1986 N/A wont rev past 4,000RPM
02-22-10, 02:38 PM
#26
Ban Peak
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If it seems like you're hitting a wall, check the ECU Ground on the Rear rotor housing. Search for Rear Rotor housing ground.
I had a car do this, and I checked the ground when I had the manifold off. Either way it loosened up. This was on my 88' GTU. I ran through everythign because i felt positive it wasn't that ground. Turns out it was, I was able to take the solenoid and UIM mount off of the drivers side and clean the ground up & resolder it. Put it back on, Absolutely no problem anymore.
I had a car do this, and I checked the ground when I had the manifold off. Either way it loosened up. This was on my 88' GTU. I ran through everythign because i felt positive it wasn't that ground. Turns out it was, I was able to take the solenoid and UIM mount off of the drivers side and clean the ground up & resolder it. Put it back on, Absolutely no problem anymore.
02-23-10, 11:01 AM
#27
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I'll pay for the 12 pack if anyone in the area wants to help me out over a weekend.
02-23-10, 02:57 PM
#28
Ban Peak
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To do the ground on an S4 you don't have to pull the UIM if you have a couple universal joints handy. Just take out the solenoid and the mount on the drivers side and it gives you some room to squeeze in there.
02-24-10, 02:29 PM
#30
Ban Peak
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02-25-10, 01:48 PM
#34
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I'll give that a shot. I'm also going to test the signal from the ECU to the 2ndaries. I pulled the ecu apart and it looked good (no cold joints or bad traces. No obviously smoked components.) I've already found some breaks in the wireing harnes leading to the TPS that has since been repaired, I wouldn't be surprized to find either the ground on the block is bad, or the leads to the 2ndaries are bad - or both.
03-14-10, 06:28 PM
#35
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Go to the two secondary injector connectors and pull 'em off. Key to ON. See if one wire in each connector has batt voltage or not. Should. Sounds like one of the two is off the injector.
Or driver the car using little pedal until you reach 5000rpm. Should. Then stomp the pedal at 5000 and see what happens. IF the engine starts acting crummy with light throttle and reaching appox 3500-3800 rpm.........then suspect the boost sensor is not seeing vacuum from the engine.
And or go to the ECU small plug and make sure each of the four light green wires have batt voltage with the key to ON. Check at the plug, not the jack on the ECU. If you get batt voltage at each light green wire on the small ECU plug, the wiring is intact for each of the injectors.
Then go to pin 2B and make sure it has 3.5-4.5vdc with the key to ON, engine off. 2B is the middle ECU plug and the counting is from looking into the wire side of the plug in a up/down fashion. 2B would then be on the lower row......far right. Brown/red wire.
Go to the two secondary injector connectors and pull 'em off. Key to ON. See if one wire in each connector has batt voltage or not. Should. Sounds like one of the two is off the injector.
Or driver the car using little pedal until you reach 5000rpm. Should. Then stomp the pedal at 5000 and see what happens. IF the engine starts acting crummy with light throttle and reaching appox 3500-3800 rpm.........then suspect the boost sensor is not seeing vacuum from the engine.
And or go to the ECU small plug and make sure each of the four light green wires have batt voltage with the key to ON. Check at the plug, not the jack on the ECU. If you get batt voltage at each light green wire on the small ECU plug, the wiring is intact for each of the injectors.
Then go to pin 2B and make sure it has 3.5-4.5vdc with the key to ON, engine off. 2B is the middle ECU plug and the counting is from looking into the wire side of the plug in a up/down fashion. 2B would then be on the lower row......far right. Brown/red wire.
I just tried all of the above and all check out.
I get 12v on 1 wire on each secondary.
I can get it to creap by 3800 with just a hair throttle but if i give it more gas at any time over 3800 it starts doing the "rev limiter" thing again and drops to 3800.
Pin 2b, does indeed have 3.5 volts on it.
Ground on the rear rotor housing was cleaned when i put the motor together a few days ago, made special note of that due to issues i had with my old car.
I am lost at this point, no clue what to try next. The engine runs perfect below 3800.
03-14-10, 06:44 PM
#36
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I also know that the ECU is not trying to fire the secondary injectors for some reason, voltage at injectors stays the same even when revving it.
Could it be the ECU? I did just buy this ECU from ebay since i could not find one locally in DFW.
Could it be the ECU? I did just buy this ECU from ebay since i could not find one locally in DFW.
03-14-10, 07:26 PM
#37
Just because the ground is secure at the engine does not necessarily mean the grounds are not an issue. Regrounding near the ECU will not hinder anything and might actually help. There are four to choose from. Pin 3A,3G,2R and 2C.
The injectors require a ground signal from the ECU to pulse properly. You could check for pulsing of the secondaries but you need the rpms to reach a certain level to check the pulsing. If you take an led light and place the red wire of the led into pin 3I and the yellow into pin 3H - light green/ white wire (front secondary) with the engine running try to reach an rpm that will trigger the secondaries and if so you will see the light flash. Remove the yellow wire from 3H and move to 3F -light green/red wire (rear secondary) and you should see the light flash under the same conditions.
03-14-10, 07:30 PM
#38
My car did the same. Open up the ecu and check for a burnt up board. Also secondaries wont open when the car is not under load unless you fool it. To trick it warm up the car, unplug the boost sensor vacuum and tps then rev it up at 3800rpm, what do you see? From what I understand from you explanation seems like secondary injectors are not even trying to open. like mine. Which had a shot ecu... shot from a shotty wires under the hood.
03-14-10, 08:06 PM
#39
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This is for an S4. Same applies for an S5 except the name and location of the pins have been changed to protect the innocent.
Just because the ground is secure at the engine does not necessarily mean the grounds are not an issue. Regrounding near the ECU will not hinder anything and might actually help. There are four to choose from. Pin 3A,3G,2R and 2C.
The injectors require a ground signal from the ECU to pulse properly. You could check for pulsing of the secondaries but you need the rpms to reach a certain level to check the pulsing. If you take an led light and place the red wire of the led into pin 3I and the yellow into pin 3H - light green/ white wire (front secondary) with the engine running try to reach an rpm that will trigger the secondaries and if so you will see the light flash. Remove the yellow wire from 3H and move to 3F -light green/red wire (rear secondary) and you should see the light flash under the same conditions.
Just because the ground is secure at the engine does not necessarily mean the grounds are not an issue. Regrounding near the ECU will not hinder anything and might actually help. There are four to choose from. Pin 3A,3G,2R and 2C.
The injectors require a ground signal from the ECU to pulse properly. You could check for pulsing of the secondaries but you need the rpms to reach a certain level to check the pulsing. If you take an led light and place the red wire of the led into pin 3I and the yellow into pin 3H - light green/ white wire (front secondary) with the engine running try to reach an rpm that will trigger the secondaries and if so you will see the light flash. Remove the yellow wire from 3H and move to 3F -light green/red wire (rear secondary) and you should see the light flash under the same conditions.
So those pins you mentioned above, does it matter which one i use? just run 1 of those to ground or all of them?
I am thinking it might be the ECU, it is pretty beat up and i picked it up off ebay.
I checked the secondaries with amultimeter, not perfect but there was never even a hint at them trying to open. and thats also what it acts like.
I will try adding some grounds, what pins/best places are there to add them?
Anyone in the DFW area have a spare ECU i could try?
My car did the same. Open up the ecu and check for a burnt up board. Also secondaries wont open when the car is not under load unless you fool it. To trick it warm up the car, unplug the boost sensor vacuum and tps then rev it up at 3800rpm, what do you see? From what I understand from you explanation seems like secondary injectors are not even trying to open. like mine. Which had a shot ecu... shot from a shotty wires under the hood.
I will pull it apart later tonight and see what it looks like.
03-14-10, 08:23 PM
#40
you can run one ground close to the computer. general area, as long as its a ground, like one of the computer mount bolts I believe? check it first I dont recall. HAILERS has something better written up but you`ll have to search it, I have no idea where I remember seeing it.
03-14-10, 10:07 PM
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you can run one ground close to the computer. general area, as long as its a ground, like one of the computer mount bolts I believe? check it first I dont recall. HAILERS has something better written up but you`ll have to search it, I have no idea where I remember seeing it.
03-14-10, 10:22 PM
#43
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Ok, i will try grounding one of those and see what happens.
BTW, never seen a pin out like that, usually the letter is the connector and the number is the pin but this looks backwards.
3A would be the first pin on the biggest connector?
BTW, never seen a pin out like that, usually the letter is the connector and the number is the pin but this looks backwards.
3A would be the first pin on the biggest connector?
03-14-10, 10:58 PM
#46
Might as well do three of them. Won't take but 15 minutes or so and if it doesn't help then it is preemptive maintenance that prevents a revisit to the same neighborhood. Pin 3G would be top row and second from the left (three doors down from 3A and the black color should be a giveaway). And pin 2R is the middle plug bottom row farthest on the left and also should be black.
03-14-10, 11:00 PM
#47
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True, although i am thinking more and more it is the ECU and not the wiring, the PO said the car ran great before the motor blew, so i see no reason for the wiring to have just gone bad all of the sudden. On the other hand i have an ebay ECU on my hands, that i think is a lot more likly.
As you say still a good idea to do the grounds though.
As you say still a good idea to do the grounds though.