94 gt help! runs for a min and then dies after intake swap

montyd · Jul 3, 2011

i have a 94 gt. it was bone stock with the exception of a cold air intake and an x pipe and bassani mufflers. today i swapped the intake out for a 95 cobra upper and lower intake. i also installed 24lb injectors a pro flow mass air off my other 93 mustang that is calibrated for the 24lb injectors. also did a kirban adjustable fuel pressure regulator. the car starts right up and runs just fine for a min or two revs up good goes back to 7 or 800 rpm for idle and then will just shut off like someone hit the key. i know these cars computers are touchier then the 93's but i have no idea what could be wrong. this isnt my first time around the block with a mustang but it is for a 94/95 car. anyone have any ideas? still has smog pump and there are no vacuum leaks. and i checked the timing with the pill out and it was at aout 35 degrees which seems way high to me but i dunno what its supposed to be hope someone has some info thanks in advance oh and also the car had a big vacuum leak which is why we decided to do the swap since we were pulling the intake anyway. have that fixed now but now have this problem

BlownFiveLiter · Jul 3, 2011

The timing should be anywhere from 10° to ~16° depending on how much initial advance you want to add. That could definitely be the source of your problems right there. That, or the outer ring is spun on the balancer and your timing is unknown. Crank it back down within spec and see how it runs then. How does it run with the spout plug pulled? May as well check codes while you're in there, too...

montyd · Jul 3, 2011

thats whati thought it should be it runs just fine with the spout plug out i call it the pill didnt really know the real name. lol. anyways the car only has 60k miles on it i didnt know the balancer could spin like that. if i get it below 30 degrees it wont run at all i thought i had the distributer a tooth off but it will barely run if i go one tooth either way. oh and there is no chech engine light on at the moment

BlownFiveLiter · Jul 3, 2011

Check for rubber sticking out of the balancer anywhere between the inner and outer rings. Usually it's found on the backside, toward the engine. If there's any at all, the balancer is toast and it's time for a replacement. There's only a certain number of codes that will trip a check engine light, but the others will be stored in the EEC and only come up when you pull codes. It's never a bad idea to check them periodically.

montyd · Jul 3, 2011

ok i will check the balancer. how do i go bout checking the codes?

montyd · Jul 4, 2011

so here is where im at. i checked the balancer it doesnt seem to have anything coming out of it. i pulled hte first plug and got it to top dead center. the dizzy was about a tooth off so i moved it and rechecked timing. with the spout connector out it wouldnt idle but over a thousand rpm it would stay runing. at 10 degrees it would run just perfect with the spout connecter back in. it would idle good rev good no hesitation but as soon as i pull the spout connector back out it wants to die. if i bump it to 20 degrees of timing it runs good with the spout connector pulled outand idles good with it back in about 800 rpm which seems normal. it will sit there and run for a minute maybe two and then its like the key gets shut off and it dies out instantly no sputtering nothing but if you start the car with the key it stats right back up and will do the same thing over again. the first plug looked black so i turned the fuel pressure back down to 32 lbs with the vacuum off. and odly enough the car stays runing good with a vacuum leak will idle fine for as long as i let it and it revs good doesnt act funny at all but when i hoock the vacuum back up it will run for a minute and die.

toyman · Jul 4, 2011

Don't worry about a good idle with the spout pulled. You just want to set the base timing between 10-14*. With the spout in the idle will improve and the PCM will adjust the timing somewhere in the low 20's. The PCM will add up to about 26* of advance for a total of 36*. If the base is too high the total advance will be outside the timing table parameters. If this happens the PCM doesn't have a valid reference point. That will most likely trigger other unwanted events.

The other issue with the fuel pressure sounds like the FPR isn't working properly. The pressure KOEO should be 40ish (39-44). and KOER in the low to mid 30's (34-36). Is there any smell or trace of gas from the FPR vacuum line? There shouldn't be any. Instead of hooking the vacuum line back to the FPR just cap it off and see what happens. I suspect the engine will run just fine.

montyd · Jul 5, 2011

well we got it running ended up having a hyperchip for it on hand for bolt ons like we have and it ran great until today. had the fuel pressure set at 40 lbs ran like a champ then today it was running down the high way and bogged out but pulled through and finished the 50 mile trip no problem. got back to work went to go home (ten min from work) and the car woildnt start. eventually started and i made it four block before it quite again. put the guage back on the fuel line to find the key on pump done running only got me 15 psi to the rail. and if i cycled teh key a few times i got 40 lbs and it ran long enough to back it out of the spot and onto the roll back. pretty sure the fuel pump is done. which we thoough was happening before but now we have a reason for a better one lol.

BlownFiveLiter · Jul 5, 2011

Before you replace the fuel pump, check the regulator first. The regulator is what bleeds pressure down, by returning fuel to the tank. If, after a few cycles of the key, to prime the pump, you have sufficient fuel pressure, the regulator is suspect. The pump has enough juice, to build pressure up to the operating limits.

WhiteCobra95 · Jul 9, 2011

You might also want to confirm that the MAF is compatible with the 94 calibration in the ECU. You mentioned that hte MAF was from a '93 and tweaked for 24's, the 94/95 cars use a completely different MAF than the FOX3's so the MAF shift for 24's might not work right with your car. To do that properly, the MAF transfer fuction and injector slopes should be recalibrated in the ECU directly, not by shifting the MAF signal (it's a poor work-around and causes a lot of issues). If you make the calibration changes directly you don't even need an adjustable pressure regulator. Good luck

BlownFiveLiter · Jul 9, 2011

The Fox and SN95 5.0's can use the MAF's interchangeably. A common swap for the Fox guys is to use a 94-95 MAF because the stock Fox one is only 55mm.

montyd · Jul 11, 2011

ok guys here is where were at. got the correct 94-95 maf sensor and installed. put in a 255lb pump swapped the old regulator back on the car just to see and it still runs like a rapped ape for a few min get ten min from home and then it all of a sudden has no fuel pressure and the car tries to die but then will come back for a few more minutes. any ideas?

fordtech28 · Jul 11, 2011

might be your PIP sensor or Hall effect sensor going bad the one in the distributor this is one of the symptoms when that sensor starts to fail

montyd · Jul 11, 2011

ok i will keep that in mind. we put a bottle of lucas fuel sysem cleaner in it and in the same distance is runs consistantly good didnt try an die out or anything. drove normally. this is my brothers car and he bought a used set of injectors and i as thinking they might be dirty or clogged a small amount or just something in a line when we had them off who knows. if it continues to do it after this i will look into the hall effect switch. but that still doesnt answer why it will go from 40 lbs of pressure to nothing at all and right back. and with the adjustable regulator you could still adjust it and if you cycle the key a few time with engine off it would still build to 40 lbs after three or four cycles.

toyman · Jul 11, 2011

Try putting the Kirban AFPR back on to see if the pressure holds. I assume it's new. Was the 255 lph pump new and what was the brand? If the pressure falls to 0 then it's either the FP, the FPR, a bad connection (power or ground) or a bad fuel pump shut-off switch.

final5-0 · Jul 12, 2011

I'd say you gotta a v leak from the intake job

Grady

toyman · Jul 12, 2011

final5-0 said:
I'd say you gotta a v leak from the intake job

Grady

He may have but that doesn't explain the fuel pressure dropping to zero.

it still runs like a rapped ape for a few min get ten min from home and then it all of a sudden has no fuel pressure

WhiteCobra95 · Jul 13, 2011

I agree, this sounds like multiple problems at once.

One thing for sure is that the fuel pressure should not be dropping like that. I think toyman has some good suggestions about where to look. It could also be a bad fuel pump relay. -- Those pumps are usually loud enough that you can hear if they're running or not from the rear of the car at idle. If you don't hear the pump whine at a stop when the pressure drops, it's either the pump itself or an electrical issue. Be careful doing this…but you might be able to jump the relay with a piece of wire to force the pump on after the engine has stalled to see if you get back your fuel pressure. If that works, then your relay might be bad, but the pump and wiring are fine. (I've done this dozens of times on others cars, but not on one of our mustangs so I'm not sure if the fuel pump relay is under hood or not.) Intermittent electrical gremlins like that are not easy to find.

As far as the suspect injectors, I would suggest putting the stock 19 lb/hr's back in if they were good when you pulled them. You don't need 24's with a stock E7-head GT motor and that would rule out one more variable. The factory SN95 MAF/injector combo should rule out any big calibration issues. If it still acts strange after the fuel pressure is resolved, then it's probably an intake leak or worst case an intake manifold crack that opens up when the motor gets hot.

toyman · Jul 13, 2011

The FP relay is integral to the CCRM. It's not intended to be repaired but I've read that it can be done (new relay soldered in).

screamin5oh · Jul 13, 2011

if the pip sensor is shot it will not prime the pump, and cause your problems, it is very typical for these to go bad and do what your describing, if its a relay its actually in the ccrm and its not serviceable, advance sells them 128$ but if you get that far you can by pass the relay for a very temporary time and see if it still does it, also another place to check is make sure the fuel safety switch is tight in the back and not rattling lose its on the back driver side of the car behind the panel in the corner, leaning towards the very very very common pip sensor witch can be fixed with a new distributor.

94 gt help! runs for a min and then dies after intake swap

montyd

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