I have been battling this STUPID idle/tuning problem for 4 months. I've tested, searched, posted, questioned and queried.

I have a S5 T2. It hesitates through the 1500-2300 rpm range, won't rev past 5500 sometimes 3300. NO power before low boost, almost stalls. High 1500 rpm idle even when warm. Or will surge between 800-1100 rpms.

My mods:
No ACV or AIR pump or cats
Walbro 255 lph hi-pressure fuel pump
racing beat downpipe and presilencer, that's all for the exhaust
hks intake
knightsports FCD
TB mod<-- hasn't run right since..too late now

I have correctly tested my ECU, TPS, CAS, AFM, coil igniters, plugs, vacuum pressure, compression
Seriously, if someone can help me figure this out I'll pay them $50

 

Here's what I would check, in order

1) Vacuum leaks. Maybe one BIG one.
2) A bad injector/injectors. Check their wiring, too.
3) A stuck-open AWSV and/or BACV.
4) A throttle cable that needs to be adjusted.
5) Plug wires - sometimes they're hard to make connect correctly - use the "burping" method.

Let me know how it goes...

Brandon

 

the burping method??

 

As no7yet asid, Vaccuum leaks are a big problem, and your BAC valve can cause a mangled idle. Once you're going, how is it to drive? is it rich? does it studder? What O2 sensor do you have? is it good? How's the timing? is the engine properly grounded? Are there any leaks around the turbo housing? My car did pretty much the same thing - turned out to be the AFM. Any more info would help.
Nick

 

I'd replace the fuel filter.

 

new WIX fuel filter only has about 500 miles but sat idle for 6 months, should I still replace it?
The O2 sensor is a few weeks old
vacuum is steady at 430 hg/mm
Timing is good and spec.
I took a resistance reading of the grounds and body and got .3 ohms, how's that for a ground?

I did find a kink in the IC outlet hose, fixing that solved part of the power problem. It still studders though.

The AWSV is no longer a part of my throttle body... I'll pull the BACV and clean it today. Thanks for the tips, I was thinking injectors or pressure sensor as well. Only more ideas?

 

If you set the whole car idle for 6 months that gas probably got all crappy, and when ran through the fuel filter it could have clogged it, I dont know how much they are for rx7's but they are only like $8 for my mustang, wouldnt hurt

 

If there is a leak in the intake system - especially after your AFM, then you'll have trouble. Make sure that there isn't a hole in the IC piping where it had bent, and check all of the fittings and tubes in the intake system. If air is being sucked in, it won't necessary show up on a vaccuum test. Try just unplugging the BAC and see if it does anything. The crank angle sensor was good? Put timing light on the pully, and see if the timing advances when you rev the engine. If it doesn't, you have a problem. Dumb question, but is the O2 sensor plugged in? (you never know) Ket us updated,
Nick

 

rechecked IC lines, they are good
CAS tested good and the timing advances when revved
O2 sensor is plugged in...
I'll unplug the BAC and see what happens

One strange thing... while the ignition is on but car is not running..the stock boost controller is busy just clicking away.. what does this mean?

 

Stock boost controller? Like the Duty Control Solenoid? That only came on 89+ TIIs? I thought your car was a turbo'd GXL...

Anyway, it sounds to me like you're having several problems all at once.

High idle - check your throttle cables and make sure your throttle plates are in spec. I'll bet that's the high idle problem.

Everything else sounds like a fuel problem. I would drain your tank, change your fuel filter, check your injector connections, and find out whether you've got that big fuel pump set at too high a pressure!!! Without an S-AFC or some sort of fuel correction, your car's going to SUCK with a big pump running stock pressures and duty cycles!

Good luck,
Brandon

 

My car ran docile as stock with a Walboro and exhaust.

 

before you go through all of these other's suggestions check your fuel pressure regulator(swap yours with a fellow rx7 owner's to check). my old car had similar symptoms and i would be willing to bet that that is your problem. my e-mail is joshe47@hotmail.com for when you have to send me the $50 he-he

 

I think the clicking you are hearing IS your BAC valve. It should click away when the key is turned to the on position, without the car being started. To verify this is the case, simply unplug it when you hear the clicking - it should stop.


To further analize your problem, take a good look at your entire intake system's piping. It very much sounds like one or more of your intake tubes are colapsing under vaccum, thereby choking the motor, causing your hesitation.

Do you only see the problems under load, i.e., while you are driving? Or can you rev the engine past 6k RPM while in neutral??

Regards,
Shawn

 

Its a GXL w/ a jspec swapped into it. ALL jspec efi stuff too.. N374

Mike

 

hey i just got mine fixed about a week or so ago...it was doing the same thing yours is doing (from your description)...did all i could to "fix" it but couldn't really find the problem, so i went and got another tb did the re-did the mod, slapped it in...and it's all better now...the problem was that:
1- the tb wasn't bolt on very tight = vac leak
2- the throttle wasn't returning back all the way when you let off the gas = high idle

and keep your $50...so you can get another tb or fix the one you have now...

 

I checked again and it is the duty control solenoid clicking (stock boost controller), not the BAC. They are on different sides of the engine plus the solenoid is vibrating when I hear the clicking. I notice that when I unplug my pressure sensor the clicking stops..hmmm

Fuel pressure regulator? you mean those vacuum controlled solenoids, that sit three in a row on the drivers side of the block...nope, i checked all those per FSM, they work fine.

 

Was yours stuttering as well? Plus I can't get past 5500 rpms..... grrrr

 

If the DSC is oscillating, then it's probably causing a vacuum leak. Unplug it, and cap the WG line that goes to it, and let us know if there's any improvement.

Also, does your car rev smoothly under no load (i.e. in neutral)?

NOTE: Make sure that you cap the WG outlet line VERY WELL!!! If you don't, you could blow it off under boost, and overboost your engine.

Brandon

 

OK, unplugging the DSC and capping off the WG lines helped with the 3300 hesitation some, thats all though

 

and "No" my car doesn't rev smoothly in neutral. It chokes from 0-1500 rpms then again at 3300-3500 then about 5500 I can't get it to go any higher.

 

Mayby start with plug wires backwards, air filter clogged, did you say you got rid of the cats?

 

Yes, no cats, plug wires are right, air filter is removed temporarily...

UPDATE** I removed my TB and there is an ungodly amount of oil/gas deposit, I assume this is an indication of an extremely rich condition....

 

Uh, it's probably more of an indication of a bad turbo if it's oil...

Brandon

 

It's only on the manifold side of the throttle plates, though. There isn't any before the throttle plates.

 

You said that you checked the TPS... Did you try switching it with a known good one? I could swear i had the same problem and it was the TPS.Good Luck