Loss of low speed smoothness

[hrforever]

For the past couple of months my car, Volvo with 95 1UZFE and w58, has been sitting around whilst I've attended to other things but I have recently started using it again as the weathers improved. Thing is, before I let it sit idle it was smooth as anything to drive from low idle speeds right up to its redline, but now it doesn't want to idle along smoothly in any gear below 2000rpm.

This first started with a reluctance to cruise in 5th at 60kph then it got worse to where taking off became difficult unless I kept the revs above 2000rpm. Think back to when you drove a car with a carburettor with no choke, first thing in the morning. That's what this feels like, however it idles without a problem.

Anyway, I disconnected the battery for 30 sec to get the ecu to reset, and the problem went away but after 3 or 4 starts the problem reappeared. A further disconnection of 12 hours also had the same short term fix. The only fault codes I get are for the sub oxygen sensors (not fitted) and the speed sensor (also not fitted) but these have always been there since the conversion 18 months ago. My guess is the ecu is playing up but is there anything else I should check that might be causing this problem.

 

[uza70]

Open up the computer case and take a look at the circuit board. Most likely cause is a dead capacitor.

Look at the capacitors, little black cylinder things. Check for any stuff leaking out of them, or the tops bulging. Give them the slightest push to ensure that their legs haven't corroded off the board.

Look for signs of heat stroke on the board circuitry, dark discoloration on the coppers. If there is heat stroke in places other than where a heat sink is, it usually means a burnt out component.

If you do have a dead Cap, read what the uF and Volts is. Buy a new one, with the EXACT same uF and either the same or higher Volt rating.

Then using a soldering iron, heat one leg of the cap from the other side of the board. Using your other hand push the cap over so one leg starts to pull out. Then heat other leg and pull the cap completely out.

Install new capacitor, MAKING SURE you get the polarity right. Gray stripe is negative.
Use new solder to ensure a good connection between cap and board, DO NOT use what is left on the board.

Once done, return computer to car.

 

[samsdad]

Lack of speed sensor... You answered your own question

 

[hrforever]

Thanks for responses. Will check computer connections today.

As for the speed sensor, where is it and why has the code always been there before and never caused a problem?

 

[spf_lexus]

no speed sensor= no speedo function


Its located at the end of the transmission tail shaft. Very easy to get to.

 

[spf_lexus]

make sure the ecu is for the engine your running. A soarer ecu might work on the celsior, but the speedo's are different and you will see a code if the ecu isnt matched.

I swapped an sc400 transmission into a ls400 of the same year and the speedo codes never went away.

 

[hrforever]

As this is a very recent problem and the conversion is 18 months old, I'm guessing it's not the speed sensor as I don't have one.

As for the computer, I have removed the front cover and everything looks ok, as in nothing looks to be leaking or bulging. Having said that, if everything runs ok after disconnecting, then reconnecting the battery, does this point to the ecu or a sender? The temperature of the car doesn't change things nor does the amount of time the battery is disconnected. As for things like dist caps, rotors, leads and spark plugs, these also would not be temporarily fixed by the battery disconnection.

As this is the first real problem to effect the motors operation, I'm at a bit of a loss as to where to look. Plugging in another computer would provide some clarification about the problem but I don't have access to another from a 95 SC400.

 

[hrforever]

Ok. So have checked all plugs, leads, covers and anything else that I can think of but still the same problem keeps re-appearing. I don't know where to go from here.

Does anyone know of a reputable mechanic/technician that knows these motors in Melb area that may be able to assist?

 

[hrforever]

Well, still trying to get to the bottom of this problem. After doing a lot of forum searching the closest I can get to a possible solution is that it may be one of the coils. The sluggishness I'm experiencing (car not me) under load/light acceleration but the ok idle and free reving seems to point this way, but how do I test this for sure short of replacing both coils. What has me querying this as a solution however is why the problem temporarily goes away if the battery is disconnected/reconnected again.

This really has me stumped.