Running Rough... Newbie help!

[TomServo]

Hi guys,
I'm newb here. I have a 5s-fe from '93 that has a bit of a rough running problem. It idles alright with a bit of hunting but when you get on the gas it bucks and pops from ide to exactly 4k. at 4k it is as happy as can be and runs right up to 6k with no problems. It didnt have an air cleaner on at the time. besides being a bad idea, could this be the problem?

Where should I start looking?

Thanks a bunch!
Tom

[Mister2.2]

Since it's a new (used) car you should do all the basics. Check and replace oil, filter, air filter, Distro cap & rotor, check wires and plugs, replace as needed. Replace fuel filter as well. A compression test wouldn't hurt either.

Check ALL the grounds on the car (very important) and make sure they are working properly, if not replace before driving. There's a sticky on the board I think on engine grounds I think Tom posted, look for that.

[TomServo]

Originally Posted by Mister2.2

Since it's a new (used) car you should do all the basics. Check and replace oil, filter, air filter, Distro cap & rotor, check wires and plugs, replace as needed. Replace fuel filter as well. A compression test wouldn't hurt either.

Check ALL the grounds on the car (very important) and make sure they are working properly, if not replace before driving. There's a sticky on the board I think on engine grounds I think Tom posted, look for that.

thanks! All the basics that you mention have been done, I'm new to mr2's but not to cars I'll check those grounds. I'm pretty sure that isn't it though as it very consistently improves at exactly four thousand. I'm new to these engines and don't know the quirks

thanks again!
Tom

[1stgen]

if you had no air cleaner on does that mean you also did not have that nifty sensor thats near the air cleaner on? or does that thing even matter because I swear that mine is broke....or did they discard that by 93? air temp sensor or what ever..

[TomServo]

Originally Posted by 1stgen

if you had no air cleaner on does that mean you also did not have that nifty sensor thats near the air cleaner on? or does that thing even matter because I swear that mine is broke....or did they discard that by 93? air temp sensor or what ever..

Yeah everything before the throttle body is gone. Is there a nice critical air temp sensor missing there?

[Redstar]

Welcome!

It's not critical, but your car will be happier with the air temp sensor installed. It's probably floating in the engine bay somewhere, I found mine tucked under the evap canister.

It sounds like your car might be switching into closed loop at 4k, maybe check for vacuum leaks and check your map sesnor.

Also, you should read this:
http://www.mr2.com/forums/na-5s-fe-3...ur-mr2-na.html

And you should also get familiar with this:
1991 MR2 BGB Online - Mechanical Index

[TomServo]

great! Thank you. I'll check those things tonight and I'll give you an update.

Originally Posted by Redstar

Welcome!

It's not critical, but your car will be happier with the air temp sensor installed. It's probably floating in the engine bay somewhere, I found mine tucked under the evap canister.

It sounds like your car might be switching into closed loop at 4k, maybe check for vacuum leaks and check your map sesnor.

Also, you should read this:
http://www.mr2.com/forums/na-5s-fe-3...ur-mr2-na.html

And you should also get familiar with this:
1991 MR2 BGB Online - Mechanical Index

[Zena]

Thanks Redstar! Okay that sounded like Dave Shappel... But seriously, that online manual is awesome.