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Discussion Starter #1
Hey guys, I've got a 90 NA. My gas milage has recently dropped from about 320 to 250 miles to the tank. Also the RPM's seem seem to be running about 500 higher then normal at all speeds, and I can smell gas fumes when I have the heater on ( which only works when I'm moving, if I stop it blows cold). I only run premium and I don't run her hard so I don't know what caused it all. She just hit 136,000 pampered miles. As many others on this site, I am a broke college kid (FSU Panama City) so I'm trying to learn to do it myself and save the $$$.
Thanks for all help and suggestions!
B in PCB
 

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Discussion Starter #3
I'm going to reset my ECU tomorrow and see if that helps. She has a new tranny with 30,000 miles, shouldn't be that should it? I just read a post on the PCV Valve, sounds like some of the problems I'm having. I'll have to look into that as well.
 

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i don't see how thats possible "to run 500 rpm's higher than normal at all speeds" The only way to do that is to change the rear-end gearing or the actual tranny gear ratios. not unless the torque converter is almost completely gone, but you'd be aware of that. Doubt the PCV system has anything to do with gas mileage, try O2 sensors, run ECU diagnostics.
 

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run the ecu codes, tranny codes if you want, and O2 sensor check. Change PCV valves too might help. I don't know about the RPM change, but this will help you out. I've got new o2 sensors, ran ecu codes and fixed the problems and got new PCV valves. Runs so much better.

Go to Twinturbo.net and under tech/faq theres a write up on how to do it.
 

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not true. you could run higher RPM at all speeds if your clutch is slipping (though unlikely it wouldn't be obvious whats happening) or if there is something wrong with your torque converter and it is working less efficiently then it should.

Either of those cases would obviously cause bad gas millage as well.
 

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" I can smell gas fumes when the heater is on (which only works when I'm moving, if I stop it blows cold)"

There are several different problems here, not all related. Can you explain further what you mean by the +500 rpm remark? Do you mean tach shows +500 at idle, and +500 at your normal cruising speed too? It's possible your tach is fine, but your speedo is reading lower than before.

Gas fumes! VERY DANGEROUS - TROUBLESHOOT AND FIX IMMEDIATELY.
Search this board for many many posts about gas smells and the cures for same. Likely causes are a missing plastic cowl over the battery, seeping fuel lines, fuel pressure regulator, fuel presuure dampener, at top rear of engine, and fumes being carried into cabin intake. Car Fire Risk! Anyone can tighten all the fuel hose clamps at fuel filter and beyond. Try this first.

Can you possibly be confusing gas fumes for the smell of coolant? At this milage you may have a failing heater core. This will cause nasty sweet smell and extra glass misting in the cabin.

Heater goes cold when car stopped? Please explain further, too vague. What temp does coolant gage read when car is fully warm? Failed or stuck coolant thermostat may cause low heat in engine and heater, could also be stuck or inop air flow doors in heater box assembly. Service manual has full diagnostic for checking heater/ac functions.
 

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Discussion Starter #11
I appreciate all of your input. As far as the RPM's, it's in the higher speeds, it feels like shes not shifting into fourth or the OD is off. Running 65 she is at almost 3000, normally shed be way lower. I'll definately look at the o2 sensor and pcv valves. I don't think the fumes are from coolant but I won't rule it out. Not sweet smelling at all, smells like someone opened gas can. The water temp guage is at low when cold and middle when warm, all guages seem to be working. The heater blows nice and hot when I'm moving, but at stop lights etc the air gets cold. Somedays I'll smell fumes, some days I won't. Could it have to do witht the weather? Living down here on the beach it will go from T-tops off during day to ice on the window at night. I'll look into all your suggestions. Thank you much for your time!
Brandon in PCB Florida
 

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All righty now .....

you need to test a couple of things....first of all the 500rpm difference is about the difference for torque converter lock-up. Also if you do not feel the car is going into overdrive that can be related. First and foremost is to check the harnesses from the tranny to the engine compartment. Make sure each lead is connected. During a tranny swap some shops can get sloppy and not connect the fluid temp sensor harness or bend the harness terminals. If all the harnesses are connected run the auto transmission codes and see if any codes for fluid temp sensor or line pressue solenoid show up. Post what you find.
MaxDoc
 
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