terrible gas mileage b6t

[Movin]

The ECM will need some test drive to re learn

[Chobobulous]

Well went for a drive. This so weird. In 5th gear it runs 14s until about 58mph. Then it drops to 10.2.

In fourth gear it runs 14s until just about 55mph then it drops to 10.2.

Im trying to find out what happens that makes it run like garbage. It can't be rpm related because there is a few hundred rpms difference between 4th and 5th at 55/58 mph.

[Chobobulous]

Late night tonight.

So I remembered I had a cheap vacuum gauge. I hooked it up and I found another symptom/problem. When cruising at 55 the vacuum reads 20, when cruising at 58, the vacuum drops to 10. So it's sucking less air in thus running rich.

Being that air is being pushed by the turbo this tells me I probably have a leak in the intake that starts to let air out at around 55mph

Using this same logic if it were taking in unmetered air I would be running lean.

Thoughts?

[Movin]

At cruise the turbo is not working if the engine is producing power. I know you have been through this before but the accuracy of the pulley marks should be checked against the piston at top center. Pull number one and use a feeler to get the engine exactly at top center. Remark the pulley if necessary and look again at the cam pulley marks. it sure might be off a tooth to run like that.

How high is your city? 6000 feet or better can trigger fuel enrichment which is normal for that vacuum drop. Your exhaust is not restricted ? If the turbo seized it will
run like that.

[Chobobulous]

I will do that this weekend. My crank pulley only had one mark on it.

Las cruces is about 4500 feet, the saint Augustine pass is 5600 or so.

Edit: My exhaust runs straight through and the intake side of the turbo spins freely, so unless it snapped in half or something I bet the other side does too.

[Movin]

The altitude doesn't help and it makes tuning harder. The festy ecm doesn't seem to add timing for altitude so we add timing for our elevation. The turbo will make a huge difference at that elevation, but any timing added for elevation will work against you under full boost unless you add race gas...but those are fun problems. I may be gone camping this weekend but there are a lot of guys on here that know a bunch about turbos, timing and cam timing or where ever this may go.

[Chobobulous]

Thank you so much for your help, ill report back Saturday maybe earlier if I get around to it. Another thing I've noticed is that is when you push on the gas it seems like the car is attached to rubber band. It goes, but it feels like something is holding it back

Have fun camping!

[Chobobulous]

So follow up.

I redid the intake with the parts I got from azgtx. Upon putting it all back together I don't have a problem anymore.... ill find out what my gas mileage is over this next tank. But the wide band is telling me I'm crusing in the 14.3-14.9 it jumps around a lot so im thinking there is still a vacuum leak. Should it be steady?

[bhazard]

No it should oscillate back and forth like that. That's normal. Something about keeping the catalytic converter happy.

[Chobobulous]

Thanks for that information, its funny how it stays pretty steady at idle but cruising it varies so much. I think my gauge is off though, it says I idle at about 25in of vacuum.

[Chobobulous]

So I loosened the gauge and adjusted it some. I think the little piece of plastic shifted.

Im at 140 miles and a little over a half tank. Not the 200 I used to be at but a heck of a lot better than the 100 I was at last week.

Does it matter which vacuum port I connect the fpr to? Right now its connected to the one right above it because it has vacuum all the time. I noticed some of the ports don't.

Also I inspect my tps. There is a lot of slop in it due to old plastic. Would it be a good idea to make it nice and tight with glue and readjust the tps? For now I wedged a piece of card board in the gap to take out the slop.

[bhearts]

Vacuum ports without vacuum. Hmm. Last time I checked, the tps was a position based switch, not a omniposition switch. So it more or less only has the purpose to tell the ecu when to stop using its idle air control circuitry.

[Chobobulous]

Vacuum ports without vacuum. Hmm. Last time I checked, the tps was a position based switch, not a omniposition switch. So it more or less only has the purpose to tell the ecu when to stop using its idle air control circuitry.

Yea they only get vacuum when the throttle is being pushed.

The tps has 3 positions that I can tell idle, cruise and wot. The difference between cruise and idle is .3mm. I get this number because of how it is adjusted. There is way more that .3 mm of slop in the plastic gear that is connected to the butterfly valve of the throttle body.

[Rocketman]

If it's a B6T then it's a full sweep TPS and one that is worn out will cause issues

[Chobobulous]

If it's a B6T then it's a full sweep TPS and one that is worn out will cause issues

Its a b6 that I t'ed