1st TBI Conversion Help Needed

[1987 GMC Jimmy]

I'm thinking the same thing. I wouldn't even consider fuel or air at this point. It's a spark problem, and from what we've deduced up to this point, it's not from a lack of quality. I would also suggest checking the EST bypass wire to make sure it's connected. It might be an issue with the ESC module since that circuit's been modified, or even a worn/defective part. That or an ECM issue. I know you've done extensive work in that department, but I'm just thinking out loud. Normally if you were having an ESC issue, you should be getting a Code 43, but I wouldn't count on it since you've had the knock sensor written out of the programming.

 

[4WDKC]

When you rebuilt the throttle body did you clean/replace the IAC? If you moved the plunger any it may be out of calibration. google IAC calibration obd1

 

[OkieFishMan]

Does it happen to have EGR? It could be that, or the IAC.

 

[1987 GMC Jimmy]

The EGR has been physically deleted and written out of his PROM. However, you said that the dead spot is right off idle, which I would concur does bring the IACV into question. IAC becomes unnecessary pretty quickly as you open the throttle because the air comes in directly and quickly as you open it. It's not instantaneous, though. The bypass air needs to be feathered out. I would go ahead and do the IAC relearn procedure and see if that helps. What you do is jump your A and B pins on the ALDL, turn the key to ON and wait 30 seconds, go and unplug the IACV connector, turn the key to OFF, undo the jumper, and reconnect the IACV connector. If that fixes it, that would be great. As mentioned, you have to be very gentle when cleaning the valve pintle, but it needs to be clean. If that doesn't go anywhere, I'd consider getting a new one. I don't think any sensor can cause an issue like this at the time when it happens besides the IACV or maybe your ESC module.

 

[MtBraun]

Sorry for the lack of responses guys, been offline for a few days travelling. The throttle body has not been rebuilt. I cleaned it good with some carb cleaner and that was it. I'll do the IAC relearn procedure when I can get it in a heated shop. Its really cold here right now. I am happy to report that it started right up after sitting outside for a week. Last night it was in the -20s so I do like the easy cold starting of this TBI.

 

[MtBraun]

Anyone here have experience with Tuner Pro? I cannot get it to recognize my cable and therefore cannot log any data. I've asked same question on Gearhead but that site just isn't as punctual as GMSB!

 

[1987 GMC Jimmy]

My homemade cable has two lights on it, if I remember correctly - it's been a while, that flicker when a, it's communicating with the ECM, and b, when it's communicating with the laptop. Does yours have something like that? Are you hitting the button with the two blue arrows to enable communication? For me, it sometimes won't do it on the first try, and it'll take two or three times. I know those are pretty basic questions, but you gotta start somewhere.

 

[MtBraun]

I was able to get connected and log a couple files. Funny thing, whenever I was recording the truck ran fine and only cut out a couple of times when I wasn't recording. This truck has a mind of its own. The only difference between today and when it was cutting out bad is that we are quite a bit warmer today (+25). I cannot upload an .xdl file to this post. Any way I could email you the file?

 

[Honky Kong jr]

I was able to get connected and log a couple files. Funny thing, whenever I was recording the truck ran fine and only cut out a couple of times when I wasn't recording. This truck has a mind of its own. The only difference between today and when it was cutting out bad is that we are quite a bit warmer today (+25). I cannot upload an .xdl file to this post. Any way I could email you the file?

I can’t help you with your issue but if you tag Jesse he will see your post quicker or quote him. @1987 GMC Jimmy

 

[1987 GMC Jimmy]

I'll PM you my email address. I don't care if the regulars on here see it, but I don't trust Bing robots and scammers.

 

[Honky Kong jr]

I'll PM you my email address. I don't care if the regulars on here see it, but I don't trust Bing robots and scammers.

That’s why you have back up emails.

 

[1987 GMC Jimmy]

Ha, I didn't even think of that. I have like three other emails from over the years, but I don't even look at those but maybe once every couple of months. It's nice to have all my priority stuff in one place.

 

[MtBraun]

Dave W from gearhead (who burned my chip) thinks it may be an AE table needing adjustment. However, the only way to know for sure is to install a WBO2 sensor to determine if it is a spark or air/fuel adjustment needed.

Not really wanting to spend $200 on a WB system.

I thought these TBI conversions were supposed to be easy!

 

[1987 GMC Jimmy]

Were you able to get anymore data or screenshots of the dashboard?

 

[MtBraun]

Not in a useable format. The one thing I see with the data logging is that it captures about every second, so in playback it can be a tad glitchy on my screen. I'm still getting used to the dashboard and I need to look at all the settings to know when one is out of range. I'm going to watch my IAC counts when engine is cold and then warm to see if that indicates a problem.