Hi I'm new to the LR community and recently picked up a 1996 Disco 1 with 141k. I was told it has a new 4.6 block with ~35k on it now and has a mixture of GEMS and Bosch parts. I was told it sat for a year and wasn't driven much.

I'm experiencing P1313 and P1314 mostly around town and saw P0301 briefly. I've never driven one before but IMO it drives fine (albeit kind of slow). No noticeable misfiring affecting drivability but the RPMs do jump a tiny bit at idle. I've noticed the engine light come on right when I start driving. If I clear the codes after driving a few minutes, it would likely stay off for the rest of the drive.

P1313 and P1314 are for bad cats, right? It has Magnaflow y pipe cats and passed emissions test with ease. Also pulled the plugs and they seem a little dirty but not wet. Plug wires say 2015 and I'm guessing the plugs, wires, and maybe coils are the same age.

I took a look at the reluctor tabs in the service port and all teeth look straight but I do notice that the gap between each pair of tabs is slightly wider on a few. Would this be enough to throw codes? I've read that the gap should be ~4.5mm but I haven't figured out a proper way to measure.

 

It will be difficult to answer with any certainty without knowing what is inside and what engine ECU is running. You've hit all the things to check other than maybe the crank and cam sensors themselves (though I kinda doubt they are the problem).

If you don't already have it, find the "gems_obd.pdf" document in the D1 section of the google drive linked in my signature which will explain how each trouble code is generated/calculated. This assumes you are running a GEMS ecu.

 

Maybe try a 4.5 mm or 3/16 drill bit or rod to measure the gaps. I think in theory, the reluctor can help the ecu determine which cylinder is misfiring or knocking, so the gap is probably important for that. I don't know how wide is too wide though.

I read some info that Walt posted. It mentions the ECU counts the reluctor pulses each revolution, with diagnostics for high of low counts.

 

Not sure what ECU is being used but I will take a look. The previous owner said it has a 4.6 block but I can find replacement parts for it by referencing a1996 Discovery 4.0.

 

I finished swapping out the plugs and wired with NGK and swapped the coils out for Oriellys Import One brand. Also cleaned out the MAF. I don't notice much of a difference since it still drives pretty well and the lights do continue to pop up randomly. The engine did stall on me once at a light but maybe that's due to the MAF cleaning? Not sure will continue to drive it some more.

 

I think there are engine size code numbers/letters stamped on the block near the middle left side on the surface that mates with the head. My '96 4.0 L is stamped 50D.

 

Fingers crossed but I believe my misfire issue has been resolved. One of the first areas I checked was the reluctor tabs. All the posts I've seen regarding the tabs show people with very noticeable lateral bends. Since mine were straight, I ruled this out and moved on. I took a second look and this time I used a caliper to measure the spacing between each pair to check for uniformity. I believe the factory specs are 4.5mm and I found 2 pairs to be wider by 1-2mm. Straightened those tabs and now my CEL hasn't come on for 2 weeks now. Hopefully, this helps someone in the same boat as me. The tabs were straight to the naked eye but had to be perfectly spaced in order to not throw a code.

Here's a special tool to help straighten the tabs to factory specs. If this eBay link dies by the time you're reading this, the PN is LRT-12-125 - https://www.ebay.com/itm/12475406276...oAAOSwFdlgt1dz