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Discussion Starter · #1 ·
Over the past week my car has been acting like its hiting the rev limiter at about 4000 rpm. This only happened so often. Today I was driving around and after the car warmed up it would not run above 3600 rpm. I replaced the coil backed out of the driveway and it died and would not start back up. It was like it was not getting any spark. I finnaly got it started and drove around the block and all seemed fine. Took it for a little further ride and it started doing the same thing. As I was coming up a steep hill it decided not to rev above 2500 rpm. Here is the thing it revs fine out of gear when there is no load. Any load and it wont rev to save its life. My next part I am thinking about trying to replace is the ignition module. Anyone have any other ideas?

It is a EFI 306 with a mild cam everything electrical stock right out a 91 Mustang.

[ April 12, 2007, 12:56 PM: Message edited by: DarkWaterCustoms ]
 

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Snake Charmer
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Check for a vacuum leak that is confusing the computer when the engine is under load.

HTH's
 

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Replace the TFI module on the dist. A very common problem. You might also want to check your fuel filter. HTH mike
 

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There is a post on one of Mustang forums about cleaning/ tightening the two 10 pin connectors. There is a lot of engine information going through them and if there are bad connections, all kinds of interesting things can happen.

Instructions were basicaly to take apart the connector use a sharp nail and tighten the female side, use dialectric grease and put them back together. Ford had a tech bulletin/ fix with a pair of short 10 pin extension cables.

It is supposed to take care of all kinds of strange engine behaviors that aren't resolved in the normal way.

 

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Chris,
Another item to look at is the TPS (throttle position sensor). If it has a dead spot above a certain point then the return voltage will drop and the computer will think it is seeing idle while the MAF is telling it something else. I had it happen on my Merkur (similar TPS) and testing the sensor did not show it up. Changed it out and had a big improvement. Easy swap if you have another handy to try out and you'll know right away.

Cheers, Rod
 

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"Its a new rotor, plugs, wires, fuel pump, fuel filter if that narrows it down at all"


Something I learned a long time ago is, There's no such thing as Old or New, it's either Good or Bad.

Sounds like low fuel pressure. Do you have a gauge on the supply or return line?
 

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Discussion Starter · #10 ·
I do not have a fuel pressure gauge. It only happens under load when I am driving so I would nto be able to see it when the problem happens unless I mount it in the cockpit. I can tell you that the gas tank lets off alot of pressure right after I shut the engine down. I do not have a line fromt the gas tank to the canister purge, I just have a rubber cap on the fitting on the gas tank. Could to much pressure or a vacuum in the tank starve the engine?
 

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Just a couple thoughts

1 ~ plug wires you can try to load it up at night with the hood up and have someone watch for the spark to jump ~ typically wires fail under load ~ spark plugs run bad all the time and cap rotors usually run bad all the time

2 ~ fuel try unplugging the regulator this will cause maximum fuel pressure all the time and may help troubleshoot it down to a single error ~ you cannot really get a good feul pressure reading unless you are driving but if you measure sitting sit try and load it up in gear to try and cosume more ~ i have only experianced fuel problems either at freeway speeds for fiter and pump volume issues ~ i do beleive it could be possible that the filter is so clogged that it boggs down ~ you may also try running with a vented feul to see if that helps my neighbors car had an issue where close to the bottom of a tank it would not run correct (tank was in a vacuum no feul allowed out of the system

the ignition module that the guys are talking about is a notorious cause of trouble as are the pins in that connector (usually after it has been messed with several years

overall i would recommend wires first
 

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Are you saying that your fuel system is not vented? If so, that would create a vacuum in the system as you use fuel and would starve the engine of fuel. Next time it happens, reach back and open the fuel filler lid, then try it again and see if it goes away for a while. If it does, that's your problem.
 

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FFCobra Fanatic
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I vote for a fuel problem. Sounds like it's starving for gas. Need to get a psi gauge and check/set fuel pressure.
Changing the module out is easy and inexpensive enough and at worse you would end up with a spare if it proved not to be the problem.
 

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just because it's new does not mean it's good test test test . Start with fuel pressure , then timing .A bad mass air sensor will do this as well and may not set a code . It can be tested with a volt meter (dvom) Bob
 

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You HAVE to let air into your tank as fuel is sucked out; something has to take the fuel's place. Take the rubber cap off the vent nipple on the gas tank, and go run it. Bet it will fix it. It also explains why your sputtering starts to degrade to lower RPMs; more vacuum working against your fuel pump in the tank the longer you run it.

I had an LT-1 Camaro that would start acting squirrely (not unlike your problem) when there was less than a third of a tank left. If I removed the gas cap, a rush of air would suck into the tank, releasing the vacuum, and the car would run fine.
 

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Discussion Starter · #16 ·
Okay here is what I have done so far. New coil and new TFI module. No change. Vented the gas tank no change. The fuel system is pressurizing I just checked the schrader valve and it has fuel coming out when I press it. I think my next line of attack will be to check the fuel filter. Cap, rotor, plugs, wires all with 200 miles on them look brand new.

This is driving me nuts I havent been and know I wont sleep till its fixed. Arggg.


Chris

[ April 11, 2007, 05:17 PM: Message edited by: DarkWaterCustoms ]
 

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My ranger did the same thing and it was fuel filter even though it showed good pressure
CAUTION Bleeding pressure from fuel rail is not enough if you have a blockage, when I removed mine
I got sprayed by fuel pressure from filter to pump
BE CAREFULL
 
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