I've tried everything I know of in the past 2 weeks to get my car running some better. I've searched everywhere and can't figure it out. The car is an 88 TII with intake full 3inch turbo back. The car has a shake to it in 4th and 5th gear under 2500rpms when trying to accelerate. Once above those rpms, the car pulls fine and strong. While doing the shaking, the turbo seems to make a fluttering noise like it can't hold steady boost. I can also see the boost gauge fluctuate up and down. I have adjusted the TPS, unhooked the pressure sensor to see if that helps, checked all vac leaks, checked the timing twice but I'm going to again this week to make sure its still okay. The 02 sensor may be bad. I'm going to replace it this week also, as soon as I get to the parts store to get it. Would that maybe cause it? Any ideas on what to try or do? Please help.

 

Are you running off the wastegate spring, or do you have some sort of boost controller?

 

rotaries have no torque so accelerating in 4th or 5th from 2500 rpm isn't the greatest and your engine probably has high mileage i'm assuming so its not going to have as much power as 20 years ago. i can barely cruise in 5th going 35mph in my n/a it shudders a lot.

 

Not trying to tell you how to drive your car but....5th at 35? our gear ratio's are close...but that is just bad. according to the owners manual, at 'around' 35 mph you go to 4th, when driving lightly to save gas. 5th is just past 45ish. picking a higher gear when moving to slow can strain the transmission, as well as kill whats left of the 7's gas mileage by bogging down the engine. Keep in mind a rotary dosnt bog down in the same manner as a piston engine dose.

As far as the shaking, have you looked at all the mounts? Both engine and transmission? What i have noticed in a few sevens, both turbo and non, under 2k Rpm's in any gear past 1st is kinda blah. Almost as if the car is begging you to pick up the rpm's by shaking and sputtering(slightly). What RPM range dose your car shake in? That might help us to better assist you. Almost forgot! have you looked the the plugs and wires? is your timing correct? how about the fuel filter? also alot of minor kinks in how are cars run is caused by the TPS being bad/out of ajustment. Good luck man

 

It is running on a manual boost controller set to stock boost. The engine has fairly low miles, somewhere around 30k to 40k miles. The timing is correct, but I will check it again just to make sure. I adjusted the TPS and it is in spec. Brand new plugs and plug wires, but I haven't changed the fuel filter. I am planning to change the 02 sensor also. The car does the shaking under 2500rpms in 4th and 5th. After that the car runs fine.

 

the O2 sensor will NOT cause this. Bypass your MBC and see it that helps. You still haven't said whether you checked the mounts or not, really sounds like a bad mount to me.

 

That might be semi-true with an NA engine, but we're talking about a turbo engine. Stock turbos spool very quickly, and make lots of torque. I cruise all the time in 4th or 5th around 2500-3000 RPM. Hell, I even do my passing in 5th gear sometimes just because of how wide the power band is. I will agree though that under about 2500 RPM is not going to produce much torque at all, since the turbo will not be building any positive pressure yet.

Under 2500 RPM is pushing it. If you're getting down around 2000 RPM or so, you'll be bogging the engine if you give it any more than very light throttle. Keep it a little higher in the RPM range, and you'll stay in the power band.

 

What is the MBT? Sorry, I checked the motor mounts and they are in good condition.

It does it at anytime under those rpms. Whether its a lot of throttle or barely any. I can barely give it gas on a level surface and it will start shaking. Just seems to me like it should be smooth but giving any type of throttle will cause it to do this.

 

^^^ MBC = Manual boost controller.

 

Ok gotcha. Sorry I was not thinking very clearly. I bypass that tomorrow and see if it helps.

 

Has the TB been "modded" (as in outer set of secondary plates removed)? I did a little test for you on the way home today, and 3rd gear @ 2000 RPM under very light throttle was fine, but if I gave it maybe 1/2 throttle it bucked a good bit. My throttle body is stock however, so the secondary plates will open gradually and prevent most bogging situations.

 

I don't believe they have been removed. I will check for sure though. I know the thermowax system has been removed and blocked.

 

i recently found my transmission mount to be about 4 turns too loose before this, it would shake the car after a hard shift. It's right in the middle a 17MM put it on and turn it hard, if it's tight, try to pick up the rear of the tranny off the mount to make sure it's not broken.

 

Ok. Thanks I will check that at some point today. I still haven't had time to check to bypass the MBC or the timing yet because of my classes today. I will let you guys know if it helped as soon as I get a chance.

 

Try it with the EGR valve disabled, see if that helps.

Also, while you are under there checking mounts, look at the front differential mount. The rubber pad fails in shear (along a vertical plane). It often looks fine when the car is on the rack (the two sheared parts line up). If it is broken, the differential can torque along the axis of the rear axles; it usually shows up as a thump when engaging the clutch after a shift. It might be a culprit at low rpm, high torque operation.

 

How would I disable the EGR valve?

Ok. I'll also check that to see.

 

Sorry it's taking so long to check everything, it won't quit raining. Finally got out today to check some things. I checked the TPS to make sure it was still set, all the mounts, secondarys haven't been removed in the TB, still haven't gotten a chance to check timing because I don't have a timing light. I will check it as soon as possible when I have a chance to borrow my dad's.

 

Still haven't gotten to check the timing. Also I noticed that at low rpms in any gear when trying to maintain a steady low speed such as 10 or 15 mph the car bucks horribly. Also there is a little nipple right above the coolant temperature sensor where coolant does come out. I have a cap on it right now just as a temporary fix, but it is leaking antifreeze slowly. Where does the coolant has that connects to that go to?

 

Could this be the stock staging point for the secondaries not coming in? It kind of seems to make sense to me. If so, how could I fix it?

 

The secondaries can't come online until at least 3800 RPM. They're not your problem.

Possible hesitation from an extra lean mixture? Maybe try disconnecting the 02 sensor to see if there's a change.

The nipple sounds like the one that normally feeds through the BAC body around to the thermowax.

Unplug the yellow EGR solenoid connector.

 

Thanks. I wasn't sure if the secondaries could cause the problem so I figured I'd throw the idea out there.
What is the best way to cap the nipple off for the coolant line.
I will give the yellow connector a shot. I just wanted to check to make sure.

 

The best way to cap off the nipple would be to remove it completely, tap the housing and thread a bolt in. Another way would be to loop a hose from the water pump housing to the rear iron nipple, which is where it eventually ended up in stock form.

 

I wasn't exactly sure how to go about doing it. I didn't want it to start leaking eventually and me not notice it. Thanks for the info. On the EGR valve if I disable it and it fixes the problem should I replace the EGR valve or could I leave it alone.

 

Where exactly is the EGR connector? Is it with the rat's nest connectors?

 

definitely not the o2 sensor. Take a look at your spark plugs. I chased what sounds like a similar problem for a while just to finally check the plugs and notice they looked like ****.