ANOTHER hesitation thread.

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Brett

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I'm gonna try and make this as descriptive as possible. The car has 112k on it, and just had a full 60k done and then some not even 3000 miles ago. here is a list of things done.

superSHO93: "Prior to intallation on his 110k engine I did valve lash adj., plug well gaskets, resealed valve covers, new Gates t-belt, new CPS, new cid, new waterpump, checked and regapped plugs, new t-stat, and inspected the wires for damage(would have put new ones on had I had any). Basically everything minus rod bearings( ran a gauge and has 15psi at hot idle). The car was getting 39psi at the rail when I finished it although the fuel pump could be going bad. His intake was not all that dirty compared to what I have seen. I replaced the wiring harness with one I had as the morons at the yard cut the engine harness. I did a tranny refresh also. That's all I think. Now you guys have a maintenence history on his car."

Now that you have a list of the things done not even 3k ago, i'll try to explain as best i can. It is most noticeable when the car is first started and ran, it gets better once you've driven for awhile. It's almost as if you hit a dead spot sometimes, you can feel the car want to pull harder but it doesnt, sometimes even bogs (i.e. bucks a bit). If you just let off the gas or shift it goes away. Now it wouldnt be that big of a deal but i really feel its holding my car back, even when the bog is cleared up it doesnt seem to pull like it should. there is no CEI and hasnt even so much as blinked since ive gotten the car. Ive pulled the entire maf and sprayed the p*ss out of it with MAF specific cleaner, allowed it to dry, no difference.

I plan on doing some mods this winter while my car sits, y-pipe, mufflers, port the runners. Perhaps even an m90 supercharger with LPM (if one of the five m90 owners do a writeup sometime in the next year! :biggrin: ). But this all seems kinda useless without figuring out my lack of power problem. So what should i do? i trust shawns work on my 60k as i havent had a real problem the whole time ive had the car. is there ANY way to pinpoint my problem? or will i have to play the guessing game? (i.e. all sensors, full pump, cats, injectors). Thanks to any response and sorry for the length of the thread, just wanted to be descriptive. Thanks to any responses, and sorry for making you go through the 10,000th hesitation thread! :hail:
 

hawkeye18

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The first thing I want to say is... fuel pump. Possibly fuel filter, but less likely. More gas pedal = more fuel flow, and if the fuel pump is getting weak it will have problems. There is a really nice writeup... um, somewhere for replacing the fuel pump from inside the car. It involves cutting up the seat, um, 21 and 31 (?) inches from the pass. rear door, and at the front of the ****... that's right over the pump access door. It's pretty easy from there.

Of course, failing that, I would redo plugs and wires, but they don't really seem like the culprit here. It seems like a simple lack of fuel. Does it bog worst when you're on the gas but you're at the point right before where it upshifts? (you have an atx, right?) My wife's car did that really bad, went away with a new fuel pump. If it's stock, at 112K I'd want to replace it anyway. It will go bad eventually.

just my two cents...
 

Brett

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Sorry for leaving a couple things out, changed the oil filter same time the 60k was done, always run 91 octane. its an MTX, and i also think fuel, it almost feels like it pulls harder at 3/4 almost WOT then it does at WOT. Is that the only way to swap pumps? you cant just drop the tank?
 

hawkeye18

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yes, you can "just drop the tank", but if you do you'll quickly find it's a major PITA. rusted tank straps, having to jack the car up, clearance issues... IMO, it's just not worth it. It's easier to cut a hole in the back seat, that way it'll only take 15 minutes to change the fuel pump a second time when the first one fails after 100 miles (not that that's ever happened to me...)

Don't waste your money on 91. It runs just dandy on 89. It runs just dandy on 87, actually. I can't tell the difference, except in my wallet...

As far as the WOT thingy goes, that's just bad computer programming. It commands a pig-rich mixture at WOT, and at 7/8 throttle it still tries maintaining a good mixture. It's a long story as to why, something about closed-loop programming and whatnot. But yeah, it's always like that. I generally keep it at 3/4-7/8 untill about 5K-5.5K then I floor it the rest of the way so it doesn't shift too early (I have an ATX).
 

Brett

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Where exactly does this cut go, under the seat? because if im cutting the seat itself id much rather just drop it. Second, im not trying to say you dont know what your talking about, when it comes to anything eletrical (including ECU) im in the dark. but ive never heard anyone else say its better at 7/8th's throttle then at WOT. thanks for your replies. keep'em comin!
 

Mr95Gl

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Brett said:
Where exactly does this cut go, under the seat? because if im cutting the seat itself id much rather just drop it. Second, im not trying to say you dont know what your talking about, when it comes to anything eletrical (including ECU) im in the dark. but ive never heard anyone else say its better at 7/8th's throttle then at WOT. thanks for your replies. keep'em comin!

You can use this site as a reference for cutting a Fuel Pump Access Door . . . . . http://www.shophoenixproject.com/fueldoor/fueldoor.htm
 

sho_me92

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did you test the fuel psi while you are driving it? cause my car seems to have the same probelm as yours. i also think it is the fuel pump getting week. im going to have a guy at the shop let me use his fuel presser gage and ill take my car around the block to see if the fuel presser drops with my car bogges down. if it does its most likely going to be the pump.
 

hawkeye18

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Brett said:
Where exactly does this cut go, under the seat? because if im cutting the seat itself id much rather just drop it. Second, im not trying to say you dont know what your talking about, when it comes to anything eletrical (including ECU) im in the dark. but ive never heard anyone else say its better at 7/8th's throttle then at WOT. thanks for your replies. keep'em comin!

Yeah, you don't cut the seat itself, silly. You cut the metal under the seat. And if you're good, you only cut three sides so you don't end up with a big gaping hole :). And hey, you can talk about how much I don't know what I'm talking about all day long, I'm just repeating what others have told me.
 

Brett

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Is there a writeup for the cut? which side is the pump on, where to cut, with a sawzle (dont think thats how its spelled)? will pressure at the rails indicate if your pump is weak or not? how hard is it to get to the rail?
 

sho_me92

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Brett said:
Is there a writeup for the cut? which side is the pump on, where to cut, with a sawzle (dont think thats how its spelled)? will pressure at the rails indicate if your pump is weak or not? how hard is it to get to the rail?
there is a threshold that is on the top of the intake that looks like a tire valve stem
 

sho_me92

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i put a new feul pump in and now it runs great. hopfully its lasts... IM SO HAPPY I GOT MY CAR BACK :)
 

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