Hey all. Posted a while back about my 1986 IROC 305 TPI getting 11 MPG.

I set the TPS back down to .54 volts, and put the minimum idle as low as it goes (car stalls now, untill i actually get up to 40 MPH or so, then it idles)

Well, after all this, driving in overdrive, and never hitting WOT, i get a whopping 12.7 MPG.

Anyone know what the hell could be going on? Is my fuel return line like, unplugged or something? I can't figure out how my 305, with its little 19LB injectors, could flow that much fuel!

Maybe i should drop in a crate 502, §hit, i flow enough fuel for one. hehe.

Any ideas?

Thanks everyone!!! :|


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1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome

 

When's the last time you tuned it up? I noticed a steady increase in MPG just by replacing the usual 'tuneup' parts, air,oil, and fuel filters..etc...

also how about fuel injector cleaner?

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http://www.tcnj.edu/~esposit3
https://www.thirdgen.org/rides/index...ew&rideid=1137
Member of FBS, The F-Bod Squad, 3 guys so far and I don't think we're growing

• '89 Trans AM, 305 TPI, 5-spd
• '86 Firebird, 2.8, Auto

AOL IM Name: JimmyTime5

 

Just spent $1,400 on a "Tune-up".

It included a new CAT, fuel injector service, a new harmonic balancer, a new Y-pipe, new plugs, fuel fulter change, and a filter recharge (i got k&n's)

Any other ideas? thanks for the reply!!!

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1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome

 

Oh my you did NOT spend $1400 on that, right? Thats one hell of a labor fee.

Replace the o2 sensor, coolant temp sensors.

 

Oop, forgot, also had the O2 replaced for that 1,400. Yes, it was 1,400, and that is the last time i go to a mechanic, without a gun in my hand, and a shirt which says, "rip me off, and ill kill your children!" hehe.

As for the coolent temperature sensor, it has always been screwy. I had the replace that too, but all they did was wire my fan to always be on.

Are you thinking that its my temperature sensor sending incorrect info to my ECU causing my cold start injector to fire all the time? Is there any way for me to test this?



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1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome

 

The cold start inj. has its owm temp sensor on the front of the engine, next to the ECM temp sensor. Do you have any rough running problems? My car was down to 9MPG until I replaced the MAF relays ( I ended up rewiring the connectors to the relays, also). Now I'm back up to 19MPG...probably be even better if I could lighten my right shoe...

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88 IROC with cobbled together (not by me)drivetrain, 86 (?) TPI unit,CE subframe connectors, Edelbrock strut tower brace, polygraphite bushings all around...it handles like a dream, but man is it hard to push!!

 

Ok, i have a temperature sensor underneath the throttle body. Which one is this? I found another sensor located between the #1 and #3 cylinder head too. Not sure what it is for.

ODB has been e-mailing me with suggestions about my problem. My new CAT rattles quite a bit. He was suggesting that it might be bad. I will have to pull it off and check it this weekend, to see if its blocked, or screwed up in some way (if i can find a place to do it).

Where is the cold start injector anyway?

Thanks!

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1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome

 

You should have 2 sensors in the front of the intake manifold. Disconnect the square one (Cold start inj) and see if your MPG goes up. It won't rule out a leaking cold start injector, but it will rule out a faulty 'switch' It's actually a bimetallic switch (Like thermostats at home). If that doesn't help, disconnect the one bolt holding the cold start injector in and start it (It should still start, and see if it's spraying, leaking...

The oval sensor next to it is the CTS and might be the next best thing to check/replace. The sender between #1 and #3 is for the temp guage, and the one between #6 and #8 is for the fan/s.

Are you getting any codes? Hopefully it isn't the MAF piggyback gizmo on the ecm, I heard they are pricy because it's a one year deal (85) and that stepping up to the 86-89 computer is cheaper.

Try unplugging the MAF and see....

Also disconnect the short vacuum line from the plenum to the fuel pressure regulator and see if any fuel is leaking through the line, indicating a ruptured diaphamn (hate it when that happens )

Hope you get your MPG's up, that's horrible for a 305!

 

Well, let my car sit for a while now. Im going to take it back to the mechanic and see if they will do anything for it.

One thing, when i accelerate, the new CAT they installed rattles annoyingly. Not all the time, but very often. When i jacked up the car, to take it off to see if it was cracked or plugged or anything, i saw that they welded it in place. That, and they did a very poor job of it. I think the welded it with the pipe still attatched to the car even. the top half isn't welded on. Could this be causing the rattle?



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1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome

 

A rattling cat won't cause a 305 to get 11 MPG's. I couldn't get my 305 to get 11 MPG's if I had my foot to the floor for the whole tank. You need access to a scan tool. Find out if the computer is going into closed loop. Find out your BLM and INT. Have you recently had an emissions test? What are your HC and CO emissions like? Hows your 02 sensor and fuel pressure? As mentioned, check the cold start inj. Keep in mind 11 MPG's isn't just a little out of tune, its really pretty bad. You could risk washing the rings if you have a leaking injector. Don't forget to diagnose in steps, and keep track! Good luck bro!

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-Jason M. 1991 Camaro Z28

 

quick tip...

i replaced my whole EGR system and noticed a hell of an increase in MPG. give it a try!!!

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'86WS7
Ram Air...
*EiyseWhite*