Running rough...but weird.

[Guyver280z]

Hi there. I already searched the forum but none of the symptoms seems to be the same so here they are.

The car Idles at 900 but it idles smooth... at least it feels smooth, it wont stall, but sometimes when I rev the engine when it comes back it stys a little in 1500 and it slowly goes down to 900.

Then when I start moving the engine start to run really rough, like coughing, but it only makes that if I press to 1/3 of the accel pedal. If i floor or go more than 1/3 or 1/2 of the pedal it jumps fast and keeps going like nothing, but of course it takes a lot of gasoline cuz I have to floor it all the time otherwise the engine runs coughing.

If I turn on the AC it gets worst, it takes more accel pedal to run fine.

No check engine light

Its a 5 speed manual

HELP PLEASE!!!

[cdvs]

I don't know what the 5 sp might introduce, but it sounds like a bad or dirty tps (throttle position sensor).

Good luck.

Charl

[Guyver280z]

Originally Posted by cdvs

I don't know what the 5 sp might introduce, but it sounds like a bad or dirty tps (throttle position sensor).

Good luck.

Charl

Yeah, thats what I tought some kind of sensor ans now that you mention it could be the TPS... but still wonder if sombody had the same or similar problem.

Is there a way to test the TPS??

In the last 2 weeks I just replaced an alternator, retrofitted the AC with R134 and im waiting for a new radiator... so I dont want to spend that much money on something.. I just want to make sure thats the problem.

[dmnknightomega6]

i had a problem which is similar, but i do not know if its related.

It worth to check

I recently recharged my AC manually with oil and refrigirant, my AC compressor actually started doing weird stuff causing my engine to stutter and shudder.

turns out, i put too much in. so i had to release some off.

I did the release by running the AC full until the AC compressor clutch engages smoothly.

Want to diagnose; follow and see:

Turn AC on at full
Watch Compressor clutch engage (its the front part spinning)
- If it turns on and off every 5 seconds , shudders the engine abnormally, then you might have the same issues I had

The AC clutch should engage on and off 30 sec on and 5 sec off approx. (correct me here tech guys)

Good luck

[Guyver280z]

Originally Posted by dmnknightomega6

i had a problem which is similar, but i do not know if its related.

It worth to check

I recently recharged my AC manually with oil and refrigirant, my AC compressor actually started doing weird stuff causing my engine to stutter and shudder.

turns out, i put too much in. so i had to release some off.

I did the release by running the AC full until the AC compressor clutch engages smoothly.

Want to diagnose; follow and see:

Turn AC on at full
Watch Compressor clutch engage (its the front part spinning)
- If it turns on and off every 5 seconds , shudders the engine abnormally, then you might have the same issues I had

The AC clutch should engage on and off 30 sec on and 5 sec off approx. (correct me here tech guys)

Good luck

I just charged my system too and at the begging I tought it was related, BUT, it was doing the same thing before charging it, and it runs rough even without the AC working. Of course with the AC it gets worst because of the heavy load of the compressor.

So A/C related... discarded.

Thanks

[cdvs]

Originally Posted by dmnknightomega6

The AC clutch should engage on and off 30 sec on and 5 sec off approx. (correct me here tech guys)

Good luck

The SVX has a variable compressor. It should not cycle because it can adjust for how much work it needs to do.

The problem you describe sounds like the high pressure switch cutting off the compressor.

Anyway, that shouldn't cause the problem he's having.

[cdvs]

Originally Posted by Guyver280z

Is there a way to test the TPS??

Yes, you can check the resistance of the sensor or the voltage output as you take it through the range. Do a search for details.

You can also take it apart and clean it. It sounds like yours is dirty or worn in the area where there is no response.

[Guyver280z]

Originally Posted by cdvs

Yes, you can check the resistance of the sensor or the voltage output as you take it through the range. Do a search for details.

You can also take it apart and clean it. It sounds like yours is dirty or worn in the area where there is no response.

10 - 4

Ill try to take it out, inspect it and clean it and see what happens.

If its in good woring order what else could be causing the problem??

Oh by the way.... when my car was running low on AC refrigerant the compressor was going in and out all the time just like dmnknightomega6 said, and just like every other car with R12 refrigerant, maybe the ones with R134 have that variable compressor.

[cdvs]

Originally Posted by Guyver280z

10 - 4

Ill try to take it out, inspect it and clean it and see what happens.

If its in good woring order what else could be causing the problem??

Nothing else comes to mind for these symtoms.

Originally Posted by Guyver280z

Oh by the way.... when my car was running low on AC refrigerant the compressor was going in and out all the time just like dmnknightomega6 said, and just like every other car with R12 refrigerant, maybe the ones with R134 have that variable compressor.

No, there are high and low pressure cutoff switches. All SVX have variable compressors. However, many other cars don't and do cycle on and off when functioning normally.

[Trevor]

Originally Posted by Guyver280z

10 - 4

Ill try to take it out, inspect it and clean it and see what happens.

Refer the how too stuff in my locker for details. Cleaning is difficult as the unit is more or less sealed. Try to get some CRC or equivalent into it via the shaft and vent holes.

If the resistance is still intermittent as it is moved, you will have to replace it, unless you have the expertise to take it apart. This has been done but it is not an easy task and may not result in success.

[Guyver280z]

Originally Posted by Trevor

Refer the how too stuff in my locker for details. Cleaning is difficult as the unit is more or less sealed. Try to get some CRC or equivalent into it via the shaft and vent holes.

If the resistance is still intermittent as it is moved, you will have to replace it, unless you have the expertise to take it apart. This has been done but it is not an easy task and may not result in success.

Well, I took it out and "cleaned" ir with WD-40... didnt took it appart, a you say its pretty much sealed.

Put it back.... same problem.

Went to the Junk Yard and got me a used one from a newer SVX, replaced it.... ALMOST the same problem, it feels like its working better... but still its not completely fixed..... but WAIT. The thing is that before replacing it the car was suddenly working properly.... and now that I replaced it sometimes it feels ok, the it goes bad again.... like a loose cable maybe???

The stupid new sensor its $175 and its a little thing.

How can I check it with my multimeter?? It have 3 connectors, and I know it works as a variable resistor but wich of the 3 connectors should I test?? ause if its working properly then its going to be something else.

[cdvs]

WD-40 is not an electrical contact cleaner. It will clean greasy stuff, but that's not what you are facing.

Do a search for specifics on testing resistance and voltages.

I was able to disassemble, clean and reassemble a TPS. I don't recall it being that difficult, but I had tested and determined it was a problem, so I had nothing to lose.

If it was working why change it?

It's difficult to explain how a loose connection would fail in a specific RPM range.

[Trevor]

Originally Posted by Guyver280z

The stupid new sensor its $175 and its a little thing.

How can I check it with my multimeter?? It have 3 connectors, and I know it works as a variable resistor but wich of the 3 connectors should I test?? ause if its working properly then its going to be something else.

Small but not cheap to produce and not an unreasonable price.

A previously advised, the data in my locker (also in the "how too' section), provides all the info you require.

You say you put it back, but did you set it correctly with a volt meter. Please read the instructions as provided.

[Guyver280z]

Ok, this thing is driving me crazy. Some days the car works great and other days it runs like sh$%t.

I found it hard to believe that the TPS sensor I got from the junk car (newer car) is damaged exactly the same way than mine... plus the fact that sometimes the car workd fine. Im thinking of a loose wire or something.

My car haves the ECUTune, could it be related? I mean something wrong in the ECUTune installation?? Anyways the Economy/Performance switch seems to be working fine, the car feels stronger on the performance mode, its just that rough "shaking" on lower rpms.

I have to say I havent tested the TPS with the multimeter because its not working anymore, and I've been buying so many thing for the car that cant afford buying a new multimeter.

I just hate that everything happened right away. Alternator, 3 days later A/C, 4 days later Radiator blown... and this thing now

Any other suggestions instead of the TPS sensor?

Trevor... how can I get into your locker??

[Sov13t]

Hmm, are you up shifting/down shifting at right RPMs?

Is your MAF functional? Check your Air Filter...

(back to the basics)