Bank 2 plugs are rich fouled

gr8ghost

Registered User
Here it is: 1990 SC with rebuilt motor 42#/hr injectors, Stage 1 comp cam, 85MM TB, 8m MM maf, MP inlet, S ported blower, Raise SC top, KW DIC, headers and 3-2.5-3 inch exhaust. New plug wires from SCP are installed.
NOW the problem;
All three of the L spark plugs are fouled rich. The R side plugs are ok. When I put a timing light with a tach on bank 1 spark plug wires the light is constant and fast. The tack reads at double the engine speed. That is as expected. When I move it to bank 2's wires The light is intermittant but when I can get it to read constant it shows the engine RPM in agreement with the car's tach or 1/2 of bank 1. I have changed out the coil and it is the same. Ideas on where look for the problem? The coils check out on my diagnostic equipment as ok.

Forgot: The car is tuned for these Mods from afar by Dave Dalke.
 
Last edited:
BOP: It's hot. When tested.

O2 sensor is worth a shot. It doesn't explain the wonky inductive tach readings, though.

Thanks for the input.
 
I found #6 injector with a bent connector and not working. I fixed it and it's not missing anymore but it still runs rich. Code 92. I have to finish checking the O2 sensor. The wiring is good. That much I know.
 
I've had O2 sensors go bad before causing it to run extremely rich. You can't tell by looking at it. You'll need to swap it out to be sure.
 
It might be a silly question, but did you double-check the plug wire order at the coil pack?
 
I have a DIS tester and all the parts test good. None-the-less I took the ICM off and had it tested at O
Rielly AP store it tested bad there. A new one will be installed tomorrow. The firing order is right. On the O2 sensor I will also test it's resistance and see if it is in the ford spec. Currently it is all carboned up. But it's got maybe 1000 mi on it.
Thanks for the input all.
 
But...if it's failed outright, it will be read as lean, not rich? Causing a rich mix as the result.
 
a hego is a voltage generator, you dont test a hegos resistance you test its voltage

if shes that rich it should be over 0.8 volts

http://info.efidynotuning.com/hego101.htm

I was reading in the ford H circuit test to check the resistance of the heater portion of the sensor. That was not an easy task. Here's where I'm at now.
1. # 6 FI was open due to a bend connector. That was fixed. It ran better but still code 41.
2. ICM was found to be bad. I replace it and the car runs better. the inductive tach still reads engine RPM on Bank 2 plug wires but it is consistent. Meaning the flash is not intermittent. It is interesting to note that Bank 1 wire read double the engine RPM. But if I hook the inductive pick with the arrow pointing at the coil Bank 1 reads engine RPM and Bank 2 reads twice the engine Rpm. Weird but I'm not going to worry about it at this pt.
3. With the above 2 fixes the HC fell from 5% to 1.0 to 1.2 % but another smog criteria was still double the allowable. So back to the O2 sensor.

The R side indicates .3 volts. The left negative 12.xxV. Since I thought I'd checked the wiring out on Saturday I replaced the L o2 sensor. The old one was no longer carbon caked. The bad news once I replaced sensor it reads the same when testing between signal return and L hego input. At this pt I can only think that I have a short to hot that I have to find. One more day of investigating and then I'm going to take it to a shop if I can't find it.

Thanks for the info on the sensors, Decipha.
 
one more thought...

I'm wondering if the Moates chip could have an error or short in it causing this problem. I think I'll test again with the chip removed. Unless there is a good reason not to.
 
The chip could cause a problem. Especially if it's not making good contact where it plugs in. Have you ever run it with the chip? Or is this the first you have tried it?

Also, is it a chip? Or a Quarterhorse?
 
The chip could cause a problem. Especially if it's not making good contact where it plugs in. Have you ever run it with the chip? Or is this the first you have tried it?

Also, is it a chip? Or a Quarterhorse?

Just to expand on what has been mentioned.

QH does have a battery shelf life.

On a personnel note I thought I had primed the ECM pretty well for the QH/Chip

At DD's he proved me wrong. You do have to be fairly aggressive to clean the contacts.

Paul
 
the inductive signal should read the same as rpm, external TFI "DIS" fires in wasted spark since two pairs are grouped, so the cylinder at the end of the compression stroke and the opposite cylinder at the end of the exhaust stroke will fire together, the spark plug with the most cylinder pressure (compression) will have less resistance and receive most of the spark

the plug wires to the coils should be like this looking at it from the front

1-2-3
5-6-4

going off memory from the top of my head but I'm about 99% sure that's correct

find which 2 cylinders are misfiring, they will be opposite cylinders, if only 1 of the three sets are faulty you know the cause of the issue

the o2 wiring sounds like you may have a bad hego relay, you did check with the key on correct? If the key is off the relay is open so you can't get anything useful from probing it, If i'm not mistaken the hego "relay" is shared with the ecu relay powered through the ICRM

if you found a fault in the hego wiring, just unplug that hego and make sure its not affecting the other hego wiring

.3 volts is pretty weak with the engine running that hego should report well over .8v is she's really that rich, now if the engine wasn't running you can't measure the hego's output (obviously)
 
Thanks

It's official the mice that invaded it once ate some wires. the R hego does not have hot running to it. the hot lead lead makes contact with ground (black/lt. grn) but the hot end is not shorted out. I can see some tape that is shredded but it's hidden by the glove compartment. I will be removing the dash the next wknd as I have been invited to my sister's elopement. I love saying it that way.

Decipha, your input has been much appreciated as now I have a much better understanding of hego function. I also just remembered that I have an EVT manual and that has more detail than the mitchel manual. Between all I am going to get this beast registered again. BTW it no longer misses it just runs rich as all hell.

Also you are right on the wiring order at the coil.
 
Back
Top