97 Transport strange engine problems
Bob Dinev
10-11-2007, 12:05 AM
Couple of months ago I had the head gaskets of my van replaced.
Few weeks later the engine began occasionally to die when idling. I went to see the mechanic, but the problem didn’t happen when we left the car running in the garage for about 20 min. So, the mechanic couldn’t say any opinion. The problem continued after for about a month – unpredictably and not every time, when idling the engine would stop. And it readily would start again after turning the ignition key.
Later the problem had evolved – now the engine never stops when idling. Instead while the car is moving, suddenly the tachometer goes to “0”. The engine is still running but the car is losing power. This could happen few times in a second or two. And sometimes this occurs when going with 110km/hr on the highway. The problem is aggravated because (you could imagine) at the same moment the computer is disengaging the transmission and after engaging it again. The effect is just as the car is kicked.
Everything looks fine – the “check engine” light is off, nothing is leaking; there is not any noises or roughly running parts. I change and check oils and coolants regularly.
Any ideas?!
Thanks in advance
Few weeks later the engine began occasionally to die when idling. I went to see the mechanic, but the problem didn’t happen when we left the car running in the garage for about 20 min. So, the mechanic couldn’t say any opinion. The problem continued after for about a month – unpredictably and not every time, when idling the engine would stop. And it readily would start again after turning the ignition key.
Later the problem had evolved – now the engine never stops when idling. Instead while the car is moving, suddenly the tachometer goes to “0”. The engine is still running but the car is losing power. This could happen few times in a second or two. And sometimes this occurs when going with 110km/hr on the highway. The problem is aggravated because (you could imagine) at the same moment the computer is disengaging the transmission and after engaging it again. The effect is just as the car is kicked.
Everything looks fine – the “check engine” light is off, nothing is leaking; there is not any noises or roughly running parts. I change and check oils and coolants regularly.
Any ideas?!
Thanks in advance
GTP Dad
10-12-2007, 11:30 AM
Welcome to AF!!
This is a complicated one but I would replace the throttle position sensor. Based on your description is sounds like it may be failing and not sending proper signals to the ECM thereby causing the engine to shut down due to a lack of signal. The TPS works at all stages of engine operation and could be the issue. It will not send an error code to the computer because the problem is intermittant. There are a couple of other possibilities such as a failing fuel pump, blocked fuel filter or a bad crank position sensor.
This is a complicated one but I would replace the throttle position sensor. Based on your description is sounds like it may be failing and not sending proper signals to the ECM thereby causing the engine to shut down due to a lack of signal. The TPS works at all stages of engine operation and could be the issue. It will not send an error code to the computer because the problem is intermittant. There are a couple of other possibilities such as a failing fuel pump, blocked fuel filter or a bad crank position sensor.
Bob Dinev
11-06-2007, 11:34 PM
Thank you, GTP Dad, for the advice.
I think you are right at least for part of the problem.
I went to the mechanic and after many tests he came to the conclusion that:
“The sensors that give information to the computer about the current R/min of the engine, give different information. One on them works properly; the other one shows the right number from 700 R/min (idling) until 1600R/min and after remains flat showing always 1600R/min. The computer checks both alternatively and get “confused” when the signals are different.” That is approximately the explanation of the mechanic.
By the way I don’t know why on this model two sensors are installed. Normally, as per the words of the mechanic, most of the cars on the market have only one such of sensor.
The mechanic replaced the “wrong” sensor (I got also the fuel filter replaced during all the preliminary checking) and apparently the things went better… for a week. Now everything started all over again, with one difference. Sometimes the tachometer goes to zero for a long time but the engine does not lose power. And all the problems happen mostly when the engine is still “cold”.
I think you are right at least for part of the problem.
I went to the mechanic and after many tests he came to the conclusion that:
“The sensors that give information to the computer about the current R/min of the engine, give different information. One on them works properly; the other one shows the right number from 700 R/min (idling) until 1600R/min and after remains flat showing always 1600R/min. The computer checks both alternatively and get “confused” when the signals are different.” That is approximately the explanation of the mechanic.
By the way I don’t know why on this model two sensors are installed. Normally, as per the words of the mechanic, most of the cars on the market have only one such of sensor.
The mechanic replaced the “wrong” sensor (I got also the fuel filter replaced during all the preliminary checking) and apparently the things went better… for a week. Now everything started all over again, with one difference. Sometimes the tachometer goes to zero for a long time but the engine does not lose power. And all the problems happen mostly when the engine is still “cold”.
canaris
11-16-2007, 10:48 PM
When mechanics do work on our cars..some of them are a little bit careless.. with all the wires and controls that litter the engine top... they pull..drag and drop a lot of them..then when they put everything back together something goes eventually wrong the following couple of weeks or month...
In my opinion you probably have no sensor that needs replacement but most likely it's a frayed wire.. or a bad connection..as you said when he replaced something the car ran fine for a few days.... so he indeed moved things around that probably moved your 'problem' wire or connection.
Check all connections with a low voltage meter.. while moving around lightly the wires on top of your engine.. pay attention to the Maf and egr connections from the engine to where they lead to... check the ignition module and all wires that go to it and as well as the crank and cam sensors...
These problems are very hard to diagnose ... and it can take considerable time and money changing sensors and CCModules needlessly..
Usually a qualified dealer with the proper scanners might find the culprit.
Good luck....
In my opinion you probably have no sensor that needs replacement but most likely it's a frayed wire.. or a bad connection..as you said when he replaced something the car ran fine for a few days.... so he indeed moved things around that probably moved your 'problem' wire or connection.
Check all connections with a low voltage meter.. while moving around lightly the wires on top of your engine.. pay attention to the Maf and egr connections from the engine to where they lead to... check the ignition module and all wires that go to it and as well as the crank and cam sensors...
These problems are very hard to diagnose ... and it can take considerable time and money changing sensors and CCModules needlessly..
Usually a qualified dealer with the proper scanners might find the culprit.
Good luck....
formula1
11-20-2007, 04:21 PM
My TransPort did something similar and your comment "suddenly the tachometer goes to “0” " brought back those memories. My problem was a repeated failure of the ignition switch burning contacts. There are several contacts within the ignition switch and various circuits can go dead intermittently depending on what switch/circuit loses power. The tachometer going to '0' was one of the symptoms I got several times. My tranny would also do a 3rd gear start sometimes, another symptom. The switch is below the steering column above the driver's shins and easy to replace. It's actuated by a rod from the key switch on the column. I finally figured out from a shop manual schematic that the electric windows were powered off the particular part of the ignition switch that was burining out. I figured that my kids and me were running windows up/down at the same time and just overloading the switch contacts. Too bad I replaced two ignition switches before I figured all this out! After we put some self-control on our window usage the ignition switch never failed again.
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