Steve Cooper

Hoping you folks can help me de-bug a mysteriously sh!tty boost problem I just started seeing in my 122,000 mile 86 951.

I'm running a Guru stage 2 kit, with the Guru j-pipe, the Guru FPR, Reliaboost set with a gauge to slowly open at about 16 lbs boost, a Link AFM and controller. I'm not using the CV, the reliaboost is metering pressure directly to the stock shimmed wastegate. I've got a stock rebuilt K26 turbo and a high flow cat converter welded into a stock factory cat exhaust.

Everything was working great until three days ago. I've been driving from Santa Cruz to San Francisco and back for work a few days a week (160 miles round trip), mostly when it's too wet to take the motorcycle. I had returned home form the city and in my driveway I heard a slightly louder than normal ticking- sounded like a lifter, rather than the typical fuel injectors click. I popped the hood and in the dark, everything looked fine, but the new tick was a concern. Odd I thought, because the car felt as strong as ever on that return leg from the city. The next morning, I checked the oil, it was down a quart and change, so I topped it up and filled up the tank with fresh gas. The ticking had vanished with the oil addition.

The next day, I drove up to the city and once I got on the highway, in high load situations, I noticed the boost was behaving very weird. The lag was incredibly long and it took forever to get the boost up to 2 bar - as indicated on the factory gauge -, then the reliaboost would open and bleed off boost. The gauge showed that boost would hang at around 1.2-1.3 bar, then it would take putting the pedal to the floor to get the boost up above that point. BTW, the Link engine management controller from Danno indicates MAP numbers that confirm the factory gauge numbers.

I thought it may be either the reliaboost clogged and stuck open or out of adjustment, or the wastegate diaphragm leaking. I crimped off the boost to wastegate hose, before the reliaboost to test it. Same behavior- extremely slow to build boost, and it would still build boost to a 2 bar level- eventually.

Now I'm puzzled. There are still a few/obvious easy checks to make, I hope the boost problem is related to something simple...

My next steps will be to dig into all the hoses and vacuum lines this weekend- joy of joys- to see if a hose is off. I did a thorough look through already and can't see any hoses disconnected. I'll likely pull the j-pipe and check out the intercooler pipes just any cuts or bad connections. check out the turbo while it's visible, and may even pull the mainfold to be sure no hoses are cut or disconected and hidden from view.

Any other steps you guys would recommend checking out? Does this sound like the bearings in the turbo are getting caked and a lot of exhaust pressure is needed to spin the turbine?

Oh yeah- a wild card in all this- I don't why, but I did this after hearing the abnormal ticking- i added a bottle of Prolong to the oil, and a bottle of prolong fuel additive to the fresh tank of gas.

I really could use some advice on what else to check.

Thanks in advance,

Steve Cooper

JustinL

How is your vacuum at idle? IT could be a major vacuum leak or maybe the old split hose on the intercooler charge pipes. I'd check this first because you might be lucky and find it right away. I had a wastegate fail in the open position, this resulted in a complete loss of boost, but maybe your's is on its way there too.

Justin

J Chen

You did not mention about whether BOV
is standard or upgraded if standard,
take it off & check it.

Steve Cooper

Good question- just checked vacuum at idle- 13-14" Hg / 350-360 mm Hg / 49-53 kPa. IC charge pipes are new aftermarket- rubber, not silicone, but they have blown off in the past at Thunderhill with big heat and similar peak boost. I'll be checking those for sure.

I'm running a stock BOV, it's a replacement unit, my first one failed and we discovered it when on the dyno just after danno first installed the Guru stage 2 kit. Luckily Efren sold me his good factory BOV off his 89 951 just afer his headgasket blew during his run on the dyno.

I checked the BOV earlier- hose to the outlet, sucking through with no flow. There's a better test I bet.

Danno

" I crimped off the boost to wastegate hose, before the reliaboost to test it. Same behavior- extremely slow to build boost, and it would still build boost to a 2 bar level- eventually."

This would seem to indicate an exhaust problem. Could be the wastegate self-destructed and is leaking exhaust away from the turbo. Could be the valve is stuck. Cracked headers is a possibility, letting you hear the valves mores, thus the tick, tick, tick... Ricardo had a leak in his crossover that was limiting his boost. When he fixed, that the boost went through the roof and blew up the engine. I would sniff around the exhaust for the problem...

We gonna see you at the Easter Pizza Run ???

dand86951

By chance do you still have the cat in the exhaust? If so is it clogged. That will definitely slow boost onset and build up.

biggles

Steve,
You might want to check the screw in the IM that holds the KLR line; mine had backed out on me and I was loosing major boost. At idle I was getting about the same vacuum and my OE boost gauge was already reading .6/.8

Steve Cooper

I think the wastegate is the problem. I was skeptical, but checked it out cause you said so. I just jacked up the car, started it up, let it idle for a few minutes, then felt the wastegate exhaust- it's really hot on both sides, and the exhaust out of the turbo is cool. Should be the other way around unless the wastegate is stuck open- correct?

Is a Tial 35mm with adaptors the right way to go?

As for the easter get together, i like the sound of that. I missed the skyline ride, was there on the blackbird a couple of hours later though. The riders at Alice's and the hot dog stand were bitching about some slow-*** group of old watercooled Porsches getting in the way of their corner carving plans. ;-)

Steve Cooper

I welded in a new high flow cat last summer, it should be in good shape. I had thought of the same idea- it seemed like it was taking big boost to blow through the exhaust, but maybe it's the wastegate...

Steve Cooper

I'm guessing from your post that you're saying my idle vacuum is low based on those numbers in my second post. I checked the KLR/IM fitting, it looks tight- good suggestion.

Danno

When in doubt, pull the engine...

Steve Cooper

Okay, so I just pulled the engine, ripped the thing apart and found a small piece of welded stainless steel propping open the wastegate. *coughs bullsh!t* ?

What really happened?... I pulled the wastegate-dump-to-exhaust-pipe and there actually was a small piece of stainless steel holding the valve open. The shard is the size of clipped toenail - middle toe. The valve looks clean, unburnt, and when i gently pried the wastegate valve open, the shard dropped out and the valve snapped shut, like it's supposed to. I'm going to do a test drive and see if that was the culprit.

Now if I could just figure out where a little tig welded stainless shard would come from. Best guess? The header?

MachSchnell

Steve, could you keep me posted on this, I've been suffering similar symptoms and had to date assumed the Profec B spec II was at fault, but it sounds similar...I'm curious to know where the steel came from...

Danno

Is it really stainless? Have your headers been welded up before? Can you give a picture of this fragment? I'd check your compression too, just in case it got caught up on one of your exhaust valves. I've got some gory pictures of some other things that went through the exhaust and destroyed a turbo...

special tool

Yeah - its not a roundish piece of ceramic, is it?