Help! Car drives okay for a while then dies.

[Lunchboxhero]

Alright guys, 87 325. 2.7. I am 100% stumped as of right now.

The other day I was on my way home from a buddies house when I noticed the car was puttering a little bit, threw up a red flag and wanted to get it home.

Bam, I was turning out of his neighborhood onto a road and it died... and would crank and start but die immediately, then if i gave it gas it would run for about a second longer then die again.

Had it towed back to my buddies house where we looked into it more, lot of people said CPS, I couldn't even find mine, I did find this pic and I have no such plug


We tried a bunch of stuff to get it running. Looked at the intake boot, perfect, then we unplugged the coolant temp sensor and it would fire and idle, but very badly at like 400 rpm, then when we would plug the connectors back in it would die again. we then tried pulling fuses 10 and 11 to the FI system, plug one back in and it still didn't start, switch that around and again it idled, badly. Plug the other fuse back in and back to a normal idle for a bit then it'd die again after a few seconds. Starting to get perplexed honestly. Then we take an automotive stethoscope and put it on the fuel pump, was kicking on fine and sounded fine, also I noted that I didn't see another pump anywhere else? I looked near the fuel filter(Which is also brand new) and didn't see anything.

Go to my work (Oreillys) and happen to catch one of my good mechanic buddies there and he tells me to replace the fuel pump relay, I did and it did nothing.
Get aggravated and call it quits for the night, We'll spark test it in the morning.

Next morning rolls around and we go to spark test it, fires up like a charm and idles right around 900 (Which was always normal for me), Dafuq? Drive it home and not a single problem. ran perfect....

Next day I had to go to the bank so I went to fill my tank because I needed gas, ran perfect all the way to the gas station (5 or so miles) Fill'er up and boom, no start. THE FUCK MAN. get it towed home on a buddies trailer and take my truck to work.

Next day (Tonight), drove to work fine and as a last ditch effort was a new air filter that my buddy suggested to try because mine was odd and DEFINITELY needed to be cleaned, threw a new cone filter on it and had it idling at work for about 15 minutes, I would shut it off, let it sit for a couple then go start it again and it would start right back up and idle fine. Dafuq. Drive it to my buddies house on the way home, fine and not a single hiccup, then I leave his house, again fine with no problems, get to my house and it dies in my driveway.


Guys I don't have the money to go throwing parts at it. I'd like to know if someone else has had this happen because from what I am seeing or thinking, something in the engine bay is getting heat soaked and doesn't wanna work. Now I tested spark another time in there while the car was running and it was fine across the board. My co worker told me it could be a coil? maybe but how is it running fine sometimes even at full operating temp?

I am at a total loss right now and Just want my car to be reliable again.

[Quadrajet]

Your may have a failing reference sensor. Which is located on the Trans bellhousing, along with an Eng. speed sensor. I don't think an eta would have the CPS pictured, unless it was perhaps, an 88 super eta. I'm not sure, as I've never had one myself.

Also let me ask this question. Do you have a 13 button OBC or a 6 button?

[Lunchboxhero]

Your may have a failing reference sensor. Which is located on the Trans bellhousing, along with an Eng. speed sensor. I don't think an eta would have the CPS pictured, unless it was perhaps, an 88 super eta. I'm not sure, as I've never had one myself.

Also let me ask this question. Do you have a 13 button OBC or a 6 button?

eta? sorry this is my first e30 and I am still fairly new to them. 13 button OBC? the check panel thing?

And would those sensors cause this after it's been running for a while?

[Quadrajet]

The 2.7 325 motors are known as 325e's or eta's, or M20b27.

The OBC is where the clock would be, above the heater controls and to the right, about a 3"x3" panel.

The reference sensor indicates to the ecu where TDC is and if it starts to go out it will affect whether the engine starts or not. Basically the computer won't know when to fire the ignition.

[Lunchboxhero]

The 2.7 325 motors are known as 325e's or eta's, or M20b27.

The OBC is where the clock would be, above the heater controls and to the right, about a 3"x3" panel.

The reference sensor indicates to the ecu where TDC is and if it starts to go out it will affect whether the engine starts or not. Basically the computer won't know when to fire the ignition.

ohhh, it's a 6 button.

That makes sense, but after a while of driving it just gets hot and stops working? sounds a tad odd to me.

[Quadrajet]

You'll need to pull the sensor and run a resistance check per the Bentley manual, to see if the sensor is starting to go south.

[Lunchboxhero]

You'll need to pull the sensor and run a resistance check per the Bentley manual, to see if the sensor is starting to go south.

Will do, thanks man!

Any other input would be awesome guys.

[Lunchboxhero]

Bumping to try and get some other ideas as to why this car is doing this.

[Lunchboxhero]

Bump, still haven't solved this. Might try the coolant temp sensor? could be telling the ecu it's still cold and dumping fuel therefore not being able to spark?

[jlevie]

The first things I'd do would be to replace both timing reference sensors (in the bell housing)and the main relay with new OE parts and tee a pressure gauge into the rail supply line and zip tie it to a wiper blade so it can be seen while the car is being driven.

[AwakenNoMore]

Had my car do something similar, ended up being the fuel pressure regulator. Worth a check at least.

[Lunchboxhero]

I will probably replace the fpr but I'm still having these problems. I replaced the crank sensors and it drove perfect for about a day and that's it. Also ordered a new coolant temp sensor because from what im reading that could be a problem too.

Any other ideas besides the afm? I'm stumped.

[Lunchboxhero]

Bump. Apparently the Iacv can cause the symptoms I am having too? Dunno. Going to replace the CTS tonight and drive her around.

[Lunchboxhero]

Coolant temp didnt work, hooked up a buddies AFM and IACV and still nothing after driving it a while, will drive fine cold but when it gets to warm it hesitates every now and then and does not restart.

[davtbaum]

I don't like throwing parts at cars, it really doesn't do anything but give you a false sense of security.

Had a bunch of no start / intermittent start issues with my e30 recently. A huge help was a Jlevie post on diagnosing no-start.

EDIT: Screw it I'm quoting

For the engine to run the following conditions must be met:

Power on DME pins:
27 Start Input
18 Un-switched Power input
37 Power Input from Main Relay

Ground on DME pins 2, 14, 19, 24

Timing data from the CPS on DME pins 47 & 48 from a rotating engine

To have spark power must be present at the coil positive and ground pulses
from the DME's pin 1 must reach the coil negative. Power to the coil is
controlled by the ignition switch via C101. When checking for spark, use the
output lead from the coil to eliminate the distributor, rotor and plug wires.

To have injector firing power must be present at each injector and ground
pulses from the DME's pin 16 (Bank1) and pin 17 (Bank2) must reach the
respective injector bank. Note that the injectors are wired as two banks of
three. With cylinder 1,3,5 being bank 1 and 2,4,6 being bank 2. Power to the
injectors is controlled by the main relay.

The fuel pump relay must have power on pin 86 (relay coil) from the main relay
output (pin 87) and power on pin 30. The DME will ground pin 85 to turn on the
relay and power the pump(s) via pin 87. Of the above, only the fuel pump power
is fused. So if the there's power at pin 87, but not at the pump, check fuse
11.

The main relay and DME pin 18 receive power from the smaller of the two wires
that connect to the battery's positive terminal. That wire incorporates an
in-line fuse. When the DME is presented with a start signal, it grounds the
main relay pin 85 and furnishes power to the fuel pump relay, injectors, and
DME.

Troubleshooting:

Disconnect the battery and the DME cable. Then:

1) Disconnect the coil negative and check continuity from that connector to
DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.

2) Check the resistance across DME 47 & 48, which should be 500-560
ohms. If the CPS is dismounted, the resistance can be seen to change
from about 500 to 540-560 when a ferrous object is brought to the face of the
sensor. Neither pin should be grounded.

3) Check for continuity from DME 36 to main relay 85 and from DME 3 to fuel
pump relay 85.

Reconnect the coil, remount the CPS (air gap should be 0.040"), plug the
relays back in, reconnect the DME, and connect the battery. Then do the
following checks:

1) With the key off, verify that power is present at DME pin 18 and main relay
86 & 30.

2) With the key on, verify that power is present at DME pin 27 and pin
18. Power to pin 18 is from the main relay and there should be power to the
injectors and fuel pump relay.

3) With the key on, verify that no voltage is present at the DME grounds (2,
14, 19, 24).

4) Verify that power is present at the coil positive and at fuel pump relay
pin 30. Those get switched power from the ignition switch via C101.

The engine will start and run (if poorly) with only those connections to the
DME in place. The other signals from Cylinder ID, AFM, temp sensor, etc., are
necessary for proper operation. But they won't prevent the engine from firing.

IMPORTANT:

A power check means seeing a voltage within about a tenth of a volt of what
you measure across the battery terminals, which should be at least 12.6v on a
charged battery.

A continuity check means seeing less that 1 ohm of resistance.

An open circuit means seeing a resistance of at least 100k ohms.

A good quality auto-ranging Digital Multimeter will make these tests much
easier.

Quick and dirty no-tools needed check of a no-start is to place the key in ON and see if the ICV is humming. That will rule out things like main relay, bad grounds (in my case), etc.