1994 Disco Backfire, no codes, no CEL...

[Macro1]

So I picked up a 1994 Discovery as an accessory donor for my 96. I dont really have the place for a parts vehicle and because this thing is in such great shape, I would prefer to sell it. The service records on this thing for the past 5 years is over 7k!

Very few leaks, great body with hardly any rust, good interior, CDL works great, new PS system and lines, new brakes with master cylinder and rebuild brake booster, New Diehard battery, New Heads 30k miles ago, etc, etc, etc.

The problems:
Backfires but there is not CEL. the idle is "OK" (fluctuates between 750-900), and when you run the RPM up to 1500 it will "pop" with a backfire from both the intake and through the exhaust. Also when you begin to drive it over 5 mph it backfires heavily.

I have seared and swapped out fuel pumps as another post seamed to have similar symptoms but it did not resolve the issue.

Possible timing?
I do not own anything to test it but I could run down and pick something up. I fear a worn cam, but wouldn't that at least through some code? If it were bad plugs or wires, would that not also through a code with how bad it is?

My dilemma is Im going to be selling it and I don't really feel like throwing a bunch of money at it. If anyone has any ideas on diagnosing these early trucks I would be greatly appreciated! atriot:

 

[redhawkrovers]

distributor rotor and or cap non oe rotors are junk

 

[singingcamel]

I second the dizzy issue, change the cap , rotor ,low tesion leads and go from there.
I would also reset the timing .

 

[cosmic88]

The symptoms made me think it is having a hard time breathing... are the cats original to your knowledge? If they are broken down, flaking or loose internally that can cause a severe enough restriction...

CEL - do you see it illuminate during the initial ignition start sequence and then go off after a few seconds?

 

[Macro1]

The symptoms made me think it is having a hard time breathing... are the cats original to your knowledge? If they are broken down, flaking or loose internally that can cause a severe enough restriction...

CEL - do you see it illuminate during the initial ignition start sequence and then go off after a few seconds?

Yes the light turns on when the ignition is on.

Not sure if its the cats as the exhaust appears to be in good shape and I dont hear any rattling noises from the cats. (not ruling it out though)

 

[Macro1]

I second the dizzy issue, change the cap , rotor ,low tesion leads and go from there.
I would also reset the timing .

Is there any way to diagnose these parts prior to buying parts?

 

[Macro1]

Looks like the LUCAS cap and rotor is the way to go. I can get it from BP-utah (and they are in my back yard) for $38. I guess its worth a shot!

 

[singingcamel]

Right on , brand name is the only way to go on ignition parts..
Pull the plugs and look at them. what kind are they?
Make sure when you replace the rotor dont pull up to hard , squeeze with some vice grips to break it. if you yank up on the rotor you may displace the weights in the lower part of the dizzy and you will find yourself looking for a dizzy as well.
Pull the cap and rotate the rotor counter clockwise and see if it returns , if not you may have reconnect the lower part of the dizzy weights and springs , just ask me.

 

[Macro1]

Im no expert, but I think those points look pretty good. Before I run up and get a replacement, is there anything that could be wrong with the rotor or cap that is not visual?

 

[riceybean]

Check the advance as well.

 

[singingcamel]

Im no expert, but I think those points look pretty good. Before I run up and get a replacement, is there anything that could be wrong with the rotor or cap that is not visual?

I bet she runs better with the new cap and rotor. Does your rotor spring back when you turn it counter clockwise?

 

[Macro1]

I will definitely test the vacuums assist tomorrow.

Singingcamel- you really think a new cap and rotor will make a significant difference and not just performance?

When I get a moment I will pull a plug and check it. It's hard to be motivated to work on a vehicle outside in 20 degree weather!

 

[singingcamel]

Sure, it would make it run better, the contact points on the dizzy are crap , not allowing good spark,
Look close ,the rotor is crap as well.
I guess is all on how you want it to run.
I think you may have a timing issue as well.
The popping is probably due to your spark either being to advanced or retarded , but I've seen crank shaft positioing sensor do this as well, but start with the timing.

 

[Macro1]

Well Singingcamel, you were on the money! New cap and rotor definitely made an improvement.

I also tried adjusting the timing (which has helped the "popping" but it hasnt completely fixed it).

It will be getting new plugs and wires tomorrow am from the new owner who is replacing his '95 with this one. I am letting him use my tools to get it so he can drive it away and I'm hoping replacing plugs and wires will fix it.

Any tips and getting the timing down right? Im having a hard time getting the timing adjusted just right as the popping in the intake goes away during idle when adjustments are being made but will reappear shorty after leading me to assume the timing is still off. The idle has definitely improved and has leveled off but is a bit rough.

The wires are definitely bad because I get freakin' shocked as I try to adjust the distributor cap!