running rough thru accel - gas mileage way down

[che13]

just changed out the alternator and now it putters during acceleration (puhpuhpuhpuh) and there is some vibration coming from the middle of the car. Gas mileage is WAY down. I just ran through a tank and got about 15/18mpg! also feels like the power is maybe 85% while on throttle - but will run 80mph all day - just accels slower

Another thing is the radio is not working now. any suggestions?

just did a full tune up on it (plugs, wires, belts, fuel lines/filter, timing belt, etc.) everything was working fine for about 2k and then the alternator went out - thats when the problems started. I did have a small exhaust leak, but fixed that - did compression test on the cylinders - everything was good - maybe the Cat is finally done? maybe an extra ground in the engine bay?

not sure - let me know what you think

[che13]

anyone - any idea?

[Adrian_Visser]

By the sound of it you may have fried some electrical components when you installed your alternator, the radio is probably just a fuse, but you may have fried something else too that would cause the problems you are describing.

What year and model is the car? that would be a big help first of all.

-disclaimer- I am not an expert so this isn't the best information.

I would test the voltage output with the car running it should be around 14v. Maybe the Voltage Regulator is fucked and the alt is putting out more voltage than it should.

This doesn't really explain the loss of gas mileage though. Test the coolant temp sensor and The CTS maybe the voltage spike fucked one of them up too... I am kinda pissing in the wind here..

The vibration from the centre of the car is just the hesitation in the engine being felt through the CSB I would guess

Could you be more specific on the puhpuh under acceleration? Is it missing on a cylinder or what?

[superultrahippo]

Seeing as your symptoms started after you replaced the alternator, go with the easy checks in that area. Ensure proper tension (too loose may not be providing enough charging voltage). Check what kind of V you're getting at the + and ground terminals.. either @ the jump terminals or @ battery while idle and again @ 2K rpm's(this rules out belt slip). See what you get and lets go from there.

[che13]

thanks guys - I will check on those things tomorrow - my car is a '90 325is -

It almost sounds like a problem with the exhaust, but don't think that would cause the other problems.

I will look around the alt. install for some clues - and I might just take it to an Indy shop down the street have have them give it a once over.

[Adrian_Visser]

a clogged cat could cause power loss and higher gas mileage, but if the problem arose when you changed the alt. I would start there.