intermittent ZERO (0) boost problem
 

My boost pattern is usually normal 10-8-10, however, today on the drive to work, I boosted fine in 2nd to redline (7500 RPM), but then had ZERO boost in 3rd.

I stayed off the boost for about 1/4 mile, then tried again, and got boost (10-psi), although it felt slow to react.

I searched the archived, and will check the following:

1) check valves from chamber and MAP sensor (original);
2) lines (vaccuum and pressure) for turbo-control actuator (TCA);
3) solenoids

Note, this is a NEW engine, with new solenoids, new VITON lines, and NEW turbo (including TCA, wastegate, etc.).

Anything else I'm missing, or that I should quickly check ?

BTW: I did have the OIL in my intake system during hard-G sweepers, which resulted in a loose BOV hose (fixed). Could there be oil in my solenoids causing problems ? If so, just spray with brake-cleaner ?

Thanks,
:-) neil

Hmm....if you have the original Mazda check valves, there could be a problem with them. BTW, the MAP sensor doesn't have a check valve - that's just a filter.

Dave Disney found a problem with the simple 2-way check valves not holding higher boost, but if you're running stock boost I doubt that could be the problem.

Could also have been a loose intercooler pipe that popped off, then the vacuum sucked it back into place. I've seen that happen.

Dale

Dale: when you say the <original Mazda check valves> are you talking about the Air Bypass valve, and the Charge Relief vavle, or something else ?

BTW: I'll take this opportunity to install my VITON check-valves I purchased from you . . .

:-) neil

Yeah, now's a good time for the Viton check valves! :)

I wasn't clear on my post - Dave found the *solenoids* in the solenoid rack can have problems holding higher boost. Here's the thread on it -

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/weird-boost-issue-341534/

Dale

I drove her home during the lunch break so she'll be nice and cool when I work on her tonight.

On the drive home and coolant temp at 180-F, she would only boost to about 5-psi. on the primary turbo, and about 1-2 psi on the secondary.

As I got closer to home, she would boost to about 10-psi on the primary, coolant temp at 210-F.

A quick visual check showed nothing loose.

:-( neil

BTW: on the ride home, the tach went dead (turn signals and speedometer work), so I'll be checking for cold/broken solder joints as well.

Could also be a problem with the ignition coil harness. A new updated harness is around $80 or so, and the stockers are known to go bad. That could account for loss of power and the sudden tach problem.

Dale

had the same problems when i was running twins. it was the check valves. time to replace the buggers :)

Ugh, all check valves, and vaccuum lines tested good (used a MityVac). I also tested all actuators, and all passed. This makes sense because at idle I have 18 Hg of vaccuum.

I really don't want to pull the rat's nest, but I noticed the charge control solenoid (F) had worked its way off of the rat's nest chassis, but no loose electrical connector or vaccuum lines.

Tomorrow is another day . . .

:-( neil

i would look into the vac chamber leaking or maybe that check valve first

ALL check valves and vaccuum chambers tested good. The chambers test upto 25-psi pressure, and 25 Hg of vaccuum.

I did David Disney's test of the charge control solenoid, and yes mine sticks at 12-15 psi.

FWIW, with needle nose pliers I was able to take off the electrical connector, and put on aligator test leads again with the needle nose pliers.

I added 12VDC, pumped in 15-psi, and it stuck for a couple of seconds before finally releasing.

David's writeup is great, and thanks to Dale for pointing me to it. More info can be found at these links:

http://rx7.voodoobox.net/howto/solen...oid_check.html
https://www.rx7club.com/showthread.php?t=341534


Time to get another one and do more testing . . .

Dead tach tomorrow . . .

:-) neil

BTW: here are some photos showing doing a test while the solenoid is still in the rat's nest and in the car.

:-) neil

PS: note the power-supply made by me from 1980!

http://www.silcom.com/~neilv/rx7/diag-setup.JPG
http://www.silcom.com/~neilv/rx7/12vdc.JPG
http://www.silcom.com/~neilv/rx7/T-tap-n-mityvac.JPG

Can you give me a pn# for the ignition coil harnessm, since I'm still having intermittent tach problems.

I replaced ALL components except the IC on the tach, and re-soldered everything. Then I cleaned with a ScotchBrite pad all of the circuit connectors, screws, and put some De-Oxit preservative as well.

Tach is working, but after a 15-minute harddrive, it went dead. Then while just cruising for about 10-minutes, the tach came back to life.

Hence, I think it's somewhere in the ignition coil harness.

BTW: I replaced the solenoid and all seems well.

:-) neil