Rough Idle/Hesitation/Backfire

[Gary Yarbrough]

I checked the TPS voltage. I get 0.37v. With smooth pushing of the accelerator, the voltages fairly smoothly (maybe 0.5 or so v increments). Flooring it, it goes from 0.37v directly to ~2.5-3.5v. Time for a new TPS?

[tomtom72]

Gary, I have a 90 and I know for sure that my TPS is adjustable...to what degree I don't know, but the screws that hold it in place are in slotted holes, therefore I conclude it's adjustable.

You may want to look closely at those screws as you maybe able to make an adjustment. If you say that the needle on the VOM moves thru it's sweep at a smooth progression then maybe an adjustment is in order.

Just a fwiw, try it, in the end you can always go spend the money if the adjustment don't work.


Tom

[secondchance]

Originally Posted by tomtom72

Gary, I have a 90 and I know for sure that my TPS is adjustable...to what degree I don't know, but the screws that hold it in place are in slotted holes, therefore I conclude it's adjustable.

You may want to look closely at those screws as you maybe able to make an adjustment. If you say that the needle on the VOM moves thru it's sweep at a smooth progression then maybe an adjustment is in order.

Just a fwiw, try it, in the end you can always go spend the money if the adjustment don't work.


Tom

It is adjustable. Loosen up both screws just enough to be able to rotate TPS and rotate until you get .54 volts. FSM gives you an acceptable range but gurus tell me .54 is optimal.

[tomtom72]

Stupid of me not to include this. When I scan my 90 at idle, in closed loop, the TPS does read .54v on my scanner. So jsut make your adjustment at idle and make sure you are up normal operating temp.

Sorry I type faster than I think.....


Tom

[XfireZ51]

Originally Posted by tomtom72

Gary, I have a 90 and I know for sure that my TPS is adjustable...to what degree I don't know, but the screws that hold it in place are in slotted holes, therefore I conclude it's adjustable.

You may want to look closely at those screws as you maybe able to make an adjustment. If you say that the needle on the VOM moves thru it's sweep at a smooth progression then maybe an adjustment is in order.

Just a fwiw, try it, in the end you can always go spend the money if the adjustment don't work.


Tom

Gary

As TT has said, loosen the TWO bolts on the side of the TPS and adjust with IGN ON so the DVM reads about .54v. Then tighten bolts
and check WOT TPS signal. Should be at 4.5v or higher. If not,
swap in new TPS.

[secondchance]

When you say back fire, do you send detonation in the plenum or hear it at the tail pipe?

I never had this situation with fuel injected cars but way back when cars had carburators, cracked ign. wire would make gas vapor explode into the air filter housing.

If it is coming through the tailpipe, its coming from uncombusted fuel detonating when it his catalytic converter.

I very much doubt TPS, even if off a little, would do this.

Lastly, I struggled with a similar symptom a few years ago. In my case it was hairline crack on one plug (very difficult to see). Cracked plug wire will behave in similar manner.

[Gary Yarbrough]

Here's where it will stand today:
I've got the TPS at the correct voltage. Operation seems smooth.
I've changed all plugs other than the dreaded #8. I'll need a new spark plug socket to put it in...will pick one up today if they have them at Sears.
All new injector coils.

Took the car for a spin: some improvement but still not perfect.
Then I changed my chip from a JVD chip to a DRM chip. Seemed a little better (or I may be imagining things). However, I feel that the JVD chip was better at the top end.
Best I can tell, it is now running okay above 2K RMP. Any chance getting the last plug in could cure the problem?

As for the backfire, it is hard to tell. I'm always in the car when it happens and I have some hearing loss that prevents me from knowing which direction sounds are coming from with any degree of accuracy.

Later, I'll get my wife to rev the car and see if I can pinpoint the noise.

Thanks for everyone's help!

[secondchance]

Originally Posted by Gary Yarbrough

Here's where it will stand today:
I've got the TPS at the correct voltage. Operation seems smooth.
I've changed all plugs other than the dreaded #8. I'll need a new spark plug socket to put it in...will pick one up today if they have them at Sears.
All new injector coils.

Took the car for a spin: some improvement but still not perfect.
Then I changed my chip from a JVD chip to a DRM chip. Seemed a little better (or I may be imagining things). However, I feel that the JVD chip was better at the top end.
Best I can tell, it is now running okay above 2K RMP. Any chance getting the last plug in could cure the problem?

As for the backfire, it is hard to tell. I'm always in the car when it happens and I have some hearing loss that prevents me from knowing which direction sounds are coming from with any degree of accuracy.

Later, I'll get my wife to rev the car and see if I can pinpoint the noise.

Thanks for everyone's help!

Best way I found for removing #8 plug is to get a socket w/ rubber insert specifically designed for spark plugs (this allows plug to be pulled out of the hole after being unthreaded. Also, combination of short extension, swivel joint,added to long extension. With this combination, I can twist the plug despite odd angle required.
Also check all plugs and see if they appear uniform.
I am sure we (with help from gurus) can sort this out.

[XfireZ51]

I use a breaker bar with a short extension and a swivel. Just need it enough to "break" plug. Then I use a 3/8" fuel hose on top of spark plug to turn it the rest of the way and pull it out of hole. Works for putting it back in as well.

[4DSZR1]

Best plug advice I ever got and it works GREAT

Socket
swivel
1" extension
swivel
Long extension


when its loose push the plug wire in and it will grab the plug