so i have an 88 FC with an rtek 2.1 FMIC corksport turbo back 75 lb secondaries walboro 255 FP all emissions removed.

today i was heading home for the long weekend. it was running fine the first 15 min and after i passed a truck i noticed it was running very odd. whenever i let off the throttle it jerks and decelerates really hard. then gas a little and it jerks and pushes really hard. so i stop at a gas station and my idle is even stranger. it bounces at 2K. wont go any lower and sounds like a have a huge bridgeport. The AFR is pegged down jumping from 19 to 20 when it does this.

while running if i try to keep it at a constant speed the AFR peggs at ten but if i give it gas it runs back at 13s.

also when i started it up the rpms shot up to about 3. i checked everything under the hood and it all seems normal. nothing undone nothing broken or leaking.

anyone have any ideas? im gonna try to plug the palm pilot up tomorrow and see if i get any error codes. its raining right now and my palm pilot sucks and wont stay connected so well see

thanks in advance
Marshall
USMC

 

anyone got an idea?

 

checked the IC hoses for leaks?

 

yeah. checked those. i originally thought it was the coupler on the AFM to the turbo but it wasnt

 

Spray a little starting fluid around the intake piping to see if the idle changes. You may have a leak in the intake system that is not obvious.

Been there done that. Had a leak on the back side of the short air hose to the BAC that was not obvious until spraying the fluid in that region caused me to remove that hose for inspection. See image. Not saying that is your specific problem, of course.

 

i forgot about doing that. man ive had some crazy times with starter fluid. helped me many many times.

ill get on that tomorrow. weather here still sucks and i havent wanted to mess with it.

 

Tps

 

just checked the tps two weeks ago. it was out of spec. used the rtek and put it at 20%. ill check it again.

i was actually thinking that could be the problem

 

ok update on this

nothing has changed. i checked the tps it was at 23% put it back at 20% same problem

sparyed starter fluid. got nothing. im not sure if im going to be able to tell if there is a leak or not because the idle is pulsing and even when i spray it on the filter it doesnt change.

i checked every hose and nipple i could think of and i cant find a single leak. its weird because when im going down the road its running rich but idle is very lean.

any help is appreciated.

this is the first time ive been stumped on a problem with this car.

 

I don't know what you mean with the TPS percents. all I know is when you spray brake kleen everywhere and the idle doesn't change you don't have a vac leak. so the only thing that would make the idle jump up and down is the TPS. then again my experience only comes from s5 since I can't remember the last time I owned a s4. now if this is not the case with the lower series I'm going to throw my coupe and vert away and snag an 10AE.

 

well when i hooked up the palm pilot there is a way to check what the tps is reading. the normal % is supposed to be 20. so it being at 23 isnt bad. it usually fluctuates every once in a while.

 

pressurize the intake system to check for leaks, you may catch something that you didn't find with starter fluid. check sparkplugs.

 

What kind of wideband are you using? Does it send a narrowband signal to your rTek? You don't have two O2 sensors hooked to the same input, right? How is your tune? Have you recently made any fuel or timing changes?

 

im using a prosport wideband. it does not send a signal to the rtek. no, only one o2 sensor. the tune is good i checked over it again. it was running perfect after the tune and this happened all of a sudden while driving and the palm wasnt hooked up.

im not getting any error codes so im thinking after i get back from pre deployment training this weekend ill take apart the intake setup and check it over again.

could the maf cause this? if it had gone bad(dont know if thats possibe) would it put out an error code?

oh and the spark plugs are good. they only have about 200 miles on them

 

you have to check the tps sweep, not just with the rtek. Unplug it and check the resistance. Forget which plugs you check but there are tons of threads on it. Idle spec is ~1k ohms and wot is ~5k ohms. Make sure there are no dead spots while you are going from idle to WOT. I doubt it is the tps though since the rtek says its in spec for idle and your idle is way off.

If you have a BAC try lowering the idle with it. It seems to me like the car is getting more air than it thinks it should be, which means the BAC is malfunctioning

 

Could it have anything to do with fast idle cam or thermowax?

 

all emissions are removed also.

at this point its either gotta be fuel or pulling air from somewhere. those are the only 2 things i can think of that would cause this. i just need a weekend to pull it apart and check everything.

 

anymore ideas?

 

This. You'll find leaks really fast

 

The TPS should read 20% on the RTEK because a properly rigged TPS will output 1vdc. The 1vdc is 20% or the possible output of a TPS. That explains why it should read 20% on a RTEK 2.1

If the engine is not fully hot, then the TPS will read higher than 1vdc but will come down to 1vdc once the engine is fully hot which makes the water thermowaxs piston fully extend.

As for the TPS being good/bad, just watch the reading of the TPS on the Palm while you slowly depress the gas pedal. The reading should rise evenly to approx 5vdc. Approx means 4.85vdc is fine and dandy. As you depress the pedal the reading should not abitarily drop from a high figure to a lower figure or flat disappear off the scale of the meter.

TPS don't cause engines to idle at 2-3 grand.

Spray the starter fluid around the rear of the throttle body where there are the nipples for the brake booster, OMP spider, air bleed hose, water thermo valve and see if they are cracked or one is wide open and not connected.

Check the air hose b/t the bac and the turbo outlet connection. Check the three nipples on the front of the intake manifold. Cracked TID inlet duct and any of those ducts connected to the turbo.

Look for something holding the throttle linkage open. I've had the black cam for the double throttle linkage crumble and hold the throttle linkage open before. It's on the left front side of the throttle body.

 

thanks hailers. this is the list of the the things ive needed to check.

your the ****. ill update this weekend when i go to work on the car.

 

Tttttttttttttttttpppppppppppppppssssssssssssssssss sss!!!!!!!!!

 

I 5hi7 you not check under where the throttle cable connects to the throttle body. My 10ae ran great one day then the next I started it and it would jump right to 3 grand and I could do nothing to bring it down. Moral of the story, acorns. Somehow an acorn jammed my throttle open. Spent the better part of a week to figure that out.

 

edit: read that wrong. although an acorn jamming the throttle blades would be kind of funny

 

Id be less curious about how it jammed the throttle plates open and more curious how it got passed the turbo if that were the case lol