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TBI issues

79rustyk10

79rustyk10

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OK, I swapped the engine and entire wiring harness from an 88 K5 into my 79 K10. I got it running ok but there is some part throttle issues. If i ease into the throttle it is usually ok, but if I hammer on it, the thing falls on its face and sometimes dies. I can rev it up in park just fine and when driving if I can keep it running long enough to get into the higher rpm range the thing screams.

I have the O2 sensor in the collector, I have hooker long tubes that are still open for the time being, Im sure that doesnt help.

I removed the charcoal canister, I hope that isnt the cause as EVERYTHING was removed, the vent lines and all.

I believe the fuel pump is ok. I do not see why it would go bad between the time I parted the K5 out and getting this running. I shortend the K5 sending unit to the same length as the old carb sending unit. I have 16 gallon shortbed TBI tank.

All the vacuum lines check out OK.

Timing is set to 0 degrees

There is no CE light on. I have the 88 and 79 gauge clusters put together to keep the 100mph speedo:D

The distributor cap/rotor plugs and wires are not new by any means but are not that old. keep in mind the blazer was a DD before it was disassembled.

This has me stumped. i had my old 89 chevy for 4 years and never encountered anything like this.

Thanks

By the way, everything is stock still with the exception of the headers. I wanted to hold off on modifying too much until all the bugs got worked out of it.
 
I have the 88 and 79 gauge clusters put together to keep the 100mph speedo
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If you're using the early cluster then you no longer have a VSS (little green box that plugged into your 88 speedo) which i'll bet is your troubles. The ECM uses it for many different things.
 
Actually I do have the VSS behind the speedo. I put the earlier gauge faceplate on a newer speedo assembly to keep the VSS there. Would getting the aftermarket VSS that goes inline by the transfer case be a better solution?
 
79rustyk10 said:
Actually I do have the VSS behind the speedo. I put the earlier gauge faceplate on a newer speedo assembly to keep the VSS there. Would getting the aftermarket VSS that goes inline by the transfer case be a better solution?
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First, if you swapped the early face plate onto the later speedo the gauge will not read correctly since the movement is different although the VSS will still function properly. You will need to have the speedometer calibrated though so the ECM is recieving the correct info from the VSS (once again this could be your problem).
 
how would I go about this? The blazer had a 700r4 and 3.42s. My truck now has 4.10s but I am unsure the size of the tire I will decide to run when it is all said and done.
 
You will need to wait until you have both the gears and tire size you're going to run then you can use one of the online charts to figure out what speedo driven gear you need to run to correct the speedo.
 
I hope that is the problem, I have had many many friends put much bigger tires, up to 35" on with no gearing correction, and without causing drivability issues like this.

not to beat a dead horse but where is one of these tables located?

The VSS makes alot more sense now after thinking about it, the truck had 2.76 gears from the factory, now with the 4.10s I bet the ecm is so screwed up it doesnt know what to do.
 
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Here is a good calculator but you'll first need to remove the speedo cable and housing from the t-case and check the color of the drive gear and then you can figure out what driven gear you need. Once again if you change either the gearing in the axles or the tire diameter that affects the speedo calibration. http://www.bgsoflex.com/speedo1.html

GM uses 1000 cable turns per measured mile.

Here is a list of the color/tooth count on driven gears.


700-R4 Speedo Drive Gears

Gray...... 15
Red....... 17
Blue...... 18
Yellow.. 19
Brown.. 20
 
Have you figured out the problem yet? Only reason I ask is because I am not running a VSS.
 
Just a slight correction from above, these setups use a 2000 pulse per mile "standard". Only used two types on these trucks, the 2000PPM, or the 40 pulse per revolution, which was only used '90-91 with the electric speedometers.

Doesn't really matter of course for the most part, but when dealing with aftermarket stuff you need to know what you've got. :)
 
lak2004 said:
Have you figured out the problem yet? Only reason I ask is because I am not running a VSS.
Click to expand...

No I havent corrected it yet. I was out screwing around with the truck today, and noticed that the issue wasnt quite as bad after it was warmed up. could the fact that I have the longtube hookers without a heated O2 sensor cause part of the issue?
 
Do you have an aldl cable and lap top you could hook up to it? That would tell you if you are getting readings from your O2 sensor I believe.
 
dont think so. post up in the region forum and see if someone can loan you that stuff or if someone with a set up would be willing to help you out.
 
79rustyk10 said:
No I havent corrected it yet. I was out screwing around with the truck today, and noticed that the issue wasnt quite as bad after it was warmed up. could the fact that I have the longtube hookers without a heated O2 sensor cause part of the issue?
Click to expand...

Hate to say it but I doubt the vss is your problem... sounds more like a bad MAP sensor or timing to me.... also look at both the injectors while its running. Do they both spray a nice cone shaped spray? No dripping?

Heated o2 is not the problem either. Is your check engine light on?

Check your firing order(I.E. plug wires) and vacuum lines also.

ALSO PUT YOUR TIMING AT 6 degrees advanced... thats what they come from the factory with. MAKE SURE YOU UNHOOK THE TIMING ADVANCE WIRE WHEN YOU SET TIMING.

Theres a ton of stuff that will cause this but thats the jist of it.
 
I am pretty sure that TBI calls for 0 degrees BTDC for timing.

well, I double checked everything. all vacuum lines are OK, all plugwires are correct.

and no CE light
 
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Did you unhook the electronic advance wire when you timed it?

I remember 6* advanced..... gimme a sec... lemme see If I can pull it up.


Edit: can't seem to find it.... lost my manual.
 
Check you injectors to make sure they are spraying correctly and look for bare wire on your O2 wire.
 
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