e36imagica

Hi folks - I'm looking for some recommendations on a strange idle and hesitation problem that my 89 TII (stock) is experiencing. Here are the symptoms:

1. When driving between 750 RPM and 2000 RPM while very lightly "feathering" the throttle, the engine runs very rough and shakes. Also happens during deceleration (in gear) from same RPM range.

2. When driving and suddenly engaging the clutch, the engine RPMs come down normally until they hit 1000 RPM, then it "pauses", then after a second, it goes down to 750 RPM. Sometimes, it'll go down to 500 RPM, jump back to 750.. or even stall every on the rare occasion.

3. When I driving slowly (ie: in parking lot) the car seems to bucks a lot, in other words, it snaps back and forward pretty violently. I know it's not normal since I don't experience this in my 88 RX7 NT.

So far, I have changed the plugs, wires, air filter, fuel filter, cleaned the BAC valve, and adjusted idle control valve. At this point I'm starting to wonder if I could have a bad TPS sensor, EGR valve, or...?? Any ideas and/or recommendations would be tremendously appreciated!

Thanks a million!
Serge

AGreen

iTrader: (11)

Did you adjust the timing, adjust the tps, and check for vacuum leaks? #2 is probably the dashpot making it pause. It's supposed to engage a little higher I believe. You should check the fsm for that.

#3 could be engine/transmission mounts.

calpatriot

How does it idle?
How does it run at high power and high rpm?

If the idle is rough, check for vacuum leaks.
Check for ECU trouble codes.
Check for closed-loop ECU operation under the conditions where the bad behavior occurs (on-off flashes 8 per 10 seconds, on a lamp connected between the center two connectors on the test connector)
Check the tps sensor with an ohmmeter, not only for the max and min values but also for 'dropouts' anywhere in the range of operation.
Broken mounts (see AGreen, above), or excessive backlash in the transmission, dirveshaft u-joints, rear end, or axle u-joints.

HungoverCat

I'm having a very similar problem, everything points to a vacuum leak, which in my case is very probable due to the condition of my intake hose between the AFM and turbo inlet. What's the condition of your hose just for ***** and giggles?

leprachaungold9

any mods? top mount intercooler to front mount? if so you should mabie get differnt fuel injectors? idk just a hunch

e36imagica

Hello gents:

Thanks for all the recommendations! I still have the stock top mount intercooler. The only mod that I've done to the engine is an APEXI BOV (made for the TII). To answer some questions and add clarification:

1. Once the engine warms up, it idles steady at 750 RPM. However, during the warmup process, the idle jumps between 1100 - 1400 RPM.

2. At high RPM/high power, the engine runs great.. really pulls strong.

3. I've noticed the past few days, a lot of time when I'm driving and I engine the clutch, when it idles down the engine will sometimes stall.

4. I have silicone hoses and they all look in great condition.

Thanks again for all recommendations. I will take a look at the TPS and dashpot.

Serge

leprachaungold9

mabie adjust the idel screw just a little bit so it touchs so when it drops in rpm it dont stall out

r3akt

So what was the issue?