95 Volvo 850 Turbo. Here the situation, my car (i assume based on how it ran) has either a chip or a R computer in it. When i got it would boost to 12-13psi ( upper part of the white line, confirmed by a boost gauge added).
I changed the plugs because it was starting to sputter and found them to be gapped wrong.
Then one day out of the blue it only boosted to about 5psi. I swapped out the intercooler hoses, vacuum lines, factory boost controller (bolted to airbox), vacuum tree seal, and about anything else i could think of but still only getting 5psi.
One night on my drive home it was poring rain HARD, i had to merge with traffic so i punched it....i suddenly had full boost and it felt great!!! The next morning i went to work and still had full boost so I assumed the computer had "learned" and was working now.
After work I had that 5psi again. WTF?? A few days later i ran it thru the carwash to get the dust off it and BAM i had full boost again!
Now I'm assuming I might have a broken wire somewhere and the water getting on it is making the bridge contact, when it dries out the contact goes away. I followed the BC wires to the harness and in the junkyard i tore apart the harness and followed it to the fusebox but couldn't see where they attach.
I have since put on a manual boost controller and set it to that 12psi i was getting and it works fine, but id like to go back to the factory set up as I'm worried ill break something.
Anyone know where this boost wire connects to in the fusebox or should i just leave it like i have it? I guess i could always move to the rain forest and have full boost year round.

 

Have you ever just pulled the ECU and reseated it? That will take the car out of limp mode and reseat the ECU in the pins. I have seen this cause what your going through.

 

Yep. Pulled the comp, sprayed with contact cleaner, then applied some electric grease. Put it in and out 3-4 times to make sure all was good. Did the reseting a week or two ago with no results. Im inclined to assume i have a bad BC wire. If it was a bad turbo it'd be blowing smoke, and it doesn't. If it were a leaking hose id assume it'd never reach the 12psi i have it set at now. The turbo is quicker to respond with he MB set up, but it just feels like it has more to give, kinda like its hitting a "blah" spot. I have a AF gauge (just a basic cheap one) that is always showing it running rich. Im wondering if i may have a bad O2 and thats whats putting it in low boost? Also when i had the BC hooked up i was getting not so good MPG. On a 400mi round trip i got 24.3 on the way up and 23.5 on the way back, around town id get about 18-19 and this was all me keeping my foot out of it. Ill try and OBD1 reading today and see what pops up.

 

Should also add a previous owner had the Cat removed so I know its not plugged up. I may have the AF hooked up to the rear O2, but seeing as theres no Cat it should read the same as the front one.

 

might be your maf, when was that changed last?

 

MAF, lol, never thought of that till now. That might explain why I get full boost when it rains too. Ive had the car about 8mo and haven't changed it so who knows when it was last done.Ill hit the JY today and see if I can find a newer looking one to throw in.

 

So i bought some MAF spray cleaner, I figured id rather spend like $8 before i send the $100 they're asking for a new MAF. The result......nothing. I looked on eBay and found new MAFs for around $25 shipped, and the local JY wants $25 for one so I think I'll give the eBay one a shot. I still need to run an OBD1 test to see what it says about the O2s

 

On a side note, when i unplugged the MAF and plugged it back in I got the ABS/TRACs lights come on. Don't know why the simple action of unplugging that would cause it. Both times I unplugged it it happened so I know thats what caused them to come on. Ignition was off when i unplugged it. They were on after the next start up till I shut it off and started it again.