rojs234

iTrader: (5)

Thought I would try this here first. Friend has a strange problem with his 5.3engine. It has 2001 intake and injectors#25317669 I believe. It has PCM # ending in #411. PCM was re-programmed to be stand alone with 2 front oxygen sensors and the usual deletes. The problem is the #2 cylinder on passenger side runs extremely rich. So rich in fact, it backfired and blew muffler on that side. Thinking the injector was bad, we tried to confirm by switching it to another cylinder. It ran clean on that cylinder and the one we relaced it with promply started doing the same thing...running rich. We tried switching coils and plug wires with no success either. We checked ohms on injectors and all seem to be somewhat out of spec, reading up around 14.8 into the 15 range instead of the 11 to 13 range recommended. Could this be a factor? If so, why just one injector? He tried a noid light and it blinks on the bad one just like the rest. Plug on that one cylinder runs black carbon, smells like gas, all others run clean. Could PCM do this on only one cylinder? Anybody ever run into anything like this? Any suggestions to try? I might add, the engine starts and runs fine except uses a lot of fuel (duh). Afraid it's going to ruin rings on that cylinder. Thanks, Ron

Rick Speed

iTrader: (55)

I had a similar problem but mine was #1 cylinder. Wound up being the upstream o2 sensor.

rojs234

iTrader: (5)

Thanks for the reply. We had considered the O2 sensors, but I couldn't see how it could affect just one injector on a bank of cylinders. I always thought the O2 sensor sampled the exhaust for the side it was on and adjusted the four injectors accordingly. I might also add that it is showing no codes. It's got us baffled.

Monte4ever

iTrader: (2)

I read a thread in the force induction section where his did the same thing with an after market AEM computer. It put so much gas in that one cylinder that it caused the starter to kick back and brake one of the starter mounting holes in the block. He was using 160lb injectors though.

96 Comp T/A

iTrader: (8)

I would check the harness. Pull the connectors off the PCM and injectors. check the resistance of the wires running to the injector (PCM to injector plug), and then to ground (either end to ground). Most fuel injection systems have injectors hotwired and then pull-up to ground to fire the injector. If you get a ground signal it would hold the injector open. You could also buy a fuel injector tester and plug it in and see if the light stays lit.

Old Geezer

iTrader: (3)

The sensors work just as you describe. They do not control individual cyl a/fr....

rojs234

iTrader: (5)

See if I am understanding you correctly. I should check each individual wire from the PCM to the injector to see what resistance each wire has, and then hook it back up at PCM and check from the injector end to see if it has continuity with chassis ground? And then reverse and check from injector to ground? If wire shows any continuity with ground it would hold injector open, right? But as I said above...would a noid light blink if wire was grounded? I am curious to see the results of your suggestion, so we will definately give it a try. Thanks...Ron

96 Comp T/A

iTrader: (8)

I would only worry about the individual cylinder you are having trouble with, but the goal here is to check continuity the entire length of the wire run from the PCM to the injector connector. Then check each wire so that it has not picked up a nick or other ground path. The noid light would show a constant light (i.e. hanging an injector open).

rojs234

iTrader: (5)

Guess I had one of those senior moments yesterday and somehow missed your reply. Anyway, thanks for confirming the way the sensors work. Ron

rojs234

iTrader: (5)

I actually think I have already done what you are suggesting, but we will confirm when the weather improves. (wind chill here is WAY below zero). I think he told me the noid light was blinking when he tried it, but not sure. He said he was going to switch O2 sensors side to side to see if he could move the problem. I'm not sure I trust the O2 sensors. When we did the swap, the engine harness was Canadian manufacture and the O2 sensors were much higher priced, so he bought some what I call universal Ebay sensors. Does anyone know if the PCM itself could somehow internally cause this problem? Either from age or a malfunction causing a different pulse width to one injector?

EVERETTDREW

iTrader: (2)

My car is running rich also. i am intrested on the outcome of this thread please post up when you find a solution.

rojs234

iTrader: (5)

We will post the results, but at this point I have pretty well run out of things to try. I guess a different PCM is the only other thing that makes sense. Anybody got any other ideas?