Hey everyone
Been having this nightmare for a couple months now.

The symptom is that my car feels like its being completely held back.

DSM link shows the engine is running fine during this "hesitation".

I had a similar problem over a year ago and it was my rear calipers sticking.
I replaced those at that time cuz i noticed my rear rotors were getting warm.
The new calipers fixed that problem.

Little after that noticed my master cylinder was leaking, replaced that and car was good.

This winter is when I started having my recent problem. Same symptoms that the car felt held back, AND now my rear brakes were engaging before my fronts.
So I changed my proportioning valve and rear calipers again, and didnt fix nothing.

Thought it was my cat converter, so i changed my exhasut with another one i have, same thing.

I can put my car up so no tires are on the ground and everything spins freely.
(checked this cuz I also put a 4 bolt rear end in with a 22 spline tcase/tranny.
I dont know if this makes a difference but it came out of a 23 splined car? To my understanding the ratios are the same? or are they not? car was fine for a couple months after this swap.

Idling, my car has about 18 or so for vacuum.. When i pump my brakes on idle, they get super stiff, vaccumm goes to 10 and sometimes lower, and car starts to suffer and want to die. after driving for a bit my pedal also feels hard. I changed my vaccuum valve between IM and the booster, even tho i tested the old one and it seemed fine, changed it, still same thing.

To test my booster, I pumped my brakes with the car OFF, till they got rock hard, and pushed while i started the car.. the pedal slowly went down with ease but no where near the floor.

Driver side front and passenger rear rotors also get real warm sometimes, without applying the brakes.... Id downshift and pull over and feel the rotors.

I also did not drain my booster when I had a leaking master cylinder...
and at cruising speed, my car use to have vaccuum of about 15, now its at 10 on cruise load... 22 on decel while in gear..
Could my booster be bad even though it shows signs of being good? could it cause that section of brakes to stay on?
The MC's were identical when i swapped them, its a reman. from part source.. could it be for a 91-94? my car is a 90.. they looked the same like i said.. is there a difference at all?
Need help before this DSM goes down in flames! lol

Thanks in advance!

No one has any input??

Everyone is stumped!!

Maybe not everybody....

Did you bleed the air out of the entire system? Sounds like maybe you didn't..

Also you should do a boost leak test.

Put 2 bottles of fluid through it when I changed all 4 corner brake lines and the prop valve, but ill do it again and try it out.

I did a boost leak test a couple days ago and found my j pipe gasket was toast, fixed that up, but nothing from the booster.

Could extra air be getting sucked from the booster if its ripped?

Would be unregistered and leaning me out... My plugs looked good tho.

I was just thinking the performance problem might be a boost leak since your vacuum gauge symptoms match.

There might be some additional steps to priming the brake booster. I don't know the specifics but from casual reading I believe it is not so simple as to run new brake fluid through the master.

Not sure what priming a brake booster is?

And I was talking about bleeding the air out of the brakes..

I'm not sure either but "bench bleeding" comes to mind and here is some info..
http://www.dsmtuners.com/forums/newbie-forum/259623-master-cyclinder.html

How I understand its just putting fluid in before installing it to help from destroying the seals and less air to bleed out.. mines not leaking though, I had replaced a leaky one a while back and hasn't leaked since.

Have you changed your flex lines? They may be collapsed.

Yea I changed all for corners with ziggys braided lines

Im going to put a bottle of fluid through and flush the system

Ill post back after i try that

Bled them again and still no good, and fixed my boost leak at the j pipe, theres a little leak behind the TPS, not bad tho. I think its been there forever lol.
Went for a ride and didnt use the brakes.. Passenger front and driver rear were ice cold.. Driver front was a little warm and passenger rear was very warm..
Vaccuum still at 10 on cruise load, but im sure the engine is working jsut a but harder from behind held back from whatever it is!!.....

When i push the clutch to shift it feels free rolling again, then in gear hesitates.. its like my tcase is cooked or something....
Rear tires were locking up before the front in the winter time.. assuming the hesitation is from the rear..

Are master cylinders the same between ABS and non ABS?

If my brake booster was ripped would it suck air into it, and into the IM.. ?

Also activating my brakes with the extra air in the diaphram? .... heads spinning with questions.. lol

That sounds totally different than ANYTHING to do with brakes or boost leaks. That sure sounds like a drivetrain issue..

Yeah it does sound like drivetrain.
But FWIW, I've had situations where the car idles fine but doesn't want to go when it's in gear. It was a MAFS problem.

Based on what Kyle said about the splines and then Reza's comment (read: hint), I think I'd be doing some research into drivetrain compatibility
Amiright?

Kyle, I think your transmission output shaft is welding itself to the center diff, or your center diff gears shims are broken or seized, causing your rear wheels to have a mind of their own.

I bet the viscous coupling is burnt out already. Take off end case, remove VC clip, remove VC, turn over and if you see the inner plastic ring has been spat out from internally, then for sure its the center diff.

Either way, I would have just removed the tranny by now. Why has it happened ? I am not sure. You have not provided enough trans info.

Of course I could be wrong, and it might just be Fred Flinstone in the back of your car with his feet down

Yabbadabbadooooooooo!

Ziggy i was thinking brakes because my passenger rear rotor gets hot, and driver side front, when i dont even use my brakes and come to a rolling stop...my car will roll just fine idling and stuff, all tires roll free when its up on stands... also only seems to be hesitation when there is load on the engine.. like its sucking air into the brake booster activating the brakes a bit as it gets on the gas it brings in more air hesitating it more as the diaphram fills.. when my car idles my brakes are alot softer then after being on the throttle.

My tranny is from Tim Grech... was apparently a fresh build... hoping its not my tranny.. put a dent in the wallet getting that off him... over a year ago .. so its only seen 10000, 15 000 km, if that.

Im not getting any abnormal reaction from the car during cornering, and I can launch at 5500 rpm with a solid take off, no unwanted noise just spoolin.

Ive had a wheel bearing seize up before (mine are all new right now) but it almost feels the same... of course not pulling or anything.. you can feel that its powering through it and wants to go, but cant.. but when she hits 25 psi it powers through and goes like snot..

"reguardless of year, all the AWD transmissions have the same center diff. and final drive gear ratios" 90-96

From what I can find, the only difference in rear end ratios is between autos and manuals, and mine came out of a 92 manual into my 90.

Kyle, I was going to suggest wheel bearing as the cause of the warmth...but you say you have replaced them all?

I know you had brake booster issues, so maybe it IS something in that area? I really don't know...

Bearings are all good, I try and feel everywhere for heat.. Hubs, axles, diff, tcase, etc... but its just rotors. My fluid comes out smooth and clear, so I highly doubt its my brakes lines... BAHHHHHHHHHHHHH !!!!!!!!!!!!!! ARGGGAKJHFDAKH.... I have a booster in my garage from part source, but if I don't need it, that $350 would be nice to pay for what I do need lol

I just want to know if its possible to be sucking air from it.

Tried to have it fixed for the drags this weekend in Elliot lake. Prolly get beat by a neon if I tried

I would do as Reza suggests, pull the end case off the transmission and check out the VC and centre diff for problems. Will not take you long at all, and you don't need to remove the transmission or any major parts to check things out.

Even if it's just for peace of mind, it would be my starting point based on the problems you're describing.

Mike

Heading outside with my beer right now.. Ill post back later today.
Thanks guys

Makes me wonder how many dsm's are being wrenched on each day

VC is still in one big solid piece

If the center diff was bad, would it still hold back my rear wheels in neutral going down a hill?

Cuz it rolls fine down a hill with no load on the motor... its almost the more load the more it hesitates lol

Of course the VC will still be in one big piece. Flip it around and look closely at it, there is a plastic ring that spits out of it when it goes bad, from the side facing the bellhousing. Even if you don't see that ring it could have disintegrated. Look for a thick dark oooze that may have come out of the one side of it.

Yes a badly messed up center diff "can" cause the wheels to lock in neutral as well, depending upon how it is damaged.

How did your tranny fluid look ? dark and silvery ?

Its not the motor, the problem amplifies itself when you put load on the tranny and drivetrain.

No plastic at all anywhere, no oozing out of it, nothing between the 2 separate splines.

Oil wasnt overly dark, didnt smell overly bad either, and yes it had a bit of a grey shine to it.

Assuming my next step is to just take off the next part of the casing and actually just check it out? Will it show signs of being toast? Of course theres possible chance it wont, but does it normally? If so what am i looking for?

You might as well pull the center diff out too since your in there. It could still be pooched. Pull it out and open it up or check for broken seized spider gears, spin it and check the operation of it.

Alright ill go do that now.
What am I looking for in signs of wear? or can you not visually see it?
Back in 15 once ive got it out.
Thanks reza

Pull it out first, it should slide out easily. If it doesn't slide right out once you have the next case off, that means it overheated and most likely seized to the pinion gear. If seen that happen enough times.

The shaft that goes into the center diff is what grinds away at the spider gears from inside.

Pull it out and we'll go from there

Turns out I dont have a big enough socket to get her off.... lol



Heading to town to buy one from Princess Auto

What size do you need?

36 mm

Call my cell if you got it for me ill come meet you.. on my way to princess now tho

Biggest i have is 34 or 1 1/4.

center diff is out.. looks fine to me, spins freely in my hands

but then again, not sure how its suppost to be !

-Rear wheels don't want to turn going around tight low speed right or left turns.
-Nasty clunking coming from transmission area.
-Car feels like it's being held back, may even die, when trying to backup and turn left or right.
-Should be flakes of metal on the transmission drain plug.
-Likely to occur after a hard launch

.... I dont really even have the symptoms though, its only in a straight line when when Im on the gas, or in gear off the gas... Like i said it almost feels like a wheel bearings starting to seize..

"Thinking outside the box, sometimes brake boosters can develop vacuum leaks that are only exposed under hard braking, and then your engine would be sucking air brake booster vacuum line, and would run lean and could stall."

Found this in a post for a different car, but this is what I had been thinking was my problem.. with the hard peddle after accelerating, car dying if i pump brake, hesitation... SO gunna change that booster if this center diff isnt my issue... but how do i check my center diff??

If im in neutral rolling, does the transfer case still fully function? so i can cross that off the list? or does it some way some how disengage itself?

Well damn! You sure all the spider gears are intact and all ? They look fine through the holes, it spins smoothly, ?
Have you opened it up to check the upper and lower gear?

What about your transfer case, have you pulled it off and check to see if it spins freely ?

What about each drive axle, any up/down play in any cv ?

Do you still have the stock line with check valve in it running to the brake booster ?

Spider gears are all good everything spins very nice.. Ian stopped in as well and had a look, he as well thought it seemed very smooth.

Transfer case I havent taken off in a bit but last time i did it was smooth, and when i had all four tires up in the air, all for tires spun free with tcase... disconnected my driveshaft and spun my rear diff by itself and it was free spinning.

Front drive axles are new and are good, rears have no play.

I changed the stock line with 8mm hose and check valve from Ziggy. Check valve is in the correct way as well... The stock line was still working fine, but i changed it anyways.

When I get it back together Im going to block off the booster from the IM.. and run without power brakes. if its still weird ill take off the pads and go for a ride down the back roads .. if theres still hesitation, i can scratch brakes off the list...


Ian and I checked my plug wires, and the resistance was very low compared to other wires i had kickin around.. they are accel 8mm

About to start putting the tranny back together, has anyone ever reused the pin on the fork? Mine is still in good shape. Safe to use again?

Back together.
Blocked off the booster from the IM, and still the same problems, and same brakes were getting warm, so I returned the booster.

While i was there i had them look through the different master cylinder to see if maybe they gave me the wrong one? im sure that would give me issues....

put some other plug wires on from another car..

Also, 1st and second are now harder to get into while downshifting... great..
Sounds to me like the syncs slips out? i dunno.. shifts.. buts its stiff.. only 1 and 2.

Anywho, nightmare continues

I have reused the pins on the shift forks with no problems (though not recommended), but for $1 each they are not that expensive to replace if you have the time to order them.

I don't know man, the problem still sounds like it is drivetrain related.

Anyone have a match? .. that'll fix er... or at least teach her a lesson..

Ill post what I do next.. and what happens lol.. thanks everyone for the help

Almost feels like Im not getting full ignition until full boost.. almost feels like a studder.. How can you tell when a transistor goes bad? or a CAS goes bad? or even my MAF?? or fuel pump?? but i figured when fuel pumps and mafs go, they just go and dont work at all...

check engine light came on 3 times out of no where, and had the same reaction to the car as fuel cut does, although i was just at cruising speeds twice, and idling another.. The light went away before i was able to pull up link and check out what it was. Happened 3 times in the past month. When my first MAF went bad, it did a similar reaction, but it didnt keep working after, i had to change it. Its a 3" gm maf with MAFT zeroed out and dsmlink for tuning.

Plugs are 7s and are gapped to 30..

Compression on a warm engine, not full operating temp, was 138 across.
I read that service limit was 122. I know 138 is not where i want it, as 150, 160 is, but cant see it being my problem..

Noticed in my logs, at steady throttle, my A/F's randomly spikes lean for no reason.. And can feel it hesitate at the point as well.

Changed

-injector clips/caps
-Aeromotive AFPR
-02 sensor
-swapped ECUs (both are from ECM tuning)
-new fuel pump (wally 255 HP)
-plugs/wires
-CAS
-coil pack
-transistor
-throttle shaft seals
-eliminated MAF, now speed density


Checked voltage at the pump, 13.8 with car running, of course i only checked at idle.

Checked the tcase and stuff as i thought it was drivetrain .. nodda

SAME PROBLEM

AND new fuel filter and Ziggy's stainless line set up from filter to rail


Also logged "fuel flow", it dropped the same time it spiked lean, and not jsut one spike, like my log looks like a jagged cave lol... then normal after the spikes....

How can i post a log?

Could there be rust in my fuel line or something?

Maybe some stainless braided line and an inline pump

When you had the booster disconnected from the IM, did you have the same issues in idle, from the first post?

Do you notice any problems in idle when playing around with throttle position?

Got a fuel pressure gauge under the hood?

Yea its on the AFPR, set to 37 psi

I never really tried pumping the brakes with it disconnected, because the pedal is solid and cant really do that.. i just drove it for a couple kms and was getting the same problem.

When I hold the throttle at say 25%, and let the RPMS and boost build slowly, it starts studdering and spiking lean.

If i knew how, id throw up the log

What I'm attempting to do is try to rule out air getting sucked into the system somewhere in the fuel delivery, something that might only be present when the pump is actually trying (not idling). I know you replaced the pump, and I'm going to assume that out of the two pumps you had, you have had to seat it at least correctly once, so I'm not sure what else could be a source of air into the system.

If you are in idle and increase the throttle directly on the throttle body, does the gauge stay steady motion, or does it flicker? Would you be able to make a correlation between your stumbles and the fuel pressure/delivery?

Best way to post logs on this forum is get a gmail account and upload your log as a google doc, then grab the link for that doc and post it up here.

It just seems like two things are going on here, something responsible for the brakes heat etc... and something else for the stumbling/hesitation. Especially considering you severed the only link between the two and both problems persisted.

What gets me the most is pressing on the brakes at idle essentially stalls your car. This would be a throwback at there might be something up in the brake booster that is only apparent while braking, but also isn't working correctly just by itself - hot brakes.

When I get the chance, I'll see what I can drudge up for the braking system and see if anything in the system could explain the diagonal pairing of symptoms.

Fuel pressure goes up, then when i let off itll drop, then idling it returns to normal

Does it hesitate at all in idle while changing throttle position? Slow and steady, or fast and sudden? Both? Or does it only hesitate while loaded?

Only while loaded, TPS volts were logged and they fluctuate pretty good with the pedal movement.

Seems to be more in the +3500 and on load, when i hit the gas hard, it definately doesnt get up and go...

Its like my deadtime is way to high and the injectors cant keep up...

Wasnt like this when i first put them in tho, car ran amazing...

But if i hold a constant pedal around 4000, it spikes and misses and is like the injectors arent squirting correctly or something.

headache, after headache, after headache.

With link, can you see what each injector is doing independently?

im not sure, i know you can test each one, but the problem is only higher rpms and under load, so they all seem equal and fine.

If anyone else know if i can log each individual injector that would be awesome..

I might be thinking of something else and I don't have my evoscan lappy with me right now to check.

I know it is a pain in the ass, but I don't think it is something you have tried, but have you tried swapping out your injectors?

No i dont have any spares other then 450s.. running RTM 95lbers right now

Maybe some of the vets can chime in whether or not this could actually be related to the injectors.

I mean, you have gone through pretty much everything in the drivetrain, and I just can't see the drivetrain causing the hesitation you are talking about.

If your pressure is good, I would say all your connections are up to snuff as well as the passages...the only thing left is maybe some gunk in the injectors that is only apparent when they try to sustain.

Considering everything else you have went about and try, it might be worth the 15mins to swap the 450s back in and see what happens. I would assume you have an old link tune that you could load up to match the injectors?

edit: if it does turn out to be the injectors, at least you have Ziggy to stand behind his products...depending on how old they are of course (can only be considered responsible after a certain point)

I have maybe 8000 kms on them.

Im pulling the turbo off just to check it out. Gotta clean up the engine bay anyways.

And I ordered some fuel line.

Next will be injectors.

IMO, throwing money at the situation won't help it.

Do you have the check valve one way line installed correctly for the brake booster?

Have you ensured your E-Brake cables aren't seizing?

Are your plugs gapped correctly?

Is your exhaust plugged? Have you replaced your cat?

Are your gears piling up on themselves?

Not throwing money at it, everything I have Ill be using in my other car, other then the fuel line, Ill be buying more. Its all troubleshooting. My valve cover was leaking a bit and I want to clean everything up now that i have new gaskets. So pulling the turbo to check it out while im cleaning up, its been on there for a while.

e brakes are disconnected, Im done looking at the brakes and drivetrain. These leans spikes at over 3500 rpms i think is from my injectors, or even one of them.

Plugs were 28, but I could bring them to 25... It does this even without boost, so i cant see it blowing spark or anything of that nature.

Not sure what you mean about piling up.

I swapped exhausts already, thinking it was the cat. Too many symptoms add up to this type of problem.

Check way valve is new and good.

Gotta get these injectors checked out.s.

Just changed my oil and there was definatly gas in it. Was thin, smelly, and could see it on top of the oil. Really starting to think I have an injector that has gone and the other 3 cylinders are overloading with gas to compensate the lack of fuel in the 1 cylinder.

Compression with the engine warm, not full operating temp, was 138 across.
I read that service limit was 122. I know 138 is low and not where I want it, as 150, 160 is. Would that be low enough for major blowby?

I found this today, number 3 injector wire is getting so hot it first, melted the stock black thick protector, I thought it was due to lose connectors, so i replaced them all. Now even with the new connectors, this has gotten so hot again that it melted again. Checked the resistor, 6.5 on all connections.



Its not from excessive engine heat, all the other wires are closer and aren't melted.

Have you tried swapping the injector resistor pack?

Nope, but I just checked the resistance and each one was 6.5

Used this method.

http://www.dsmtuners.com/forums/newbie-forum/367248-bad-injector-resistor-box-how-test.html

I guess it's time to swap the injectors! Or you could just move the one and see if the problem follows it.

I was thinking of doing that, cuz i dont really wanna put my new FIC's in and have it short one of them out.. Do you think a bad injector would cause a short and heat up the wire?

The engine runs, idles and everything pretty normal.

Question, with link you can check the individual on idle, all were fine... With ignition on, car not running, can I test check for proper power? Unplug and throw a volt meter on it?