Shudder anytime over 2K

TBSCoupe

Registered User
I have searched and found numerous answers to the question, but need a little help in saving money so I have taken it a step further. First off, I am driving a 1993 that has been sitting for 3 years. Love the car, but after the first full tank of real gas I developed a problem. (not sure if it is related to the gas) After first I was doing some spirited driving seeing about the up shift indicator and what not and had no problem (just a little missing here and there). After words, I tried again and couldn't get it above 7 PSI with out it cutting out/shuddering which felt like a Rev limiter. I was scared for a second. Limped back home for some underhood investigation. Everything looked fine and double check the filter and MAS. Tried it again and the same thing happened. Since this was my primary transportation, I didn't want to push it. in traffic the car acts normal, but as the car heats up, it starts doing it earlier in boost. With the car hot, I can't get it above 2 PSI without it bucking. Plugs have little miles on them and I just replaced the wires on a hunch from this board...Same thing. since it is related to heat, is there any quick diagnosis? I also ran a pressure check on the fuel rail and it stayed the same (32 PSI) up until the throttle was let off then it dropped to 24 PSI but went right back to 32. Also changed the fuel filter. Have it narrowed down to Head Gaskets, Bad Plugs, Bad Fuel pump, Bad DIS. Is there a cheap way to figure this out? Thanks all
TBSCoupe
 
New info....Took the bird out for a little bit just now. The trouble starts when ever it does too far into boost regardless of the RPMS...I was driving around town at about 70 and slowly pushed the peddle until it started. After warming up, it would do it at 2 PSI regardless of RPMS.
TBSCoupe
 
It still sounds like a plug and wire problem. A problem here tends to show up at low boost levels. Factory plugs & wires? Maybe need to pull 'em and check 'em. I've had a couple of cracked boots on newer wires before.
 
I would start with the plugs. My 95 was doing that when I bought it. It had 109,000 miles on it and still had the original plugs in it. The plugs were just flat worn out on the 95.

I think that you need to do a full tune-up. Air Filter, Fuel Filter, Plugs, Wires and PCV Valve.

Bob
 
Other than the plugs, everything else has been changed. PCV, Fuel, and wires. I was assured the plugs had less than 100 miles on them and were replaced by Ford (saw the receipt). So I guess my next step is to hit the motorcraft table and pick up some replacements. Thanks all, I hope SOOO much this is the problem!
Regards,
TBSCoupe
 
Well, after kicking myself and finally being able to have the time, I jumped outside and ran another fuel pressure check. I did this because I refused to change the plugs again (call it a mental block, or call it laziness). What it revealed was something interesting. After letting it idle and warm up, I took it slowly up to 5K with no problem, but as soon as the vac disappeared on the second run, it started to shudder. I double check the fuel pressure gauge and ran it again, this time taking it out of vac an into boost, the gauge dropped to 0 the instant it went to 0 vac. I also noticed at idle that the gauge would flicker slightly from 32 PSI to 20 PSI. Because I was planning on a 300 HP SC eventually, I am going to go ahead and try replacing the Fuely pump with a 255 LPH. I hope this is the problem <figures crossed>. Any suggestions on 255 LPH pumps?
Regards,
TBSCoupe
 
Could also be a fuel pressure regulator. Although if you are planning some serious upgrades then the forced induction 255 pump is the way to go. You do know where to get it at a good price right?
 
Kevin Varnes said:
Could also be a fuel pressure regulator. Although if you are planning some serious upgrades then the forced induction 255 pump is the way to go. You do know where to get it at a good price right?

I saw a link to Autoperformance engineering on this site from a couple days ago. I might try them, but it really depends on if I can find a local place in Miami that can get me one tomorrow (fat chance I know, and I would even get a 190 if they had one in stock local). If not, them I will contact them, should be able to get it here by friday if need be. Any other ideas?
Regards,
TBSCoupe
 
Well if that doesn't work, I really recommend trying another set of plugs. After spending 3 days trying to figure out what was making mine do that, I found that one of the plugs had a crack in the ceramic causing it to ground out. Good luck
 
Just to followup with everyone. I fixed the problem today. FUEL PUMP. Replaced the factory pump with a Walbro 255LPH and the car screams. I am sure the headgasket is starting to go now, but at least I was able to problem solve and replace the pump!
TBSCoupe
 
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