Possibly bad tps need some help

35th

Registered User
So having a studder issue when opening op throttle and random idol changes followed some post about checking tps so I metered the ~~~ wire and got 5.04 volts KOEOFF but it doesn't ever change no matter how I open the throttle body whick is a BBK 70mm so does this mean tps is bad?? I would assume thats what it means
 
Absolutely no offense ment so don't take it wrong but do you (kmt) have another job only reason I say that is cause you're the 1st person to answer every question and and certainly appreciate you and your knowledge and willingness to help me so I think your right I was probably on the wrong wire as I do not have a evtm manual and basically am new to the Super Coupes so it is and has been a learning cure but thank you for the guidance I will check it based on what you said
 
I'm retired, love these cars, always willing to learn more about them, and happy to share info/give back to the community when I can. I've heard it's not so busy here as it is on facebook, as an example, but I don't spend time there, so...

In addition to an EVTM, don't forget we can access factory wiring diagrams here on SCCOA. This is the link for a 1990 SC:

http://www.sccoa.com/WiringDiagrams/1990 SC Wiring Diagram.pdf
 
That makes 2 of us

I am retired too, and do not spend time on FB. SCCoA is my "go to" place always. However, my hat's off to KMT as he is one of the real 'Ambassadors to the many' who come here for Super Coupe / XR7 knowledge.

The wiring diagrarms I've found to be even more helpful than the already good EVTMs.

Cheers :)

Colonel Glenn
 
Well gentlemen the both of you are greatly appreciated and your knowledge is exceptional
 
KMT has helped me quite a few times. I’m always amazed at how fast he responds to posts and how much he knows about every problem I seem to have.
 
Just measured tps following your instruction and I get. .8 with the throttle closed and 4.4 at wot that sound right of course this is Key on engine off
 
Sounds like you're doing it right ;)

What did you observe while gradually going back/forth open/closed? As long as the volts increased/decreased smoothly and consistently, with no sudden jumps/drops, I'd want to say that TPS is good.

I have seen some TPSs act up under different temperature conditions, or break contact at far end of either swing, so keep that in mind.

Remember, it's not about the -exact- voltage output at a given point with our cars, it's about the range between low/high that the EEC looks at.
 
It seemed to me as it was smooth as I slowly went from 0 to wot the volts changed consistently and also from wot to 0 so it seemed smooth to me I wonder what else would be acting up then.
 
Hmm, well...stutter - let me think.

Let's go over the basics and see what the factory Emissions Diagnostics Manual has to say.

Is your issue best described as:
  • rough idle
  • low idle
  • misses under load
  • hesitates or stalls on acceleration
  • lack of power
  • surges at steady speed
Is the check engine light on and sorry if I missed it, have you pulled codes?

How many miles on the BBK?

What vacuum do you see at idle?

I've got some ideas, but if possible I want more info first, thanks.
 
Most issue is under medium to heavy acceleration feels as if your slightly pressing the clutch but it certainly not coming from transmission cause you can audibly hear the engine change and no CEL until it studder the light will come on for about 2-5 seconds and go right back off last time I pulled codes didn't have anything about that there where some codes but unrelated not sure what they where now I don't have a way at the moment to vacuum test and don't know mileage on bbk bought the car with it already on I've driven the car aprox 300 miles so far
 
And by change of engine I mean rpm stops going higher momentarily instead of going up without accelerating as it would with a slipping clutch rps don't fall they just don't go up smoothly more of a jump as it climbs sometimes it does it very little other more haven't been able to pin a factor of what causes it worse times than others
 
Last edited:
Most issue is under medium to heavy acceleration

I assume you've no idea how old the plugs and wires are? Does the tach jump around or engine shut down when it happens? Is the car ever hard to start, taking more than one try?

Have you cleaned the MAF?

The book keeps pointing to TPS and/or injectors, but, missing/hesitation on our cars frequently points to plugs/wires. That said, 100 miles/tank screams injector problems. if one or more is leaking/stuck, it can cause a misfire, among other problems, including raising hell with O2 sensors & cats. Do you smell fuel on the dipstick? Can you put a fuel gauge on the injector rail to check/watch pressure?

I know on my car the injectors were not in good shape when I did headgaskets last year. Mileage went from 12 before the work, to 25 mpg. after. I had a spare set of injectors I sent out for cleaning/matching and used them when I put the engine back together.

Might need to pull spark plugs and take a look, which would be a good excuse to install fresh plugs and wires. Tricky on our cars, so search for tips or speak up.

Pull the vacuum line off the fuel pressure regulator on the back of the driver side head and see if there is raw fuel present in it, or in it's port on the regulator.

no CEL until it studder the light will come on for about 2-5 seconds

I've never seen it, but I've heard a severe enough misfire can cause CEL to blink. Might be one or more components acting out when hot, from DIS to crank sensor, etc. I'd want to know about any codes before throwing parts at it.

don't know mileage on bbk bought the car with it already on I've driven the car aprox 300 miles so far

BBK should be a good enough product, I think, but I've seen complaints about vacuum leaks and chasing TPS signals when the shaft/bearings get worn. Unless yours is really worn out/old, I doubt it's a player in your current issue.

You may have more than one issue, but I'll take a guess where I'd focus efforts:
- plugs/wires
- injectors
- EEC itself

Read codes first, do what I suggested above (MAF gentle clean & FPR/pressure check, you want to know how much at idle, under boost, and how long pressure holds when the engine is hot and shutdown/sitting), then start with plugs/wires. Looking at the plugs might finger point to injectors. Based on what you find, you may decide to do the work to take the injectors out and have them checked/cleaned etc. Or, you might just do plugs and wires and see if that fixes/helps the issue.

If it does, great. If not, and there isn't clear evidence (without removing them to check) that the injectors are giving you grief, I'd want to look at the EEC next. BTW, best way I know to test one is to replace it with a good one. All of this includes knowing what codes were being thrown. Good news is refurb'd EECs should be easy to locate and not too pricey.
 
Last edited:
Plugs and wires have 100 or so miles on them I'll try mad sensor clean then start looking at injectors and fuel pressure
 
No jump in tach and always hard to start cold after first start up will start fine the rest of the dayand I only drive it 2 days a week
 
I do have a plugged vacuum line that ls was plugged when I got it there are 2 larger vacuum lines coming off a vacuum tree on the drivers side near the clutch fluid resivor one goes to the Super charger the other has a bolt threaded in there and I've looked and looked for where it was supposed to go but even with the engine out of the car I couldn't find where it attaches that could be significant just don't know what it goes to and hard to explain
 
Back
Top