low speed hesitation (please read)

[dan catalyst]

so i boought a all stock 90 gsx about a month ago. it had a bad turbo, so i replaced it and she fired right up.the only thing is there is a bad low speed shutter,hesitation,bucking ect.whatever you want to call it.ithappens before boost just when i tip into the throttle.the car is almost imposable to drive at a constant speed, but drives perfect under harder acceleration.the problem soundds exatly like the 1g maf hack vfaq, where the guy removed the lower half of the maf.my car's maf is untouched though.
things ive checked so far:
all tb sensors,fiav,ips,iac,tps, biss adjusted to vfaq's specs
timing (cam and ignition)
plugs and wires

the only things i couldnt find test procedures for are the cam pos sesor and the maf.if anyone has any info on those two please let me know.

 

[boostngsx]

check your FPR. My FPR went bad and for a while after I just start it I got the same problem.

 

[flying_eagle]

i had a 94 talon and at lo speeds it was doing the sam thing and all it turned out to be was the thermal vacuum valve right next to the thermostat housing

 

[dan catalyst]

I forgot to mention that i bypassed the egr, so it isnt the thermal vacume valve.the car has no egr, and no isc,no fiav,has the tb coolant bypass and the star is out of the intake tube,also has the boost solinoid mod.
the hesitation is present whether the car is hot or cold. ill check the fpr when i get home.was your running a lil rich when your fpr went bad? mine is deff a lil fat.

 

[nfernotalon]

Check for boost leaks that fixed mine

 

[dan catalyst]

no boost leaks at all.sorry , i keep leaving out important info.i realy think its the cas for some reason.i guess ive checked everything else. also my tach goes to zero when i press down the gas more than half way.any thoughts on that?

 

[dsmmaniac12787]

That exact thing happened to mine. I rewired the fuel pump and replaced the cas. Thats what fixed mine. It was probably more the fuel pump though.

 

[ekanddsm]

Have you considered the ecu?

Mine ran great on boost but couldn't cruise at all, it would stutter and backfire, all the inputs looked good. So I had the ecu repaired, I dont solder that great. Wow what a difference.

It was like whenever the factory boost gauge was in vacuum the car ran like crap.

Don't rule it out it is an old car

 

[asd_gst]

Have you considered the ecu?

Mine ran great on boost but couldn't cruise at all, it would stutter and backfire, all the inputs looked good. So I had the ecu repaired, I dont solder that great. Wow what a difference.

It was like whenever the factory boost gauge was in vacuum the car ran like crap.

Don't rule it out it is an old car

yes!!! same thing happened to me with my 91 gst. but my car would sometimes run on only 2 cylinders, then i would turn it off and back on and it would run fine, my car would run fine boost or no boost up till about 3600 rpm, bought a new ecu that was rebuilt and wow it ran fine, then it started to shutter and run like crap again so bought a new fuel pump and that fixed it the 2nd time, so check your ecu look to see if your caps are leaking, smell it, it will smell bad if they are, rewire your fuel pump no matter what, and i would just buy a new one now if you plan on doing down the road.

 

[silver bullit]

Boost leak test.

Also check everything else out, and test it.