Hey guys!

I finally got my truck into roadworthy enough condition to try going for a drive around the block. Prior to now, it has just been up and down the driveway (barely get out of 1st)

Now, I've found that the truck has very little power, and pops out the exhaust all the time when you try to put any load on it. I have a constant SES light on the whole drive (only code 43) and my IAC is making a loud sucking noise (no air filter at the moment)

I'm wondering if the code 43 is related to the poor driveability? If not, where does a guy start? I've got a rich idle, due to my camshaft, but you'd think it'd be alright in the upper ranges...

 

Hi, Code 43 on a tpi is a bad knock sensor. Make sure you get one for a 90-92 5.7 Z28 if you are using a 7730 computer. Last weekend I worked on a friends 68 chevy truck with a 350 tpi and it was doing about the same. It had a code 43 and 51. Changed the knock sensor for the 43, new computer fixed the 51. Adjusted the tps and iac and idle per the tech article on this site, set timing to 6 degrees and put fresh gas in it- it had been sitting in the bodyshop for a year and the gas was nasty and bright yellow. Anyway it had nothing to do with the prom or programming just the basic mechanicals. Ran great then. So maybe verify that stuff first. Jon

 

Hmm, I bought a new knock sensor when I was planning to run MAF, but installed a resistor to get the resistance that the `7730 is looking for. However, when I tried to ohm it out, I didn't get any resistance at all... Is there a special trick to it? I just put the one pole on the connector, the other pole to ground.

If my knock sensor is indeed no good, would it cause the ECM to massively retard the timing, and cause the backfiring out the tailpipe I am getting?

I just recently filled the tank with fresh 92 octane fuel, so bad gas shouldn't be an issue...

This truck does have an aftermarket cam in it. Running the stock TPI intake with 24 lb injectors, stock mid 80's smogger heads that were already in the truck, with a comp cams XE262-H camshaft. The truck should be sitting around 8.5:1 compression or so (I know, sucks, but I'm not done my new engine!) so I shouldn't need the 92 octane, but put it in there anyways just incase the timing is way off or whatever, to prevent detonation. I am running stock fuel pressure (43.5 PSI without vac, 38 with), and have adjusted my prom for the 24 lb injectors. Timing is set at 8 degrees initial advance, and yes, I did adjust the prom to 8 degrees initial from the stock 6.

The truck idles at about 950 RPM or so which is apparantly the target idle the engine is aiming for according to TunerPro RT. I cannot get the IAC to drop below about 45 - 50 counts, even if I open the throttle body way up, which should close the IAC in an attempt to lower the idle, right? I would prefer a 750 - 800 rpm idle, and programmed the prom for it, but cannot figure out why the ECM is adding the extra RPMs on. I am running a manual transmission, so park neutral switches shouldn't have any effect. I'm pulling just over 15" of vaccum idle according to the MAP sensor, though I have not put my mechanical gauge on to confirm that reading yet.

I don't want to fiddle with the VE tables in prom until I am sure that it is a prom issue, and not a mechanical issue. I just want some guideance to figure out what to do, as this is the first EFI system I've tuned up. I've gone through all the stickies, but I'm still feeling a bit in over my head. I've got a good idea what to do, and how to do it due to the stickies, but just don't know where it is best to start with an engine like I have.

I really appreciate any help you guys can offer, even if it is just emotional support, LOL

 

I thought code 43 was the ignition module under the distributer cap. I had a code 43, changed that module and everything was fine. When code 43 is set the ecm no longer controls the timing and the timing used is whatever the base timing is set to, in your case 8*.

 

That would definitely explain the lack of power and backfiring out the exhaust!

I'm going to set tommorow morning as my day to figure it out. I personally think that my problem is more likely going to be related to the knock sensor, as I used the distributer that is on the engine for quite some time on my 89 with no trouble at all, the ECM and memcal are both good for sure.

 

The 350 KS = 3.90 K ohms.
I bought a new one and confirmed it with a meter to be 3.89K.
HTH