[firechicken]

I've run 3 tanks of fresh fuel through in the 3 weeks since buying the car, it's that much fun...lol

While I wait on the new maf, can anyone explain to me how the fuel is handled in the situation I'm having the issue with what would be the accelerator pump on a carb?

Is it all in the programmed tune or should I be seeing the short fuel trim adding the 'pump shot' when blipping the throttle?

I ask because the short fuel trim goes max rich when I snap the throttle open but the engine doesn't respond and bogs. To me this seems like the ecu is attempting to cover for missing fuel that should already be there but it's not enough. This leads me to believe there is not enough flow through the injectors. Since fuel pressure check is good, doesn't that just leave the injectors as the culprit?

Edit to add - This would make sense except that unplugging the maf basically cures the bog indicating the fuel flow is capable but it's being held back by the ecu somehow.

I may run out to the pick n pull today and see if I can find a maf. I found a list of cars that use the same one so might be a quick way to test this.

[mgarblik]

Does the engine run the same, (bog), no matter what the temperature is? Trying to figure out if closed/open look has anything to do with the bog. Basically cold, open loop, fuel delivery is primarily determined by MAF, temperature of water and air and throttle position. Once in closed loop, (warm), the front O2 sensors become the primary inputs for fuel delivery, but the other sensors are still used for fuel trim. If it runs the same cold and hot, (open and closed loop), again the MAF comes into question. You will get it!

[firechicken]

Originally Posted by mgarblik

Does the engine run the same, (bog), no matter what the temperature is? Trying to figure out if closed/open look has anything to do with the bog. Basically cold, open loop, fuel delivery is primarily determined by MAF, temperature of water and air and throttle position. Once in closed loop, (warm), the front O2 sensors become the primary inputs for fuel delivery, but the other sensors are still used for fuel trim. If it runs the same cold and hot, (open and closed loop), again the MAF comes into question. You will get it!

Good question. I can try to test that this morning while the engine is cold. It comes up to temp very quickly and goes closed loop. It has a low volume cooling system apparently for that purpose and it's warm summer temps here now.

[KS circutguy]

I may run out to the pick n pull today and see if I can find a maf. I found a list of cars that use the same one so might be a quick way to test this.

Make sure these ECU parts are OEM type not aftermarket junk.
If you start putting unknown manufactured parts on, especially computer controlled components it'll lead you down the wrong path.
Only change 1 at a time to confirm or not the parts effect on the problem.
It could also be wiring or connector related.
I'd grab those at the bone yard if available, new ones are pretty costly and rare to find new OEM.
Also grab a factory manual for the vehicle on Ebay.
Good luck.

[firechicken]

Well, I almost don't believe it but a boneyard maf sensor from an 07 Subaru Outback and it's fixed. I guess the other one was just too sluggish or something. I'm ecstatic, this thing runs like a dream now. Noticeably better everywhere.

Shout out to Baron Von Zeppelin, you nailed it.

mgarblik and all others, your valuable time is much appreciated!

[KS circutguy]

nice work.

[Baron Von Zeppelin]

Think we all had our bets placed on the MAF sensor.
I was maybe a little more sure of it.
Those things can stick their dirty finger into any unlikely piece of a puzzle

Great luck that you found a suitable replacement in a local boneyard ! Wow
Are the originals made by Hella ?
KS's part source listed Hella as OEM @ $55

Sports car convertible with a V8 and 52k miles sounds like a Winner.
Did you get it cheaper because of the bogging gremlin ?
You mentioned it was just a small investment bought on a whim.

[mgarblik]

Glad it's fixed. When you can get a bone yard unit cheap and try it, it's a quick and easy deal. When you have to buy a new one and they are hundreds of dollars, you just cross your fingers and hope. Pretty hard to diagnose unless they are dead. Because it's hard to find the voltage specs. and frequency specs for a given system. Trying a known good part is usually easier. Enjoy that car.

[firechicken]

Originally Posted by Baron Von Zeppelin

Think we all had our bets placed on the MAF sensor.
I was maybe a little more sure of it.
Those things can stick their dirty finger into any unlikely piece of a puzzle

Great luck that you found a suitable replacement in a local boneyard ! Wow
Are the originals made by Hella ?
KS's part source listed Hella as OEM @ $55

Sports car convertible with a V8 and 52k miles sounds like a Winner.
Did you get it cheaper because of the bogging gremlin ?
You mentioned it was just a small investment bought on a whim.

I think the factory maf was a Delphi. The one I replaced was a Denso. The one I got from the yard has a couple part numbers but no name. Go figure.

I feel now like the guy knew something was up but it really wasn't that noticeable having never driven the car before. It was just a slight lag off idle when driving casually and was totally drivable. It's a whole new experience now. If this happened to him in reverse, he was probably quite worried. I don't think he was much of a mechanic.

I paid 8k Can for the car thinking that left some room to spend a bit of time and buy some parts if necessary.

[Baron Von Zeppelin]

Runs like a dream now ... Whole new experience now

Sounds like its going to be a really great car.
Very low mileage for a 24 year old car - killer deal .

I have no faith in Denso parts.
They hung me out to dry in just 2 years after buying all new coil$ (6) for my Acura TL.
The original Hitachi's lasted 16 years. I bucked up and bought Hitachi this time.

Delphi is supposed to still be a premium quality brand.

[mgarblik]

With new electronic parts, I generally just buy from my NAPA store or the new car dealer. I have such a good relationship with my local NAPA store, they will stand by all the electronic stuff for at least 3 years or longer, no questions asked. They will also let me return electronic parts in the rare case I need to. Most of the Echlin branded stuff is made by them or re-boxed OE parts. I don't buy anything NAPA sells under the "Performer" line. That crap is just re-boxed white box Chinese garbage. They sell it to compete with Auto Zone and Oreily's. Your lucky to get 3 months out of the majority of it. NAPA sells Delphi parts as well. I have had good luck with that line as well.

[KS circutguy]

BTW;
Here's the best free source on the inter-web for OEM part numbers and location-list.
For most manufactures.
https://www.nemigaparts.com/cat_spares/