vivalavolvo Posted October 16, 2012 Report Share Posted October 16, 2012 Alright, so, i have an intermittent vac leak that seems to happen within the first few minutes of a cold start, on chillier days. There are two scenarios when it happens. 1: While cranking there's a weird hesitation right before the engine starts and i read only 10" of vac at idle but will come back to 18-19" after some throttle play. 2: Again, within first few minutes from a cold start it will kinda 'click' into 10" of vac while in gear at idle, but flick the throttle a bit and it comes back. I can't see anything obviously lose, i have changed most of the vac lines, including the brake booster hose. I did recently install an ARD Green 17PSI tune with a 4.4 upgrade, I'm not sure if it is that or the recent cold snap causing things to stick. Other then that it runs just fine. Any leads, as always, will be appreciated. 1995 T5 ARD Green, Motronic 4.4 Link to comment Share on other sites More sharing options...
Rsterns Posted October 17, 2012 Report Share Posted October 17, 2012 I'm a bit lacking in vintage details, Do you have a SAS system? If so, it opperates for the first 90 seconds or so on cold startup. There is a vacumm port involved, worth checking. Link to comment Share on other sites More sharing options...
MattyXXL Posted October 17, 2012 Report Share Posted October 17, 2012 Have you checked your MAF? Link to comment Share on other sites More sharing options...
vivalavolvo Posted October 21, 2012 Author Report Share Posted October 21, 2012 I'm a bit lacking in vintage details, Do you have a SAS system? If so, it opperates for the first 90 seconds or so on cold startup. There is a vacumm port involved, worth checking. No SAS in this car, i was thinking EGR maybe? Have you checked your MAF? I have not. To help me understand better, can you explain how and why the MAF could cause this? I think it has something to do with something computer controlled. Colder it is out side, the sooner it happens, and when it happens it lasts for the same amount of time, and it has become more predictable. But still only happens once after a cold start, if i turn the engine off and back on it goes back to normal quicker. Thanks guys. Link to comment Share on other sites More sharing options...
vivalavolvo Posted October 21, 2012 Author Report Share Posted October 21, 2012 Oh and one more thing, i did hop out when it happened and listened around for a leak but could not hear it, one of that size im sure would have been loud, i have heard smaller leaks that don't register on the gauge with ease. Link to comment Share on other sites More sharing options...
vivalavolvo Posted October 23, 2012 Author Report Share Posted October 23, 2012 I reset the ECU after adjusting the waste gate pre load, so far it hasn't done it but we'll see. Link to comment Share on other sites More sharing options...
MattyXXL Posted October 24, 2012 Report Share Posted October 24, 2012 The MAF is computer controlled, If its not giving the correct reading to the ecu at first it will cause a issue similar to this when it starts taking a crap.. try un plugging the maf then start it and see if it changes anything.. If it doesent shut it off, plug it back in and unplug your IAC, start it again See if that changes the issue Remember you vac is going to decrease when there is a load applied to the motor, or the motor stumbles.. Link to comment Share on other sites More sharing options...
vivalavolvo Posted October 29, 2012 Author Report Share Posted October 29, 2012 The MAF is computer controlled, If its not giving the correct reading to the ecu at first it will cause a issue similar to this when it starts taking a crap.. try un plugging the maf then start it and see if it changes anything.. If it doesent shut it off, plug it back in and unplug your IAC, start it again See if that changes the issue Remember you vac is going to decrease when there is a load applied to the motor, or the motor stumbles.. Ah thanks. Usually when i restart the issue clears up quicker, can i pull the MAF while its running and see what happens? It seems if i let it warm up to at least 1/4 on the gauge, it wont do it. It only does it cold and after i put it into gear and start moving. Link to comment Share on other sites More sharing options...
MattyXXL Posted October 29, 2012 Report Share Posted October 29, 2012 Yeah you can unplug it while its running, but try not to plug it in unless the car is off. Link to comment Share on other sites More sharing options...
vivalavolvo Posted November 1, 2012 Author Report Share Posted November 1, 2012 Alright, so i unplugged the MAF while it was running, other then the expected effects, the vac did not leave 10". I tried again with the IAC and the vac went back to normal, although idling low. Not sure if coinicdance or that was the issue. I grabbed a can of intake cleaner and a can of MAF cleaner, then cleaned out the IAC and MAF. Maf didnt look all that bad the IAC was quite dirty, but the valve moved freely. Also installed a new filter while i was at it. I won't know if any of this did anything until tommorow when the engine completly cools. Link to comment Share on other sites More sharing options...
vivalavolvo Posted November 2, 2012 Author Report Share Posted November 2, 2012 no change. today i had to get on it in traffic during the leak. it didnt even try to boost, but when it 'clicked' back to normal the boost was just there and cought me off gaurd. should i try a new MAF? Link to comment Share on other sites More sharing options...
troyhyde Posted November 3, 2012 Report Share Posted November 3, 2012 Flick of a switch vacuum comes and goes.... I think I'd be looking for a binding throttle plate or cable connection. Link to comment Share on other sites More sharing options...
vivalavolvo Posted November 4, 2012 Author Report Share Posted November 4, 2012 Flick of a switch vacuum comes and goes.... I think I'd be looking for a binding throttle plate or cable connection. It's all in good working order and clean. It only happens after a cold start and it always lasts the same amount of time. I can log data from the ECU on my phone. Is there any information i should log that would help any one diag this? Link to comment Share on other sites More sharing options...
troyhyde Posted November 4, 2012 Report Share Posted November 4, 2012 I think the car will run open loop for 60 seconds or so on startup. Might eliminate a few things such as O2 sensors. Have you checked the coolant temp sensor, especially the circuit wiring, this could cause problems like this. Any boost hoses sucking themselves closed / collapsing? A bad MAF could certainly cause this as well, can you swap a used one in there to eliminate it? Link to comment Share on other sites More sharing options...
vivalavolvo Posted November 4, 2012 Author Report Share Posted November 4, 2012 I think the car will run open loop for 60 seconds or so on startup. Might eliminate a few things such as O2 sensors. Have you checked the coolant temp sensor, especially the circuit wiring, this could cause problems like this. Any boost hoses sucking themselves closed / collapsing? A bad MAF could certainly cause this as well, can you swap a used one in there to eliminate it? It wont do it until i put the car in gear and start to move, but wont if i let it warm up a tad. Temp sensor looks to be working right, monitoring over OBDII it shows normal values. And all the boost hoses are FCP silicone and they all appear to be solid. I do not have a spare MAF but i might be able to get my hands on one, either a used one or i was flirting with the idea of a cheap after market. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.