Stumbling at 5psi

[ryostyle]

Just bought an 87 USDM Turbo and it is stumbling at 5PSI. It has a rebuilt head, HKS stopper HG and ARP studs as well as a Walbro 255. Everything else is stock.

Car stumbles when you get to 5PSI and slightly bucks. Any suggestions would be greatly appreciated. Thank you in advance. Just bought it yesterday and would like to get this sorted out. :nono:

 

[Enraged]

First off, congrats on the purchase.

Here's the service and repair manual: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/default.aspx

Read through the ignition section. Check for codes.

 

[ryostyle]

Second time owning a MK3 Turbo. Just spoke to the previous owner and he said this issue started when he shimmed the WG and "played with the timing". When I get home I'll check the timing to make sure it is to spec. I have unshimmed the WG. Do you think screwy timing is likely a cause for my issue?

 

[hvyman]

Either timing or boost leak.

 

[ryostyle]

Timing was off the charts. I adjusted the idle then set timing to 10. Still have boost issues. I will inspect piping tomorrow.

 

[ryostyle]

I am also getting code 11. Off to check grounds.

 

[hvyman]

Code 11 can also be Ecu power related.

 

[ryostyle]

Fixed code 11 and swapped out the coils from my 91 I have. Now code 11 is gone and I have code 51......this car is a pain.

 

[hvyman]

Was a/c switch pressed when you checked for codes?

 

[ryostyle]

Was a/c switch pressed when you checked for codes?

No it wasn't but I haven't done anything but adjust the idle screw

 

[ryostyle]

Put it in the shop today for a boost leak test with smoke. The accordion hose was cracked at the turbo and the fuel injector o-Rings were going bad. Had all of that replaced. Timing was checked again. They will tackle the TPS being out of adjustment tomorrow. Would code 51 cause the hard hesitation that I get if I go anywhere near boost? This is the only code I have remaining. It is idling at 1100ish due to the TPS.

I also tried replacing the AFM with a spare I have and no change.

 

[ryostyle]

My gut feeling is I have a clogged primary cat. When the car is on the lift later today I'll have the downpipe removed after the turbo elbow and see if it makes boost. Keeping my fingers crossed.

 

[Enraged]

either gut the cat, or put a new complete (ie, eliminate the elbow) downpipe. A separate elbow on the downpipe serves no purpose other than pissing you off when you need to take it apart Get something like this: http://www.driftmotion.com/3-Inch-DP-with-Elbow-7M-GTE-p/dm906.htm

if you run the car with just the elbow and no downpipe, you run the risk of fire (duh) and cooking the speedo cable.

 

[ryostyle]

Goes without saying. Just want to find out if this is the culprit before I gut it

 

[ryostyle]

Dropped the downpipe... No change. This is killing me. Any other ideas. The shop has had it for 2 days. Would a video help? Feels like a fuel cut immediately when boost comes on. Almost like launch control. Sputtering, just when boost tries to come on.

 

[Enraged]

What happened with the code 51? And you reset everything after fixing the codes (pull EFI fuse or disconnect battery)? You swapped coils, but did you check the plugs? Correct heat range and gap? Plug wires inspected?

 

[ryostyle]

Still have code 51, need to remove the throttle body to access the bottom Phillips screw. The shop today said it loses fuel pressure under load, essentially a fuel cut issue.

The fuel pressure isn't keeping up with demand.

The previous owner put in a Walbro.

Could be a clogged fuel filter or a kink in the line. Maybe they botched it dropping the tank.

 

[Enraged]

That's easy enough to check then. Might be worth buying a spare pump so you have one on hand if you need to replace the one that's in the car now.

 

[ryostyle]

after searching the web for days I read a bunch of threads that say that the Walbro 255 has issues with the stock Fuel Pressure Relay, staying at 9v and dropping fuel pressure. I'm going to bypass it when I get home and see if this fixes the issue. The previous owner installed the Walbro but didn't do anything else. It whines crazy loud too. I'm also told that Walbro pumps hate being powered at anything less than 12v.

 

[ryostyle]

Didn't fix it.