Off Idle Problems

[johnmbod]

I am having a problem off idle with my 87. It has no power and pops and backfires as soon as I put the motor under load.
Backstory:
I bought the car, off of a well respected individual. When I got it, the motor would break up when it approached 20lbs of boost. I figured it was blowing the flame out so I changed plugs and dropped the gap to .028". The problem was still there but marginally better. I decided that I "needed" The TR6 ignition so I bought it. I installed the Ignition and the car wouldn't start. The Ignition was throwing a cam alignment code. I set the cam sensor alignment and the car fired right up. I tried to drive it, and this popping stuff started. I re-checked the alignment because I thought maybe I made a mistake and got it 180 out. After resetting the alignment, (which was correct) the problem continues. I pulled a known good MAF out of another car, yet the problem continues. Also to be noted, even when I first got the car, I had to roll into the throttle, I couldn't just jump on it. I am stumped. Any Ideas?

 

[earlbrown]

IAC numbers are way too high. Open the throttle blade a little (You'll most likely have to adjust the TPS from doing that)

Odds are the transition from an extremely closed blade to an open one is giving you an off idle cough until the computer can start adding fuel.



......actually not that I've read your post again I noticed the engine wasn't warmed up. Post another log with it in closed loop.


When it's warmed up, does it still idle fast and have such a high MAF reading?

 

[johnmbod]

IAC numbers are way too high. Open the throttle blade a little (You'll most likely have to adjust the TPS from doing that)

Odds are the transition from an extremely closed blade to an open one is giving you an off idle cough until the computer can start adding fuel.



......actually not that I've read your post again I noticed the engine wasn't warmed up. Post another log with it in closed loop.


When it's warmed up, does it still idle fast and have such a high MAF reading?

Here it is after warming up. One is idle, the other is under load.

 

[earlbrown]

Is it my screen or are you really idleing at 450 with an IAC count of 86?

 

[No disintegrations]

the throttle is closed and the injectors are at 1 to 3 % duty. How can it be under load? Is it idling in gear you mean? or wrong screanshot?

 

[johnmbod]

The first is a screenshot of foot brake with the accelerator cracked. The second is idle in park.

 

[johnmbod]

Bump! Any ideas here.

 

[dank GN]

Adjust your IAC as stated . Turn the throttle blade screw in to open your blade then set your TPS to .42

 

[dank GN]

And what's up with your map sensor ? Do u have one hooked up to your powerlogger so u can record boost ?

 

[TurboBuRick]

Is it a rhythmic pop that continues until you lighten up on the throttle? Might have a worn cam lobe.

 

[Chuck Leeper]

From what you are labeling as hot/idle, and hot/load, it looks like there's several ??
Idle:
20g/s, 1.13tps, 1025R, 175iac, 12.9V, 29.3*, 4.56 ipw.
But, under a load I see:
5 g/s, .40tps, 450R, 86iac, 11.8V, 23*, 3.04 ipw.

Sumptin wong!
It looks to me as tho you have the logs labeled backwards. In any case:
At that temp, and a load, the engine should be in closed loop.
As Earl mentioned, no way it's idling at 450.
IAC at 175, bad info.
12.9 to 11.8 volt drop? Have you actually checked the alt output?
IPW dropping from idle to load?
I'd suggest you check all grounds, the integrity of the Powerlogger connections.
If, in fact, the batt volts are only 11.8, and is at that volts at 20# boost, the ign system is in question.
What is fuel pressure? I don't see that you are logging it.

Just my $.02....

 

[johnmbod]

Here is a new screenshot. this is warmed up at idle in park

 

[johnmbod]

Here is Idle in drive

 

[johnmbod]

in drive with part throttle, (foot brake) if I give it any more throttle

it pops and stalls

 

[johnmbod]

From what you are labeling as hot/idle, and hot/load, it looks like there's several ??
Idle:
20g/s, 1.13tps, 1025R, 175iac, 12.9V, 29.3*, 4.56 ipw.
But, under a load I see:
5 g/s, .40tps, 450R, 86iac, 11.8V, 23*, 3.04 ipw.

Sumptin wong!
It looks to me as tho you have the logs labeled backwards. In any case:
At that temp, and a load, the engine should be in closed loop.
As Earl mentioned, no way it's idling at 450.
IAC at 175, bad info.
12.9 to 11.8 volt drop? Have you actually checked the alt output?
IPW dropping from idle to load?
I'd suggest you check all grounds, the integrity of the Powerlogger connections.
If, in fact, the batt volts are only 11.8, and is at that volts at 20# boost, the ign system is in question.
What is fuel pressure? I don't see that you are logging it.

Just my $.02....

Battery was dead the other day. I charged it for the latest round of screenshots. The screenshots are now labeled more clearly.

 

[turbo nasty]

Instead of posting screen shots have you done the recommended adjustments to the iac? Its still way to high...it should be 10 to 50

 

[johnmbod]

Instead of posting screen shots have you done the recommended adjustments to the iac? Its still way to high...it should be 10 to 50

First off I posted the screenshots because there seemed to be a ton of confusion as to what was going on.
http://www.gnttype.org/techarea/faq/IACresetscan.html
Now that I found this I will do so. I have never worked on a FI car. That is why I am here asking for help.

 

[mikestertwo]

The first thing I would do is take the car out and let the computer "learn". I noticed all your BLM's are at a default value of 128. Once the computer has "learned" and the motor is fully warmed up then I would take all the readings to try and diagnose the problem. JMHO

 

[earlbrown]

He mentioned posting of the screenshots because you can post the actual log. Anybody with the powerlogger software can view all the pages and interpret the data a little more easily.

In the case of your IAC being so open, that means your butterfly is damn near stuck shut and the car is idling off of the bypass circuit only. When you crack the throttle the engine sees a giant jump in airflow and it literally takes a second or so for the MAF to notice, command the ECM to start fueling, and the injectors to get on the clock....

By opening the blade a little, the IAC passage will close down and the blade will be open a little more so when you crack the throttle it won't be such a dramatic transition.

Keep in mind as much as you're going to have to move the blade, the TPS reading will most likely move up out of idle range. You'll need to adjust it back down to .42 or so. It's a balancing act getting those two set right and it takes a few tries as they mess with each other when you change one of them.

 

[johnmbod]

I fixed the IAC problem, I pulled the valve off of my other GN and got it running. Now the car backfires as soon as it goes into boost. I can't drive it around because it backfires so much. I will post the log next time.