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TBI won't idle and running really rich

Kay86K5

Kay86K5

1/2 ton status
GMOTM Winner
Joined
Mar 9, 2012
Posts
3,911
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Location
Emmett, ID
Alright, little background. Today me and a few buddies just started working on the wiring for the TBI motor swap on my K5. We went through my original harness on my 86, and then went through the harness from the 89 TBI and pulled everything we needed. We hooked up everything to get it to where it would start. Once we got it started, it didn't want to idle worth a crap and was running extremely rich. We checked timing and it was dead on. Most of my vacuum lines were pretty jacked, but we got them on pretty good, but I was wondering if vacuum leaks can cause rough idle/running rich? Also, we were thinking maybe a temp sensor or maybe even a MAP. No, I have not pulled a code yet cause we haven't got that all hooked up yet (like I said, just hooked everything up to get it fired up), and that will probably be the next move, but if anyone has some experience with a similar situation and/or some advise and direction for my research, that would be much appreciated. Thanks! :thumb:
 
Un plug the TPS while it is running. See if it changes. If not, it's not getting power to or from the TPS. That's what my issue was. One wire end was bad.
 
ktmoutfront said:
Un plug the TPS while it is running. See if it changes. If not, it's not getting power to or from the TPS. That's what my issue was. One wire end was bad.
Click to expand...

I actually just read that on another thread today. I will end up trying that. Thanks. I still think I have some vacuum issues too. Is there anywhere that you guys know of where you can buy a full replacement vacuum hose kit for these, or anyone know of a link that will aid me in the right direction?
 
If you have it handy, that would be nice to take a look at. I know there are not that many, but a schematic would be nice
 
Actually I'd like the vacuum line diagrams as well! :waytogo:

Vacuum leaks are killer for TBI to run right. Check everything including TBI adapter plate.

Also check CTS sensor, when they go bad it reads -40c and adds fuel like crazy.

Since it's a conversion the return line could be restricted, this raises pressure.

When you get ALDL port in you can use CEL to see what error codes are stored:
http://coloradok5.com/forums/showthread.php?t=240425
 
eagle mark said:
Actually I'd like the vacuum line diagrams as well! :waytogo:

Vacuum leaks are killer for TBI to run right. Check everything including TBI adapter plate.

Also check CTS sensor, when they go bad it reads -40c and adds fuel like crazy.

Since it's a conversion the return line could be restricted, this raises pressure.

When you get ALDL port in you can use CEL to see what error codes are stored:
http://coloradok5.com/forums/showthread.php?t=240425
Click to expand...

I don't have a TBI adapter plate. I pulled motor and tranny as a whole from an 89 K5 donor rig I bought, never even seperated motor/tranny, and then put it into my rig. So it is a bone stock 89 TBI w/ a rebuilt 89 700r4 in my 86. But maybe I need to check CTS again, because it is running so rich that it nearly smokes us outa the shop when its running :D. Also, I pulled the TBI tank and factory fuel lines out of the donor and bolted them into the factory location on mine. So I am pretty sure that fuel lines are all good and clear. I do need to get the ALDL port in so I can pull the codes. Thanks for the link too :waytogo:

I am thinking about buying some new plugs, wires, and a new cap just cause, to see if it can help a little. I just keep coming back to that I think it's vacuum. Cause a couple of my vacuum lines were broke from the removal/install of the motor, so I just got some hoses that were laying around the shop and thew them on to start it up. So that may be my first order of business is to get those looking good.
 
The Jimmy has all after market vacuum hoses. The factory get brittle and brake. I have pulled every vacuum line off at some point in time, while it is running, to see what the change is. Fast idle yes, but did not make it run rich.

I'm still leaning on the TPS.
 
ktmoutfront said:
The Jimmy has all after market vacuum hoses. The factory get brittle and brake. I have pulled every vacuum line off at some point in time, while it is running, to see what the change is. Fast idle yes, but did not make it run rich.

I'm still leaning on the TPS.
Click to expand...

I don't think it is TPS cause we messed around with it for a little while. Even pulled the TPS off a donor TBI unit we had laying around the shop and threw it on (also replaced the connector cause it was broke to hell). Throttle response seemed better after that, but no change in idle/running rich. But I am planning on checking again hopefully this weekend.

I think eagle mark may be on to something with the CTS, cause I have read multiple threads of people saying that when that goes out, it runs really rich. And with how cheap they are (~$10), I purchased one just cause. Also purchased new plugs, wires, and cap just to see what happens (and I don't know how many miles are on the current set).

I will keep you guys posted to see what happens. Thanks for the help!
 
Have you check to make sure you don't have a vacuum leak? Mine will always run rich when I have a leak. Have you gone through the Air Idle Control reset procedure?

The best way to start tracking this down is to spend the 60.00 on an ALDL cable and download WinALDL (free). This way you can see if vacuum is low at idle, what the O2 sensor is providing, and what your TPS is reading.

Here's a couple of links that might help you troubleshoot.

http://www.73-87chevytrucks.com/techinfo/TroubleshootingTBISystems.pdf

http://www.gmcmidwestclassics.org/Web pages/Tuning the TBI.pdf

Good Luck
 
Thanks for the replys, I actually forgot about this thread. So been doing a lot of stuff to the wiring. We did throw on a new CTS, and it didn't make a difference at all. But we started looking at the wiring by the ECM, and there is a third plug that deals more with the VSS sensor (off the back of the speedo...cable driven), the ALDL, and some of those. There was actually a connector hanging there from my original harness that was a perfect fit plug for the third plug off the ECM (the plug not connected to the actual computer....don't know if that makes sense). So we just pluged it in when we did the initial start up. Well, we started looking more at those wires and disconnected a 100%, hot all the time wire because we thought it was in the wrong port on the connector. Then, it started up and ran just fine and would idle just fine, and not really running rich at all.

However, when I turn the vehicle off and put the key in off position, then go to start it up again, it takes about 20 sec or so before it will idle again (runs like crap, doesn't want to idle, have to keep my foot in it or it will die). But like I said, after about 20 sec or so, it runs totally normal. :dunno:

The only thing we can think of right now is that because we don't have the 100% hot wire hooked up (in the right position in the connector on the orginal 86 harness side so it transmits to the new harness/ECM correctly), that once I turn the key off, it makes the computer completly reset. So once I start up again, the computer has to run through all of its processes to figure out what is going on before it will run right, basically every time I turn the key off, since there is no power to it anymore, it doesn't save the data it collects when the motor is running.

We have to do some more research. Hopefully will get a chance to work on it this weekend and figure out what is going on. Been looking at wiring diagrams like crazy lately. If anyone could follow this rambling at all and has some experience, let me know :waytogo:
 
The 20 seconds you keep mentioning makes me think of the Hot Fuel Module on some of these HD truck systems where the fuel pump runs for 20 seconds after the key is off. Just wondering if this little extra box is in your wiring and if it were backwards cause a 20 second delay?

Or is it just coincidence you mention 20 seconds?

There is a wiring diagram Sticky here with everything you need. It will show the Fuel Module AKA Hot Start module. It can be removed and not needed.
http://coloradok5.com/forums/showthread.php?t=302678

But there are some Red and Orange wires that need 12 volt always and Pink wire black stripe that need key on power for the ECM to operate properly and save the little memory it has.
 
eagle mark said:
The 20 seconds you keep mentioning makes me think of the Hot Fuel Module on some of these HD truck systems where the fuel pump runs for 20 seconds after the key is off. Just wondering if this little extra box is in your wiring and if it were backwards cause a 20 second delay?

Or is it just coincidence you mention 20 seconds?

There is a wiring diagram Sticky here with everything you need. It will show the Fuel Module AKA Hot Start module. It can be removed and not needed.
http://coloradok5.com/forums/showthread.php?t=302678

But there are some Red and Orange wires that need 12 volt always and Pink wire black stripe that need key on power for the ECM to operate properly and save the little memory it has.
Click to expand...

I think the 20 sec may be a coincidence, but I'm not willing to rule it out too.

I have printed all those pages out from that link and have them in the cab, trying to figure it out. I just need to go through it again. Yoy mentioned an Orange wire, that is one that we know was hot all the time (gave a good shock when it touched metal :D) that we disconnected, so I am thinking that it the key. I will just go through all those diagrams again and double check everything. I know 95% of the wiring is fine, cause I didn't mess with any of it when I pulled from the donar. I just unplugged from ECM, pulled out with motor, and then plugged right back in when I installed the motor in my rig. So I am really close, just need to do some more work.
 
Subscribed as mine is doing the same thing. Running rich as he'll and will die if you don't keep your foot in it for the first little while. I need to find my adl cable and use tuner pro and figure out what's going on.
 
Well just did a test run with my one transistor aldl cable and was able to get data in winaldl and tuner pro rt. Found one of my problems right away with tuner pro rt. Bad CTS reading -35C, put a spare I found in and it reads 3C. Now this is just key on, didn't want to disturb the neighbors.

I am going to do an actual running data log this weekend and see what else I can find. Seeing what my motor is doing is pretty cool! What else should I be looking for?

aldl.PNG

aldl2.PNG
 
Having a faulty CTS and fixing it will make all the difference in the world! :waytogo:

Definately look at the Error codes in the Item List pull down to see if any codes are present and need to be addressed. Sometimes these will set when working on a vehicle, like Error 42 when setting timing. After looking if there is one or more note it and then disconnect Batt to clear codes and run again to see if they come back.

There's lots of things to look at and it's all a balance. If you want go ahead and post your data log from TP, it's an XDL file so needs to be Zipped for attachment here. (EDIT: Zip files are not approved attachments so they have to be hosted elswhere or emailed to me) I'll take a look and point out any issues, then you'll have an idea of what to look for.

I see your using the TunerPro RT files I wrote so that's a good thing! See the Parameter tree on right top for the XDF? Click the Category view as it simplifies what you are looking for. It's an option to set up in TP that most don't spend the time to set up.
 
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