Bad hesitation at part and WOT? - Mustang Evolution

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Old 06-13-2013, 10:35 PM   #1
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Bad hesitation at part and WOT?

I'm looking for advice on a problem I can't seem to get to the bottom of.

My '86 mass air equipped car has a bad stumble/hesitation when under load...it's fine in neutral and in first gear but in second and up it just won't run right!

I've checked my fuel pressure at the rail and its at 40 and replaced the plugs and wires but it still does the same thing. I then replaced the whole ignition system thinking it was the pip in the distributor and still can't seem to trace down the problem?!?

It runs like a beast in first and even at a quarter throttle in second it'll fry the tires but if I get anymore into it, it bogs down. Anyone have any suggestions???
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Old 06-13-2013, 10:44 PM   #2
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Interested in the answer to this as well although my problem sounds a little different. My car is still speed density equipped, and runs good most of the time, but I will notice a hesitation sometimes. Ill floor it, the car will will go OKAY, but then it'll feel like someone flipped a switch and she goes like a bat outta hell. Ive yet to do plugs, wires, cap, or rotor, but I have all of it just waiting to be installed.

Very interested in this answer!
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Old 06-13-2013, 10:56 PM   #3
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Yeah man, I'm stumped...I guess I'm just missing something. I've looked at all my vacuum hoses, wires and replaced the whole ignition with the performance distributors kit from LRS, and still have the problem.
It runs like a champ if I just putt around...lol

---------- Post added at 10:56 PM ---------- Previous post was at 10:54 PM ----------

Also it will not run with the spout connector plugged in??? That's why I replaced the distributor, thinking that the pip was bad but it still won't run with the spout in.
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Old 06-13-2013, 11:11 PM   #4
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Quote:
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Yeah man, I'm stumped...I guess I'm just missing something. I've looked at all my vacuum hoses, wires and replaced the whole ignition with the performance distributors kit from LRS, and still have the problem.
It runs like a champ if I just putt around...lol

---------- Post added at 10:56 PM ---------- Previous post was at 10:54 PM ----------

Also it will not run with the spout connector plugged in??? That's why I replaced the distributor, thinking that the pip was bad but it still won't run with the spout in.
Well my problem sounds a little different than yours, but still pretty similiar. My plan is going to be to replace my plugs, wires, cap, rotor, and then I want to check/adjust my timing and see if that helps any.
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Old 06-14-2013, 09:05 AM   #5
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I bet with just the plugs, wires, cap, and rotor you'll notice a good bit of difference in performance and it might take care of the problem you are experiencing from time to time.
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Old 06-14-2013, 11:47 AM   #6
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Yeah Ill definitely try that.

Thinking about your problem, Im thinking theres a possibility it could be something with your MAF sensor.. Because I know my buddy had a 2.0 Turbo Passat that was built, and whenever he would floor it, the car would almost want to shut down because it wasnt really used to that amount of power.. Like the car was basically thinking that it was over-boosting and then it would cut the ignition at WOT for the sake of not blowing it up. He changed the MAF sensor, and the car runs a 12.8 now. Talk about a sleeper. Obviously your car doesnt have a power adder of any sorts because youd probably state that, but it sounds awfully familiar with me.
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Old 06-14-2013, 12:55 PM   #7
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I bet your right! I've thought about replacing the maf sensor and getting a canned tune in the hopes that it will fix my problem, I'm just wondering if anyone else has had this type of problem before I go and through more money at it!

I was pretty disappointed after the $500 ignition upgrade didn't fix it!

I was almost sure that the pip was bad in the distributor because I couldn't run with the spout in and it had the hesitation but now I'm just praying it doesn't need a new CPU!

I don't have a power adder anymore but it's about as built as it can get...stock blocked 347, edelbrock Rpm heads, cam, Gt40 tubular, 30lb injectors, aero adjustable fpr, Nos inline pump, a very old pro-m maf, pullies,
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Old 06-14-2013, 07:13 PM   #8
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Well I ordered a C&L 76mm MAF earlier and it should be here by Tuesday so I'm praying that fixes my problem!
Will post results...
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Old 06-14-2013, 09:23 PM   #9
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Well I ordered a C&L 76mm MAF earlier and it should be here by Tuesday so I'm praying that fixes my problem!
Will post results...
Well hey man I hope that fixes your problem! I actually just got a 1986 Explorer with a 5.0 in it to use in my car, so I should have a little more power with that motor than I do with the flat top pistoned boat anchor in my car now! And I can convert to MAF too!
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Old 06-14-2013, 09:58 PM   #10
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Awesome bud...I'm sure you will like the power difference from the motor you have now. I don't know the numbers off hand but I think it's quite a big gain.
Yeah I hope the MAF solves my problem too...
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Old 06-16-2013, 08:13 AM   #11
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I had the same problem and it turned out to be the distributor
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Old 06-16-2013, 12:50 PM   #12
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I had the same problem and it turned out to be the distributor
The distributor itself or the cap and rotor?
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Old 06-16-2013, 01:24 PM   #13
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The distributor itself
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Old 06-16-2013, 07:53 PM   #14
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Yeah that's what all my researching pointed to but it wasn't the distributor...
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Old 06-16-2013, 08:01 PM   #15
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Is your MAF calibrated to your injector size?
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Old 06-16-2013, 08:17 PM   #16
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Yes

---------- Post added at 08:17 PM ---------- Previous post was at 08:15 PM ----------

But its a real old pro-flow unit so I bought a C&L fri. Just waiting on it to see if that's the problem
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Old 06-16-2013, 09:23 PM   #17
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TPS in range?
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Old 06-16-2013, 10:52 PM   #18
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Yes sir...
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Old 06-16-2013, 11:00 PM   #19
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I've checked every electrical connection, every vacuum hose, TPS voltage, engine and computer grounds, cleaned MAF sensor, reset timing, new Distributor, TFI Module, Coil, Plugs, Wires, and I've got a new MAF and CAI on the way.....

If that doesn't fix the problem then I guess I'll have to buy a new A9l but not really wanting to spend 300 bones on this POS...
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Old 06-16-2013, 11:19 PM   #20
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You do know just checking fuel pressure with key on engine on or off won't properly check fuel pressure right ? You sometimes have to check it on the road under a load I will route it where I can see it going down the road and put it under a load that's only true way to see if you are getting proper fuel pressure.
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Old 06-16-2013, 11:31 PM   #21
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That's a good point! I thought about that as well but setting your base pressure at idle without vacuum should hold if your pump is working properly and I'm sure it is, or at least it should be...
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Old 06-16-2013, 11:56 PM   #22
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So if I had 30lb injectors what size MAF would I need
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Old 06-17-2013, 12:03 AM   #23
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Prolly a 70-76mm but it would need to be calibrated for 30 lb. injectors. You can have whatever size you want but if its calibrated for 19 lb. injectors and you have 30 lb. injectors it's going to throw off your A/F mixture
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Old 06-17-2013, 12:09 AM   #24
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A completely shot pump can read fine at idle and have far less once being driven so no there is no "should be or supposed to be"
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Old 06-17-2013, 12:18 AM   #25
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I also have a 70mm spacer TB if that means anything... And how would I tune it
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Old 06-17-2013, 01:03 AM   #26
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A completely shot pump can read fine at idle and have far less once being driven so no there is no "should be or supposed to be"
I have two pumps...I doubt both are bad

---------- Post added at 01:03 AM ---------- Previous post was at 01:01 AM ----------

I have a 190lph in tank and 50gph inline
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Old 06-17-2013, 01:43 AM   #27
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Why ask for help if you won't listen ? Forget it man.
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Old 06-17-2013, 01:55 AM   #28
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I'm not trying to be prick...I'm just saying I have two pumps running and have plenty of fuel pressure!
Thank you for your insight and suggestion but that's not my problem!
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Old 06-18-2013, 03:21 PM   #29
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I just got my new 76mm C&L And cold air in the mail and put on and will be taking her out of the garage in a bit...praying it fixed the problem!

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Old 06-18-2013, 10:24 PM   #30
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Guessing it didn't
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Old 06-19-2013, 10:12 AM   #31
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Guessing it didn't
Nope...I'm quite disgusted about it at this point. This car is kickin my a$$!!!
Do you know what would be the cheapest way to run my rail gauge up where I can see it?

I really don't feel like spending $200 on a electrical fuel pressure gauge just to use it for diagnostics!
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Old 06-19-2013, 10:38 AM   #32
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Thats sucks dude. Really thought that'd be the fix
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Old 06-19-2013, 10:45 AM   #33
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Yeah me too, think it's time to sell and get an '03/'04 cobra...lol
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Old 06-19-2013, 10:53 AM   #34
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Yeah me too, think it's time to sell and get an '03/'04 cobra...lol
Or you could sell it, buy MY 86 Gt, and I'll buy the cobra!
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Old 06-19-2013, 10:58 AM   #35
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Lol...
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