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View Full Version : Need a little help...94 SC auto...Hesitation on Hard acceleration...



lube70
05-04-2005, 09:59 PM
Well, My wife has a 94 SC with 54,000 miles. The car has new fuel filter and is all stock. Since I got it, when you get on the throttle hard (real hard, almost floored), the car will hesitate and buck like you cut the fuel or spark entirely. The car otherwise runs GREAT!! One thing I did notice is that the boost is up there, almost 15 PSI on this car. Seems very high for a 94 auto. Since my 95 is modded and my 91 is a stick, I figured I would throw this out for some possible answers from the later model community.


Again, the plugs and wires are older, that is my next step. Was wondering if the TPS is maybe to fault. Just seems weird that it falls on its face so hard upon a certain throttle point.

I can get on it hard and it runs great until 7/8 throttle.

Any help is appreciated with this. I know the obvious like plugs and wires.

Thanks in advance guys and gals!!!!

P.S. No codes at all. :confused:



Don

rlong
05-04-2005, 10:39 PM
im thinking clogged cat cause of the high boost my 90 auto is still on original plugs and wires at 93 k MILES , i hardly ever floor it cause with stock exhaust it doesnt have the power after half throttle like my 89 with good exhaust . i dont want to blow a hg i think my cats are getting clogged too

lube70
05-05-2005, 08:28 AM
Other points to mention are that the car runs like a champ. No running issues, no tach going nuts, no part throttle miss, nothing of that sort.

I also notice that this only seems to happen under low RPM hard acceleration. I'll be running the car on my Snap-on scanner and seeing if I can get any codes or see what is happening when she's running.

Again, anyone with a late model with a similar problem, help is appreicated.

Early models are also asked to chime in because I think that it could be a stupid thing I'm over-looking.


Thanks again guys and gals!!!!

Don

lube70
05-05-2005, 10:19 AM
I ran the code scanner on the car and got NO CODES!!! KOEO and KOER. So, also drove car and really paid attention to when it's doing it's thing.

Seems that under a large load the engine is knocking and pulling timing.

My question is...do these cars pull THAT MUCH TIMING to make it fall on it's face???? Actually, my scanner cann't read the knock sensor (go figure) and I can't tell if I'm getting spark knock or not.


Please help!!!


Don

pablon2
05-05-2005, 10:44 AM
I ran the code scanner on the car and got NO CODES!!! KOEO and KOER. So, also drove car and really paid attention to when it's doing it's thing.

Seems that under a large load the engine is knocking and pulling timing.

My question is...do these cars pull THAT MUCH TIMING to make it fall on it's face???? Actually, my scanner cann't read the knock sensor (go figure) and I can't tell if I'm getting spark knock or not.


Please help!!!


Don

What grade gas do you run in it?

lube70
05-05-2005, 01:10 PM
I scanned the codes again and nothing. Did a live datalog of the EEC and found that the Short Term Fuel trim (thanks to XR7DAVE) is a little high. Meaning that the car is running lean. I am changing the plugs and wires and putting some fuel system cleaner in to try to clean out the system.

Wish me luck,


Any other ideas would be helpful!!!!

P.S. Paul, running super 93 octane...ALWAYS!!!


Don

Joisey Jim
05-05-2005, 01:54 PM
I would have said it's either bad gas (maybe low octane), fuel filter, regulator or fuel pump. Try Sunoco Ultra 94 if you can get it in your area. I had a similar problem on my 93 - 5 speed years ago and eventually hooked-up a fuel pressure gauge. I connected it to the schraeder valve on the fuel rail and had enough hose to be able to tie the gauge to one of my wipers. This way I could see the pressure while driving. In my case the pressure would bog down at about 55psi @ WOT instead of about 62psi (according to Lee over at C&L) . The problem turned out to be a bad fuel filter.

XxSlowpokexX
05-05-2005, 07:15 PM
Maybe mass air..

My 94 does teh same thing except I get a check engien light...WHich doesnt show up as a code on the scanner...Im going to swap in a stock mass air and see what happens

lube70
05-08-2005, 12:54 AM
Doing plugs and wires on her on Monday. Any other ideas on the problem???


Thanks,

Don

XxSlowpokexX
05-08-2005, 01:40 AM
Plugs and wires didnt ghelp my lil problem

lube70
05-22-2005, 10:10 PM
I replaced the plugs and wires (which REALLY SUCKS!!!!), and the problem seems like it's gone.

I used Dave's plugs (autolite 764's) and I'm kinda regretting it. I am HORRIFIED at the thought of having to change those plugs again!!!!!


Anyway, one plug was gapped to .075 so that would cause a huge missfire.


Hope this helps others.


Don