So I put an engine in this '91 vert. First 15-20 minutes it runs (after disconnecting the battery) it runs "good enough". After that, it starts wanting to die at idle, or coming up to a stop light, and it runs pig rich. I had used plugs in the car, and threw some new ones at it hoping that would solve the problem. It didn't.

Here lies the problem. There's 11ty billion vacuum hoses. I've checked the ones I can easily get to, and I marked most of them when I tore the thing apart. I did find one I hadn't connected, which made it run much better until I got to the current problem. My biggest problem is I'm aboslutely clueless about these totally computer controlled cars. I've heard bad things about individual components like this electric OMP, etc. If it was my car I'd just go to a Weber or something so I can feel at home.

For all I know somebody could've adjusted the mixture or idle or something somewhere along the way, but this EFI stuff is well beyond me. Of course, the car running like it is wouldn't be a problem for me having driven carb'd cars on the street all my life but the twenty-something chick owner isn't as savvy about it as I am (she did have a first gen as well as a Miata before this puppy, bonus points for her).

Anyway, solving this problem means so much to me that if you help me out I'll give you a power steering belt (or is it A/C? I can't remember) that ended up extra after the install. Not as good as a cookie, but hey, free stuff rules, right?

 

Did you replace all of the vac lines or just slip them back on?? Since you take off the UIM to see most of the vac lines I would replace them with silicone hose. Old lines are too easy to just come off again. -Dave

 

After thinking for awhile it sounds like just maybe your idle adjustment screw might have backed itself out abit during installation of the engine. It's under a black rubber cap about the size of a nickel on top of the throttle body and just turn the screw in and out to see if that helps you with the idle problem. --Dave

 

Dave -- that seems to be the the same thing the '87 Manual I found in my office (!) says. She's going to bring it back tomorrow or I'm going to make a house call and see if that's it.
I've got my fingers crossed! Thanks buddy.

 

Alright, more questions, fewer answers.

The TB that was on the car had no cover on the idle adjustment screw, and I could turn the screw with my fingernail. Swapped a TB from a '91 I've got here (man, this chick is lucky I bought that thing on a whim!), and the problem actually seems to be worse. Of course, I'm a knuckle dragger so I could've left something unplugged. I'll check it out again in the morning.

I didn't clean the plugs before I ran it again, but I ran it for a while over 2k, which it would do OK before and would not do at all now. In the morning I'm going to clean 'em and check everything and try again, but I'm not hopeful. I was planning on the "new" TB being my ace in the hole.

Which leads me to this question: is there an idle mixture adjustment anywhere on this thing? According to the '87 manual there is on the Turbo cars, but not on the lowly N/A. Of course, a lot can change in 4 years (this car is a '91).

Fortunately I'm not rotary ignorant, but I'll be the first to admit this EFI/Computer control owns me.

Thanks in advance, dudes.

 

As far as I know mixture adjustment is controlled by the ECU but I have an 86 N/A. I'm thinking that after the TB change, it sounds like a vacuum leak somewhere. If it was me with this problem, I'd pull the UIM off again and replace every vac line, I know there is a lot on my 7 cause I replaced vac lines, water hoses, and fuel lines just last week with silicone hose and to be completely honest, it's sounds and runs alot better, most vac lines just slipped right off, but it's up to you. If you do go down that joyful road, take lots of pics with a digital camera, it helps!!!

 

Take it to a shop or mechanic that can fix this for you.


-Ted

 

Check the compression.

 

The sad thing is, I am a shop, and I'm the only shop in the phone book that knows how a rotary works.

(well, ok, there's probably two places in town that know how it works, but I've already worked on two cars one of them did, and needless to say I undid a lot of stuff the owner of the car was billed for... :oops: )

I may end up taking the vacuum hose route... everything I've done has resulted in little improvements, but it's still not running anything near "right". Looking at the TB that came off of it, it had this problem with it's original motor, and somebody just screwed stuff up until it would idle. "Aww, it won't run over 2k? Oh well, at least this sucker idles!"

 

Okay, so you've taken the throttle body off at least twice now.. you DEFINATELY need to just replace all the vacuum lines.. they're probably cracked and/or slipped off. You also need to replace the gasket between the upper intake manifold (that was probably removed at some point, too) and the lower one, as well as between the lower one and the engine (if that was removed).

Don't fear the EGI stuff, it's your friend, and once you get the hang of it, it's easier and more powerful to tune than carbs

Now, the rear question is: How is the power when it's running "good enough".. you're saying if you disconnect the battery (resetting the ECU), then it runs great for about 20 to 30 minutes.. .after this, do you lose power? Is your Check Engine Light on? If it is, I think you may have a bad Oil Metering Pump (OMP)...

 

Hehe... yeah, about that CEL... apparently somebody didn't like this thing coming on, so they took that cluster apart and dealt with the light with a pair of needle noses.

The hoses on this thing are fairly new, but I picked up a spool of new stuff. I've got a couple other things to try first, and then it'll be re-hosing time. The symptoms are vaguely vacuum leak, but it just doesn't act quite like it. Plus, there's like 11ty billion of these things... I dont know how you guys keep sane.


I found this while I was meandering around the web. It may be old news to you FC-nuts, but it was helpful in finding some of the shadetree stuff that's been done to this car in the past:
http://www.johnr.com/cpucodes.html

 

And now, to confuse me even more....

With the ECU from MY '91, it starts up with no throttle input and runs "ok". Still not right, but I've given up on getting it back to perfect running order... that would cost several thousand in labor at this point...

Next up, remake the vacuum lines!

 

how hard is it to remake the vacuum lines and how expensive? sorry to jack your thread...

sounds like a vacuum leak to me...sorry im not of much help.

 

You buy them. www.rx7store.net

 

Time to download & print the "fuel & emissions" section of the factory manual.
I have a mirror copy at the link in my sig.
It shows all the hoses and how the blink the codes.

The EFI systems make sense after working with them.
Then there's the 3rd gens.
Then there's the renesis.