drittens

*Never had/driven/been around a running '7 before this one*
170,000 mile 85 GS 5 speed w/ Rx7carl's emmisions delete. Leading plugs are nice and brown, but the front trailing is a bit whiter and the rear is black. I used the intake and carb, but installed a new block because one of the housing was cracked from a wreck on the original. Got it running w/o rebuilding the carb (here is a link to hear it idling http://myspacetv.com/index.cfm?fusea...ideoid=8558145 ), but it wouldnt go over 5k (I assume because the accel pump diaphram was pouring gas and the secondary butterflies were frozen shut. Pulled the carb apart and cleaned/rebuilt it. Still didnt run right; pulled it apart again and got it running much better, but it wont idle and is very cranky when it is cold - I have to drive it w/ the choke(choke doesnt stay out because I think that got deleted as well? - not sure what part controls the choke staying out on its own). It SCREAMS when you get after it above 2k and got it to idlish between 13-1800 rpms. When I decel or cruise at like 45ish or less it bucks (~2k rpms), but does fine when I run on the highway @ 3k(until I decel ofcourse). I noticed a slight vibration as I approach 3k in every gear, but is gone by 3k.

OK, now to where I am: I read that usually the jerking is a dashpot or shutter valve - dont have 'em. I saw maybe driveline slop - I can't twist the driveshaft at all when it is in gear like I could on my old 66 GTO(could clunk it back and forth). I feel like sometimes there is a bit of rolling resistance maybe from the rear on decel off the highway(I have plenty of fluid in both trans and diff), but cant really hear anything over the mostly open exhaust. I read that people say that these cars will do that below 2.5k, but that seems odd that you cant run @ 2k w/o major jerking.

Could it have to do w/ the ignition system?(because of the trailing plug differences) Fuel problem even though the leading plugs say it is running fine for highway cruising and runs like a champ when reved? Rear going out? Also, I had to mess w/ the idle/mixture screws to get it to idle, though poorly, and I have read that they only affect the carb under 2k, is that true?

drittens

oh yeah, I imagine its caused by teh trailing plugs, but during decel, I can hear minor backfiring(not the loud "POW!"(never done that), but just popping of the exhaust like its finishing off the unburnt stuff.

steve84GS TII

Shutter valve.

Its there to cut fuel to the rear rotor under decel,which prevents bucking.The rear anti-afterburn valve permits air to bypass the shutter and enter the rear chamber,to prevent high vacuum from pulling oil in,but there is no fuel.The EFI engines do the same thing by cutting out the rear fuel injector when decelerating.My TII engine makes the same stuttering sound when slowing down.
My old carb'd engines did the same thing,so I replaced the shutter even though at the time I was running no emissions equipment.Once I switched to a Yaw car with no provisions for a shutter,the bucking came back,although not nearly as bad since the Yaw carb had the engine running so much better than my tired old stock carb.

Are you sure the replacement block has the right flywheel?
The vibration in each gear sounds like engine balance,and not all rotaries take the same flywheel/rear counterweight.

Idle screws only affect idle and off-idle mixture.Setting the idle is a balancing act between the mixture screw,idle RPM screw and the RPMs.Its gonna be tough to set right until you get the carb issues sorted out.....1.5-3.0 turns out on the mixture screw is a good baseline to start at.If it wont idle in that range,youve got other issues.

drittens

So, you suggest reinstalling the shutter valve...I bet I have one lying around...how do I need to modify my emissions delete to reinstall it?

Its an 84 engine w/ 82 flywheel/front balancer...I guess I need to swap out for the busted engine's(85) flywheel and counterbalance then...could that cause some of my issues?

Thank you for your help!

steve84GS TII

Yea,thats all bad.
Simply changing the front/rear counterwieghts wont put the engine into balance.Sure the weights themselves are in balance with each other,but the 82 weights are designed to balance 82 rotors........the 83-85 rotors are 1/2lb lighter each, than the 76-82 rotors.It might not seem like much,but over time itll eat your bearings and stationary gears up,especially at high revs.

The bucking can be lessed with good tuning.My engine bucked far less with the finely tuned Yaw carb I used to run,and there was ZERO emissions gear/dashpots/valves on that setup.The stock carb is tuned to run with stock smog gear,and many drivers experience niggling little running issues after removing the rats nest and solenoids/valves.Plus,it sounds to me like you have lots of low/mid speed tuning and mixture issues already.It would be best to cure/lessen the idle and cruise running problems before attacking the bucking issue........but first you need to resolve your engine imbalance problem.

drittens

Well, swapped it all this weekend and, wow!, what a difference! Idles much better and has no roughness will reving, not to mention the shuttering is much less as well. I can even from a full night's sleep start it w/o the choke! I was told that you HAD to use the choke on these cars :P

I still have a vaccum leak to source it seems, and I have another question as well.

Before the pull, I would floor it and it would go, but then after a second there would be a kick and it would start pulling harder(like my secondaries were slow to open). Well about 3 days before the pull, I lost that kick, as if the secondaries dont open at all anymore. I had someone floor it up to ~ 5k so that I could watch if they opened, and they didnt. Is this probably caused by the vacuum leak?

Kentetsu

Reading about the difference in the color of the trailing plugs, I was wondering if you might have the plug wires routed incorrectly. Make sure that each wire is going to the correct plug. I know that's a no-brainer, but it does happen sometimes...

steve84GS TII

Its almost impossible to get the secondaries to open when sitting in neutral.
Check the linkage,then pull the diaphram cover and make sure the diaphram isnt ripped and the rubber gasket is good where the housing and carb mate.You can make the secondaries open sooner by cutting down the diaphram spring,but go too far and your gas milage will be seriously bad.