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Discussion Starter #1
I've got a 1987 2.8 tbi. In the last year I've replaced intake gaskets and tbi gaskets. New ignition coil, new ignition module, new cap and rotor. 6 new spark plugs. I've checked for vacuum leaks. New iac valve. New fuel pump and fuel filter. Problem now is the truck cranks and idles fine. But when I'm driving and go to stop the truck will idle low and if I'm not carefull it stalls completely. I can't figure out what it is. I also seem to have occasional misfire in my passenger cylinder bank. So I don't know if it's fuel injectors or some other part of the ignition. If I rev the truck up it will act fine again. Are the injectors suppose to constantly spray or pulse really fast?


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Awww..you ain't got shit!
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Did you check to see if there are any codes present? Not much to these truck's EFI systems. Could be the IAC stepper motor going bad or dirty. It's in the side of the TBI. Has a four wire plug on it. Square 2x2.

Anybody remember the steps for testing it?
 

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Discussion Starter #3
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Those are my codes last time I checked. Coolant sensor is new with pigtail. So I doubt that's a problem and like I said the fuel pump is only a year old. I just replaced the relay for it too
And I replaced the egr about 3k miles ago and I replace the idle air controls valve not sure if I replaced connector

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Discussion Starter #4
I will test fuel pressure tonight but I don't know if it's going to be accurate because when I crank it up it acts fine. I don't notice a lack of power even running 31's. We've adjusted timing before and it always ran best with the mark of the degree plate but I could have it set wrong and it be way to lean. And our truck only have map sensors right? Could that be it? Throttle position sensor? Do you know what a meter is suppose to read on the map sensor, throttle position sensor, fuel injector wires?


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What is this? I can't remember. But when I unplug it idle drops and goes up when I disconnect vacuum hose and plug it back in idle shoots up for a minute. If i plug vacuum line rpm drops and if I just plug in the connector without vacuum rpm goes up too also. I've got 3 relays on the driver side 2 5 wire relays and 1 4 wire. I don't see that wire pattern on diagrams


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Discussion Starter #6
Alight keep in mind I was messing with the map sensor with the truck running. But now I'm pulling 13, 32, 33, 34. Messing with the map probably set those codes off. I'm not getting a o2 reads lean anymore, and I'm not getting a code 54 anymore. Should I reset the ECM and do it again? How do I reset it


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Discussion Starter #8
Alright I reset. Now I'm only pulling a o2 code. Which I unplugged it yesterday. I'll pop the new o2 sensor in and see what happens. But the guys at autozone said a o2 sensor was almost useless on a 87 so that's why I never put it in. If it's not that it's something on the engine that doesn't shoot codes. I didn't find any vacuum leaks. And my idle air control was working fine when I tested it. It's only while driving when you let of the throttle. People are saying the torque converter could be doing it. Does anyone know where the switch or solenoid is for the tc?


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Discussion Starter #9
It's been acting better with the o2 sensor. Hadn't thrown any codes. Until last night when I took it up to 85(very fast for my engine). And them it threw 2 codes. 3 flashes followed by 2 and then 4 flashes followed by 4. Which I'm assuming is 32 an 44. Egr circuit and o2 reads lean. My egr valve is brand new almost so idk whats all included in the egr circuit. And I know lean could be egr, timing, fuel pump, injectors


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Reset the ECM to clear the codes.

Drive it normally and keep the speeds down for a couple of days. Pay attention to how it runs.

Just curious to see if everything is normal with normal driving.

I'm going to guess that 85 is getting close to pushing the limits of fuel pressure supply versus actual demand.

Stock PSI is about 9psi.

Repsonse is much better across the board when closer to 13 psi, but to do this, retuning of the tables in the prom are required.

Oh, don't pay attention to the "guys at autozone" and what they say, especially crap like that.

That's why they work at autozone....idiots....
 

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Discussion Starter #12
I did a couple days ago, the o2 helped a good bit but it still did it deceling from 45-55 on occasion. I disconnected the vacuum to the egr. I know the egr is new but I'm guessing the valve is faulty and letting to much egr. So it's been doing better the last day or two, even idling cleaner sounding. But I live where I work so on a daily basis I usually don't hit over 35 down the dirt road. Once I get the time I'll check fuel pressure, check vacuum on the intake, and probably do another tune up and adjust timing.

Could an adjustable regulator in the tbi help? And are there any aftermarket Equipment for cheap that I could tune it with?


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Boozebag
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A remote fuel pressure reggy can be installed, but it is not as easy on a TBI system since the stock reggy is built into the TBI body.
Here ya go:
http://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=tbi+adjustable+fuel+regulator&_sacat=6000

Tuning is a lot more complicated... You need hardware and software to change the fuel/timing map in the ECU. You also need to know how to adjust the maps.
There are chips available that improve the fuel delivery, they are a good improvement over stock, but are still a compromise.
Here is an example:
http://www.ebay.com/itm/Hypertech-ThermoMaster-Computer-Chip-1988-S10-15-2-8-TBI-Auto-/391157042670?hash=item5b12c6cdee&vxp=mtr

Good luck, if you go for any of these improvements, post your results.
 

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The ecm expects base timing to be set at a specific value, I.E. 1228062 ECM BINs run a 10 degree initial advance whereas 1227747 ECM BINs are 0 degrees.
 

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Discussion Starter #15
Whenever I took the timing down to 10btc it idled very low and would almost shut off my motor had a 15-20 degree timing plate and my timing mark isn't even on the plate anymore just slightly off it probably needs a timing chain


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You won't be able to put a regulator inline with the tbi unless you take out the regulator in the injector pod first.
 

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Your BLM values will go rich globally. Knowing how much will be a guess without data logging.
 
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