my car is acting funny. at idle, it seems ok. when i take off it sputters into motion. at cruising speed it is ok i guess. when i punch the throttle it cuts in and out like there is no fuel for a second then its back, then gone again, then back again on and on .....

what could this be? would a dying fuel pump do that? mine is an electric in tank pump.

could it be the fuel filter? fuel injectors?

the other thing is that this is intermittent. it does this 80% of the time.
other times, i take off from a stop and it pulls hard right away!

could that mean its an electric or timing issue? may the problem lie in my distributor?

any help guys. its driving me crazy. thanks.

85 5.0 with TPI headers and exhaust, 300k miles. no other mods yet.

 

Last month I had somewhat of the same issue as you are describing. My car would be fine at idle, but when i hit the gas it would sputter and "buck" then sometimes backfire too! Checked the timing and it was fine, so i put in a much needed set of spark plugs. Im not sure the plugs would have made the differance, but b4 i took the car out i check the distributor cap and one of the clip nut thingers wasnt locked down and the cap was a little crooked. Since then ive prbly put a hundred miles or so on it and havent had anymore of the same prblms. Just my 2 cents.

Jordan

 

Also make sure the plug wires arent burned.

 

ok i pulled my plugs and they looked kinda bad. my wires were crusty in a few spots and a couple of cracks as well. i plan on changing em out this week sumtime. hopefully that solves it. so you guys dont think its anything to do with the fuel system?

 

My car has the same symptoms, only they're 100% of the time.

I replaced my entire distributor, plugs, and wires, and I still have the problem. I hope you have better luck than me.

 

more than likely u need a tune up!if u want to start to diag the fuel system start off by checking the pressure,put a gauge on it,turn the key on and keep an eye on it for a few minutes to see if the pressure bleeds off!if it bleeds off theres a problem,system should hold pressure i think for like 8 hrs or so.should hold about 45 to 50psi i think.if it holds the pressure start the car and see what happens,it should hold at 35 to 40 i think,but if ur it that ballpark your fuel system should be fine.i believe theres a tech article on that!

 

well i replaced the plugs and wires all brand new. still having the same problem. at about 80% throttle and higher, it kills in and out like its getting bubbles in the fuel lines or something.

i do have a fuel pressure gauge somewhere but i have to dig it up to check it out.

might my fuel filter be clogged? or maybe my fuel pump is giving out?

 

Keep us updated if you find a fix, both my car and my buddies car are doing this BAD. I have been fighting this problem for months, I cant figure it out!!

 

I had the same problem on my 3.1L. I changed plugs and the cap. That didn't cure the problem. I'm going to have the oil changed and the fuel filter along with it. That seems to be the simplest fix for now. Check your timing....and if your distributor has a mechanical advance, see if your springs are wore out. It seems like a possible solution. On my old 74 truck w/ 454, it had some of the same symptoms and was a pain to get to crank over. Finally it flat out died. Could have had the distributor rebuilt but bought a MSD one because I needed the truck now.

Check it out. Hopefully that is the solution. As for mine...I have no clue how the distributor is put together.

 

well i replaced the pickup coil not too long ago and the dist cap. while i had the distributor out, i checked it all out and it was good other than the part i replaced.

my timing was checked and good as well.

its gotta be something fuel related. alot of my friends say either the filter, injectors or pump.

im betting its the pump because now it sputters to death with any amount of throttle and barely stays running at idle.

im going to replace the pump and filter in about two weeks when im off and see if that does the trick. if not, i guess the injectors would be next.

but this sounds like what happens when a fuel pump gives out right? does anybody know? its an electric in tank pump.

 

When I still had FI, and my pump was going out, I didnt really have those symptoms. The car would occaisonally idle real low and threaten to stall, and sometimes stall, but would only sometimes start back up. Usually the symptoms of a failing pump are that the car will only drive for a certain distance before totally shutting down, whenever the pump got too weak to supply the motor. I dunno, though.......

 

I would change the filter and see if you get better results. Dropping a tank on these cars is a major PITA as I have read all over these boards.

 

Eh, it gets easier every time you do it. I have done it 4-5 times now.

 

ok i changed the fuel filter. it was really bad! very clogged. i blew in one end and it barely flowed at all compared to the new one which was flowing as easy as a straw.

but it still didnt fix the problem. so thats not what it was.

i have a fuel pump but im hesitant to replace it because alot of people keep telling me that when a pump goes, it just dies. no sputtering or crapping out slowly. is that right? id hate to replace it and it not need one. thats money i could spend on the real problem, whatever it is.

anyway, i will try to throw a vid up of what is wrong if i can. until then im going to check my timing again, and try to dig up that fuel pressure gauge to check that.

i will keep u guys posted.

 

Please do.

I am still where you are. 2 new fuel filters, 1 new fuel pump, 3 distributors, 3 sets of wires and spark plugs, 7 valve lash adjustments, and countless other attempts at finding the REAL problem. Yet, there the problem remains, laughing in my face.

Put a fuel pressure gauge on the feed line and see what PSI it reads, if its good than your pump is good, vice-versa.

 

ya i have to dig that thing up. but i just tried to check the timing but was unsuccessful. i cant check it because the car wont maintain an ideal idle. and when i try to manipulate the throttle, it sputters bad then revs high then back to sputtering.

but like i said, its a ghost problem! one of the times i started it after trying to check the timing, it went fine! idle went up smooth then sat perfectly at about 800rpm and when i revved it, it went up smoothly and easily!!!! no sputters for about ten seconds and then it was back to crap.

its driving me insane. im going to have a friend of my dads look at it. supposedly hes really good with cars.

until then, the bastard eludes me.

 

hey bradley23150, theres another thread similar to this one ...
No idea whats wrong....??
he fixed it by replacing the fuel pump! well he said it was some kind of tube near the pump. read that and see what you think. its the second to last post on that thread.

but you said youve done the pump and that didnt solve it right?

 

Correct.

I have had the tank dropped 4 times, replaced the sender once, I know that hose is fine. I appreciate the idea, though.

 

Any chance it could be your timing chain? With 300xxx miles and with that being a sports car its def. seen some rpms. Or (I know its a long shot) problems with your fuel pump relay. See if you are getting accurate and constant voltage to the fuel pump.

 

well i havent considered the chain but i dont see how that would be it. a chain is either intact or broken right? no inbetween?

as for the pump, i hear it prime just fine when i turn the key on so i dont think its a voltage issue, just a function issue. but i will give it a shot. how exactly would i check that?

 

A chain can become loose, and the timing will be off. I don't know if it can actually cause all of your problems but I know on an old 350 we got around the house that the timing wanders pretty bad because of it and causes it to surge and stumble a bit.

 

well i found my fuel pressure gauge and hooked it up to my fuel rail. zeor psi, or maybe two, but it was low or not there at all. so thats it unless my gauge doesnt work! i didnt get a chance to put it on anything else to test it tho.

so i began to pull the tank and planned to swap the pump. BIGGEST PITA i have done so far! man its hard! the tank just wont come out! i removed my exhaust and the rear suspension bars and still dont have enough clearance to remove the filler neck! i may just have to bend it to get it out!

anyways, i only had two hours to do it so my car is still jacked up with the tank hanging halfway out from underneath it. i am going to take the pump to get tested and then install the new one either way. that may take me another week though because i barely have enough time.

well once i get the new one in and everything back online, i will retest the fuel pressure and let you guys know whats up.

 

I had to bend my filler neck to get it out. It bent right back without any cracks or anything. I've had the same problem as you for a couple months though and I just can't figure it out. Replaced all vacuum lines and the top end gaskets, distributor cap, rotor, wires and plugs. Fuel pump and filter, IAC, MAP, cleaned the EGR, and it's still running terrible. If you know someone who can read the codes that could be a big help. I got mine read today and it gave me 13(O2 sensor), 23(MAT), 32(EGR), and 42(EST). So tomorrow I'm hopefully going to work on the O2, EGR, and EST. I'll let you know if any of these help it and maybe it'll help you out.

 

ok i got the new pump installed and the tank back in. it was tough but its all done now.

the problem is still there though!!!!!!!!! i hooked up the fuel pressure gauge again after putting it all back together and i still have 0 psi. but i still dont know if the gauge is broken or not. im going to test it this weekend and see.

i just cant figure it out! someone suggested i check all vacuum lines. im pretty sure they are all good. do any of you know where and how i should check?

i do have a friend who can hook my car up and give me the trouble codes. i will try to get with him on sunday as well.

until then, does anyone have any other ideas????????

 

I'm out of ideas honestly. But getting the codes read should give you a good idea of what's wrong.

 

Even to me this sounds far fetched...but how do your fuel lines look? It seems that a bad pump would cause low pressure...but as you stated, it's not the problem.

Its gotta be in the codes. It should verify a low pressure, if not...your gauge is bad.

 

still no progress on the fuel pressure gauge yet.

i did however check the engine codes.

it gave me 13, 23, 24, 33 and 34.

any ideas guys? because the chilton manual says 23 is MAT (Temp LO)... or ... M/C Solenoid (open or ground) which one is it?

any help on the other codes will help too. thanks.

 

The code reader I used said 23 was MAT. Which I knew it should throw a code since it just hangs there. 13 is O2 I believe, which can cause the car to act up, though I don't know if it's enough by itself to cause the issues we have.

 

Well if people could order the right part I'd be able to tell you if replacing my EGR valve fixed my issue. So I might be able to figure something out Thursday or Friday.

 

Nope, EGR didn't fix the problem. So now on to playing with the timing and installing the new collectors with the O2 fitting. Fun times.

 

When mine was still computer controled, my ignition module would act up and cause power problems. But like what was mentioned earlier about the timing chain being bad, yes they can stretch and cause your timing to go crazy therefore affect the way it runs. You can check it by taking off your distributor cap, turn the crank pulley with a socket 5/8 I think, until the rotor moves then turn the oposite direction and see if the rotor moves or pauses. If it pauses before it moves, you can figure the chain is toast.

 

Ghost problem is messing with me again. I had a friend of mine check my gauge for me and he said it worked. I hooked it up and it still said zero. maybe he didnt actually test it or maybe i really do have zero, but i depressed the valve when it was running and fuel did spurt out. not all hardcore but it did spray.

so I dont know but im still having problems. maybe my adjustable fuel pressure regulator is crapping out on me. I will check that next. I may also do that thing with the cap to check the chain as well.

But its a ghost problem! I started it up last friday and it ran ALMOST perfect! it idled pretty good, took off with only mild sputtering and stayed running fairly well! I was rather impressed! I shut it off and turned it back on immediately and it ran like crap! like it was a totally different car! I DONT GET IT!!!!

I also found a small vacuum leak and plugged it up but no improvements were to be had. Five more weeks until my schedule REALLY clears up, then I will have lots of time to figure this out.

 

Same thing with mine. But I'm pretty sure I've singled it out to the timing chain. The EGR fixed the issue of it running worse at night. And I retimed it yesterday and it ran like a dream until today and it started up again. I hope I've finally found the problem and can be done with this nightmare.

 

I checked the cap for movement. It was the slightest bit delayed when i turned the crank. but barely. i dont exactly know how much of a delay to look for. i did notice tho that something under the cap was very loose, i think. here are the pics...


this piece here is pointing about two thirds of an inch to the left of that screw. it moves quite a bit to the right when i wiggle it.


when i move it to the right, it is now just slightly to the right of that screw!

is this normal??? the distributor shaft that it is attached to does not move when i wiggle this part. should this bracket be solidly attached to the shaft? it should right? is this what could possibly be throwing off my timing???

 

If I understand what your saying, than yes, that is normal. That is your centrifugal advance, and it should wiggle if you try to move it.

 

Could the catalytic converter cause the problem?

 

No. not the cat. I dont have one nor have i since i did my exhaust 3 years ago.

However!!!! I took it to a local shop because it was driving me crazy! guess what his most likely idea is... the MAF. He disconnected it and said it was in limbo mode and it was running pretty good! well, all i did was back it up in his driveway and then pull it forward into his bay, but it seemed to be running solid!

So thats his idea. hes gunna check and make sure its not the wiring or a bad ground or something electrical with it. if theres nothing else, he said its most definately the MAF.

So!!!! have any of you guys tried disconnecting your MAF to see how that affects it running? if not, try it out and let me know!

 

yup! definately the MAF. he checked it for shorts or bad wires to the computer and for any bad grounds... nothing! he disconnected the MAF and i drove it home and it was almost perfect!

well, you know how the car runs without it plugged in, just a little delayed or sluggish. But the fact that it was crapping out must have been sending all kinds of malicious info and readings to the ECU.

so now i need to buy a new one. $309.99 on www.hawksthirdgenparts.com that kinda sucks but maybe you guys can try that and see how it works for you. the diagnostic cost me $100.00 so maybe that can save you that much.

also, he checked the fuel pressure at the rails and it read like 58psi. when i put my adjustable fuel pressure regulator, i set it to like 50 - 54psi. it must have gradually changed over time but he adjusted it back to 54 for me as well.

check that out boys and post the results!

 

I don't have a MAF.

 

man that sux. i thought i solved it for u! what about your friends? do any of them have MAF?

and for you, are there any sensors that may be causing that problem? you checked all vacuum lines right?

 

The reason that I dont have one is that my engine is carb'd. I was just hoping for some ideas here.

Truthfully, I gave up on the problem. I am going to replace the cam, intake, carb, timing chain, and the valve springs when I get the money.

Glad you got her all figured out, sucks that its such an expensive part!

 

thanks man, i appreciate it. i hope u solve yours soon and that its not too much.

 

Thanks.

Basically, I am trying to just park is ASAP, so I can do all the other things to it that I want to do, without having to rely on it, ya know.

Good luck!

 

Well I've had the same issue and I'm in the middle of replacing my timing chain with gears. If this fixes the problem for me, I'll let you know. I've already hit all the sensors, so this is the last thing I can think of.

 

Yeah, but my motor has ~300 miles on it, no way the chain got messed up. Its cool, I dont really care anymore, lol.

 

Problem is resolved boys! I finally got the new MAF and installed it today. Runs like a dream! Im so glad thats over with!

 

um......40-45 is stock fuel pressure

 

set fuel pressure with car running and vacum hose from pressure regulator disconnected. set it to 40-45 psi, too much will make your car slower