?
what pump was in there before and what pump did you replace with (OE equivalent for your model)? An “upgraded” pump overpowers the stock FPR quite easily. Not saying that’s what happened, but it’s worth asking.
It was an "OEM" replacement from autozone. Some brand I didn't recognize but it was easily available so I just went and bought it. I also bought a adjustable FPR kit on amazon which will get here Sunday, I forgot to mention that. I'll test all that out and see if the problem persists. Somewhat busy with work though so I will not be able to do a ton of testing / diagnosis soon.
It was an "OEM" replacement from autozone. Some brand I didn't recognize but it was easily available so I just went and bought it. I also bought a adjustable FPR kit on amazon which will get here Sunday, I forgot to mention that. I'll test all that out and see if the problem persists. Somewhat busy with work though so I will not be able to do a ton of testing / diagnosis soon.
Hopefully you bought something good, like the forum favorite Aeromotive A1000. A fuel pressure gauge to go along with it will be very help for troubleshooting things like this. It's always a good sanity check when I'm having a problem.
Hopefully you bought something good, like the forum favorite Aeromotive A1000. A fuel pressure gauge to go along with it will be very help for troubleshooting things like this. It's always a good sanity check when I'm having a problem.
The problem seems to have disappeared. I unplugged the TPS to see if the car stopped cutting out like above, and it did but ran like ****. I plugged it back in and I heard a buzzing noise, adjusted TPS until it was gone, went for start. Car ran perfectly until I went to rev and it started cutting out as before. I began adjusting TPS until the idle smoothed out and then went to rev, it revved perfectly and without hiccups.
After letting the car warm up I adjusted the TPS some more until it was a smooth and solid idle, went to rev and it had hiccups. I guess the temporary solution for now is to lower RPM's to about 700 and let it idle rough (it hasn't stalled in a few hours of driving it like this). Now when giving it any amount of gas as soon as it comes off idle it revs smooth and perfect. Linear power curve and strong pull.
I took it to "mexico" (ironically just a few miles from El Paso.. lmao) and proceeded to come into a 4 way intersection where there is construction going on and no traffic, kicked the clutch and started doing donuts. I left the intersection, came back, did the same thing but when I kicked my clutch it just kept spinning and I smoked my clutch a bit. Now it will start to slip when I go WOT from a stop. Lmao. Time to replace the clutch I guess.
Best guess as to what the issue is, I think my TPS may have dead-zones now? I already ordered the adjustable FPR which I'll install next week, I'll be back if it comes up with any new issues.
It seemed to run fine for a day, the next day I went for start and it would not hold an idle but ran smoothly. I adjusted TPS one way and got it to idle but ran like **** and hiccuped, or hesitated all the time when revving. When I went the other way it would rev up a bit, suddenly cut out, and then when it got below 2k rpms would pick back up again seemingly regularly.
I got out my multi-meter, and I went for the voltage method of tuning the TPS. (Ohm meter doesn't work?) I found that I can get it to idle "alright" and run "just alright" but not great if I adjust the TPS to 1v when cold. Otherwise it won't hold an idle at all even after thermo-wax is heated up. Once this is done I need to monitor it and maintain it at 1v until fully warm and then fine tune it here and there after running it.
After driving it a mile down the road it has moments where it decides to have a "fit" and starts "acting up" again. I'm going to reread this thread, and when I can get my multi-meter fixed I'll test the TPS for deadspots and other issues.
When it has it's "fits" idle drops from 900 or so to about 300 or 400 and runs very rough, requires gas to stay alive or it will die after a minute of idling like that. It also does not respond well to me using the gas pedal, doesn't want to pick up RPM's until it is done "acting up".
I know explaining the symptoms and not having results of certain diagnosis can make it difficult to pinpoint the issue but it's all I have to go off of until this next weekend or so.
New radiator comes in before Friday and my fuel pressure regulator came in tonight, no time to install right now. Both will go in next weekend and then I will have the time and money to go in and get what I need to continue diagnostics. Until then any help would be appreciated.
Aluminum radiator goes in tomorrow (hopefully) and I'm replacing thermostat and the thermo sensor while I'm at it.
Tested TPS, several deadspots, definitely shot. Readings all over the place. Adjust to 1v and then touch throttle once and it jumps all over the place (spring doesn't move). Took it off, cleaned it, took it apart and cleaned it out. Same results. I have a new sensor on the way.
Updating my build log on another thread, will be back here with results. Should feel like a completely different car within the next month.
06-03-20, 04:43 PM
. So soon?
