89 Turbo, really bad fuel mileage, fresh stock build. Timing off? need advise!

[87nasupra]

Ok, so I got then engine in the Supra rebuilt after spinning a rod bearing. Before the build it ran great. No problems what so ever. Spun a bearing and poof, time for a rebuild. Stock type build, .20 over stock pistons, rods, 1.4 mhg and arp's throughout. It runs great, pulls harder than before but, my fuel mileage sucks ass. Its guzzling fuel at the rate of 5 miles to the gallon. I've checked timing 4 times and it shows 10 degs stock timing, at tempature, ecu jumpered. It idles at around 550-600 rpms. It should be, in a perfect world, 650 from my understanding. I even hooked up a narrowband afr gauge just to see what it shows. It shows super lean to stoich back to super lean. It doesn't smell rich, I don't see black smoke under acceleration. How is it possible to actually run super lean on a supra to begin with? I have heard of the harmonic balancer start to spin on itself if its stock and your timing be off. Would this cause a lean condition though? I've searched many times and not heard or seen a post regarding a condition like what is happening to my car. Any advise would be greatly appreciated.

Scotty

 

[Abe's 1987]

From what I've read running lean could mean one of these

– Bad fuel pressure

– Vacuum leak

– Stuck open EGR valve

– pump regulator

– Insufficient fuel

 

[87nasupra]

Fuel pressure is 35psi without vacuum and 27 with so im within range. vacuum on my gauge reads 20-21 at idle, so no leaks. egr block off plates are in place, so thats why i was wondering if it was timing related.

 

[3p141592654]

Can you get a wideband and measure A/F at cruise 2000 rpm or go to a shop that has a 4 or 5 gas analyzer?

Alternately, do this test.

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=119

 

[87nasupra]

I was actually looking at widebands the other day since i was going to put all my bpu goodies on that i've been collecting. I work out of town during the week so trying to trouble shoot leaves me two days before i leave town again. I drive it to the shop and it sits 4 days and I drive it home. I dont drive it around town much so its been ongoing for a month now. I will try the oxygen sensor test tomorrow. I replaced the o2 when i got the car 2.5 years ago so, that could be a possibility.

 

[87nasupra]

Update. I went back and checked my fuel pressure. I am between 4-6 psi high with or without vacuum. I think I have another fpr laying around and will try that. I will be going to check the o2 sensor just in case. Im leaving to go out of town for a few weeks with work so I will post results when I get back.

 

[87nasupra]

Update on my running issues. Stock FPR was replaced with a new Toyota unit. Fuel pressure is now within range. Still shows lean even with a friends WB hooked up to it. AFR's are slightly off and timing shows no effect. Where else can I look? I run premium fuel, injectors are stock and should be ok ( they were before the rebuild ). I'm afraid to put any go fast goodies on for fear of hurting the engine any. Although it does show slight improvement on power, fuel mileage still sucks ass.