Still stalling and rough idle - UPDATED

[Falco]

Howdy,

If you remember I posted about my stalling problem at gear changes a little while ago. I still have this problem but beside this my idle went bad too. First it came occasionaly, usualy after longer trips. Now it's always there a few minutes after startup, once the coolant is around 150-155 F. It's hunting 100-150 RPM's...

No vacuum leaks so far, that I could find. There is one at the TB shaft, I've already ordered my new TB, but it's not here yet.

WOT performance is still great, that's why I guess it's not an ignition problem. Beside this every component in my ignition system has been replaced recently one-by-one.

Tried to play with fueling. Just the dumb way, changing the fuel pressure. The problem is definitely worse with more fuel pressure. Now my base FP is around 46 psi, and I don't wanna go leaner. My AFR is also hunting between 14.3 and 15.9 at idle. (Sometimes I can see 17.9 at idle My WB could go wrong sometimes!?). I've no leaking injectors, my system can hold the pressure quite well, enough pressure at WOT etc...

Anyway. I'd be very pleased to hear any ideas. Should I go to adjust my idle fueling in the chip? Or changing the FP proved it's not a fueling issue? That's a 50v4 BTW...

TIA,

 

[ed hess]

falco

go search my thread where turbo tony was helping me chase my stall problem.

as i recall there was soemthing odd when i would try the fp changes he had me do. they never seemed to work correctly as he expected them to.

Something tells me you are going to find the same culprit i found after that motor came out. the gaskets and seals under the lower intake had a vac leak that wouldnt show on a gauge, or with a bike tube.

but if i were you i would try the new tb before i take the intake off just to check..... . and dont bother trying to simply tighten the lower intake. it wont help.

ed

 

[leroy]

What's your IAC doing?

Jim

 

[Falco]

Ed,

Yep, I've seen that thread. My upper and lower intake were off last winter. I took my time, when I put them back. Not a perfect test, but I also tried to spray WD40 around the lower and upper, but it hasn't changed the idle...

Jim,

Sorry, I forgott to mention this. It's in the 30's range at idle. My MAP is in the 28-30 kpa range, fluctuating a bit.

Thanks,

 

[ed hess]

falco

again not saying its the intake as i realize this is the most pia thing to fix related to idle issues. but like i said when the motor was out it was the only thing i found. unless my tb swap made the difference.

hopefully the tb swap will fix yours.

fwiw nothing i sprayed around the intake made any idle increase or decrease either!

get the tb on there

ed<-------keeping fingers crossed for falco and his new tb

im off to yank a broken tranny

 

[Falco]

Thanks Ed...

Jim,

Could you take a look at this:

http://www.tragacs.com/Download/startup.zip

It's a DM file zipped, from startup till the truck warms up. There are a few things I didn't catch. First it's cold enrichement, that's fine. The AFR goes up till the RPM reach the desired 800 RPM. Then the AFR comes down around ~13.5. Then after a while it goes up to ~17.3 and starts to fluctuate between 16.5 and 17.9. That's the point where the idle becomes real bad. I waited a bit, reved it a bit and put it in drive. In drive the AFT stops fluctuating, it's stable 17.9 . Idle a bit better, but still bad, IAC now in the 20-30 range compared to the 1-3 in P. Finally I put it back to P and the same goes on. Bad idle, erratic AFR.

Any idea?

TIA,

 

[Falco]

Howdy,

I played with idle fueling a bit today. Burnt a couple of bins with different settings. I let the truck to warm up, no problemo. Warmed up, the RPM is at steady 800, the AFR is around 13.0-13.5. As I changed in F29E, the AFR followed it as it should be. Anyting leaner than 14.0 and the idle starts hunting.

However what ever I do after a minute of idling the AFR starts to lean out still it's reaching 17.9, which I belive is the leanest value, that it could display. I restarted the truck couple of times when warm, it's allways the same. A minute of good idle, then it's leaning out and the idle goes erratic. IAC values seems to be correct, fuel pressure is steady 41 psi or so.

What is very interesting, that my BPW is not changing while it's leaning out.

Any idea, what can cause this? I'll replace the fuel filter tomorrow, but I don't think so it will help... I've out ideas... Pls help if you can...

Later,

 

[leroy]

Sorry, it's been awhile since I've had a chance to revisit this. It looks like a vacuum leak. Your IAC counts drop to zero after warmup.

HTH,

Jim

 

[ItsMyTy]

Yep, you've got too much air getting into the engine from somewhere. The bigger the vac leak, the lower IAC goes to try and compensate. If it's at zero, then you've got such a big leak the IAC can't compensate and that's why you're going lean. It looks like when the engine warms up, target idle speed drops and the vac leak becomes more of a factor. Try blocking off all vac lines and pcv line.. see if IAC goes up a lot. Then check for leaks around the intake manifold. Dont forget to check the egr valve, if you've still got it installed. It could be leaking exhaust gases into the intake when it's supposed to be closed, and act just like a vac leak. Another thing could be a worn throttle body that's not closing enough to allow for a low idle speed.

 

[sytyguy]

Don't forget to check for a vacuum leak around the cruise control. I chased my tail for a wk-end a few years ago and it was a faulty CC unit. Even starting fluid couldn't find that one, so I took a gamble......luckily that was it.

May not be the case with you, but something to check in addition to all the other trouble spots (A/C vac line, TB gasket, TB shaft bushings, upper to lower gasket, and all other vac lines).

Good luck,

Hood

 

[ed hess]

falco

I sure hope i am wrong!

put that tb on!

ed

 

[Falco]

Thanks guys, I appreciate your comments.

I've no EGR and cruise control any more. I'll do a bike tube test once more. As I've mentioned I've a leak at the TB's shaft ends, beside this I couldn't find any more leaks.

I've ordered a BBK TB, but it was on back order, so I've to wait a bit to get it.
If it doesn't help I'll pick off my intakes and put them back with new gaskets.

Will report back if I could find anything...

Later,

 

[SuperStockChamp03]

A vaccum leak will cause the IAC counts to go low, but the MAP sensor will t tell ECM to add more fuel if you have a leak, remember we don't have mass air sensors. I have been chasing idle problems and I have just spent a large amount of time working on my idle fuel table. My truck idle great when in drive or with the a/c on, but with no load it hunts. I did find some thing that helped a great deal, but first I would like to know your BLM and INT #s.
What MAP are you using 2bar or 3bar, and what injectios? Closed loop or open?

Good luck
Troy

 

[Falco]

Troy,

50's injectors, 3 bar, open loop. So integrator and BLM are 128 all the time...
BTW, mine is hunting in both D and P and N. However I've no A/C, so that's not an issue any more.

Thanks,

 

[SuperStockChamp03]

Falco,

I just tried to submit a long message but it didn't work, so this message is mostly is a test of the BB.
What programing software R U using?

Troy

 

[Falco]

Troy,

Promgrammer... If you prefer you can send me a mail to falco@tragacs.com

Appreciated,

 

[SuperStockChamp03]

Falco,

What is the value in your f28 table mine is .10
What___________________f30 table @ 800 rpm mine is 30.9
What___________________f29e 20 30 40 50
________________________600 18.0 18.4 18.8 21.9
________________________800 16.8 17.2 17.2 20.7
________________________1000 18.4 18.8 17.2 20.7

My fuel pressure is set at 44 psi base. These values seem to work for me, but I am still tuning. My chip runs closed loop. I lowered the fuel pressure way down (from about 47 to about 36) and the idle smoothed out I looked at my scaner expecting the int to go up but it went all the way down to 80 this was with the blm fixed at 128. I think this is a clue! My first thought is that the 50lb hi imp. injectors don't like hi pressures and short pulse widths.
I also need to change my plugs, I went 12.5s on two year old plugs. I may also need to open up the gap I thinks I set the at about 030. For those of us running close loop chips it realy helps to set intergrator delay (update rate) higher.
If anyone in the KC area want to do any tuning send me an e-mail to
syclone@bartnet.net.

 

[Falco]

Troy,

Thanks for your reply. My F30 is 36.3@800RPM.

F29E

20 30 40 50

600 23 23.4 23.8 24.2

800 26.2 27.3 27.7 28.1

1000 26.2 27.3 28.1 28.1

My base FP is 47 psi now. So obvoiusly yours should be much leaner than mine, but that is not the case. As far as I can see at least 14.5-15.0 AFR on my WB the idle is acceptable. However as the truck warms up the AFR leans out. Anything leaner than 15.0 and my truck idles like crap. I tried to lower the values in F29E, but idle became noticable worse.

We might find the difference in closed loop vs open loop. I'm running open loop. I might want to switch closed loop and tune it like this. How can I switch it back to closed loop? I can remmember discusson like this, but can't dig up the details.

Later,

Anyway, that's interesting. It would be nice to know your actual AFR values with a WB...

Later,

 

[z28camaro]

Your problem sounds like the one I had. I had 30lb/hr high imp injectors on my 305 SB and my idle was very unstable to the point my car would die. I finally pulled my plugs after replacing a bunch of other stuff to find that some injectors were not firing at idle. I was asking to much out of the high imp injectors. I swapped over to 35lb/hr low imp injectors and wired it up like a turbo sunbird and all of a sudden my idle was stable. Datamaster is reporting .8-.9 millisecond pulsewidths at idle and the closed throttle conditions are great. You could also try lowering the min. BPW hysterious value from 1 to .8 or so if thats what your comanding at an idle. But chances are your high imp injectors won't be able to react fast enough.

 

[Falco]

That makes sense. Thanks. If I remmember right, my BPW's at idle are in the 1.30 range.

If that's really the case, I could step up to 55lb/hr. This would require the change of the injector drivers, but I couldn't get them anywhere here. On the other hand, a bunch of people are runnig the high imp 50's without any problem. If this would be a general problem it has been showed up several times already, I guess.

Anyway. Is there anyone out there, who I can get the Faichild (or similar) injector drivers from?

Later,