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OK, I have a 91 ss basically bone stock, i was having some hesitation problems and a cel, So i ran diagnostics came up as 22 (knock sensor) so as i was replacing it i broke a nipple off coolant tank, took that out fixed that,and while that was out i decided to replace valve cover gaskets (both sides), and while i was in there i put ngk plugs in gaped at .40. I still have hesitation throughout the power band starting at about 2750 on the rpm side right when full boost starts (or at least i can really hear the spooling of the turbo), So brought the car home and decided to clean all the ground wires i could find, that didn't do much if anything. So im trying to figure out whats next

:Alex

Any one up? Any one have an idea

My first guess would be a boost leak.

Hi,
Just checking - you meant .040 on the plug gap, correct?

I agree on the boost leaks..car is 20+ years old and the vac lines, hoses and such are getting brittle.

Make sure you clear the codes in ECU, too.

Td

Ya sorry I ment .040. ok on the vac lines im going on a trip downstate and when I get home I will have to replace all my vac lines, any of them imparticular I should check b4 I go?

I have no boost gauge yet, I'm looking at the depo ones just haven't got the money for one yet, any one had experance with them? Any other suggestion on boost gauge is walcOme

And yes I've cleared and reset the ecu

I wouldn't go so far as to replace all the vac lines. Just inspect all the hoses on the intake manifold and charged side of the turbo. Could be as simple as a cracked/unplugged hose.

Ive been meaning to replace them because there all kind of hard and brittle
but ill inspect them b4 my trip

If you can get a vacuum gauge to see what your engine vacuum at idle is, that would be helpful and give you an idea if you have a vacuum/boost leak.

Can you elaborate on the hesitation any more? Does it happen with light throttle or just under medium or heavy throttle?

the hesitation is in the mid and high range usually anywhere past 30, im starting to wonder if the stock boost solenoid has failed

Try bypassing the boost solenoid and just route the compressor port hose into the wastegate solenoid vacuum/boost port. You will only get wastegate boost, which isn't much, but that should eliminate the part being the problem.

I've got a voodoo mbc and depo boost gauge on order. I'll install those and replace some vac lines and then go from there...

Ok, sorry it took so long but it's been cold here and work has been really busy, besides the point tho... Ok I have installed the boost gauge replaced the o2 senser and that cleared up a lot of the hesitation... But I've been watching my boost pressure while driving the past 2 months seance I installed it and hav noticed that when I step on it in any gear at any rpm range I will hit just under the 9psi range and then about 2 seconds later it will drop to 5 psi, any ideas why... Well just today I installed my boost controller and only drove it about 5-7 miles so far just tuning it and I'm running it just under the 10psi range ( I believe I've read on here that that is safe to run without an inter cooler, please correct me if I'm wronge) and from what little I drove it this evening it seems to have fixed the dropping off boost but I will keep u updated. Also I'm looking for sugestions on what to do for mods next. Thanks everyone this form site is stuffed to the gills with information once u learn how to use the search .

I'm not sure about the boost dropping off, it could be vacuum/boost lines, boost control solenoid, or another sensor input to the ECU that is in turn causing the ECU to drop boost.

What new boost controller did you install? Is it a MBC or electronic?

Yes, it's a MBC , the brand is VooDoo off eBay I found good reviews on it and so far it has worked flawlessly and absolutely no boost drop now I think it was the stock bcs failing... But I'm stuck here what should I do on the car next?

What do you mean, what should you do next on the car? In terms of modification or fixing a problem?

I think he was asking for suggestions for mods to do next on the car. You say the car is bone stock so I would suggest a Forester TMIC, TD04, and 3" Turbo Back Exhaust (TBE) for starters.

Yes Robert as in what mods to do next and thanks for the response there is absolutely no hesitation now it flys like a bat out of hell I never knew this car had this much power

Interesting username.....

Hell if you're running good might as well start collecting parts for a td04 w/ tmic swap or start collecting DOHC bits

Both of those upgrades will net you some reasonable power upgrades.