alritzer

A couple of weeks ago I had a problem with my 86NA idle. I adjusted the TPS and now it idles OK.

But now if I try to hold the rpms at say 2500, they rise and fall several hundred. Like say between 2200 and 2800. Its not possible to hold the rpms at any one place. And it doesn't matter if the engine is hot or cold. If i'm trying to just slowly cruise through the campus, the car surges forward and then slows, over and over. Very annoying.


HELP


ashley

crazyasu

adjust your tps again..check for resistance usuing a DMM

kungfuroy

iTrader: (6)

did you short out the check connector after your adjustments?

stevej88na

If I remember correctly, last time you ended up grinding down the TPS plunger because you couldn't get enough adjustment out of the adjustment screw by itself. That may mean a bad TPS, or with a shortened plunger, it may not be reading past the TPS's idle range ever (i.e. the plunger can't get pushed far enough anymore). Do you have access to another TPS?

alritzer

Well, I didn't actually grind down the plunger, I just lenghtened the hold down slots so I could move the tps. I couldn't find any way to adjust it otherwise. A friend has an explorer that doesn't provide for adjustment of the TPS and that is how they did hers. I don't have another TPS to try but maybe I could pick one up someplace. I know several people that have RX7's.

I think the resistance values for the TPS were within range but I'll be sure to check the TPS first thing.

The engine idles really good now but is almost impossible to keep at a constant rpm above idle.

I think it is totally strange how the problems arose after I had the cat back exhaust changed to a more free flow design.

Several years ago I had a porsche 928 that had the same symptoms and the garage said it was related to a drop in compression in one of teh cyclinders.

But that should not be the problem now because I only have like 400 miles on the engine since it was rebuilt, and I never run it hard.

I never had the 3800 rpm hesitation problem before but I do now....big time, it like it almost like it stops firing for a couple of hundred rpm.

Could the variances in rpm be caused be the same problem?

ashley lynn

stevej88na

I get it now. FYI there's a screw with a spring on it to adjust the resting position of the TPS; check the last photo on the TPS page:
http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1

Was the TPS within resistance spec with the throttle plates fully opened as well? You can twist the throttle arm (attached to the throttle cable) to check. The resistance should have a smooth transition between the idle position and WOT as well.

I hear a bad TPS will cause hesitations, and since it's part of a feedback loop, it can also cause oscillating RPM. Out of curiosity, does the oscillation have about a 1 second period? Does it only oscillate when you hold the RPM constant? Did the hesitation only start after adjusting the TPS?

alritzer

Yes, anytime I try to hold a constant rpm above 1500. If I try to hold it at 2500, it will rise to 2800 and then drop back to 2500. It probably takes about 2 secs from 2500 uo to 2800 and back to 2500.

I appreciate everybodys help.


ash