I have overboost/ high k.r. on my 87 GN. I just fixed the code 51 with a new Joe L. 94 chip for the new 38# inj I just installed. I first changed out the wg actuator and bypassed the wg solenoid, manually adj the boost, boost steady. Not the wg actuator, so changed out the wg solenoid(it was new), same overboost. Checked/removed the hoses(they are new) and no leaks. So from reading the archives, that leaves me with wiring and ecm. What/where is this ecm/sol fuse and where does the ground wire go to from the wg solenoid? Any ideas? TIA, Tim Roark (troar@tigerpaw.com)
I have been out of town, just got back, and was looking for an answer to my previous discussion group post on overboost diagnosis, the question is listed there. At this point I am not sure what to do next to fix the problem. Email me direct if you want with any info, it is appreciated. Thanks, Tim Roark (troar@tigerpaw.com)
You say you have 'overboost'. How high is the boost going? I trust that you are reading it with an aftermarket gauge and not the inaccurate stock one, correct?
To eliminate all other controls, I would suggest simply running a hose from the fitting on the compressor to the actuator directly. This will eliminate the ECM, solenoid, restrictor in the Y, etc. This should actually produce lower boost at WOT since full pressure will be directed at the actuator. You should be able to adjust your actuator to sub-stock levels hooked up this way.
Scott K., yes I have a vdo boost guage, scanmaster, and have already ran the hose from the compressor to the actuator, eliminating the solenoid. I was able to manually adjust then to normal boost levels, but I would like the original setup to work, and the chip/ecm/solenoid to work correctly. Then I changed out the solenoid, same overboost problem. The boost is over 20 and I just get out of it because of my high k.r. scantool readings. The boost really spikes using the stock setup even with the actuator arm as loose as it can be before not building boost(loose puck). I did not have this problem until I put the 38# inj and Lubrant 94+ chip in. From some research, I read that the following could be a problem - the ground wire on the wg solenoid, a ecm/sol fuse(?-location), or something I don't understand with the new chip. Thanks for the reply, Tim Roark
I have not yet found the cause of my overboost. I have not found in the service manual where the wg solenoid grounds and if there is a fuse associated with the connection of the wg solenoid and the ecm. I had read in the archives that this could cause overboost. Anyone know how I can find these items to check them? I have checked the obvious trouble items by changing out these parts; wg actuator, wg solenoid, and hoses, and ran the hose from the compressor to the wg actuator without any overboost. I may have to run the car with this setup and manually adjust the boost, but I would like the chip to control it. Has anyone had this problem? This info and additional posts are listed in the on the discussion board. I had also thought that Joe L. 94+ chip I just installed with my 38# inj. may be creating the overboost, and I am unable to lower the boost with the adj wg arm(even all the way out prior to the puck becoming loose and not building boost). This is the only other item I think may be causing the high boost condition. Could the chip be recalibrated to correct this condition? I have been working on this for a while now, sorry for so many questions, but I want to drive my car after installing the new injectors (the tech pages really helped). Thanks, Tim
I doubt you have any ground or wiring prob. The way the ecm tries to control boost is crude and lacks finess. Aftermarket (vendor) chips can exacerbate this by modifing the fuel curve and timing for better performance. Add in different turbos and wastegate actuators and you have now changed the system dynamics.
There are (expensive) devices that use feedback to exactly control boost.
You could try a "performance" actuator with a heavier than stock spring. Or use the manual valve you mentioned worked for you.