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E-Type Backfires

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Crisis

Jedi Hopeful
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Dear Members,
I have had a 1965 E-type for 2 years now and have encountered a new problem that I am looking for help with.

I took the car for a spin yesterday for the first time since last fall. Initially it ran fine. Started ok, idled ok, drove ok for a short 10 minute test. Then I thought I'd take it out for a little longer and strange things started happening. It started to backfire (very loud from muffler) at low speed, wanted to die at idle, hard to accelerate and would backfire more. Once I was up to speed it would be fine but then approaching a stop I could tell it was going to stall and when I give it some gas to keep revs up it would backfire again. No water or moisture anywhere, and it was a warm but not hot day (75*).
Some history, at least what I know:
-I just replace the muffler. This is why I didn't have the car on the road till now. Seemed to go ok. Could be a slight leak but I haven't had on a hoist to give proper inspection.
-Just prior to my purchase, PO put previously used points and condenser back in distributor so he could give his buddy the Pertronix Ignitor module he had been using. He then included a new Ignitor with the car but not installed (still not installed).
-Everything "looks" ok under the hood. Carbs not wet, fuel filter bowl looks clean, no visible signs of anything wrong around intake.
Any advice would be appreciated. Beautiful fall weather and I'd like to put some miles (finally) on this car. Kinda embarrassing the way it is.
Thank you,
Reid
 
How old is the gas? My E type did that a couple of years ago ,it had sat for several months and when I drove it, it bucked and backfired. I changed out the gas and it ran fine. I've put only hi-test since then.

Marv
 
Yes. The gas is nearly one year old. I thought maybe that would make it difficult to start but once running it would be fine? Maybe you're right and I'll give it a shot. Thanks Marv.
 
Change plugs too! Not hard, but they could be fouled and causing the rich condition that creates the backfire. If not check carbs.
 
Further on this matter, I installed the Pertronix and cleaned the plugs on the car and took for another test drive. Started fine, ran fine for a while, then same problem occurred. Car would backfire, loss of power, occasional total miss. Barely made it home and into garage. I agree with most of you that this is ignition.
Other observations: very low slow idle speed (300-400), ran better with choke, even with choke fully on car only probably made 600 rpm.
Comments are always appreciated. Thankyou.
 
First thing I would do, would be to pull all the plugs at once after a short run with NO choke, lay them out in order, and look at the colour.
The actual inlet manifold is three parts, isn't it? If you have an issue with one bank, it will show up in the plugs, right now.

Super rich, very lean, causing idle issues, stalling issues, too much fuel maybe backfire....too lean? who knows.

Once you have determined if you have a bank issue, look at that carb. No leaks, like high float level? See if you have gas in the bowl like stuck needle.

Look for loose inlet nuts, bad gaskets. Gaskets can be found at idle with a can of Carb Cleaner with a wand...spray around the gaskets. If it suddenly picks up speed, that's where the issue is.

Brakes okay, like the booster hose hasn't rotted or come adrift?

90% of fuel issues are ignition, 90% of ignition issues are carburettors.
 
Modern gas I have read, will lose most of the additives within 60-90 days to evaporation. As suggested, if you haved drained and refilled the tank I would do that.
 
Still haven't solved this problem as I really haven't had time and winter is fast approaching here. Another issue today when I tried to move the Jag so I could get the Tr6 out; small puff of smoke behind start button. Car still started, and nothing caught fire??
 
Now we are getting somewhere. Check connections to start button. Wisp of smoke tells you something is amiss. Pull and clean and check for marks around back of button, might have to replace. Try and wiggle button as car idles and see if ignition cuts out. Might be a culprit. Good luck. If backfire out back usually an ignition problem. Backfire thru carbs a fuel and timing problem.
 
Just a comment....my Jag a week ago decided to idle at 300..popped and ran rough...wouldn't accelerate worth squat...thought I was driving a Triumph.....

The vacuum check valve (fairly recent) to the vacuum cannister behind the right headlamp had popped apart. Why I still had power assist to the brakes I have no idea.

Fixed it, problem gone.

Take a pair of pliers and squeeze off the vacuum hose for the power brakes while idling...if you cannot keep it running, use vise grips.
 
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