Car is hesitating

[TrickStang37]

well heres another thread of what seems to be like half the problems on stangnet. basically, the car begins to hesitate when i gas it. it idles perfectly though. it will hesitate even at WOT. not always though sometimes it runs perfectly too. i cleaned out the salt and pepper plugs, the spark plugs are new, changed them twice actually, spark plug wires are perfect (new), new cap (3 different ones), new rotor (2 different ones). I tried a different TFI, same thing. no vacuum leaks. the only codes that come up are the same ones that have that have been there for years (removed smog pump) that have never given me problems. if it were a sensor, what sensors work during WOT? maybe coil? maybe fuel filter? fuel pump? I do have a fuel pressure gauge but its only located under the hood (schrader valve).

 

[Daggar]

You checked your TPS sensor? If it's out of range the computer can report incorrect throttle position and may not be reporting WOT position at all. A quick check for this (although not full proof) is to open the hood... take the air intake hose off the throttle body and rev the motor up by hand. If you here an excessive amount of "sucking" noise then the TPS may be off or bad.

Edit: sometimes you can even slot the screw holes inthe TPS to advance it.

 

[TrickStang37]

yeah tps checked, everything fine with that. sweeps fine through the voltage too. any other ideas? if it were a lifter that collapsed or something like that, it would tick loudly right?

 

[HISSIN50]

yep, lifter should tick on ya. i can tell you a couple of sensors that dont work at WOT: EGR system and lambdas.

i like the FP idea. do you have a cowl hood or any way to check it with load? please dont say you know the guy with the mullet dino (the truck axle).

i dont have any other ideas for ya. the other thread was getting too long - i could not keep track of what was what.

good luck.

 

[Daggar]

Yeah, you'd hear a collapsed lifter. If you're sure it's not a vac leak then you're pretty much left with spark and fuel. You could try dropping your timing back a few degrees or running the fuel injector test through the computer. If it were only a part throttle problem, I'd say to look at your MAF too but having the problem at WOT kinda rules that out. Have your coil checked at a parts store too.

 

[TrickStang37]

Yeah, you'd hear a collapsed lifter. If you're sure it's not a vac leak then you're pretty much left with spark and fuel. You could try dropping your timing back a few degrees or running the fuel injector test through the computer. If it were only a part throttle problem, I'd say to look at your MAF too but having the problem at WOT kinda rules that out. Have your coil checked at a parts store too.

i need to get the coil checked tomorrow. and if you mean the cylinder balance test, it tested all good so rules that one out. does the MAF function at WOT??

 

[2002BLGT]

Tap the MAF with a screwdriver lightly while its idling , if it stumbles its bad , if its doesnt , take it apart and clean it GENTLY ...rubbing alcohol and qtip works ......could be the IGN coil , pickup in the distributor also ......bad injector etc ......... thats why its good to find a spare car for parts LOL.....

 

[TrickStang37]

ive cleaned the MAF, no difference. tried a different distributor but who knows it that one is working right as well.

 

[Daggar]

As I understand it (I'm no MAF wiz), the computer does nothing with the inputs from the MAF at WOT. One of the similarities between that and SD. The computer reverts to preprogrammed fuel tables and disregards most all sensor data.

 

[mr5o]

i spent tons of money on my car this year and had the same problem and actually still do ... cant figure it out

 

[TrickStang37]

well, tested the TFI, tested bad so i bought a new one ($95!). also ran a fuel gauge out of the car so i could see what the fuel pressure goes to during hesitation. THE CAR STILL DOES IT!!! grrr. the fuel pressure stays constant (doesnt drop) during hesitation. so now what? what could it be? how do i test the coil? could still be the pick up in the distributor. how do i test that? cleared codes, drove for like 20 minutes and pulled codes. all clear on KOEO and pulled a 42 on KOER. cylinder balance test passed. hmmmm.

also, after i reinstalled my distributor, when i was spinning the cap (getting cylinder #1 on cap to the rotor aligned) with the key in the ignition, the motor would make the sound it normally makes when you do KOEO test (electrical sound) but then would make a clicking sound as if power was cut if i spun it too far, then would make that same sound (electrical sound) when i would spin it back. is that normal?? never noticed that. i tugged on the harness to see if it was a bad connection but did nothing, only with the position of the distributor would it do it. maybe Ill start a new thread on that.

 

[HISSIN50]

someone within the last two weeks noticed the same thing about the dizzy. i dont remember the whole gist.
with the key on, the injectors, etc get their marching orders from the PIP, IIRC.

good luck.

 

[TrickStang37]

well just an update. i tested the coil with an ohm meter, tested within range. tested black/white wire from baro to TPS and EGR, tested less than 1 ohm (tested fine). Tested all my plug wires, tested well within range 1.95 - 2.7 k ohms. Need to test ECT and AIT sensors. Any suggestions? how can i test the MAF?

 

[jb89coupe]

Old o2's can play tricks on you like this, but I'd be looking for a hard fault somewhere first. Bad injector is the first thing that comes to mind. Might be worth it to have them tested or at least have them professionally cleaned.

 

[2002BLGT]

well just an update. i tested the coil with an ohm meter, tested within range. tested black/white wire from baro to TPS and EGR, tested less than 1 ohm (tested fine). Tested all my plug wires, tested well within range 1.95 - 2.7 k ohms. Need to test ECT and AIT sensors. Any suggestions? how can i test the MAF?

you can usually test the MAF by tapping it lightly with a screwdriver while its idling , if its bad the engine will stumble and or die out ......

 

[TrickStang37]

i'll try that today. the o2's have less than 200 miles on them (i bought them new). same with injectors.

 

[HISSIN50]

Trick, remember lambdas are not used at WOT. as i recall, you are having the some of the issues at WOT. and since yours are new, i might not look there first.

good luck.

 

[TrickStang37]

Tested AIT and ECT, tested within range. MAF checked out fine, getting between .67-.70 volts at idle. i did notice today for the first time that my TPS voltage dropping sometimes from .90 at idle to .35 then sometimes it goes back up .90 then drop slowly down to the .6 range or lower. and when messing with the throttle, the voltage stayed really low, never above 3 when the voltage was lower than normal at idle. hopefully (pretty sure) that this is the root of my problem. this would explain also why it would run like **** at WOT, because the computer never knew it was there! hopefully ill get it done in the morning. Ill post the results.

 

[HISSIN50]

with the way your TPS sounds, i would check the wiring to it as well. sometimes TPS's just go south, but i wonder if your ground is intermittantly bad on the TPS.

worth checking. good luck.

 

[TrickStang37]

DAMNIT!!!!! still no cure