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Strange Hesitation


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The hesitation happens while cruising and then lightly pressing the gas while accelerating out of a gentle curve or speeding up on the highway. It feels like someone either stomps the brake or shuts the engine off for a split second. It doesn't happen predictably and I can't replicate it.

 

I do know the motor is starting to go and I have a weak hesitation nothing like what is happening on bad days off the line when its knocking. Would this be knock sensor or something else? Center diff binding? Power napping?

 

Thanks in advance.

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To best describe this, it doesn't feel like an electronic nanny messing up causing a stumble. Its more of a WHAM like smashing the brake pedal about half way then letting off. My check underpants light lights up every time

 

Will clean sensor if I have some cleaner left...

 

Just recently i paid $190 to have my trans and rear end fluid changed because the car was making a terrible whining noise like straight cut gears. Mechanic said fluid looked fine and was not low. I have a feeling this has something to do with a failing component that is binding either motor or drivetrain.

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Yeah, but if your car is making an awful noise, its 15 below wind chills and the asshole Chinese engineers that built the car hid the dipstick (and google is of course worthless) so you don't know if your transmission fluid is critically low... Do you drive it home or fix it before you dump a trans? I also had some minor radiator work and they seem to have fixed the leak so it was in a sense worth it. Its my bad for not changing it when I got the car (PO said it was changed though)...

 

I drove it all day today and no hesitations like described. I did have alot of knocking and off the line hesitations from the knocking, but I know that problem.

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Yeah, but if your car is making an awful noise, its 15 below wind chills and the asshole Chinese engineers that built the car hid the dipstick (and google is of course worthless) so you don't know if your transmission fluid is critically low... )...

 

I thought it was Japanese?

The only reason I look at other peoples cars is so I can see my Subie in the reflection - Carver Snell

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My 99 LGT does a similar thing when I press the throttle to speed up. It mostly happens at lower speeds and I believe it's due to the CIA I have installed. Mostly because it's worse when the engine is cold and its cold outside. Clean the MAF and drive it a little after so the ECU recalibrates.
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  • 4 weeks later...

After cleaning the MAF (had to buy a security torx bit set....) I haven't experienced the random-while driving hesitation anymore. I still have a hesitation when accelerating from a stop which is either the hill holder being a B, TPS, bearing knock setting off the knock sensor, or ignition related.

 

Thanks for the input guys.

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Hello;

The knock sensor helps the computer to determine the timing advance. A bad one can actually make the engine knock because the computer does not have that third eye. Sound travels thru an engine block. What you might think you hear on the right is actually coming from the left. If the engine is worn out and rods are knocking or the mains rattling, then a sensor will not help you out! Steven.

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The car took a turn for the worse. Horrible misfire, flashing CEL. Randomly goes from running fine to running like ass. Will never accelerate from a stop without falling all over itself. Pulled codes was for the cat converter running below efficiency (bank 1) well no **** sherlock the car is only running on 2 cyl!

 

I discovered oil leak on spark plug 3 (had misfire code for cyl 3 after driving for an hour, finally) cleaned the oil off of the spark plug and boot, and the hole that it leaked into, retorqued the bolts on the valvecover gasket. Still have misfire.

 

Checked and calibrated the TPS with the Torque App on my phone. Man that works slick. TPS all fine.

 

Cleaned, lubed the IAC. Was really dirty and idles better but again, no diff in the misfire and still stumbling bad off the line.

 

Got desperate, pulled the knock sensor. That looks really good if not new, and the PO said it had a new one 30k ago.

 

Really fishing with dynamite here, cleaned all the grounds I could find, which were not all that bad. Still not much of a difference, but the 2 cyl thing is down to a dull roar but still happened a couple times on a test drive.

 

I am down to cam and crank sensors (which I know are clean because I just did the timing belt) perhaps fuel pressure, and lastly the coil pack itself. All the ignition parts besides the coil are new ish.

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Replaced coil pack with good used unit. No diff. Tried diff spark plug wires. No diff.

 

Helps if the fuel injector number three is plugged in all the way. That little click makes a big difference. Went to remove injector harness to test injector resistance per your instruction monkey... What the... this thing isn't connected all the way.

 

However the car still falls on its face off the line. Dumped in a whole can of seafoam grabbed new plugs and a fuel filter... let's see if we can knock it out.

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clean the cam position sensor plug and make sure its getting good contact right bellow your oil fill tube. i had the same thing happen right after 2k rpms after i spilled oil on it.

 

edit: never mind see you have it taken care of

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  • 2 weeks later...
  • 1 month later...

Subiedam... I have a manual trans with basically new synthetic fluid in it. Good to know though!

 

Well guys the car ran ok for about 2 months and now the hesitation is back.

 

Off idle revs have a slight stumble.

 

Putting the engine under load at about 1500 or below causes extreme bucking/kicking missing. I putz around alot on my commute to save fuel so I tend to hit this zone alot. When the car is running correctly it would lug out to 1000 even 800rpm without going into fits.

 

Taking off from stop lights can elicit bucking kicking/stumbling fits.

 

Essentially I have replaced/fixed/done all these things due to this misfire and poor performance. I am really, really, really lost at this point. Car tested very solid on compression 180psi across the board (not bad for a 200k rig) and it runs ok at higher RPM.

 

November/Dec last year: Air filter, timing belt, water pump, timing cover, idlers, cam seals, valvecover gaskets. Car was out of time a couple teeth (perhaps one) on drivers side, but the performance really did not change.

 

Feb: Cleaned MAFS, cleaned spark plugs.

 

March: replaced old coil with nicer used coil, cleaned all grounds (all of them wow), calibrated TPS, new fuel filter. A motor knock and a bad misfire was solved by plugging in an injector (also wow), and the off idle stumbles were fixed by NGK platinum plugs.

 

June: cleaned my MAFS. One injector was unplugged slightly (I don't know why they pop up like that). The engine sounded slightly better but the hesitation still there. One plug boot had some oil on it but nothing to raise alarm (thanks Fel-Pro for making very shitty valvecover gaskets)

 

I also always run premium fuel either 91 no ethanol or 93 with ethanol, am religious with oil changes, have a properly adjusted hill holder, all the sensors are clean, tires properly inflated.

 

The only thing I can think of that might be the problem is I get an intermittent P0420 code Catalyst Below Efficiency Bank 1. I would think that a plugged cat would affect performance at high rpms (which seem to be just fine).

 

Any more ideas???

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Resealed and torqued the valvecover gasket... Cleaned up the plugs but they look BRAND NEW and don't suggest a running problem, cleaned all the sensor connectors I could reach from under the hood all looked good...

 

The inside of my engine is squeaky clean compared to how it was from this November! What a little TLC does I guess.

 

Pop the throttle, (IE, take off from a light type acceleration) the PCV valve rattles pretty hard while the engine is stumbling. Almost sounds like a spark plug wire grounding out. Have never heard that before.

 

The valves are only "bad" when they don't rattle, and I can't think of anything this indicates. I took it out and cleaned it (it was clean, I've never touched it) and it seemed to function right..

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O2 upstream sensor plugged in, looks newer, PO says replaced a year ago

 

Injectors all 16.6 ohms.

 

I looked for two hours for a vacuum leak could not find one. Unless one of the three vacuum gizmos on the passenger side is bad...

 

Coil pack 12.92 K ohms on both banks

 

Wires are Cyl 1 6.4k ohms Cyl 2 7.9k ohms Cyl 3 7.9k ohms and cyl 4 8.1k ohms...

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You know I just read the entire thread and when you said you replaced the plugs and it cleared up I was going to say the problem would come back. I've seen this a lot with mysterious misfires and guys installing fresh plugs it goes away and then it comes back. I would do this, drop down the exhaust manifold and look into the exhaust ports. What you want to look for is if all of the valve guides are evenly sticking out and they should be out about a 1/8". My 96 had the same problems and I tried plugs it went away and came back. I googled my issue and found a huge amount of info on the valve guides dropping down from being loose and causing cylinder misfires randomly.

Another thing to check is get a can of carb spray and while it's running spray where the intake manifold meets the heads. Spray a lot and if there's a gasket leak the engine will suck in the carb spray and the engine will want to die. If you have access to a evap smoke machine it's a lot easier plus you'll find any other vacuum leaks in the system. GL.

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