I bought my 87 turboII at the end of november off of a member on this site, it had a hesitation or load up under light throttle at 3k rpm's and under. After 3k rpm under light throttle it runs how it should, and mid-wot it runs how it should as well.

I tested everything on the car, did a tune up, tested everything I could with my DMM and I couldnt find anything wrong besides the tps wouldn't read past 2k ohms.

So I had it towed to JPR Imports Dec 2nd. He sent out the injectors to get cleaned, thought they could of been it but they were not the problem. He tested out another ECU and that wasn't it either. Jim said after that he checked all of the wires on the wiring harness and they are all fine.

He said he doesn't know what it is but it's not electrical, so he's going to do a compression test, he thinks maybe a seal is stuck.

I only got to drive this car for one day, the motor pulled very strong and pulled good vacuum as well and only had that problem under light throttle so I figured the motor was perfectly fine and it had to be something electrical.

What do you guys think?

 

The TPS not going beyond 2k ohms is an issue that should be addressed and could very likely have a lot to do with it. With the TPS not going over 2k ohms the car would likely get stuck in closed-loop under moderate throttle.

 

From what Ive read the slightest problem with your TPS can cause these problems.

 

He replaced the TPS from what I understand cause I made sure he knew about that before he started working on it.

It only exhibits this problem under 3k, but could it possibly be a ground cause I remember seeing the ground on the engine looked a little rusted, or could it be the wiring at the fuel pump?

I just don't understand how it could be the motor, it idles even, no smoke, pulls extremely hard under wot and pulls good vacuum

 

I'd check the TPS and it's sweep range to make sure it's within spec (just for giggles). Grounds can sometimes be an issue as the secondaries come online, but that's usually not right at 3k rpm.

 

Just to add to the theories...I wouldnt think it is fuel pump wiring because you would really know if it was messed up there. Id definitely check all the grounds because that would be good for the car in general.

As for the TPS again, he says he replaced it, but Ive heard they are fairly hard to acquire. Maybe he told u he replaced it but didnt. If it isnt reading as it should then fix it

 

The car is still at the shop otherwise I would be able to check the tps and clean the grounds.

I just talked to him 2 hours ago and thats when he said I tried another ecu and checked the wiring harness and everything is fine then said he thinks it could be something in the motor like a stuck seal.

Its been in his hands since dec 2nd. It idled even, 0 smoke out of the exhaust, good vacuum, and pulled hard under wot, so I don't get how it could be the motor.

I figured it would of been a simple fix and would of had it back by now since its currently suppose to be my daily driver.

I just don't know what i'd do if he says its the motor even though I don't see how it could possibly be the motor since the only problem the car showed was a hesitation or load up on light throttle under 3k rpm.

I made a post on here before I put it into the shop, told you guys id update you guys on what was wrong after it got fixed.

I am just trying to think of anything that could be causing this besides the tps, ecu, injectors and the ecu wiring since he said he either checked all of those or replaced them.

 

Id have to agree with you, sounds like a logical pattern of thought...But that doesn't address the fact that your TPS only read less than 2k ohms. Is that WOT or idle or what?? From what Ive learned its supposed to be up at 4k to 6k @ wot.

 

before I put it in the shop I set it to 1k at idle while opening the throttle it went up to 2k ohms which was almost at wot then at wot I would get no reading from the DMM

 

It should move from ~1k ohms to ~5k ohms, if it goes open (or to infinity) on your MM it's a short in the TPS and will cause all kinds of silly hesitations and trouble. Have you driven the car since the new TPS was installed? I'd figure a new TPS (that tests fine, at both the TPS and the ECU) would've resolved the issue after saying that. Also, the S4 TPS is narrow range, it typically reads from 1k ohms at idle to a max of about 5.2k ohms at around 35% throttle, afterwards from then on to WOT it just reads it's highest value. It shouldn't be linear all the way to WOT, it should max out pretty early.

 

When you tried to check your tps was it disconnected?

 

No I havent driven it since he said he put in a new tps, the car is still in the shop, I havent went to the shop at all yet since I had it towed there.

 

I checked it when it was connected and disconnected after I had the car warmed up. JPR said it was faulty and said he replaced it.

 

I think at this point, if your TPS really was faulty originally it was very likely the cause of your problem. I'd have the new TPS tested to verify it sweeps from 1k-5k (or around there) from closed throttle to about 30-40% throttle. If it takes full throttle for it to sweep, or it's not sweeping there's possibly something wrong with the linkage that's attatched to the throttle plates. Have them check the TPS operation, if it checks out my guess is your problem would be resolved.

 

Ok so your saying when I go to get the car check the tps. It should sweep from idle (1k ohm) to 30-40% throttle(5k ohm), if it takes wot to get to 5k ohm or if it doesnt go to there then I should look at the linkage connecting to my throttle plates and see if its damaged correct?

 

In short, yes. Or even ask your mechanic to verify that the cars having problems with the new TPS installed. I would think that given what you said previously about your old TPS, this would've solved the problem completely. An engine issue would result in idle/power issues, usually not have much to do with light throttle at all. I usually find it's either because the vehicle sticks in closed-loop too long, or there are 'blow-opens' in the TPS sweep.

If you check the TPS and the new one is having issues (either only reads to 2k at 30-40%, or takes all the way to WOT for it to sweep up to that value), look at the TPS plunger itself, you'll see it rides on a metal cam which slides against the plunger and pushes it in as the throttle closes. If that metal cam is in contact with the plunger throughout the entire range, it's either been damaged, or tampered with.

I've seen people intentionally modify it to do this for use with aftermarket ECU's or even SAFC's so that they have full throttle feedback, but on a stock ECU it'll introduce trouble.

 

I will call tomorrow and ask, I remember when I was checking the tps and the cam that rests on the plunger would move way further then the plunger at wot.

The plates being out of spec does seem like that may be it because the engine might be getting more air then its thinking causing the hesitation on light throttle under 3k rpm.

 

I have a quick question, if I bought a rtek 2.1 ecu installed it and tune the fuel and timing tables wouldn't that be a way to rid of this hesitation since the maps are based off of load and the tables are programmed into the ecu? It would know how much fuel and timing to deliver at each rpm point so I would imagine that would resolve this issue that can't be figured out.

 

I decided not to call today cause I really don't want to bother him since he said he replaced the tps, cleaned the injectors, tried another ecu, and checked all of the wiring on the harness.

I just thought that this would of been a simple fix like replacing the tps since it seemed like something minor due to the hesitation only occurs under 3k rpm only under light throttle.

Never did I think that I would be without a vehicle for over 6 weeks and there would be something wrong with engine.

I'm just hoping my luck will turn around soon and not have to deal with so much stress.

 

Have the guy check the injector clips to the Injectors.Primary injectors.(for the hell of it.)
I had a slight Misfire/bog on my car and it was a bad connection at the injector.It was just "on there" but not totally connected,when the engine starts 'vibrating' due to Revving it would shake the primary injector clip and create that scenario.

 

When he calls me I will ask, I would imagine that he tested them with a DMM since he said he checked all of the wiring and said if the ecu swap doesnt benefit at all then he would check the injector wiring to see if its bad at any point in the wiring.

 

I talked to him this past wensday, he said the car is all apart and since he has so much time into it he said he has to fix it. He asked if I had a wiring harness for it which I don't so I said no, so I guess hes going to try another harness and see what happens. I am hoping this will be finished soon.

 

Ok JPR imports called me yesterday, he said he replaced everything around the motor like the coils injectors etc and said the car still showed the hesistation/load up under light throttle below 3k rpm.

He said hes tried everything and it must be the wiring harness cause thats the only thing he hasnt swapped out for a different one, so he wants me to find a harness and get it to him so this thing can be fixed i hope.

He even tracked down the original owner of the car, said the original owner said when he dropped in the new engine it showed the problem and he couldnt figure it out and thats why he sold it, and im guessing thats why the forum member on here sold it to me.

I really would of never thought that this car would be in the shop for over 2 months, figured it would be a easy fix for JPR and I couldnt figure it out. Figured he would of had it fixed within a week but instead seems like it turned into a nightmare.

 

Damn this really sucks, I feel like im screwed and def got screwed. Getting this thing to run correctly on a stock ecu/wiring harness correctly isn't going to happen

 

Well, lets start from the very begining again. Can you better describe exactly what's happening? For example, if you're at a stop sign/light, cars idling at 750rpm, you rev to about 2k, ease the clutch out and roll forward @ about 20-30% throttle or so, does it kind of hesitate/buck/surge around 3k rpm? Describe exactly what it's doing and I'll toss some more idea's out. I'm afraid to know what this is going to cost you, especially since they kind of went at it from the 'lets just randomly replace everything' approach.

Also, it's going to be a real pain to help when you don't have the car in your posession. Like it'd be useful to know if the car goes lean/rich at this area, and it'd go a long way to having a passanger with a DMM to do some tests while you're driving around reproducing the issue.