Hi, I recently returned from Iraq and bought my dad's truck (he finally would sell it). Its an 85' C10 completely rebuilt with a 383 stroker running the 88' 454 TBI and the DynamicEFI ECM. When the truck arrived here in Colorado Springs, it was having some idle issues, so I did the following steps to try and fix it:

Reset the IAC
Changed the 454 injectors to 350 injectors
Reset the IAC again (ran like crap, same idle issues)
Changed back to the 454's, reset the IAC (same issues)

Adjusted the thottle, now it doesn't go dead when i put it in drive or reverse, runs better (better throttle response), but still idles up and down at lower RPM's (driving or still).

I'm at 7000+ feet elevation here, with 10-12% less Oxygen, but the minor throttle adjustment i made helped with the dying out, but still the surge. I scoured the internet, and I don't think it's the coolant temp sensor, or the MAP sensor, or the EGR. I don't really have a way to check for vacuum leaks (Dad verified all these and said they were good). I'm kinda new to the whole tuning thing, and like i said, the truck is drivable, but where should I start with this? I'm totally lost on how to get this idle to even out. Thanks!

 

Thank you for your service!
Does it have an egr valve? Try disabling it.
Is the throttle postion sensor slotted? May have to adjust it.
What kind of manifold vacuum are you getting? Should be higher then 16" at hot idle.
Double check the grounds to the ecm, check for throttle shaft wear (vacuum leaks), & make sure the engine is getting up to temp. (180 to 200*).

 

The EBL disables EGR valve. So no EGR is in play here, sorry if i wasn't clear about that one before. The truck is up to temp, running in a closed loop, which is required to do the IAC reset. I start the truck, and i get the surging up and down, even with the IAC disconnected. It's basically the same behavior with it on, or off.

No check engine light is on, so I don't believe it is the O2 sensor. Injectors have a good spray all around. As I mentioned before, i really don't have a way to check the vacuum presure on the truck, I have a limited amound of tools here. Grounds all look good, not many wires on the truck that have a lot of wear, everything is in fairly good shape. Thanks

 

Is it the EBL Classic (uses a PROM) or the EBL Flash ECM? Do you have a laptop? Along with the cable, connector, and CD that came with the EBL system?

If so hook it all up and start the What's Up Display (WUD). That will show the IAC counts at idle, the manifold pressure, fuel trims and everything else pertaining to the engine.

If not email me at the update at dynamicefi dot com address. I'll send the latest release.

RBob.

 

Thanks for the reply RBob. Actually you already sent me the files! I installed them on my laptop and was trying to connect through my modem, but i guess it's out of service. Never used the thing for the 2 years I had it, and it figures it would work when i actually decided to use it. So, I just ordered a RJ11 to USB adapter on amazon, should be here in a few days.

I did notice however (returning from best buy on the failed adapter mission) that when i pull into the driveway, the truck had settled into a semi-reg idle. Not surging anymore, just regular idle (a few hundred more rpm than i would like). When I put the truck in park, the idle jumped up about 500-700 rpm. Are you thinking that it's probably in the computer is where my problem exist RBob?

 

Not really, it actually sounds like the IAC is bad. But don't change it quite yet. Once you get the WUD running you will be able to see all of the sensor values and so on. And what the ECM is doing with the sensor values.

The WUD diagnostic display shows the actual raw sensor values. Great for troubleshooting.

The main WUD display will show the commanded IAC steps. Which can be used to adjust the idle stop screw to get 5 - 10 IAC counts at idle (no load, warm engine). If the IAC goes to zero and the idle is still high then need to close the blades some.

If the idle doesn't drop down and the IAC commanded steps keep going to zero, then odds are the IAC is bad (sticky usually).

The TPS setting isn't important, and is most likely not adjustable either. The ECM will auto zero the TPS. As long as it is between 0.2 v and 0.8 v it is good to go.

Note that you can't connect via the modem, need a serial port, so the USB/Serial adapter cable is the way to go. If the one you purchased has the FTDI chip set lower the latency setting once installed:

http://www.dynamicefi.com/USB2SerialSetup.php

If it has the Prolific chip set they don't always work (has FIFO sliders instead of a latency set up).

I noted this: "RJ11 to USB", the EBL included an RJ11 to DB9 (serial) adapter. Need to use that and a USB to Serial adapter cable. Or straight into a serial port if the laptop/PC is equipped with one.

RBob.

 

Thanks again for the quick reply RBob. As soon as the part gets in i'll give the WUD a whirl. Might not have a repost untill next weekend because of training this week. Look forward to actually getting this thing running right! Seems like a lot of potential is lurking under the hood. Will post when I get some numbers and we can go from there. Thanks!

 

Spent about an hour and a half on the forums and saw some guys having the same issues. So I went out to my truck and unplugged the MAP sensor, and "well looky there", truck idles with no surging.

I also read i shouldn't drive it unplugged because an unplugged MAP sensor pulls off a table of base data, causing less fuel milage. However, it's really getting crappy milage having to give it throttle while i'm at the redlight in traffic so it doesn't go dead. It really takes a lot of concentration to drive it in traffic, but on the open road it runs great. I'm still waiting on the adapter to come in, and i still have to drive the truck to work and back. I will post the data i get off the WUD, but does this narrow it down any? And, can i drive it with the map unplugged?