Hello everyone and thanks for reading. My 92 RS 3.1L manual trans has been running great for the longest time. Recently out of nowhere its been giving some hesitation issues, and I just got this baby painted black too Here's a description of the problem

- When trying to accelerate from a stop, as I press the gas it will kind of "choke", for a second the engine stops accelerating then it will catch and allow me to accelerate

- also if I'm in a parking lot going low speeds it sometimes cuts in and out as I'm giving just a little throttle

- other than that it still runs good besides a slight lack of power, at higher speeds there are no real issues noticed. it only seems to act up the most when I'm in the lower throttle ranges alongside trying to accelerate from a stop.

parts that have been replaced within a years time before now:

distributor
distributor cap
plugs
plug wires
Ignition Coil pack
map sensor
EGR
O2 sensor
IAC sensor
PCV valve
thermostat
fuel filter
TPS sensor - (just replaced the tps trying to fix this problem, it didnt help)

also oil and air filter have been changed recently.

Any help would be appreciated I look forward to hearing your thoughts.

 

Try cleaning your iac valve. If its sticking just a tiny bit it could be robbing air from your engine just for a second.


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thanks buddy, i suppose its possible the iac could be sticking or maybe got some gunk. ill check that as soon as i get off work and post a result

 

Alright. Let me know


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so i removed the IAC, it still looked brand new and the pintle had no problems moving like it should. scratching my head at this point

 

Have you checked the coolant temperature sensor/connector?

 

is that the sensor that controls my temp gauge on the dash?

 

I don't know about 92s.

Some cars have 2 sensors. 1 for the gauge and 1 for the ecm.

Some cars have 1 sensor. 1 for the ecm AND the gauge.

On my 88 there are a total of 4 sensors. 1 fan switch, 1 gauge sensor, uh, 2 ecm sensors? lol.

The reason I ask is because a broken temp sensor will default to -32'F and will tell the ecm to begin dumping fuel into the engine - seriously destroying driveability. It's a common failure to check on older cars.

Your car will probably have a 2 wire sensor that looks like this - located in the front of the lower intake manifold. Wires should be black and yellow.



This is part # SU109


This is the resistance table you reference when checking the temp sensor. You will need an OHM meter to check the resistance. Also closely examine the plug to see if its corroded or broken.

 

Thanks dude, after inspection I do see that I have two separate sensors, one with a single wire (which is for the temp gauge) and the one you speak of which has two wires. I dont have an ohm checker, but I looked up the part and its only 10 bucks so I may just throw a new sensor in there and see if that fixes it, will let you know what happens as soon as I can change it out

 

It's just a stab in the dark but I hope it works out for you.

 

sorry its been so long since I posted. Okay, I switched out the coolant temp sensor and it made no difference. for some reason my car is idling at 1500rpm now and the idle is really choppy and rough. im not sure whats going on

 

Have you checked it for vacuum leaks?

 

i visually checked for vacuum leaks and even did the wd40 spray test and found nothing. i just went to get pizza and it seems like its getting worse. when im approaching a stop sign with foot off the gas it will stay at 2000rpm then after i stop it will drop right down to 1000-1500. also i was at a red light and when i pressed gas to go it acted like it was gonna die then started going after a small struggle. everytime i drive it now im scared its gonna stall out in traffic.

 

Another note, these idle issues didnt arise until after i messed with the tps. Is it possible i did something wrong with that? Theres no adjustment you just bolt it on

 

YES. THAT COULD AFFECT IT. Tell me. did you just put it straight on and bolt it on?


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the tps had to be rotated counter clockwise a tiny bit to match up with the bolt holes.

 

And so you lined up the teeth on the tb and tps then rotated it counter clockwise afterwards then bolted it down?


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yes exactly

 

Aight. Well you did that right then. Have you checked out your intake manifold gasket? Your tb gasket?


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Those were replaced in like november, i didnt really look at them.

 

Do you have an aldl connector? Just to check if all sensors are working? Ohhhhhhh. Check the iat yet?


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broken wires at the MAF connector. Give them a jiggle and see if it changes anything.

 

Dont have any diagnostic equipment. If youre talking about the iac it was clean.

 

You dont have a maf. You have an intake air temperature sensor. If the wires are broken that will cause huge problems


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Is that the sensor located on the canister for the air filter?

 

Yeeesss! It is.


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Check resistance across the sensor. Then voltage output. Or take a screwdriver and hit it while the car Is on. if it stumbles then it's bad


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Ill look at it tomorrow. Ive been dicking with the car all day and im tired lol. Whenever something is wrong with my car it really eats away at me. Ill tinker with it and repost later

 

I get you. I've got a 91 camaro 3.1 and my girlfriend hates my car because I spend more time working on it then with her xD well. Let me know tomorrow man.


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So i tapped on the air cleaner sensor with the car running and it didnt make any changes. I took off the tps and reinstalled it just to make sure it was on correctly, my idle improved a little but its still too high and not as smooth as it should be. One of those damn torx bolts for the tps snapped! So now my tps is being held on by one bolt. I hate those things and have no idea where to get replacements

 

Oh damn. That sucks. Really you could get one from a scrapyard. I have like 8 extra from various runs. Since the fuel rail has them the iac everything lol.

Back to the iat. Are you running rich? (can you smell the gas?)


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As far as i can tell theres not a strong gas smell coming from it. And i cant figure out how to adjust the idle. I read that theres an adjustment screw but i dont have an adjustment. I pulled a spark plug to check that and the tip of the plug was white i wonder if thats the issue

 

Hmm. Well you stated that the plugs were new. So something is messing it up. Does the white stuff wipe off? And have you done a compression test?


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The plugs were replaced late 2012, and i have no way to check compression. The only equipment i have is sockets and wrenches. Im at work now im gonna have to look at it more when i get off

 

Um, did you remember to disconnect the battery for a few seconds after replacing the sensors? The ECM needs to reset and get used to the new parts first.

The IAT and the CTS should have nearly the same resistance when the engine is cold as they are pretty much the same thing except the CTS has the thermistor enclosed in brass to protect it from the hot coolant. Tapping on either won't do anything as they aren't vibration sensitive like the knock sensor or the MAF in earlier cars.

Pull ALL of the plugs and take a pic. The plugs are the best indicator of how the engine is running since they are the only readily removable part exposed to the combustion process and can tell you the condition of the burn.

 

When i replaced the tps, i disconnected battery first then reconnected after installing the part. I Just put in a new coolant temp sensor a couple days ago. Im gonna pull every spark plug and see whats going on with those

 

So i pulled the plugs. The plug pictured is what every single one looks like. Then check out this sleeve, its gone like a ****. This has got to be part of my problem from the looks of it lol that sleeve is horrible! Replacing the plugs asap and that bad wire asap. Will repost as soon as im done. I would buy a whole new set of wires but cant afford it after buying 6 new plugs so im just replacing the bad one.

 

So i replaced the plugs and that shot wire, the car does run a little better but still has a bad idel and some sluggish issues. I got ahold of a fuel pressure tester and my fuel pressure wont go above 30, does that mean my fuel pump is bad?

 

it could mean that. since you do have the pressure tester. remove your fuel filter and stick the pressure tester there and just prime the pump (turn the key to run) check pressure. if its higher than 30 then your filter is restricted. if when you pull the filter any color but clear gas comes out thats a problem. replace on spot. if you do get 30 psi at the filter then its pretty safe to safe yes you probably need a fuel pump. in which case. check something... lift your rear hatch. push your back seat forward then pull the carpet from the front. see if someone has cut a hole in the metal there. if not then your dropping the tank to replace the pump. :/

 

The pressure tester was a loaner from the parts store, i dont have it any more i used it in the parking lot. But i did replace my fuel filter a couple days ago trying to fix my problem so it cant be the fuel filter right?

 

Correct. Means either your lines are clogged. Or your pump is weak. Check the voltage at the fuel pump relay. (driver side engine bay) ( to the right of the brake booster)


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on second thought i was under the impression that if a fuel pump went bad, it just doesnt work anymore and you cant drive the car. I didnt think there was an inbetween where it works just enough for the car to be drivable. like i said before, once I get up to speed the car still cruises almost like normal

 

Probably a dumb question, but did you put the fuel filter in the right way? They only go in one way but can be installed backwards due to both ends having the same fitting. There is an arrow on it saying "FLOW ->", with the arrow pointing TOWARDS the engine.

And with the way that plug wire boot looked, you may be looking at a new ignition coil as well if not a module also. The secondary ignition system doesn't like having the spark go to ground any other way than through the spark plug gaps.

Also, the only plug worth using in the 3.1 is a standard Delco R43TSK. Anything else and you're just putting money down the drain (looks like a platinum plug there, you can buy 2 R43s for what you paid for just one of those!).

:edit: The fuel pump can fail to flow as much as originally designed, in which case, it gets replaced. But only after making sure that there are no restrictions between it and the fuel rail.

 

He covered it all. Thank you Mav


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I was very careful to install the fuel filter correctly. It does indeed have the correct flow. and the ignition coil and module were both replaced with new ones earlier this year, dont know if that makes any difference. funny thing is, im hoping it is the fuel pump thats going bad so i can stop guessing whats wrong lol

 

I understand that completely. I've had a rough idle since I got the car and replaced damn near everything. It's a frustrating feeling for sure.


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I just want some reassurance here from you guys before I do the daunting task of replacing my fuel pump this weekend. My fuel pressure wouldnt rise above 30 psi, and my fuel filter is brand new, its GOT to be the fuel pump right?

 

I want to tell you yes so much but I can't. Without properly testing pressure all the way to the fuel pump and testing voltage to it you could do it and it could be something else. Has your car sat for a long time before you got it? **** your tank might be bad. It might be the sock on your pump. Without proper testing throwing a pump at it is like saying I have a power steering leak I must need a power steering pump. Know what I mean? I say borrow the gauge one last time and check for sure. Because dropping the tank is not easy. I've done it 3 times now and I hate it so much.


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mcrandrz i had another question. youve installed a tps before, we are certain that the tps on 1992 3.1L does not need any type of adjustment right? my idle is still really weird too and the idle issues didnt come up until i put in a new tps. I even tried reinstalling the old tps and it didnt change anything. I did disconnect the negative battery cable before changing the sensor

 

100% non adjustable. I promise.


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