Rickey_85TA

My car acts like it's going to stall when I slightly press the gas pedal, then revs back up if I keep pressing the pedal further.
It started doing this while sitting in traffic Friday night.

On the highway and when I can keep the RPM's above 1000 the car runs ok. It also idles just fine.

This past weekend I replaced all of the rubber vacuum lines to fix my HVAC vents selector, I did the throttle body coolant bypass and adjusted my TPS to the correct voltage range. The car ran great for a couple of days after I fixed these things.

I just need some help by pointing me in the right direction to fix this problem.

malcom2073

Sounds like it might be a vacuum leak, and since you've just replaced all the vacuum lines before it started that'd be the first place I would look. Spray some carb cleaner (The flammable kind) around the lines while you're idling. If at any point the RPMs change, that means you have a leak.

Rickey_85TA

I'm not convinced it's a vacuum leak because all of the rubber lines are new. I checked the connections and they are all snug and tight. On an added note, I pulled one line off about an hour after I turned the car off and it still had good vacuum.
Could this be a fuel problem? Maybe a bad injector or fuel pressure regulator?
I'll do more troubleshooting tomorrow when it's daylight.

skirkland1980

iTrader: (2)

Yes, sounds like a lean mixture, which could be a vac leak. Does this car have a MAF?

Rickey_85TA

If by MAF you mean mass air flow sensor, then yes.
If the car is running lean, would that cause the intake plenum to get hot?
I did the throttle body coolant bypass mod, so the intake should be cool to the touch right?

skirkland1980

iTrader: (2)

You can try cleaning the maf. Some of them are sensitive to certain cleaners, some you can just use brake clean. A vacuum leak can cause a lean condition. That includes leaks between the mass air flow sensor and throttle body. Your intake will always get hot naturally.

Anti-Venom

I would do a tps sweep and check for a dead spot. They usually wear out and send a bad reading where it tends to live the most. Right around cruise to mild acceleration range.

FP issue is going to get worse with load and rpm. Vacuuum leak is going to effect your idle. And a dirty MAF is going to throw a bad reading under any conditions and clear up only under WOT when it goes open loop. A bad TPS is the most likely culprit here.

Eliminating the vacuum to the climate control as being the cause is simple enough. Cap it off from the intake and go for a drive. Those little hard plastic lines can be a pita as they get brittle and can be easily damaged if you've been messing around them. NAPA sells the stuff to rebuild new lines if needed. Just heat and bend.

Rickey_85TA

Thank you to everyone that gave input.
I did some troubleshooting with the vacuum lines and pulled the line off of the intake plenum. The car dies slowly with the line removed and so I simulated a vacuum leak with my finger over the whole, letting some air through, and the idle was very rough.

Can anyone tell me what the big vacuum canister next to the air filter does? I noticed it has some type of sensor on the top of it.

Then I checked the TPS with my digital multi-meter. I did see a jump from .055v to .057v on one turn. I kept testing and the voltage was not a steady incline. Reading .054-.055-.057-.056-.057-.058-.059.
After testing this several times it stopped reading weird and now there is no shudder when pressing the throttle..?
Looks like there was a dead spot in the TPS but it went away, so I'm definitely replacing the TPS.

IROCgiraffe

iTrader: (3)

Did replacing your TPS solve your problem?

Sojer

I would think a MAF

WolfmanTA

Hi There! Just wanted to let people know I had a problem with my 86 TA TPI engine stalling when I gave it gas. Looked up on here for some idea's to fit it. I went to start to take apart stuff. Well I found the problem a easy fit. I started to take off my round K&N Air filter off my MAF sensor and a round chrome cap fell out. Well that came off the center off the inside of my air filter. So I started up my car and gave it gas to my amazement no more problem. I guess that cap was being sucked up to the screen on the MAF sensor cutting off some of the air making the car stall out. I was so glad that was a easy fix. Hope this helps some one out. Cheers....