OK, so I am finishing up my 350 TBI conversion and am running into a couple issues so I come to the wealth of experience here in hopes of an answer. First, this is a 1970 fj40 with a 1993 5.7L out of a suburban, (the burb had an auto in it) now with a SM465 4spd. I am not going with a VSS as it would require installing a reluctor ring as well as the sensor and I do not think it is as necessary without the auto. Upon initial start-up it ran a bit rough, would die, and would not accelerate well, throwing codes 22, 43 and all the codes looking for the auto tranny. I did a full tune up inc. plugs, wires, cap and rotor, replaced the idle air control, throttle position sensor and knock sensor. The only relevant code it is now throwing is the code 43 (knock sensor low voltage). Here is the weird thing, I have the Factory service manual for emissions / fuel control and in the trouble shooting of the knock sensor it says to check the voltage on the KS lead which should be 5v and it is 4.9v I think OK, then it says to pull the lead off the KS and check the resistance between the KS and the block, (it should be 3.9k ohms) when I check, it's 99.1k ohms the new one and the old one are exactly the same (99.1k ohms). I am wondering, do I have the wrong sensor? If so, how do I find out which one I should have? I would assume that since I am getting the exact same reading on both sensors, it is not the KS. I have also read a lot of threads about this and it seems that other things can cause this code. Lastly, when I start it now it surges like it is looking for idle, when I unplug the IAC it smooths out, plug it back in and it surges, after it warms up it idles smooth, by the way it accelerates GREAT now very fast. I am going to get a chip programed without the AT so it won't keep throwing the AT codes, could it be the fact that it is looking for the AT that is causing the idle surging problem? Thanks in advance for the help...
350 TBI conversion help (1 Viewer)
- Thread starter PhatFJ
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what's your fuel pressure?
Adjust/replace your IAC and/or TPS. The IAC acts similar to a choke, either opening or closing a little port in the side of the TBI. Once it warms up, you it closes and runs great... Under hard acceleration it should open up depending on how the computer is set up. I'm not sure on stock to be honest... I just set my to allow maximum air in above 3500rpm...
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- #5
Already replaced see first post..
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- #7
I have not pulled the injectors but they do have a good spray pattern. The EGR is there, have not pulled the intake. I could pull the egr and take a look at it and the port. I was wondering if the TBI might need a rebuild, could this be one of the symptoms? I would have thought that I would get a code for other components.
VSS is a good thing... you will have continious issues without one. You need a new chip for your ECM as the ECM are not programmable and the chips have to be burned...the ECM will always expect to see the auto trans until this happens. I would replace the knock sensor. Assume you have all the other sensors for the TBI setup to include 02 sensor and that they are operational. First of all you have to get setup with a new CHIP for your ECM.
x2 u need a chipped ecm.. good luck
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Also agree... some have luck without a vss but most do not even if they have been deleted out of the ecm.
Sent from my DROIDX
Sent from my DROIDX
The vss is important but is not going to cause symptoms as severe as what you have. I might try throwing the old IAC back in once just to see what happens. I think there is a procedure to get it set right as well when you install a new IAC. Can't remember off the top of my head but google it and check that.
Are you running a heated o2 sensor?
Are you running a heated o2 sensor?
My4x4FJ40
Open 6 days a week
tbi
Pull the tbi off and look under the bottom to see how much carbon build up from the pcv, and egr valve. I have seen the port completely stopped up from carbon thus affecting the iac from working as it should. If there is a lot of carbon I would put a kit in the tbi. Also check base timing with the tan jumper wire disconnected, it is real close to the ecm on the wiring harness I think? witch would have been RF floor of Burb. I hope this helps.
thanks
lee
Pull the tbi off and look under the bottom to see how much carbon build up from the pcv, and egr valve. I have seen the port completely stopped up from carbon thus affecting the iac from working as it should. If there is a lot of carbon I would put a kit in the tbi. Also check base timing with the tan jumper wire disconnected, it is real close to the ecm on the wiring harness I think? witch would have been RF floor of Burb. I hope this helps.
thanks
lee
whitey45
SILVER Star
dont forget that a simple vacuum leak will cause all sorts of issues with a tbi set up and you definately need to burn a new chip...
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- #14
Thanks guys I really appreciate the input!! About the VSS, I have done a lot of research on this, even bought a VSS from JTR and ended up returning it due to the requirement of a reluctor ring for my year which is NOT even available yet and is a custom machined unit that they are working on. I agree if you are running a automatic tranny a VSS may be required for accurate shifting and performance. My setup would also require a VSS buffer which is a another story, again this is all fine and good IF you are running an AT. I will remove the TBI and take a look at it, I think it could use a kit anyhow.. I should be getting this on the road in the next week or two and will update this post as to the results.. One other thing about the ECM, I have checked quite a few resources on chips and it seems that to get a chip burned to eliminate the AT tranny codes and VSS will cost me $170.00 
I think I will see how things go with the stock program and put the money into obtaining the equipment to program and modify my own chip, saving me lots of money and time in the long run..
I think I will see how things go with the stock program and put the money into obtaining the equipment to program and modify my own chip, saving me lots of money and time in the long run..- Thread starter
- #15
Not running a heated O2 and getting no related codes.. Just knock sensor code. I will try putting the original IAC back on after I pull the TBI and check for carbon buildup... Yes you do have to recalibrate the IAC after you replace it (pull battery - , reconnect, start motor and let idle 5 sec, turn off and set sit for 10 sec, restart)..
what type of exhaust manifolds are you running? if the sensor is to far away it defiantly needs a heated 02 sensor because it will take a while to warm up or not stay warm enough and function correctly. I don't think it would throw a code for this it just doesn't get to closed loop very quick. It may not be the main issue but is something to check as well.
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- #17
They are Sanderson Block Hugger headers, O2 is right at the base of the -Y- pipe, real close, I don't think I need a heated O2 but will keep it in mind. Had the ECM disconnected for the last day or so to do some welding, plugged everything back in tonight and started it up, idled better than it ever has yet, did the IAC calibrate, started again and it was very smooth..
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- #19
Correct, I will have to burn a new chip for the ECM. One more thing to learn
the good thing is once I do, I will be able to download and re-program the chip if I make any changes to the 40...
i deleted my VSS with no issues so-far