I've got a couple of problems with my N/A 1988 SE that may be related. I'm hoping that some of you out there have seen these before and actually know what's causing them. Please don't provide Service Manual answers like 1. replace computer 2. replace engine.


Problems are:

1) if car has been sitting overnight, upon starting it will rev up to 3000 or so (good), but then it settles down to about 1500, and the revs fluctuate between about 1400 and 1500. You can hear it loudly revving up and down. This goes away after about 5 minutes. It just started doing this recently. After driving a bit, it will idle at about 750, fairly steadily.

2) At any point after engine is warmed up, it is impossible to hold it at an exact constant RPM. For example, if I press the clutch and then the accelerator and try to hold it at say, 2000, it will fluctuate within a range of about 100 RPM. You can see the tach fluttering and hear the revs going up and down. The RPM target for this test doesn't matter -- it will do this no matter what RPM you try to hold it at.

3) While driving, I get this "bucking" when I ease up the load on the car. For example, if I'm just driving at say, 3000 RPM in 3rd gear, and let up on the accelerator just a little to hold my speed constant, often the RPM will bounce around 2900-3000 and the car will buck back and forth. This happens in all gears, at seemingly almost any speed.

4) Floating redline problem. The redline buzzer goes off at different RPMs (not always 7000). On any given trip, the buzzer always sounds at the same place, but it will be different for different trips. It doesn't matter if the engine is warmed up or not. Sometimes it sounds as low as 5300 RPM.

If someone knows what is going on here, please let me know. Thanks in advance.

 

A few of your problems sound TPS related. Have you adjusted it? If not you can search and find quite a few threads on it. The buzzer, Id ignore. The Reving up, is part of the startup procedure when the car is cold. Your cold start system sounds kind of out of whack. You can download the factory service manual at www.fc3s.org and there should be a section on it where you can track down the problem.

 

yes some of the bucking problems sound like a TPS issue, the other ones sound like a major vacuum/exhaust leak

possible upper/lower intake manifold gaskets, or exhaust leaks

 

I was thinking intake leak too, but he mentions it eventually comes down to 750rpms.

How many miles are on your car?

 

Normal to a point. the 3000 RPM is the AWS. After so many mins, 750 idle is normal.



TPS I would bet on it.



TPS..

And here is how to fix it...

http://home.rmci.net/panther/tps.htm

And here is how to pull your codes

http://home.rmci.net/panther/ecu_codes.htm

Jarrett

 

BlackR1 dude i love your sigpic, i just sat their and watched for god knows how long. Anyway back to relevance, I had the same problem. Check the idle control, use premium gas for a while (detergents to clean out the injectors) and spray some carb cleaner in the throttle body. With a couple of weeks of tweaking and patience, i now get a steady idle at 1000 . If you have cruise control also check that to see if the throttle screw is too tight or loose. I forget. Anyway all those can have an effect on your idle. Good luck

 

My '88 SE, since I come home on the weekends to drive it, it hasn't been started in roughly 4-5 days each week. It usually goes up to 3000RPM's, then settles to 1500, and gradually, after 5 minutes, settles down to 750. When I'm driving the next day, it doesn't take as long. Maybe about 2-3 minutes by the time its down to 750 again.

 

the proble could be:
1: vacuum leak
2: bad tps setting
3: bad bac

check for leak with starting fluid, fluctuating idle is sign of a vacuum leak.

 

Thats normal too.

Jarrett

 

Thanks for all of the replies. I should add some additional detail / clarifications:

1) The cruise control works perfectly on the car

2) After startup, I realize that the drop down to 1500 RPM is normal, but what isn't normal is that the revs are now "fluttering" between 1400 and 1500, and not holding steady at 1500 (which is what it did before)

3) I don't want to ignore the redline buzzer (I actually use it for shifting). Also, ignoring it or disconnecting it is kind of like "well my finger hurts, so let's cut it off".

4) Mileage on the car is 109K miles.

5) I already have tried injector cleaner a couple of times with no effect.

6) I use 89 octane fuel, which is what they call "mid-grade" around here. Premium is $2.39 a gallon (ouch !).

Thanks again for all the replies. I will check the TPS, vacuum leaks, and follow the links people have suggested. If anyone has any other ideas, please let me know. Thanks.