Smeddy2

Been trying to work out the kinks of a top end rebuild and I'm narrowing things down to fix. Right now I have a CELS 51 and 52 on when I jump the terminals. The CEL 51 is on (I think) because I just don't have my A/C belt on because it was being stubborn so I just left it to put on later. The 52 I understand is a Knock Sensor Circuit failure (the wire, sensor or ECU are bad). I want to know if either of these codes explain my acceleration problem. When I first start up it runs fine but after a few yards of driving, the problems start. I can accelerate in the low RPMS but as soon as I hit a certain level, the power takes a dive and I have to floor it to get anywhere. I have to keep in it 2nd or 3rd to make it up a hill going 35 mph and the engine is screaming. I haven't set the timing but I think its pretty close and it idles okay. Replaced the cylinder head, fuel injector gasket kit, all new gaskets, dizzy, rotor, oil pressure sending unit, plugs, wires, water pump, oil pump, air filter, fuel filter, fuel pump, battery and I think thats it.

xxxtreme22r

if the knock sensor is bad it will screw with your timing making your motor run like crap. download the FSM and test it. make sure the connections are good too.

Smeddy2

I'll probably still test the circuit to see if it's okay but tell me if this makes sense. I wanted to have enough power to at least drive the truck around so today I advanced my timing by turning my distributor to offset the ecu retarding my timing due to knock sensor failure. Well I did and now I don't get a check engine light. My truck runs better than it ever has. Is it possible my timing was off far enough that the ecu couldn't advance my timing enough to get knock and therefore misdiagnos my knock sensor circuit as not working? That's the only thing I can deduce after reading that tech article on CEL 52 and it's causes.

Smeddy2

Just in case anyone looks at this later, my theory was wrong. I am still getting the code 52 despite my timing adjustments. Good news is when the ECU kicks out the code, the "fail-safe" mode doesn't drain my power so bad I can't drive. Looks like I am back to testing wires and sensors. I painted my block before I put it in but I don't think I covered that sensor whole. Would that be enough to cause the knock sensor to not get a signal?

andykrow

Hi there. If I remember right 51 also goes for no idle signal from the TPS so go to 4crawlers website and use his instructions for setting it. Then make sure you have the truck warmed up fully and the test connector jumped when you set the timing. My buddies truck did a similar thing - decent power up to 2300 rpm then a total dog until like 3k. He had code 51 as well. Also, you'll know your TPS is sending the idle signal because your idle will drop when you jump the connectors.

Anyway we got the tps set right and then his timing was SOOO OFF it was actually after tdc at least 5 degrees instead of advanced 5 degrees. After that was set it was like he had a new truck.

Smeddy2

I'll do a check on the TPS as well, then. I have doubts it is the TPS, though because it drives and idles fine when I first start it up. I don't get the check engine light until I've been driving a minute or two. I'll try to get that A/C belt on again and I'll see if that TPS measures out alright. Hopefully that will cure the 51 code....then I just have to figure out this stupid 52. I think it might be a wiring issue because now my oil pressure gauge and my temperature gauge are not working either. (both have worked since the rebuild and they just stopped working the other day)