Newbie in a bit of trouble....

[Doely]

Hi people,
New to the forum and would be grateful for some advice....
I just bought a 2.0ltr tacuma. It developed an enourmous hesitation on the drive home. Since then I have replaced the fuel filter, spark plugs, air filter and a couple of oil contaminated breather hoses. I havn't replaced the plug leads yet (will do that next pay!). Since then It has got better but still hesitates just of idle and sometimes bogs badly. Seems to lack power, but when revs pick up it performs well.

I have had a diagnostics check and was informed that there were no codes. The mechanic gave the car back to me worse.... he left the throttle cable so slack the TPS wasnt working properly.

Revs remain high through gear changes and take a second to come back down after my foot is off the accelerator.

The car starts fine and idles perfectly, but hesitates (like fuel starvation) there is no spluttering, just bog, then go, bog then go......
The car is 2001 with a low 55k's so I'm thinking this could be a fuel pump??????

Thanks in advance, any ideas appreciated.
Matt

[DDRaptor]

Does it bog down when you hold the accel down steady? i have that problem with nubira it would start and idle fine but when running at constant would loose power because the EGR gasket was messed up. Try disconnecting the egr wires or vacuum line to see if your problem still stays.

[Doely]

Cheers thanks will look at that.... but mine is manual, do manuals have an egr system? It only happens of idle, bit like there is a vacuum leak somewhere.

It doesn't happen when cold though, which is a bit confusing (ie. not a vacuum issue).

The really annoying part is when changing gears (manual transmission) the revs don't drop between changes.
Matt

[DDRaptor]

All modern vehicles have an EGR systems it allows for a higher C/R to gain more power out a smaller displacement. Ummm....
You could use a multimeter to check the map sensor and throttle sensor as well. You can check them by having the car on but not running and checking the voltage output of the sensor. It has has three leads one is +5V the middle is USUALLY output and third is ground and the way it works the more throttle that is given to it the higher the voltage will be. The map sensor has to be done with the engine running because it needs air pressure to work but it is the same method. When you checking these two sensors look for "repeated" spikes in voltage for example if you moving the throttle slowly and it goes from 2.0V to like 3.9 all of a sudden you may have a bad TPS.

Sorry for the disorder of information. Another thing you can try is to remove the fuse for the ECU and reset the car's computer to recalibrate all the sensors. (that can go both ways)

Good Luck. Happy New Year.

[Doely]

Cheers, the workshop manual says only autos have an egr system... i cant see one on mine... if there was something wrong with a sensor wouldn't I have dash light?

[PrecisionBoost]

If it runs fine when cold, but then it has problems when warm it sounds like you have too much fuel going into the system.

At idle the ECU runs off a predetermined map and does not rely upon the oxygen sensor.

My initial thought is coolant temp sensor, if your sensor is damaged and reading -30 deg C it will not trigger a code.

What will happen is that the car will sort of run allright in the cold but when it's hot it will simply be drowning the cylinders in fuel.

There are other posibilities, but I would check this one out first, it's very simple to measure the resistance accross the Cooland temp sensor when cold, warm, hot

Your manual should give you a resistance versus calculated temperature number.

good luck

[DDRaptor]

Cool, did'nt think of the Coolant Temp sensor. Good call.

[Doely]

Geee coolant sensor, would of never have thought of that. Thanks. Every time I do something to the car it gets a little better. Now there are two prominent symptoms.

- Revs remain high between gear changes, makes it quite difficult to drive. ie, change gears at 3.5k, take foot off gas, revs stay there for a second then come down
- Once warm bogging below 2,000 rpm. Once above 2,000 rpm it goes well.

Would the coolant sensor cause this?

[DDRaptor]

It seems what your saying that that It might be a coolant sensor if theory of operation is right if the engine always thinks it's in warm-up it will always spray extra fuel as precisionboost said. and then when the rev's get high enough there is enough air to mix with the excess fuel and combusted completely. On that note is your Fuel economy poor? If you have a multimeter you can use the ohmeter function to check the sensor. If you don't have a multimeter you can disconnect the sensor and leave it open and then jumper it, the car should give you a code for both those events.

hope this helps.

[Doely]

Thanks for your help guys.... I've been tinkering and noticed that there is a small oil weap from the rocker-cover. There is oil on some of the connectors around the coil pack area... could this be causing incorrect sensor readings?

[Doely]

... fuel economy is ok at 12lts/100kms...

[Doely]

I removed the sensor and tested it with my multimeter. I put in cold water and got a reading of 1500 with the meter set at 2000 ohms. Then in hot water and got a reading of 900. However, I tested it a little while later and the readings were all over the place..... for hot and cold. My meter only has settings for 200, 2000, 20k, 200k and 2000k. I'm thinking it could be this sensor... but not hugley confident my meter is correct.

The exhaust is very sooty, so running rich seems to be a symptom.
Thanks again,
Matt

[Doely]

Thanks guys, new CTS has improved the car....
Still has high reving between gears though and bad power delivery below 3,000 rpm. It's all a bit dissapointing really, we had a renault scenic 1.6 8v. It pooped all over this tacuma in terms of performance and engine response. I'm starting to think the ECU is on the way out. I know these arent meant to be fast but I'd hoped the tacuma would be better than a basic renault......