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90 K5 Tbi Timing Issues UPDATE

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wayne

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Ok here is the scoop. It's a 90 K5. Swapped in a used tbi crate engine that ran fine in the Burb I pulled it from. Swapped it in the K5. Engine I pulled ran fine but smoked due to bad rings. I put headers and dual 2.5" exhaust on with no cats and installed a 3 wire heated O2. It has new plugs (AC Delco rapid fires with the gap at 38) MSD wires, MSD coil, Napa cap and rotor. New ignition modual. Everything is new. The TBI was cleaned and rebuilt. I also put in a new fuel filter, Walbro fuel pump, and gas tank. Here is the main problem, when I set the timing at 0 without the computer unhooked it will start and run and idle all day. Shut it off and hook the wire together for the computer and it will start and die instantely. If I give it a little gas I can keep it running but it will miss and backfire if I try to open it up. If I keep it running with the computer hooked up the service engine light goes out after it starts. Any ideas on what is wrong or where to start looking?

Update. I switched tbi units after getting the timing sorted out. It runs good and is snappy but it will run for a little bit and just cut off. Start it back up and it runs for a little bit then just cuts off. It will continue to do that. While it sits idleing it sounds fine and it just suddenly dies. If I stay in it and just give it a little gas it will stay running with no problems. I am going to get a new IAC and try that. I am also going to check the TPS and make sure it is right. Anything else I should check?

UPDATE 2:: Well I popped a new IAC in and it ran great for about 10 minutes, idle was a little high but it never stalled or anything. I shut it off to let the new IAC calibrate itself and waited a minute and started it again and it started and shut off. If I give it gas I can keep it running and I can open it up and it runs fine. It just will not idle. I am going to mess with the idle speed and see if I can get it to idle higher, not quite as high as it was after the IAC swap. My guess it was about 1100 or so rpms then. My timing light has a tack so I am using that to go by. Everything seems to be working and I have no service engine light comming on except when it shuts off.
 
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well. it has something to do when the computer is in play with the timing, i would get a scanner and plug in to see if there is any odd readings, or maybe it has trouble going into closed loop so fast, u run that heated o2 sensor before doing all this? and where did u get it? never heard of one for these trucks but now i want one.
 
chevyuser74 said:
well. it has something to do when the computer is in play with the timing, i would get a scanner and plug in to see if there is any odd readings, or maybe it has trouble going into closed loop so fast, u run that heated o2 sensor before doing all this? and where did u get it? never heard of one for these trucks but now i want one.
Click to expand...

http://www.tbichips.com/default.htm
 
Read the codes first.

There is one finicky part on these TBI systems, the EST. This is the module in the distributor. Have it tested at the parts store and insist it be checked three times. If it fails any of these three times it's defective. When you disconnect the wire for timing your turning off the EST. (not exactly sure how the ECM does this)

Did the Suburban you pulled this out of have an updated chip?

Was the ECM working fine in the K5? Really should have swapped ECM as well as motor if the trans was the same.
 
eagle mark said:
Read the codes first.

There is one finicky part on these TBI systems, the EST. This is the module in the distributor. Have it tested at the parts store and insist it be checked three times. If it fails any of these three times it's defective. When you disconnect the wire for timing your turning off the EST. (not exactly sure how the ECM does this)

Did the Suburban you pulled this out of have an updated chip?

Was the ECM working fine in the K5? Really should have swapped ECM as well as motor if the trans was the same.
Click to expand...

Burb was stock just like the K5.
 
I think I'd leave the IAC alone. If you really want to play with it you can pull it and clean it, but if the truck idles, but dies randomly, I wouldn't assume it's bad. If it would never idle I'd be more convinced.

Fuel or spark would be where I'd focus. :)
 
I set the idle and checked the TPS voltage. The voltage is a little high at .60 but I can't get it any lower unless I set the idle lower. I have a new EGR valve to put on but I don't think that is the problem. I have a few spare sensors to swap in to see if any of them help. It's not storing any codes either so no help there.

How do you replace the pick up coil? I already changed the ign modual and everything else looks pressed on in the dizzy.
 
I believe the distributor has to come out and be completely disassembled to get the pickup out.

You set the idle how? Not just with the screw, right?
 
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