'99 Boost Surging

[AfterhoursFab]

I have a '99 Suburban 2wd that I use for towing a car trailer (amongst other things) but it has been driving me crazy lately. When cruising on the highway, it sounds as if the PCM is constantly opening and closing the wastegate. You can hear the turbo spooling up, then it stops. Then it spools, and stops. Constantly.

Not a big problem when just cruising the highway but if I have the trailer on, its almost as it senses the load and goes into FU mode. Going up steeps grades the turbo almost never spools and Im stuck going 40mph with the flashers on. The last time I drove it it did it to me in a 35mph zone and I literally could not do more than 10mph up the hill. Of course this is not with my foot in the floor; when I hear it not spooling, I baby it. Any more pedal than necc results in large amounts of black smoke.

I did some research and saw quite a few problem areas. Would it be better for me to just make the manual wastegate controller and bypass the computer controlled crap? Or should I throw money at it until its better? :/

I had a few no-starts and one time it shut off on me while driving so the PMD is on its way out so that's on the list as well as boost and EGT gauges.

[jtge]

I had a similar problem, and replaced the turbo boost sensor that goes in topo of the manifold. that solved my problem.

Regards

[AfterhoursFab]

I do have another 6.5TD engine in the shop I can swap it with to see what happens, thanks.

Also forgot to add, after prolonged occurrence I do get a code, I forget which one but I believe it is for Turbo Efficiency.

[DmaxMaverick]

Check for vacuum leaks and pump performance. At idle, the vacuum pump should produce a steady (no bouncy gage) 22-26" Hg, and the wastegate actuator line should show modulated vacuum at 15". It may also help to flush the wastegate solenoid valve with WD40.

[AfterhoursFab]

Ok, will do, thanks.

[AfterhoursFab]

Just a follow up.. I switched the boost sensor with another I had off a 2000 engine and the surging is much improved. With no load on the trailer, there's almost no surging, just steady boost. However with it loaded and going up grades on the highway, it still surges some. It seems as tho the computer just can't control the waste gate fast enough, you hear it close it, make boost, then open again, then close, then open, ect. Perhaps there is another kink I the chain somewhere but I'm probably going to get rid of everything altogether and put a spring in. For now it is satisfactory tho.

FYI the trailer is about 2000lbs and the last load was around 6000lbs, so I'm pulling a decent amount but nothing crazy.

[JohnC]

Before you spend any money or time making major changes, swap the waste gate solenoid with a known good one.

[AfterhoursFab]

Ya I may have to use the trailer again next week so Ill try to swap it out before hand.

[Jesus]

Just a follow up.. I switched the boost sensor with another I had off a 2000 engine and the surging is much improved. With no load on the trailer, there's almost no surging, just steady boost. However with it loaded and going up grades on the highway, it still surges some. It seems as tho the computer just can't control the waste gate fast enough, you hear it close it, make boost, then open again, then close, then open, ect. Perhaps there is another kink I the chain somewhere but I'm probably going to get rid of everything altogether and put a spring in. For now it is satisfactory tho.

FYI the trailer is about 2000lbs and the last load was around 6000lbs, so I'm pulling a decent amount but nothing crazy.

Prolly a airleak somewhere or the used part you put in service has a hole in the membrane..