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Old 12-21-2006, 10:28 PM
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Just did a TBI conversion and need some advice

as above.. I have a 1981 3/4 4x4 I converted to tbi. It is a 350 with th350 tranny. I took advice from local shops, google searches and wrecking yards..WELL I got led around in a big circle. First off.. They say the 305 sensors, esc, knock sensor, ecm, will swap and it will run fine NOT !!! I did as I read and was told (hey.. not trippin or complaining as free advice is better then none) but once I got all the wiring in .. start it up.. it runs like a flooded mule, timing won't set right, has like a miss or bad plug/wires.. so I do some reading and find out.. the ecm is the same.. chip isn't.. fine. I swap it and the throttle body from a 350 and now it runs 10x better, but I have a 305 knock sensor and a "suppose" to be 305 esc.. faint miss at idle every once and a while.. My question is (if you haven't fell a sleep LOL) is should I change the knock sensor and the ESC to a 350 ? and how do I find out if the ESC (which is new, came out of a 305 or so I was told, and is new with WELLS written on it) is truly a 305 one.. I have also read that driving it a few times will cure the bugs etc.
Second..I unplug the brown wire that controls the timing to set it up (suppose to be 0 and replug it in) but wondered the correct timing settings.. 4 seems to run good, 6 better etc.. mind you I tried timing the beast with the wrong computer in it...I'll retry after I get the right way to do it advice.. thanx and sorry for the long ost MERRY X-MAS !!

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Old 12-22-2006, 08:03 AM
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You`ll need the 350 knock sensor, since it goes by frequencys, a 305 bore is smaller so the frequency will be different. Set the timing by disconnecting the wire, then set it at the factory setting of 0, shut the engine down, disconnect the negative battery cable for over a minute, this will dump the computers previous setting, then reconnect the wire and the battery and fire it up. Is the egr present? if so make sure it`s working correctly and the correct restrictor is installed, you may have to play with the restrictor size since you went with more cubic inches. Any time a engine swap is done to a bigger engine, the ecm, injectors, knock sensor,all must be changed to the bigger engines specs. make sure there isn`t any exhaust leaks either, any leak will make the engine run richer, since the oxygen sensor will pick up the air and think the engine is lean and add more fuel.
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Old 12-22-2006, 09:48 AM
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re engine swap

Thanx.. I am going to change the knock sensor and I am going to buy a new accel ESC module, wires. I am running delco plugs 43XX etc Merry Xmas
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Old 12-23-2006, 11:10 PM
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well My main roblem was 5 and 7 wire reversed.. BUT...

now it won't idle... it stalls or is erratci.. jumps up and down 300 rpm at a time and I have checked for leaks.. no leaks.. I found out tonight that the torx screws on the tps were loose.. so the tps may need to be adjusted now.. What volt meter setting do I put it on to check the settings... thanx for the help.. I am learning but getting pissed at how tempermental this thing is.
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Old 12-23-2006, 11:44 PM
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You could have a number of problems. Or just one. Without scan data or a code your going to waste a ton of time and money. You also need to understand the data and code diagnosis. Is the data link still intact? You will need to wire one in if its not. You knock sensor will not cause a misfire. A faulty ESC can cause a misfire, but the failure rate of those is low. You most likely have a faulty or unhooked sensor. make sure the coolant temp sensor for the ECU is hooked up. Make sure all the ECU grounds are clean and tight. Make sure the map sensor has good manifold vacuum source. Do you have the O2 sensor hooked up properly. The O2 sensor is a big player in driveability. Fuel pressure needs to be between 9 and 14 psi. Hope this helps some.
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Old 12-23-2006, 11:50 PM
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thanx for the reply

All the sensors are hooked up, the check engine light works..if I unplug a sensor it comes on. I noticed tonight, that the egr valve is not working... I checked it with a pump and id don't budge.. I'll replace that asap, My problem now is that it won't idle..it revs up and down.. not high revs..like for example.. at 800 idle (example) it jumops to 1000 and back down the back up etc. I have checked for leaks at the throttle body.. to no prevail. I may have overtightened the throttle body as I had no guide to the the specs ans cranked it by hand till it felt pretty tight...I could have crushed the gasket etc.. I'll replace that an repost my results... It is funny though it ran it's best with the miss due to 5 and 7 wire reversed.. weird eh.. I checked the MAF sensor vacuum from the back of the throttle body and it is good....
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Old 12-28-2006, 07:32 PM
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I just ran through the same thing kind of. Mine turned out to be a number of things that together were creating havoc on me. Try running it with the EGR solonoid unhooked, this will tell you if your EGR is faulty. Also the biggest issue I had was using a used harness for the swap, there turned out to be a charred main power wire that was grounding out every now and then. One wire will be powering sensors, and most importantly the injectors (believe gray wire)?. If you have low pulse to the injectors it will not want to run right either and stuble in low RPM. One important component that some folks overlook is the VSS... Without hooking up the VSS the computer will not know if you are stopped or not and will also make it not run right.

I ended up switching to a Painless TBI Harnees and that eliminated all of my wiring woes. Biggest thing you can do is invest in a scanner or something like WinALDL and a laptop to troubleshoot what is going on. Good luck.
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Old 12-28-2006, 07:40 PM
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got it going thanx

It was the wiring harness.. I found out 2 days ago. Bent TPS ground wire in the plug not making contact. After I soldered, shrink wrapped the new conector on.. it has ran fine ever since.. The egr was bad so I replaced it and I bought a new o2 sensor, and ESC module. Next time I do a swpa, I am going to buy a new wiring harness.. this little ground wire screw cost me about $300 to find.. As for the laptop program ..I have downloaded it and have everything ready to try.. Thanx for the reply
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Old 12-28-2006, 08:16 PM
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When I did my TPI unit on my 62 Nova I tried to use the factory harness. I quickly learned to buy an Painless harness.. Worth it weight in gold.


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Originally Posted by ghomer
It was the wiring harness.. I found out 2 days ago. Bent TPS ground wire in the plug not making contact. After I soldered, shrink wrapped the new conector on.. it has ran fine ever since.. The egr was bad so I replaced it and I bought a new o2 sensor, and ESC module. Next time I do a swpa, I am going to buy a new wiring harness.. this little ground wire screw cost me about $300 to find.. As for the laptop program ..I have downloaded it and have everything ready to try.. Thanx for the reply
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