miataman86
miataman86 Reader
6/22/12 6:25 p.m.

Just did the timing belt/water pump/engine seals replacement today along with the fuel filter replacement and although the rough idling issue has been solved and the engine seems to run better than ever, the bucking issue pirsists. Went to get gas after replacing the fuel filter and she drove horribly both to get gas and back to the house. I'm thinking it could be the transmission/clutch. The car would stuggle to keep accelerating both up hill and down hill, but was it was way worse up hill .Also, the RPMs were dropping at a speed like when I push in the clutch pedal, except I had my right foot on the gas and my left foot was on the dead pedal. Dont see it being the fuel pump as it has a nice steady flow of fuel foing to the engine and it fires up like a brand new car everytime. There are 141k miles on it and I seriously doubt the clutch has ever been changed. The transmission had some serious grinding noises coming from it and it bucked like all heck. Short shifting seemed to help get it to the gas station and back home, but I was shifting into 4th at 20 mph....and it still was struggling to accelerate any and wanted to start bucking....yeah there's something wrong. Any ideas as to what it is? I have the 01 transmission and an OEM Mazda clutch already at the house, so I'm seriously hoping that it is the clutch.

z31maniac
z31maniac UberDork
6/22/12 6:38 p.m.

Bucking?

When the clutch is going, it slips. IE you press the gas pedal and the Rev's go UP, but the speed stays the same.

Just because the car runs fine at startup/idle, doesn't mean the fuel pump isn't struggling to provide fuel under load.

miataman86
miataman86 Reader
6/22/12 6:44 p.m.

True, I'm really not sure what it could be. The grinding noise from the transmission was really bad under acceleration. Whatever it is, I think its gonna be a PITA to fix.

z31maniac
z31maniac UberDork
6/22/12 6:47 p.m.

Is the trans grinding when shifting gears, or just when in A gear and you press the pedal.

If the latter, yeah, I have no idea.

miataman86
miataman86 Reader
6/22/12 6:55 p.m.

It's grinding in 2 or 3 gears, under accelration load and the transmission isn't sounding as quiet as it did before when shifting. Pretty much, the latter, but kinda both....

Woody
Woody UltimaDork
6/22/12 7:24 p.m.

Check to be sure that one of the spark plug wire hasn't come loose, especially #4 (the short one).

miataman86
miataman86 Reader
6/22/12 7:45 p.m.

Plugs and plug cables are on nice n snug. I talked to a guy I know that works on Miatas and parts them out from wrecked Miatas and he said it could be my Cat or my coil pack. He's been in the Miata scene for quite some time and he knows em pretty dang well. I'll look into getting them replaced. I can take off my cat and drive it around the block to see if that will cause it to drive any better. The cat may be clogged he said. If it persists, I will look into the coil pack. Still want to get the new clutch in as well as the 01 tranny. love the NB transmissions! Any other info to help troubleshoot this would be awesome.

Spinout007
Spinout007 Dork
6/23/12 1:27 a.m.

Fuel pressure gauge taped to the windshield with a long lead. See what it does while bucking and kicking. Easier than cat removal.for "testing", besides mine has almost 220k on it and the cat is fine.

Spinout007
Spinout007 Dork
6/23/12 1:28 a.m.

Borrow a coil pack and try swapping it, takes 5 min max.

iceracer
iceracer UltraDork
6/23/12 7:36 a.m.

Much forgotten tool will show what direction to look. Even indicate plugged exhaust.

Vacuum gauge

miataman86
miataman86 Reader
6/23/12 10:04 a.m.

Where does a vacuum gauge connect to?

miataman86
miataman86 Reader
6/23/12 10:35 a.m.

Ok...got more details. The engine wont rev above 2500 RPM in neutral and it wont rev past the first or second notch above 2000 RPM. Seriously short shifting to prevent the bucking.

miataman86
miataman86 Reader
6/23/12 11:21 a.m.

I think its the tps harness that connects to the little black box that's on the side of the throttle.

freestyle
freestyle New Reader
6/23/12 11:40 a.m.

As the car idles try wiggling the connector and wires to the cam angle sensor. The motion of the engine along with the heat tends to eventually break the wires or plug.

miataman86
miataman86 Reader
6/23/12 4:33 p.m.

It was the throttle posistioning sensor (tps) that was causing the problem. The wires for the harness got cut by the alternator/water pump/ crank belt. Got it rigged up for now. Should have the new harness in by tuesday. The wires were pretty bad. Amazed the thing even ran at all. Runs like a champ now!

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