germanturbo

86 951 stock except for test pipe, recent work includes unsuccessfully trying to set proper idle with screw in top of throttle body (mine was missing) and replacing plugs, cap & rotor with proper parts (regular bosch plugs, not platinum)

car has always had this problem and I'd like for it to go away

accelleration is very uneven, irregardless of throttle positon...it is herky-jerky accelleration...but when you get above say 3 or 3500, it will smooth out and launch like it should

any ideas?? any help would be greatly appreciated

ehall

need more specific info.

germanturbo

I think best way to describe it would be that the power seems to go in & out rather rapidly...like maybe supply is extremely erratic or timing is all over the board or something like that.

If you drive it like a normal car, feeding in gas as the revs climb, the power comes in & out, in & out, etc, from the time you let the clutch out until about 3000 or 3500 RPM.

If you drive it like a sissy, feeding gas gently as you engage clutch, then waiting for revs to climb, it does the same thing.

If you try to drive it like you stole it from the word "go", it still behaves the same way. Car is cold / car has been driven 3 hours, doesn't matter. It always does this and has always done this.

I have also installed a new, correct 02 sensor.

Any ideas on what I should check? Also, any pointers on properly setting the idle screw in the top of the throttle body? Thanks for the help, folks, i need it.

ehall

check the throttle position switch
check the fuel filter ever changed it? 18 year old car?
Check all of your vaccuum lines.
Check all battery leads, +'s AND grounds The insulation gets really bad, and cables can arch to whatever metal is closest.
Do you have a known good DME relay?

There's a quick start.

germanturbo

check the throttle position switch -
check the fuel filter ever changed it? 18 year old car?
Check all of your vaccuum lines.
Check all battery leads, +'s AND grounds The insulation gets really bad, and cables can arch to whatever metal is closest.
Do you have a known good DME relay?

-how do I check TPS?
-new fuel filter
-will ck vacuum lines
-bat cables & grounds all good
-which relay is DME relay? if same as on NA car, I can swap out for spare

thanks!

reno808

check coil
do you build boost?
check wastegate and bov
check your afm

ehall

best way, that I found, to check tps, is too disconect it. The car will idle about 300 rpm high, but run fine. It's just an easy elimination. Look on the inside of your relay box, and you'll find a little relay map. Get too know it well.
Said it once, i'll say it a thousand more times, the battery cables "look" good, but are usually crap in our cars, that's why Iceshark can get SO many people to buy his cables. His a great. Ours are lousy. Mine looked super. After checking every possible symptom, I found the problem too be way down by the bellhousing. Double check.\

There is also more than one ground.

Charlotte944

You need to go here: Clark's Garage and do some reading through his Garage Shop Manual.

Additionally you might want to update your profile and signature with stuff like where you are and which cars you drive/own. This one small thing can go a long way towards getting in touch with someone in your area.

On the face of it I suspect you have an intake/vacuum leak. It sounds like the engine is starving for air until the boost builds, and I'd bet a 6-pack of cold ones that intake vacuum is going to 0" Hg.

germanturbo

great advice, will double check cables, grounds, etc.

new BOV

wastegate functioning properly...did the grab-the-pipe test...in addition, car won't overboost

builds boost very well...1.8 on internal dash guage

what's best way to check AFM? coil? plug wires? DME relay?

thx guys, you're a lot of help

germanturbo

have checked out much of what you guys have suggested, thx again for the help. (have also read 90% of clark's garage, what an amazing resource)

What's the best way to thoroughly check for vacuum leaks on a 951? I know you can pressure-test a NA 944 from the intake boot back, is this possible on a 951? If so, please explain how.

thx again