Troubleshoot help - no turbo pressure
 

Just reinstalled my engine in car I bought last summer and had apart for 4 months. 94 R package - I don't believe the motor has every been opened except for valve cover and oil pan. Had engine out to do housekeeping - no internal work. Engine started fine and drove it around the block to check for leaks. All is good. Drove 4 miles to get fresh gas (was just about empty) and on drive home, after turning it off to fill fuel, no turbo pressure!!!! Boost gauge shows vacuum to 0 psi - won't go over 0 psi. No turbo noises.

Have 2 1/2" exhaust that goes to 3" CAT - then 3" all the way back. Garrett turbo from 300ZX turbo - don't believe it's a bearing type. Manual boost control. Cast exhaust manifold.

Here are changes I made with engine out - FM Happy Meal clutch/flywheel, FM oil filter relo kit, water pump, timing belt, new seals all around, idler/tensioner, wrapped exhaust manifold and down pipe with the type of wrap that does not need sealer, fresh water and oil hoses for turbo (except oil feed hose which was good). Combed out some wiring but no changes. Fresh T6 oil. (Side note: Used Mobil 1 synthetic trans fluid - huge improvement over whatever was in it before - very smooth and silky shifting).

Took off intake to compressor and it spins very freely. Did not remove downpipe from turbine. Oil pressure is good around 60 at start up and down to 50 after a few miles. Wastegate actuator moves ok against spring pressure. Turbo made pressure on the way to gas station - didn't push it but it got to positive boost. Normal blowoff noises. Then after shut down for 5 minutes to get gas no boost at all. Engine idles fine and runs smooth but it is like a 120 hp 1.8 should run - slow.

Mystery so far and I can't find any threads about this particular problem. Have only one idea, but I'm new to turbochargers, so I'm hoping some of you with years of turbo experience have some troubleshooting advice.

Sorry for the long post but I tried to give you relevant info right from the beginning. Looking for ideas - please!!!

You do realize you posted this in "The Front Desk" right?

You do realize you posted this in "The Front Desk" right?

No I didn't realize that - thanks for letting me know. Was having trouble finding process for starting a new thread. New to this forum. So how do I start a new thread in the correct place?

Why, click on this link - https://www.miataturbo.net/private.php?do=newpm&u=1133

Be sure to be as detailed as possible, don't leave out a single detail no matter how irrelevant it may be!

You recommend sending a private message to "Hustler"? Is that correct? If so, who is "Hustler"? Good resource?

Why, there is no better resource on this forum than Hustler! Except for possibly Brainieack!

I moved this thread to the DIY section as I did not know what setup you actually have.

Did you hear any pops on the way to the gas station? I am willing to bet one of the intercooler pipes came undone and that is why you are not building boost.

Your wastegate is no longer being held shut.

It's either stuck open, or else the actuator rod is no longer attached to the gate lever.

https://www.miataturbo.net/attachmen...ine=1363266928

Pay no attention to "wastegate actuator needs to be shortened a few turns" - only the "C-Clip" portion of this internet image is applicable

Thanks for ideas. Wastgate actuater is attached and I can move the rod toward the wastegate by overcoming the spring pressure. So I am guessing that the wastegate is closing. Will need to disconnect downpipe to confirm that action.

Checked intercooler tubing - and all seems to be in place. Will check in more detail and report back.

After reading additional threads last night here's a thought. Could my CAT be giving me trouble? It's a 3" CAT. I added heat wrap to the manifold and downpipe to help with underhood temps (I know that's controversial, and I may remove it all). Could I have introduced higher exhaust temps to the CAT and damaged it? Doesn't seem likely as I only drove about 4 miles and hardly any of that at boost - and ambient temp was around 50 degrees. But what do you think?

Another question --- Since the compressor spins freely does that necessarily mean the turbine is also spinning freely? Is it possible a connection between the two impellers is not functioning? Is it possible that the hot turbine is spinning but not the compressor blades? I've never looked inside one so I don't know the structure of the internals of the turbocharging assembly.

Thanks to all for any help. Will carefully inspect all plumbing from compressor to throttle body.

This.

I had this happen to me and it gave me all the same symptoms you describe.

The cat is not the issue.

You would know if you lost the rear compressor wheel. It would have made a ton of noise going down through your exhaust.

I would carefully check every intercooler pipe for a good solid connection. It is possible that it has only slipped out a little bit and be hard to tell that it is not sealed tightly.

Also the Lotus7 in your signature looks nice. I will probably be starting to build a locost sometime in the next few months with using one of my spare miatas as the base.

Going to check plumbing at lunch - I work from my home and the car is in the garage. Very convenient.

Re the Lotus - it's with my son in Boulder CO. We built it from chassis up. Ford Sierra as donor car (Merkur XR4TI in the states). MK Indy chassis with Yamaha R1 motor. No reverse gear - motorcycle trans. Weight without me is 1050 and the motor makes about 175hp. It's a screamer. My other son, also in Boulder, has an R8 (with the 8 cyl motor). We had a Ferrari F430 for a weekend out as a reward in a charity auction. Took the R8, Ferrari and Lotus for several hard drives in the mountains. 40 - 100mph kick down the Lotus pulled both the Ferrari and the R8. Very satisfying to have a $25k home built be faster than a couple of the best that Europe can offer.

Good luck with your build. You'll just love the Locust when it's done. It will be begging for a turbo. Would be really cool to have about 250hp at the wheels of one of those.

Found it!! Thanks to all. Dumb mistake but it seems I always make 1 of those when doing an engine install. Tube from intercooler to throttle body is a three piece assembly. The T clamp at one of the union points was not tightened. Tube was completely disconnected (but almost perfectly aligned). Need to get underneath to reattach but I'm sure that's the problem.

Awesome. I am glad that it was just the intercooler pipe and you found it. I have had mine pop off multiple times at various points. It is always hard to tell how tight a clamp needs to be.