I've been having this problem for a while now
it's strange because it's not consistant but it mostly happens when i'm decelerating
but the problem is when i'm going in or out of the gas there's a point where my RPMs start to drop and I'm not getting any response from the throttle
it happens when i'm barely pressing in as to slow down or try to keep my speed steady (if that makes sense)
if i start pressing in on the gas it will eventually lurch foreword making my car jerk around
if I keep the pedal steady my engine will start to bog out
like I said it doesn't always happen but it's starting to become worse and I can't keep a steady speed on the road

I gave it to a local shop that did my heads when they started going bad so I figured they would know, I left the car with them for 2 days and they were clueless :( I know I can't afford to take my car to Subaru dealer but I'm thinking I might have to

I should also mention that my TPS, timing belt and spark plugs have replaced recently
I would greatly appreciate any imput you guys would have

Has the EGR valve been checked? If it is sticking and not closing properly it can cause symptoms like this.

I should also mention that my TPS, timing belt and spark plugs have replaced recently

Did the problem start after this work? If so, I would suspect that the TPS needs to be adjusted.

Did the problem start after this work? If so, I would suspect that the TPS needs to be adjusted.

I second that. Subaru TPS are tricky to adjust. Go to dealer.

You might also want to adjust your throttle cable to take out any slack.

yes this happend after the TPS was replaced and the throttle cables were checked for slack

I don't think the TPS was adjusted
I think the mechanic said it had somthing with the ECU adjusting to the TPS?
if this is the case then I'll have to take it to Suabru
any idea how much this would cost?

Thanks guys! :D

Are you saying, how much would it cost to adjust your throttle possition sensor?, Or are you saying how much would it cost to have a Subaru Tech check out your ecu?

Because You could adjust your TPS as long as you own a phillips screwdriver. If you want a tech to look at it, at the very least, it will be $75 for them to even look at it.

No, I think the dealer needs to make good on his prior work and adjust the TPS for free.

they should but I'm not so sure they know how...

I asked the service station about it and they said that the TPS can't be adjusted but if I could find some documentation on it they would happy to help me so I'm searching Google and all I've found so far was this link about adjusting it for a SVX

http://forums.nasioc.com/forums/showthread.php?threadid=3801

I also found Alldata.com but I have to purchase that information
if anyone knows where I can find some info on MY 98 impreza that would help out a lot

Check out this thread: TPS Adjustment (http://forums.nasioc.com/forums/showthread.php?t=646948).

As it turns out, you can't adjust the TPS, but you can adjust the idle switch.

(your board settings prohibit you from receiving PMs, btw)

oh that's probably because I was in the process of changing my email address
I actually saw your thread while I was searching today, hopefully those diagrams will be what the shop needs to fix the problem

well I had my TPS examines by Suabru and they said nothing is wrong
they suggested I change my fuel filter so I did, still having the same problem
any other suggestions!?

Water in the fuel, maybe? Throw in a bottle or two of injector-friendly drygas and see if that helps.

As it turns out, you can't adjust the TPS, but you can adjust the idle switch.

Just for the record, on a 98 2.5 RS, the TP sensor CAN be adjusted and there is NO Idle Switch.

yeah, Subaru told me it was adjustable but it was functioning normally

its your spark plug connections either coil to wire or wire to plug!!!!!!!

i say so on because this happened to me yesterday on way to help out at an autocross/driving school in heavy azz fog the car was horrible on the highway i had to keep over 50% throttle or the car would just slow down... i got there in notime coincidentally

i found heavy buildup on the coil-wire connection and there is evidence of arcing so i need to see what i can do about stopping that. it happened again mid-day when i was doing a slalom in pouring rain. cleaned the connection and its ok.

i hadn't driven it in a few weeks i thought something major had took a crap but its just a crap connection. good luck

Just for the record, on a 98 2.5 RS, the TP sensor CAN be adjusted and there is NO Idle Switch.


For the REAL record no Subaru TPS is adjustable. They come pre-set from the factory. DO NOT under ANY circumstances adjust it.

You have the famous "phantom problem" and most places will tell you the same thing. Just wait till it gets worse and it becomes reproducable then bring it in. If you have a tps failure or any other sensor failure usualy the check engine light will come on and a hard code will be stored. Go get your OBD II scanned and see if any stored codes are found.

I have access to alldata trouble shooting procedures but if you don't know what you are doing you could do damage to your car. If you feel you know what you are doing and have an appropriate high impendance multi meter (20mega ohms would be fine) I can send you the data on where to check at your ecu harness and what values to check for. I suspect though that something is loose between the tps and the ecu or the tps is defective. Why was the tps replaced to begin with?

For the REAL record no Subaru TPS is adjustable. They come pre-set from the factory. DO NOT under ANY circumstances adjust it.

Adj789 said that S U B A R U confirmed it can be adjusted. Alldata also confirms it can be adjusted and has a procedure to do so. If you wanna go argue that it cannot be adjusted go argue with subaru and alldata.

For the REAL record no Subaru TPS is adjustable. They come pre-set from the factory. DO NOT under ANY circumstances adjust it.

Mitchell also shows it as adjustable.

Adj789 said that S U B A R U confirmed it can be adjusted. Alldata also confirms it can be adjusted and has a procedure to do so. If you wanna go argue that it cannot be adjusted go argue with subaru and alldata.


And if you would read Subaru's manual's and go to the proper service manual corrections, oh and also be trained by Subaru you would know that it is not to be adjusted.

And if you would read Subaru's manual's and go to the proper service manual corrections, oh and also be trained by Subaru you would know that it is not to be adjusted.

You are an idiot. So if the tps is replaced then how would you go about NOT ADJUSTING IT so it works properly? I understand that it is factory set and should not be messed with unless it is replaced but that is not the point. The point is IT CAN BE ADJUSTED. Which is exactly 180 degrees from what you claimed.

Adj789 said his tps WAS REPLACED. Hence it needed the adjusting that you said could not be done. Funny how SUBARU said it was adjustable. So who is right you? (who claims to be subaru trained) or SUBARU ?

You are an idiot. So if the tps is replaced then how would you go about NOT ADJUSTING IT so it works properly? I understand that it is factory set and should not be messed with unless it is replaced but that is not the point. The point is IT CAN BE ADJUSTED. Which is exactly 180 degrees from what you claimed.

Adj789 said his tps WAS REPLACED. Hence it needed the adjusting that you said could not be done. Funny how SUBARU said it was adjustable. So who is right you? (who claims to be subaru trained) or SUBARU ?

You are not even worth my aggravation

Since you chose to come out here with the name calling I will no longer be providing any help her. The end user cannot properly adjust it, so if you want to choose to continue spreading mis-information and help him screw his car up then be my guest.

I'm done with this thread.

Um, for the record, I'm pretty sure hondaslayer is a Subaru tech somewhere, so it would logically follow that he has the knowledge (or at least the access to the proper knowledge) to tell you something as simple as what can and can't be adjusted. Just my opinion. Read some threads, he generally knows his stuff.

You are not even worth my aggravation

Since you chose to come out here with the name calling I will no longer be providing any help her. The end user cannot properly adjust it, so if you want to choose to continue spreading mis-information and help him screw his car up then be my guest.

I'm done with this thread.

It is black and white C A N the tps be adjusted. People here have said it can and you said it cannot. Alldata said there are screws you can loosen and turn the tps to adjust to proper voltage (.45-.55v dc at E30 connector between terminal 4 and 15) reading when throttle closed. I even went by the local subaru dealer to confirm. YES THERE ARE ADJUSTMENT SCREWS ON THE TPS.

This is pure and simple statement of fact which you said was false. You are wrong, it C A N be adjusted.

How can an end user not properly adjust it? The only tools needed are a screwdriver and a Multimeter. Oh yeah, lots of training needed for both of those "expert only" tools. :rolleyes:

Um, for the record, I'm pretty sure hondaslayer is a Subaru tech somewhere, so it would logically follow that he has the knowledge (or at least the access to the proper knowledge) to tell you something as simple as what can and can't be adjusted. Just my opinion. Read some threads, he generally knows his stuff.

It was his "for the REAL record" snotty remark that started this. Now had his snotty remark been true that would have been the end of that but it's not. I have confirmed through Alldata that it is adjustable. I passed by (on way home from work) a subaru dealership and looked under the hood myself. (new car though not a 98) I also talked to the service manager which didn't know so he walked me to a REAL TECH. That REAL TECH said on 98's impreza you can loosen and turn to adjust the tps. Snotty remarks should at least be true.

You are not even worth my aggravation

Since you chose to come out here with the name calling I will no longer be providing any help her. The end user cannot properly adjust it, so if you want to choose to continue spreading mis-information and help him screw his car up then be my guest.

I'm done with this thread.

Hmm the name calling thing, that was in rather bad taste. Borne out of frustration on why someone would say something different from what several people had said to be true. None the less my apologies for name calling. It was improper and out of line.