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« Last post by Greg B on Yesterday at 12:12:59 PM »
Yea, this could be a fuel/ignition double wammy here. Here's another tidbit for the diagnosis: when it's cold (i.e. the choke is on and mixture richer) it stumbles a bit less.
I'll check this too tomorrow.
Thanks so much for you thoughts and help,
Could be the accelerator pump in the carb if it only stumbles just when you first poke the gas. You can check it. With the engine off and the air cleaner off, look down the throat of the carb and pull the throttle linkage back all the way quickly. You should see/hear gas squirting down the throat.
« Last post by Greg B on January 23, 2015, 10:45:27 AM »
Thanks again. I checked one of the grounds; didn't know there were 2. Will recheck both.
UPDATE: drove about 50 miles yesterday - combo of highway and local. At speed, she purrs; step on peddle slightly and she moves; push it and she stumbles. Same from stop; slight acceleration and she's ok; push and she stumbles. I did got one good "POP" of a backfire at speed when I pushed it once; think I degraded my muffler - damn.
Steps this weekend: check grounds; re-check compression (at least get a baseline); regap plugs; put diagnostics on and check vacuum again, timing, carb idle screws, etc. If continues, I'm swapping back the old distributor; if that don't work, it's off to have someone competent check the carb.
Just another shot in the dark - check the engine grounds to make sure they are clean and mechanically good. There should be one on the block near the alternator (it comes from the battery) and one between the cylinder head and the firewall on the passenger's side of car.
Best of luck!
« Last post by Greg B on January 21, 2015, 11:36:06 AM »
Yea, a real head scratcher. Here's my plan: recheck plug gaps and timing. (Vacuum gauge internet/You Tube gurus say this could be issue.) I may actually put the old distributor back in to see what happens as, although I like the Flame Thrower, my MG experience (and the vacuum tests) suggest a possible problem.
If that don't work, well everything electrical and mechanical has been done, redone and done again. So, it's off to the carb and fuel pump. I'm thinking like you. I'll mess with the idle set screws too to see if that affects the vacuum test.
Whatever it is, it's starving the engine on acceleration.
Wish me luck on my Pony (and my marriage!),
I'm grasping at straws - about the only thing I can think of is to check the fuel pressure under the engine miss conditions and checking your carb over to verify the float levels are correct and that there is not a screen at the carb fuel inlet that's plugged.
« Last post by Greg B on January 20, 2015, 10:02:38 PM »
Hey again Topless,
And thanks for continuing with me. Here we go:
Rain on trip back caused massive missing. Cap was only ignition part I didn't have with me. When I replaced it, the engine did improve but was not perfect. Real issue then was bad missing after 40' of running. I suspected head gasket but wanted to check other things first. More on ignition later.
I did bring the head to a machine shop and they did clean of surface of gunk and checked it was true. I also took a straight edge and feeler gauge to the block and it seemed ok.
On the crate engine, it is a Ford 289. And the plugs are right. It ran over 3000 miles that way.
OK, Pertronix: my "guy" suggested switching out points a while back. So, when I was doing different diagnosis, I put a tach on each of the plug wires and, on 5/8, there was a needle swing. Since the cap was new (and so were the wires and plugs at that point), I decided to get the full Pertonix distributor, and not just the drop in pointless system. I have one in my MG but the first one sent was actually bad. Broke 2 caps! So, I'm beginning to think it may be the culprit here too. And, I followed wiring instructions and it was verified by my guy.
Will mess with the wires as suggested.
Vacuum advance going to ported vacuum. I have tried driving with it disconnected and no change.
Finally, yes plugs are correct. I'm in the process of rechecking gap. Recall these are not the plugs that made the trip but were part of the "cheap" solutions in trying to isolate the problem.
UPDATE!!: As I was putting a vacuum gauge to the engine, I did connect it to the vacuum advance port and, when I revved the engine, nothing! So, I pulled the hose, blew through it and nothing! Squeezed it along its length and guess what I found? A ball bearing stuck in it. Don't ask how it got there as I have no idea.
She is running a bit smoother on acceleration now but still missing; when I push/punch she misses badly.
This has been a classroom test of all that could possibly go wrong. I am not making this stuff up, believe me.
BTW, vacuum on manifold vacuum is 18 but waivers a about 1-1.5 lower. Pulled each plug wire and each pulled plug causes further drop. At higher speed idle, the needle is steady as a rock.
Ok so I have a 1990 5.0 mustang LX.... So this all started one day, I changed batteries because the original one wouldn't hold a charge. I started the car before I took out the original battery started right up no problem. When I put in the new battery and tried starting the car it turned over fine but just wouldn't start so after awhile after looking to make sure everything was connected right I noticed that my fuel pump relay was clicking nonstop. This would stop when I unplugged the fuel pump relay. So thinking that was the problem I replaced the relay. No change. So over a period of time and doing a little research I started replacing things thought to be the problem. Items replaced- fuel pump relay, tfi mod, pickup coil, distributor, cap, coil, fuel filter, Eec power relay, inertia switch, oil sending unit. No luck. But now my fuel pump stays on without the key even being on. Only thing I can think of is a bad computer or a faulty wire somewhere? I don't know what else to do. How can I check for a bad computer? Or does anyone have any other ideas of what could be going on? Any help would be much appreciated.
So I'm wondering what the original symptoms were (you mention distributor cap and pouring rain)? Did replacing the cap fix the problem completely?
You mention a high engine temperature and replacing a head gasket. Did you have the head checked to see if it was warped or otherwise damaged when you had it off?
You mention 289 but then later mention crate engine. Which? Are you sure that you have the plug wires going to the right cylinders? The firing order for most crate engines is not the same as that for the 289.
Is the Pertronix wired per the manufacturer instructions (getting full 12V if called for)?
When you replaced the distributor are you sure you got it in the right place with respect to TDC? If you missed your timing will be off and the engine will not run well.
Do you have a bunch of plug wires running in parallel close together? Try separating them a bit and making them a little "messy" by crossing them at angles - especially if there are two together that fire in sequence.
Do you have a vacuum advance hooked up to the distributor? Is it going to manifold vacuum or ported vacuum from the carb (should be going to ported vacuum). Have you tried driving it with the vacuum advance disconnected from the distributor and plugged?
Are the spark plugs all the correct type and gapped properly?
« Last post by Greg B on January 18, 2015, 08:07:39 PM »
It's virtually brand new but I've opened, cleaned it, blew it out with compressed air and reinstalled. Thank you for your suggestion.
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