Code 32, Code 44, Thermostat. Wondering which of the three would be most likely causing my bad MPG?

86 GT car, 87 2.8 V6, Auto, Air, Cruise

After my engine swap, I have been trying to eliminate my codes. Code 32 and Code 44. In that process I swapped gas tanks and then swapped them back again. Then I started checking my mileage again. I'm getting about 17 mpg. The car starts easily, idles great, runs very strong with no hesiation or problems other than the codes.

Code 32 - EGR. The EGR system is supposed to re-direct exhaust gas back to the intake to reduce the amount of oxygen going through the engine. With less oxygen, less fuel is needed so it is supposed to save gas. Since I've been getting the code, my system has obviously not been working correctly. Just put another EGR solenoid on yesterday so my fingers are crossed and my mouth is shut so I don't jinx myself.

Code 44 - Lean Exhaust. The O2 sensor is telling the ECM that the exhaust is "lean". This is most likely due to my exhaust headers which I know are not tight enough. I will be putting VW Bug exhaust gaskets on soon to fix that. In the mean time, I assume when the ECM sees the "lean condition" signal, it dumps more fuel.

Thermostat. My gauge reads in the 170*F range when warmed up.



Don't know if the gauge is right or not but it is rock steady. If it is right, the engine is not getting fully warmed and therefore not running as efficiently as possible. Stant Superstat 195*F #45819 and ACDelco ECM coolant temp sensor #213928 both on order from Rock Auto.

Which of the three do you think is causing my bad mileage? Combination of all? More of one than the others?

Would it be a good idea to disconnect the O2 until I have time to do the exhaust? That would eliminate the ECM possibly dumping fuel in reaction to the lean signal.
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Jonathan

'68-69 GTO Nose - The Project has Begun!
My '85 L67 Build Thread

[This message has been edited by Boostdreamer (edited 12-01-2013).]

32 and 44 screams vac leak.
EGR solenoid likely bad to. use PFF search

Yes 44 then ECM will add more fuel to try to prevent running lean. Lean can and will destroy the engine. Discon O2 is a bad move. See my Cave, Scan Tool Help

get ECM scan tool. never trust dash gauge

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

1. The EGR itself may not be working. So changing out the solenoid might not 'fix' it. If this new solenoid doesn't, check the EGR valve for proper operation.

2. The O2 sensor might be working or it might not. They are inexpensive and relatively easy to replace. Yeah, you might be replacing a perfectly good sensor. But unless you have something like TunerPro and know how to read the logs you won't know if it is good or bad.

3. The temp gauge might not be reading correctly. Buy/borrow an infrared temp sensor and see what it says when the engine is warmed up.

Your problem could be of any or a combination of all those.

I'm sure it is not REALLY running lean. The O2 sensor just thinks it is because of the exhaust manifold leak(s). It seems to me that if I disconnect the O2, the fuel will be metered by the MAP and the coolant temp sensor and should run fine.

The EGR valve (correct term?) tests good. It will hold vacuum (if it ever gets applied...stupid solenoid).

I went through the vacuum lines with a fine toothed comb and I don't know how there could be any leaks. It idles great, runs great, cruise control works incredibly well.

Jonathan

Sorry but Many/Most exhaust leaks won't cause DTC 44 w/ "old style" O2. (Maybe newer "wide-band" sensor can see smaller exhaust leaks. Still depends on if leaks let air into exhaust.)
Needs a medium to large leak to let/suck Air into the exhaust. small leaks and weak gaskets very often leak exhaust out but very little air gets inside. Many times you won't see even high BLM on scanner on exhaust leaks.

How big? I broke duke manifold before O2 sensor and did not trip 44. (like to break were side tubes are welded to middle section.) That easy lets allot of exhaust out but still didn't suck air in and trip 44.

You can try replacing O2 but might not help.

I have had the 32 code for years. It has never affected my MPG. I haven't been able to figure out where it comes from as I have replaced EGR solenoid and lines. The 32 code can pop easily with a small intermittent vacuum leak.

Code 44 only hits every so often and only for a few seconds at a time. I changed the exhaust bolts to studs during the swap and they will not stay tight. I keep finding them finger loose. I see a reduction in frequency of Code 44 after I tighten them. In all of the things I've tried, that is the only thing that has made any difference.

I was keeping records before the swap and I was getting 20-24 MPG with this thermostat and had the same gauge readings.

Jonathan

[This message has been edited by Boostdreamer (edited 11-27-2013).]

EGR on a small engine doesn't do much for MPG and I have seen 30+ MPG on a 2.8 with it removed, so its not the issue for your low mileage.

Any exhaust leak can mess with the O2 sensor. You can disconnect it for 1 tank and see if it improves things, but running open loop normally adds more fuel too, so you might not see much of a change.

It could also be a true vacuum leak on the intake side. When I try and track down idle/drivability issues down, I start with blocking off the EGR at the manifold and remove/cap off all the vacuum lines and run a new hose to the MAP and fuel pressure regulator. Check for any vacuum leaks at the IAC tube and intake gasket surfaces. Then set the timing, idle and get some baseline drives in. Once it runs like it should, then I start hooking all the other stuff back up. If it runs worse after adding the other connections back in, I start taking things back out (one at a time) until I find the culprit.

Not sure what headers you have, but if they are longer/larger than stock then the O2 sensor might not be staying hot enough to work correctly. Switching to a heated sensor would help this.

The hotter the coolant, the better the MPG, so changing back to a 195 probably isn't a bad thing, especially in winter.

Also, fuel mileage in winter tends to drop 1-3 mpg anyway due to the extreme cold, which means the throttle is more closed, so you are pulling more intake vacuum and seeing higher pumping losses.

I have the stock headers but the restrictions have been removed. Does disconnecting the O2 sensor prevent it from going into closed loop? No performance issues to report. Runs and idles great. Idles smoothly at 7-800 RPM. Timing was set recently.

Jonathan

I ran through a half tank of gas. Mileage went up to 19.8 mpg. That's about a 3 mpg gain from what I was getting before. This gain is the result of the EGR system working correctly during this period. No other changes were made. This was possible because of a third EGR Solenoid being tried. So far this soleniod is working.

I still feel like the majority of my mileage problem is is the O2 sensor telling the ECM that there is a lean fuel condition and extra fuel is therefore dumped into the cylinders. My next test will be with the O2 sensor disconnected. I'll run through another half tank and see what the mileage is.

I received my thermostat and ECM Coolant Sensor from Rock Auto. The thermostat swap will be my following test. I may or may not put the O2 Sensor in. If disconnecting the O2 Sensor solves my MPG problem like I believe it will, there won't be any need to change the ECM Coolant Sensor.

Jonathan

I disconnected the O2 and put in the new thermostat. I know I was supposed to wait but I just really wanted to see if it made a difference. If anything, this new 195*F thermostat makes the car warm up slower and makes it run cooler. That is what the dash gauge is telling me at least. Maybe I'll try different gauges. I should have a few of them around. Maybe one of them will read closer to what I want to see.

I also noticed that start-up idle was very high. About 16-1700 RPMs. Wonder if that was O2 Sensor related? I'll watch and see if it continues and if it goes back to normal when I plut the O2 back in.

I'll drive some more and let you know what the MPG looks like later today or tomorrow.

Jonathan

[This message has been edited by Boostdreamer (edited 12-02-2013).]

quote Originally posted by Boostdreamer: ...put in the new thermostat. If anything, this new 195*F thermostat makes the car warm up slower and makes it run cooler.

That obviously makes no sense, unless the new thermostat is faulty or incorrectly installed (or the old thermostat was stuck closed).

quote Originally posted by Patrick: That obviously makes no sense, unless the new thermostat is faulty or incorrectly installed (or the old thermostat was stuck closed).

It makes sense. The new one is very similar to the old one. I don't know what the old one is rated for. Maybe it was a 200*F thermostat? Maybe the old one is "broken in" and works better and the new one needs to cycle a few times? Don't really know. There isn't much difference in the indicated temperature. Only one tick mark different on the gauge.

Still, I will look into swapping the gauge internals to see if I can get it to read closer to the middle of the gauge when warmed up.

Jonathan