Help! Engine holds back.

[85zoom]

Help! I've been trying to figure this out for months. When I go WOT, my 85 starts accelerating, then when she hits about 14 lbs of boost, the engine starts holding back, and boost drops to about 10 lbs. If it's KR-ing, it's suttle. I've felt/heard a big KR before and this wasn't it. Adding xylene seems to help a little. I've tried runs from a dead stop, manually shifting, and also in D, and in OD. Also doing 40-45 mph, then going WOT, whether in D or OD, engine still has the holdback. On one run,when running t-link, at 3550 rpm had 2.6 deg KR. Car continued to climb to 5150 rpm and KR dropped to 0.2. Then shifted to 2nd, rpm was 3880 and KR upped to 4.5 and lowered as rpm's rose. 3rd and 4th showed no KR. Car has adj fp reg(40 lbs static), hot wired hi-vol pump, street chip, hi-flo cat, plugs are clean, new fuel filter. The car never did this for the first couple of years I owned it so something has changed or gone bad. I realize I may not have filled in all the blanks, but this is all I can think of right now.Any suggestions are appreciated. A friend suggested a leak in the turbo to intake coupler.

 

[WFO]

valvesprings?

 

[national84]

That'd be my guess

 

[COPTZR]

A leak before the turbo inlet and after the MAF sensor could do it, but I honestly don't have any idea. My 84 is holding back also, but I also have an 87coil and 84control module on. I have no idea when the fuel system was last improved upon(if at all), so I can't really tell you a definate. I would check for a leak though. Coudlnt' hurt.

 

[85zoom]

Thanks for the replies. If the valvesprings were worn, would they still let me reach rpm's in the 5000's? I was hoping I could rule them out because of others saying they couldn't reach up into the 5000 rpm range when theirs were tired. Or were they referring to 3rd and/or 4th gear top end? I also read in the archives that one driver's cam sensor was slightly off. Will try checking mine after the rain stops.

 

[85zoom]

OK, I figured it out. Found 2 spark plug wires that had the boot over the plug, but not "clicked" in. In fact, the connection at the end of the plug wires had crud in it, probably from arcing since it wasn't seated on the plug. I'm surprised spark even reached the plug. I also changed the plugs while I was there. Nobody ever mentions how fun the passenger side plugs are to change!!! So far, I'm up to 16 lbs boost, no KR, and no holdback. If I had checked EACH plug like my buddy told me to do months ago, I would have found it. Instead, I checked ONE plug on the driver's side (easy), it was clean, and then said"yeah, my plugs are OK." CHECK THEM ALL ONE BY ONE!!! Hope this helps someone.