Idle Problem when letting off the gas NOT VENTING BOV either

SmokinV8's · Oct 5, 2005

My problem is my idle but only after letting off the gas and coasting or stopping at a light. (I am not venting my bov either).It drops down to 400rpms and almost stalls. After a minute of fumbling it catches and idles normal. When i try to rev it up when its fumbling it kinda stumbles and then rev's like usual. I have checked for boost leaks and don't have any I have also changed my maf with a 2g one and still have the same problem. I've also tried way rich and way lean on my safc with no luck. About a month before this problem began i was a victim of a leaky weapon r afpr and i was sucking fuel through the vacuum line. What damage could this have done and could this be my problem? I am running a walbro 255 also with the stock fpr for now but i have run that problem free for over a year before the afpr accident. When the problem first happened i was getting an airflow sensor error on my logger. I have cleared the error and reset the ecu but still have this problem. I have noticed that its worse in the morning when its colder outside and my lights and heat are on. Also on the logger my battery volts are only around 12v when its stumbling.

Any info will help
Thanks

pUtInExIm · Oct 5, 2005

The reason for the Volts droping is due to the low RPM. At lower RPM the alternator will spin slower which will cause it no to charge as much.

90BlueGSX · Oct 5, 2005

sound like, something I'm going though. idle suge

Corpsegrinder · Oct 6, 2005

Yup, look in the vfaq for the idle surge checklist or whatever(I forgot the name), and check if the symptoms apply to you. Maybe ISC related.

SmokinV8's · Oct 6, 2005

Corpsegrinder said:
Yup, look in the vfaq for the idle surge checklist or whatever(I forgot the name), and check if the symptoms apply to you. Maybe ISC related.

It idles fine right at 750 rpm's and don't surge they only drop when I come off the gas and come to a stop or rolling in neutral. If i start the car and let it warm up and just idle it is fine this only happens after coming off the gas no other time. The ISC seems to be doing its job as my rpms barely dip when all the lights are on and the a/c is also on. I had idle surge in my 1st dsm and this is not the same. It does almost the same exact thing my 1st dsm did when the bov was vented only thing is my bov is recirc on this dsm.

Corpsegrinder · Oct 6, 2005

Check the alternator and the belts as suggested. Also check to see if your bov is in good condition.

SmokinV8's · Oct 6, 2005

Corpsegrinder said:
Check the alternator and the belts as suggested. Also check to see if your bov is in good condition.

The bov seems to be working good it holds 19psi with very little to no leaking and i can hear it release when coming off boost.

Thanks for the suggestions

rgj · Oct 7, 2005

Grab a ISC and try it.

me shakes fist · Oct 7, 2005

How big is the turbo? Bigger turbo's when used with a MAS can cause a rich condition when letting off the gas.

compuman99 · Oct 9, 2005

If you get into the throttle and just let off the gas quick I bet it kicks a couple of times first too. I'd be willing to bet its the stock FPR not being able to get your fuel pressure down.

SmokinV8's · Oct 9, 2005

compuman99 said:
If you get into the throttle and just let off the gas quick I bet it kicks a couple of times first too. I'd be willing to bet its the stock FPR not being able to get your fuel pressure down.

Nope it runs fine the only problem is when I put it in neutral and the rpm's fall from where ever they were when i was cruising they fall below 750rpm's and takes about 30-40 seconds to catch itself. I cranked up the safc to +20% at 1000 rpms and its almost all gone (5-10 sec delay) but according to my logger my low fuel trim is maxed out (81) trying to take fuel away. I did find a leaky crack today in the boost gauge T i replaced it so maybe that will help. I do agree that the stock fpr probly isn't helping but it ran fine for a month or so before this started. An AFPR is on the way.

Thanks

stevep · Oct 9, 2005

The ECU looks for the IPS to close and it the car is moving per the Vehicle Speed Sensor in the Speedometer it will hold the idle up around 1k to make sure the power steering doesn't bog the car down. Once the car come to a stop the idle will drop to 750.

If you car doesn't then you need to check the IPS, the VSS, the ISC and ECU drivers, and make sure the BISS is correctly adjusted. Any vacuum leaks will cause problems too.

Steve

SmokinV8's · Oct 10, 2005

Here are a few things i noticed today. I fixed the boost gauge T and it didn't make any difference. I noticed that if I set my low fuel trim to 100 usually around +5% on the safc and then i turn on the rear def and the a/c the car idle's around 600-650 rpm's but the low fuel trim max's out trying to pull fuel. I can also hear my fuel pump boggin down but as soon as i bring the rpm's up the low fuel trim also starts to come up and the fuel pump sounds normal (not rewired). Why would running the def and the a/c make the car run so rich that the ecu tries to lean it out so much that it max's itself out? This don't make much sense to me. The only thing that i changed since this problem started was i had to take out my leaky afpr so i think i will start there.

Thanks for all the info guys

SmokinV8's · Oct 12, 2005

I just might have fixed this problem once and for all. After installing the 2g maf i set the my safc at zero and reset the ecu to start tuning all over again. While driving around part throttle i was getting 40 counts of knock between 2-3k rpm's so i cranked up the safc to about +13% just to get rid of it. Well after my med and high fuel trims adjusted themselves i was back to knocking like crazy and couldn't get rid of it no matter how much fuel i added so i it must have been rich knock. I lowered it all the way to -14% from 1-4k rpm's and have 0 knock at all at part throttle and after i made these adjustments my idle was back to normal. I tried it with nothing on and then i tried it with my lights my a/c and def on and the rpms caught right at 750rpms and stayed there. The real test will be tomorrow morning when the temps are much colder, that seemed to be when i had the most problems with this. I can see now how much of a pain it is to try and tune with the stock fpr being overrun.

Idle Problem when letting off the gas NOT VENTING BOV either

SmokinV8's

pUtInExIm

90BlueGSX

Corpsegrinder

SmokinV8's

Corpsegrinder

SmokinV8's

rgj

me shakes fist

compuman99

SmokinV8's

stevep

SmokinV8's

SmokinV8's

Top Contributors this Month

Recommended Communities