throttle response - engine wants to die after throttle closed

[Quickstop [UK]]

If I start the truck, I need to crack the throttle and that seems to help it start.

At idle, it runs reasonably well and if I open the throttle, it responds nicely. If I open the throttle wide though and then allow the blades to snap closed, the engine bogs and often dies.

I have replaced the IAC to no avail. It has done it on multiple tunes. I'm leaning on a vac leak somewhere but wouldn't that make it have a higher idle?

When I took out the IAC, the plunger had soot on it - is that normal?

Does anyone know where to look?

Thanks!

 

[Flyin Ryan]

Re: throttle response - engine wants to die after throttle closed

I had this issue and incleaned the iac and it slightly helped so I replaced with new and pulled the ECM fuse to allow the ECM to relearn and it fixed the issue but in ur case I have no idea as a vac leak would increase the idle like u mentioned

 

[dgoodhue]

Re: throttle response - engine wants to die after throttle closed

Where is the iac counts when the engine is warmed up at idle.

 

[Quickstop [UK]]

Re: throttle response - engine wants to die after throttle closed

Just looked at an older log I had and the IAC goes to 32 instantly when I put it in park and then the IAC climbs to 90 ish for idle. I think that the set screw must be in the wrong place.

I'll adjust it so It's around 15-20 at idle and see how that responds. I found this which helped:

IAC and idle screw

Slow and steady wins the race. It was actually E-Rue's build thread that made me think this was the case...

iv been having minor cold start issues, intermittant stalling when going from drive to park, and what seemed like slugish response form the IAC when id drop the throttle really fast. i kept thinking that it would go away when i was done tuning it and that it was a minor tuning issue that would fix itself once the tune was nice and super tight. well it didnt...... after 6 months of off and on tuning, the truck was so well tuned, that i couldnt find or feel any drivability issues whatsoever regardless of outside temperature or weather. the IAC issues continued. ...

after thinking about it one night i had an idea. went outside fired up the truck..... it did its usual low idle while cold, even tho the IAC was full open. i took the throttle body set screw and dialed it in about 1 full turn. the idle immediately jumped up about 400rpm. once it warmed up the computer had no trouble idling down to the desired 900rpm. so i figured i had made a good change. the previous issues seemed to have mostly gone away on the test drive, so i adjusted it another full turn. now on off throttle is better, cold start is better, hot start is better, and theres no intermittant stalling going from drive to nuetral.

It's the first thing I am going to do to the truck next week when I get home. Fingers crossed.

:cmas:

 

[midnightbluS10]

Re: throttle response - engine wants to die after throttle closed

The "high Idle" could be effectively cancelled out by the IAC. If it's working properly, it should close, allowing less air to enter the engine, letting the leak be the source of air the truck uses to idle.

 

[dgoodhue]

Re: throttle response - engine wants to die after throttle closed

I would fix the vacuum leak, first. This your typhoon with heads/cam/gt35r right? If I has a higher than stock idle, the iac counts is how the ECM raise the idle, that would explain the high iac counts. The tune could be responsible for the stalling on decel as well.

 

[Quickstop [UK]]

Re: throttle response - engine wants to die after throttle closed

No vacuum leak. Steady idle at 90 counts = too little air. I put my hand on the turbo intake and the engine dies. I can always turn the screw back.

The tune runs on another truck with no IAC issues so I am optimistic this is the solution. I never touched the idle screw after Matt Blum worked the TB so this seems sensible anyway.

 

[RealFastV6]

Re: throttle response - engine wants to die after throttle closed

I agree with you on the screw adjustment.

 

[Quickstop [UK]]

Re: throttle response - engine wants to die after throttle closed

I would fix the vacuum leak, first. This your typhoon with heads/cam/gt35r right? If I has a higher than stock idle, the iac counts is how the ECM raise the idle, that would explain the high iac counts. The tune could be responsible for the stalling on decel as well.

Thanks btw - I know what you mean but it was idling fine at about 900 rpm. This is easy enough to try. Wish I could do it to the truck right now instead having the week of anticipation ahead!

I agree with you on the screw adjustment.

Thanks :tup:

If I am wrong then it's probably the easiest change to reverse :tup:

 

[dgoodhue]

Re: throttle response - engine wants to die after throttle closed

If your idling at 900 rpm that is probably why the IAC counts are at 90, the stock idle is something like 625. I would adjust the TB stop, first. It still could be the tune causing the issue, not every engine is the same when the heads/cam/turbo have all been upgraded.

 

[Quickstop [UK]]

Re: throttle response - engine wants to die after throttle closed

Yeah but also, remember that I need to have my foot on the throttle to start it. That extra crack, and who doesn't like crack in one form or another , seems to be esential.

By TB stop, you mean the idle screw or is there another? I'm nowhere near the truck at the moment.

 

[dgoodhue]

Re: throttle response - engine wants to die after throttle closed

Some might mistake it as an idle screw, but it is not an idle screw. The idle is controlled by the ECM unless out the range of the IAC.

 

[Quickstop [UK]]

Re: throttle response - engine wants to die after throttle closed

RESULT:

We have a winner!

Just turned the screw in two turns and the truck responds noticeably better to the throttle. After I close the throttle, it idles along merrily - none of the bogging it had before. Also, P to D, N or R, the engine note changes but it doesn't die. The idle went up initially with the turn of the screw then the IAC adjusted and the idle settled down again. I just got done driving 5 hours to get to the car so once I am rested, I'll get TPRT v5.0 on the case, verify the IAC position and adjust the screw to get 20-30 counts at idle.

Very happy.

:tup:

 

[TNPhoon]

Re: throttle response - engine wants to die after throttle closed

Woo Hoo!

Now don't go take it for a drive and get pulled over for an expired license.

 

[RealFastV6]

Good deal.