tylerwerrin

Hi guys,

I had posted a while back regarding a DTC34 (low voltage, high vacuum). It was very odd, because while at idle, the code would not come up (idling til closed loop). However, after 10-15 minutes of normal driving around town, the check engine light would come on, and I'd have a DTC34 on my hands.

Anyways, I noticed the car would start stumbling/sputtering at around 2500rpm. At freeway speeds, however, i wouldn't get the stumble -- it's just cruising around, usually holding around 2500 rpm that i get the stumble.

The DTC still is coming up -- i've ordered a new MAP -- but when I did the diagnostic in the manual, everything went according to plan. What could be the problem? O2 Sensors fouled? Does another else have any info regarding the DTC34 that I can mess with, or has anyone else had a similar problem?

bw_hunter

When I first got this car, years ago, I had the same random check engine light and code that you describe here. Changing the map, and the connector, solved the problem. Following the diagnostics at the time I got the same sort of responses you did...usually nothing would show up as wrong.

Really check over the connector for the map, they get tired and cracked and loosen the connection with the sensor itself. There is also a green o-ring where the sensor enters the manifold. That can get pinched sometimes and mess up the readings...

tylerwerrin

Changing the connector is my last option i guess -- do you know of a supplier that sells the connectors whole?

Injuneer

You can get a "pigtail" that includes the connector, and short lengths of wires to splice to your harness. Shoebox has part numbers on his website - look at the right hand column on this page:

http://shbox.com/1/Parts.htm

tylerwerrin

I'll give it a shot -- Also, perhaps it is one of the spark plug wires that is giving me the stumble -- I noticed one of the wires (i believe it is 5) is sitting very close to the exhaust manifold, and was very hot after a short drive.

I'll try covering the boot with a cover that I found on amazon.

The only thing about replacing the connector to the MAP -- it looks like the connector is OK, no visible damage. Is this consistent with the problem you guys have seen?

tylerwerrin

I replaced the MAP sensor today with a brand new one -- no change, if anything it's gotten worse. I'm going to pull a couple of the plugs to see if they are fouled as well as check the oxygen sensors. I haven't replaced the MAP connector yet -- but i fear that due to the rich running conditions recently even if i install a new one my plugs & o2 sensors will be ruined.

Is it possible this is opti related? i haven't gotten any misfire codes, but it really feels like the car is not firing on all cylinders. I'm not sure what else to do. Any other input?

Guest47904

OBD I does not have missfire detection.

Is the DTC still present? It indicated no signal, as in no contact with the connector and is probably as bw suggested earlier. If that is the case, changing the MAP would not have changed anything.

Clear all codes and run the engine again. Check for codes.

If the DTC is still present, you should measure the MAP connector contacts for the presence of 5 volts and ground. Use the meter from the black wire to the grey wire with the key on. If 5 volts is NOT there, your problem is the loss of 5 volts. If 5 volts is there, then the next thing to do is check the green wire to the PCM connector.

You can check continuity of the green wire to the PCM with an ohm meter which is a pain, or you can jump the grey wire with a paper clip to the green wire with the connector off.

If you reset the codes and put the paper clip jumper from the grey wire to the green wire and start it up. It should give you a DTC 33. If 5 volts was there and you jumped it with a paper clip to the green wire and a DTC 33 did NOT come up, the problem is somewhere on the green wire.

If the code came up as expected, the problem is likely the connector as bw said. Remember you can always test the theory by using some way of making better contact. Pull the wires from the connector and put them directly on the sensor without the connector housing. Or jump pins to sensor (more difficult). My point here is you can always come up with a way to test what you suspect. Don't always just buy something.

Also, with regard to the connector. While the connector may not be making good connection to the sensor, it may be possible to "tighten" up the contact pins, to force it to make better connection.

However, it may be near impossible to get them out of the connector housing without damaging them. I don't ever remember looking at how they extract from the housing, so I'm flying blind here.

tylerwerrin

thanks speedy... i'll try the diagnostics you reccomended. I feel like my plugs will be fouled and the o2 sensors as well as I've been running out of whack for about 100 miles now (it only recently got to the point where it really had to be addressed....)

Ugh i just wish there was a little more daylight in the days!