Run really rough

[RoyLuke]

1996 Discovery 1 Petrol 4.0
Hello All:
I pieced-together another engine for my Disco !. (engine change #4). It runs. It doesn't run good. It misses, runs rough , Backfires and smells of petrol.
Especially until it warms-up really good.
What could be some of the causes and troubleshooting procedures?
When this engine goes (notice I said "when"), then I am going to try the Chevy engine conversion !!!!

TNX
Roy

 

[Toran]

Whats the condition of the spark plugs and wires?
Fuel injectors?

 

[DiscoClay]

GEMS?

 

[DiscoClay]

Regulator and fuel pressure? [GEMS] crank trigger? I had an old regulator O-ring in the fuel rail.. it jammed in the regulator.. causing the pressure to skyrocket and caused an injector to stick open. ..followed by very rough idle and a cherry red starboard side cat.

 

[RoyLuke]

There is a heavy fuel smell so maybe one or more cylinders are not firing. Got to find out which ones.
Even being a '96, this engine has way too many electronic weak-links.

 

[DiscoClay]

I don't know much about GEMS (assuming yours is a 1996 NAS Discovery-1 4.0 GEMS system). Here are a couple files I have that outline the system; maybe they can help with building your Adventure Map:

The first lists all the parts used in the GEMS (and also the CUX and Bosch systems, separately).
The second is a TALL jpeg screen scrape of a similar list, but I think it has additional details.

Notes:
- It may take some time to fully load it (and my mac Preview won't load it at all, but Brave and Opera browsers don't seem to mind it's freakishly tall dimensions).
- I wrapped it in a PDF container to get the discoweb server to load it up (too large for jpeg display = it doesn't let it load as an attachment/download file)

 

[RoyLuke]

Just took it round the block (after it warmed to operating temp in the driveway).
It seems that the spar is missing intermittently and perhaps cross-sparking.
Spark plug wiring or maybe the ignition coil?

 

[DiscoClay]

Plug wire boots looking warn? Cracked boots with dirty oil leaking from the valve covers creates a path to ground that is cheaper than the spark gap sometimes.

Also, I have seen cross spark from REALLY dirty distributor caps (on the underside... carbon and grease/oil buildup from various origins). Oh, but this is a GEMS right? so.. no distributor.

Have you checked your crank trigger?

If you have never changed the wires, you should, as a baseline.

Regarding the coils, I am not familiar with the GEMS coil packs, but I have an RX-8 and it is notorious for burning through the bottoms of the coil packs and shorting (sparking) directly from the coils to the coil mount.. A standard upgrade kit includes a thick urethane insulator. Is there any chance the GEMS coil packs suffer the same defect?

 

[RoyLuke]

today I put some different spark plug wires and coil-pack with some I had lying round the garage.
It still runs rough and is "skipping" heavy petrol smell.
any ideas what to try next?
Roy

 

[DiscoClay]

How long did it sit? I know lots of guys say this but it's right: drain and clean the tank.. Get a screw on fuel pressure gauge (*if the GEMS have a Schrader valve on the fuel rail like the 14cux) and watch it for output.

I had that lift pump hose fail ( the one in the tank, which caries the fuel from the sump pump up to the egress line on the top of the assembly). It would spew enough PSI to get the wagon started and then under any significant load it would barf.

 

[RoyLuke]

I am sure that this is electrical. It is randomly missing fire on the cylinders. Where is the computer module that controls the ignition located?
I don't think it is the coil pack or the spark plug wires.

 

[DiscoClay]

I am not a GEMS expert.. or aficionado.. :-/

If you think it's truly random, check the connection to the ECU, the engine grounding strap, and the wiring (hah, that's a loaded statement).

The GEMS ECU controls fuel and ignition.. As opposed to the prior ECU (14CUX) which just controlled the fuel.

 

[DiscoClay]

Did you check that the coils aren't arcing to ground, as I mentioned up there some where^? The GEMS guys here should be able to provide lots of insight.

 

[p m]

Is there any chance the GEMS coil packs suffer the same defect?

Not really.
My lazy first step would be to hook up any OBD-2 tester and check for the codes (GEMS is pretty good at flagging misfires) and live data.

 

[RoyLuke]

I checked with a different coil pack, No difference
The ignition misfire seems very random.
I assume the "ECU" is Engine Control Unit. Where exactly is it located?

 

[p m]

I assume the "ECU" is Engine Control Unit. Where exactly is it located?

on NAS GEMS D1s, in the engine compartment, passenger side, inner fender, near the firewall.

 

[kris812]

I would start with fuel pressure gauge to check regulator, ohm the spark plug wires out, compression test, Then maybe some fuel injector cleaner on an empty tank.. New wires and plugs... Then and only then would I start digging deeper into misfires. Whenever you pull the plugs to change or clean, they will tell you a LOT..

These 1 hole injectors can spit and clear out rocks from themselves. But yeah probably electrical or a bad head gasket leaking water into cylinders. Once warmed up heads seal better..