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Kustom Tbi Issues.....

1K views 5 replies 4 participants last post by  86k30 
#1 ·
Sorry for the long read in advance

Last year I decided to go cheap and put tbi on my 79 bronco. It's a stock 400M with an aluminum intake.

So first things first.
-Throttle body and wiring harness from a 94 chebby 2500 with a 350
-airtex e2000 fuel pump, stainless lines and motorcraft F.I filter
-Every sensor is new from napa, the expensive line of sensors.
-Holley square bore to tbi adapter.
-Red/Blue connector computer I think its a 7747
-Memcal and chip tuned with some free software off the interwebs



Only picture I have of it, this was mid conversion. I have since cleaned up the wiring

The issues I'm having started in october. I was driving my shit to Alto for the halloween run (about 2 hours at bronco speed:smokin:) I was cruising up some slight grades at half throttle at about 80mph and the check engine light came on and it started backfiring through the exhaust while climbing the hills.

When I got there I checked connections. I have had problems with the brittle plastic connectors coming apart. The ICM and MAP sensor connectors like to come out every once and a while. They seemed good as I had zip tied them tight before. I put an ohm meter to the TPS and it checked out fine.

It ran like shit for the weekend, stumbling at full throttle under load with the check engine light on.

So I pull codes and get a ton of codes that don't make sense. Almost everything that it threw codes for have been cut out of the chip.

DTC - 13 Oxygen sensor circuit open or no activity
DTC - 13 Left bank O2 sensor circuit open or no activity
DTC - 59 Trans fluid temp sensor circuit error (high voltage)
DTC - 67 A/C pressure sensor circuit error
DTC - 75 Digital EGR solenoid #1 circuit error
DTC - 82 3x Crankshaft position sensor circuit error

When I hook a scanner up to it, the scanner cannot read the computer. I think it may have something to do with the wire that grounded itself in the cab last year at katemcy. It's a pink and black wire (not sure i'm colorblind:laughing:) connected to the check engine light. I replaced the wire but I fear it fucked something up.

So to try to remedy this problem I have
-put a new computer in it
-Looked for broken connections on the memcal, blew the chip out like a n64 game
-Changed the fuel filter, dropped the tank and put a new sock on the sender, blew out the fuel lines with an air compressor
-Changed the following sensors
-Tps
-Iac
-Map
-ICM
-took out the distributor and cleaned the tone ring and pickup
-replaced computer grounds
-replaced the coil
-put a new fuel pump on it

From what I can tell the fuel injectors are flowing well. It really feels like an ignition problem. I can rule out fuel because if I turn the truck off and on a couple of times the light won't come on and it will run fine. If I let it idle with the light off it will eventually come back on.

If I give it throttle slowly it will climb as normal but if I goose it, it just stumbles. If I go from idle to WOT immediately it will almost die.

I've been searching for a solution for a while but my symptoms confuse everyone I have talked to. The only thing I can think of is that my truck hates chebby and is sabotaging itself. I guess it can't help it.

Any help with this would be greatly appreciated. I'm not a chebby person so i'm not up to date with tbi problems. The guy who helped me install it graduated and moved away.
 
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#2 ·
Pretty sure you're not running a 7747 ECM. There is only ONE O2 sensor for that one, no left/right bank O2. '94 TBI will be OBDI, you shouldn't necessarily need a code reader, just a paper clip. Some of them codes you've listed aren't 7747 OBDI either (for example, there is NO crankshaft position sensor on TBI OBDI).
 
#3 · (Edited)
I'm 99% sure its the 7747(im in Germany for the week I can't go look). It has only one o2 sensor. That's what doesn't make any sense. Its making up codes for things it doesn't have. I did the paperclip trick, thats how I got the codes I did. The first time I read them I looked them up and was sure I read them wrong, so I read them 2 more times when I was sober and they were the same.

This is like that move where the robot gets hit with a lightning bolt and becomes alive and reprograms itself........:grinpimp:
 
#5 ·
I just redid the tach wiring to put an autometer monsta in there. There are two wires going to the positive side of the coil and two going to the negative side. One on the positive side goes to the autometer tach.....so there should be one more?
 
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