xzodion

Hello all.

Car has run great in the last few weeks.

This morning while driving to work, it loss all power. No throttle response at all, even with the pedal floored.

Then after a second or so it “grabs” and has throttle response again.
It also has a electrical “wobble: the volt gauges goes up and down, and the lights. Both headlights and dash lights seem to dim and brighten. Tested battery its good, test alternator it’s putting out the correct voltage.

Things that have been done:
New opti just over a year.
New water pump just over a year.
New coolant sensor about a year ago.
New rad, and coolant tank, six months ago.
New fuel pump, six months ago.
New TPS two months ago.
Cleaned the IAC and MASS two months ago.
New thermostat and flushed cooling system, two months ago.

Any suggestions would be great. We take the car in to our mechanic, and it runs fine. I thought maybe because it has been a little cooler the last few days, but I don’t see a connection.

Thanks again for all your help.

Injuneer

Could be a problem with the ignition switch.... seems to be a problem cropping up more frequently as these cars approach 20 years old.

Does the volt meter vary in response to engine RPM? That is, does the voltage drop with RPM, because that might indicate a weak alternaor. But if the voltage varies at random, could be a bad ground for the engine. A bad ground at the PCM could also account for the sudden power loss.

xzodion

Is thier a way to test the switch, and did you mean the electrical switch or the lock tumbler?


the voltage goes up and down at low rpm or idle. but she also knoties the lights flickering while driving, not as bad, but slightly. today she was leaving a stop light going up hill, and she had no power, car woould not accelerat and the rpms were all over the place.

When i get to see th edata that we recorded. i will post more.

also we bought a Launch Crecorder
Launch Canada
to monitor the car while its driving as this is a intermitant problem.
we downloaded the programe and pluged the recorded in to the car and ran it for a bout a minute to make sure it all worked. we downloaded the data, and as far as I can tell every thing loooked good. the car idled fine, no hickups or hesitations. When i was looking at the data i knoticed that the vehical speed sensor was all over the place, recording Kph, up to 70 and as low as 2 kph. the car was just idleing, did not get put in to gear, and only rev'ed once. could a faulty vehical speed sensor be telling the engine the wriong speed and screwwing up air/ fuel mixtures?

If any one knows how to read, these reports, I can attatch a copy .

thanks again for the help.

Injuneer

If you post the data log on an FTP site, I can look at it, as long as it's in .csv, .uni or an excel format.

If the PCM thinks the vehicle is moving, it will elevate idle speed slightly. If the PCM thinks the vehicle is decellerating with closed throttle, it will cut fuel to the injectors down to a certain RPM, to reduce emissions.

xzodion

Ok, i will get that data log up tonight, and let you know then. thanks

Also i think im going to go over as may of the ground conections i can this week end. I know thiers one on the passanger side fender well. Where are some other points i should do an inspection of.

Chimera96

drivers side head, near coil. there are a few wires grounded to thaat stud, confirn all are good

Injuneer

The PCM grounds to the engine block, right near the starter.

xzodion

Ok, so we bought th Crecorder. Pluged it in to her car and she drove to work. has a massive loss of power, no acceleration, rpms all over the place. She gets to work downloads the data, and it only recored 15 of her 35 minute trip, and missed the event.

Plugged it in again on the way home, and again it only recorded 15 minuts.

I played with the settings, could find any where that gives you control of the length of recordings.

Put the recorded in to my 2012 chevy cruze, drove around for 15 minuets stopped and unplugged recorder, drover for 40, minutes stopped left it plugged in, drover for another 10 minutes. got home and downloaded the data, and it recorded every thing.

so now im thingking thier is something that is maybe casueing the ECM to screw up. we just replaced it about two months ago. Put in a re-built Cardone unit.

Is thier a change that the chip, that you have to swap over could be bad??

could a bad ground cause this?

what else could cause signal to stop going to the computer port?

Injuneer

96 (assuming we are talking about the car in your signature) does not have a removable chip.

The fact the RPM readings (I assume based on looking at the tach) are "all over the place" could be due to a problem with the high resolution pulse signal from the Opti. As long as the cam position sensor is putting out a high res signal, it will not set a code, even if the signal is corrupt. But you would probably get a code for the CKP sensor, because the PCM does check the rationality of the CKP sensor, using the high res signal from the Opti.

Did it record the first 15 minutes or the last 15 minutes? Might be worth uploading what you got so we can look at it. I know my data logging system (not a stock PCM) only records 15 minutes of data as max sampling rate, but it dumps the older data to make room for the newer data.

If the ECM was acting up, I would expect a code for the EPROM, checksum, or something like that.

xzodion

ok so I got some data, I'm just tryng to figure out how to load it to a FTP site, the CRecorder program does not have a easy way to export the file.

but we did see two things that were interesting.

drive the car to get gas, drove fine for about 5 minutes, the as we were getting neat the gas station it did one of its stumbles, RPM dropped, had to give it some gas to keep it running and it had no acceleration. This lasted for maybe 5 seconds, then the car evened out.

we took out the recorder at the gas station so not to lose the info. got home and loaded it. when looking at it we saw the coolant temp sensor spiked down from 89 deg to -40 for a second then back up to 89.

the b2s2 oxygen sensor output voltage also showed a spike from 0.05 volts to .=0.81 volts that dropped back down over about 2-4 seconds. it showed 0.05 from ignition till the event, then when back down to 0.05 for the rest of the drive


the other three o2s all showed active volts outputs ranging from .05 to 1.0 throughout the whole drive.

also what is short term and long term fuel trim, see a lot of graphs for these not sure what they are?

thanks again guys.