Car stalling AGAIN, Updates- none of them good. Options

[yellowporky]

Did you ever replace the board on your TPS? 914 rubber sells them

[rjames]

Did you ever replace the board on your TPS? 914 rubber sells them

No, and not discounting it, but I'm stuck on how it would explain the engine stalling since the car will still run with the TPS unplugged. I did clean the board last summer even though the contacts looked good. It's been calibrated.

[second wind]

Something about the idle changing with amount of running time keeps pointing to a vacuum leak. Isn't it possible that the throttle body has a leak underneath it where it attaches to the plenum? The rising temperatures open it and then it closes again after cooling. Just had to throw my 2 cents in. Sure sounds like a vacuum leak. All the best....
gg

[rjames]

Something about the idle changing with amount of running time keeps pointing to a vacuum leak. Isn't it possible that the throttle body has a leak underneath it where it attaches to the plenum? The rising temperatures open it and then it closes again after cooling. Just had to throw my 2 cents in. Sure sounds like a vacuum leak. All the best....
gg

I'm open to anything being possible at this point. However, I when I had a vacuum gauge hooked up to the TB below the butterfly while the car was idling, the gauge showed 17inHg with no loss of vacuum when the idle fluctuated up- in fact the vacuum increases when the idle RPM increases. My understanding is that vacuum at idle below the TB should be anywhere from 15-18inHG, so I'm on the upper end of that.
A vacuum leak also wouldn't explain the engine wanting to stall.

Appreciate everyone's ideas. Keep 'em coming. (IMG:style_emoticons/default/smile.gif)

[Highland]

Did you ever replace the board on your TPS? 914 rubber sells them

No, and not discounting it, but I'm stuck on how it would explain the engine stalling since the car will still run with the TPS unplugged. I did clean the board last summer even though the contacts looked good. It's been calibrated.

Another WAG, but if your TPS is worn and intermittently telling the ECU you're at idle, I can see how you can go way rich or lean sporadically (depending on ecu and MPS settings) especially as engine compartment temps change.

Do you have a variable resistor between the cht and ecu? I find that adds an extra knob to dial everything in.

[rjames]

Did you ever replace the board on your TPS? 914 rubber sells them

No, and not discounting it, but I'm stuck on how it would explain the engine stalling since the car will still run with the TPS unplugged. I did clean the board last summer even though the contacts looked good. It's been calibrated.

Another WAG, but if your TPS is worn and intermittently telling the ECU you're at idle, I can see how you can go way rich or lean sporadically (depending on ecu and MPS settings) especially as engine compartment temps change.

Do you have a variable resistor between the cht and ecu? I find that adds an extra knob to dial everything in.

I like WAGs.
The premise makes sense to a point, but then doesn't explain why when the idle surge is happening, the rpms continue to surge when I open the throttle a bit and hold it in that position. In that condition the TPS wouldn't be reporting an idle state to the ECU.

I don't have a resistor between the CHT and ECU. Car ran great for 7+ years without one before this issue cropped up, so I haven't felt a need to put one in. I've also got 3 CHTs that I've tried, both used and new ones. All test in spec when measuring resistance cold and warm.

[rudedude]

Have you taken the tri-ground and actually taken out the case bolt and cleaned it to make sure it isnt loosing ground while warm? It seems like you have done virtually everything else. It sure seem electrical somewhere.

[yellowporky]

It seems like 2 different things happening here.
The surging from what i understand tends to be a lean issue typically caused by a vacuum leak and the stalling would tend to be a heat related electrical issue.
How do the spark plugs look? Are they all colored tan or is one or more white?

Do not assume anything is good until you 100% rule it out. Go to 914 rubber and buy all of the vacuum elbows, connectors, TB gasket, cold start injector gasket ect.. Auto Atlanta has a good vacuum line kit too, Put clamps or good zip ties on the plenum to intake runner hoses and also it is not unheard of to have a crack in the plenum itself.
Check the intake nuts for proper torque too.

For the electrical issue make sure as stated above, remove and clean the 3 prong ground for the FI and then go to every other ground one by one and do the same.

Hope you find it soon. Unfortunately this is how most of us learn about these cars.

[rjames]

Do not assume anything is good until you 100% rule it out. Go to 914 rubber and buy all of the vacuum elbows, connectors, TB gasket, cold start injector gasket ect.. Auto Atlanta has a good vacuum line kit too, Put clamps or good zip ties on the plenum to intake runner hoses and also it is not unheard of to have a crack in the plenum itself.
Check the intake nuts for proper torque too.

For the electrical issue make sure as stated above, remove and clean the 3 prong ground for the FI and then go to every other ground one by one and do the sam

All vacuum hoses are new and have zip ties on them. Intake hoses are new. Gaskets for the intake runner, TB and cold start injector are new. I tore down all of the FI and intake stuff and cleaned it and checked the plenum for leaks

Used a smoke machine to hunt for any vacuum leaks. Used vacuum gauge at idle to verify vacuum was in speck (17inHG).

Bolt that grounds the 3prong connector on the FI harness was removed and cleaned up (it already looked fine but looks better now).

Vacuum doesn't seem to be the issue- at least not on the topside of the engine.

Haven't checked the ground point under the relay board. What wire is connected to it?

[BeatNavy]

Robert, sorry this issue has resurfaced (IMG:style_emoticons/default/sad.gif) It's either so obvious it's staring us in the face or buried so deeply we can't find it among the usual suspects.

Those are good suggestions about the relay board. Is that in good shape? It's a little tedious, but since you've tried just about everything else, you may want to remove the relay board from the car and test continuity between the traces. As a minimum once you remove the relay board you'll see the multi-wire ground in front and below the board that it's connected to. Worth cleaning, inspecting, tightening, etc.

Not long after I picked up my '72 I went through the whole D-Jet. The relay board was suspect, so I removed that for some TLC. While I was at work my wife actually took the time to scrape all the tar off the back with a bucket of solvent so I could inspect and repair. Nasty job, bless her heart (come to think of it, that may have been the LAST thing she did for me on that car.... (IMG:style_emoticons/default/idea.gif) ). Anyway, I did end up finding some questionable connections and soldering or reinforcing those before sealing it back up again.

EDIT: Sorry, Robert, I realized initially I put a "happy face" in the first sentence. Not my intention. It's changed now in my post (anyway) to a sad face to show that I know this sucks. I'm sure that makes you feel a LOT better.... (IMG:style_emoticons/default/headbang.gif)

[rjames]

Robert, sorry this issue has resurfaced (IMG:style_emoticons/default/smile.gif) It's either so obvious it's staring us in the face or buried so deeply we can't find it among the usual suspects.

Those are good suggestions about the relay board. Is that in good shape? It's a little tedious, but since you've tried just about everything else, you may want to remove the relay board from the car and test continuity between the traces. As a minimum once you remove the relay board you'll see the multi-wire ground in front and below the board that it's connected to. Worth cleaning, inspecting, tightening, etc.

Not long after I picked up my '72 I went through the whole D-Jet. The relay board was suspect, so I removed that for some TLC. While I was at work my wife actually took the time to scrape all the tar off the back with a bucket of solvent so I could inspect and repair. Nasty job, bless her heart (come to think of it, that may have been the LAST thing she did for me on that car.... (IMG:style_emoticons/default/idea.gif) ). Anyway, I did end up finding some questionable connections and soldering or reinforcing those before sealing it back up again.

Good suggestion- you probably can guess how I'm going to answer- I have a stack of 4 relay boards and spare relays. Continuity has tested good on all of them, although I swapped the one in the car out anyway. I will check the ground connection there though, somehow I missed doing that.

[904svo]

Just a WAG , check the ground strap from the transmission to the body

[rjames]

Just a WAG , check the ground strap from the transmission to the body

Done, but keep 'em coming. (IMG:style_emoticons/default/smile.gif)

[yellowporky]

Not sure it is possible to cause a stall but is your ignition switch goofy?

[rjames]

Not sure it is possible to cause a stall but is your ignition switch goofy?

It's crossed my mind, but because the stalling seems to be tied to the idle fluctuation, I'm inclined to think the ignition switch is ok.

[yellowporky]

So when the car is warm it idles down and stalls? Not like it cuts off.
Is the decel valve functioning? On my 73 with everything nos or rebuilt it has some strange return to idle behaviors and I just assume that it is the goofy old d-jet. When warm the engine returns to idle pretty slowly and sometimes stays around 1,200 rpm for a bit before settling down but often times the light will change and you are off again before it completely idles down.
With how off your compression numbers are you only have that remaining
A friend reminded me of the product Sea Foam the other day and he runs a can through his fuel tank every once in a while to keep everything super clean

[rjames]

So when the car is warm it idles down and stalls? Not like it cuts off.
Is the decel valve functioning? On my 73 with everything nos or rebuilt it has some strange return to idle behaviors and I just assume that it is the goofy old d-jet. When warm the engine returns to idle pretty slowly and sometimes stays around 1,200 rpm for a bit before settling down but often times the light will change and you are off again before it completely idles down.
With how off your compression numbers are you only have that remaining
A friend reminded me of the product Sea Foam the other day and he runs a can through his fuel tank every once in a while to keep everything super clean

Everything is intermittent. When it does stall it stalls immediately when taking my foot off the gas pedal with seemingly no loss of power beforehand. Usually by the time I limp it home, the stalling goes away. :/
To be fair, the car hasn't stalled since I replaced the ignition and FI harnesses, but I haven't driven it that much either.

The idle surges are intermittent too. The last time I took it out, the idle was stready at 1000 RPMs after warmup. After driving it a bit, the idle crept up to 1200, but was steady. More driving led to the idle surging from 600-1200rpm. Got back home and the idle surge range changed to 1000-1200rpm.

Seems like if it was a compression issue it would be constant and the engine would be lacking power, which doesn't seem to be an issue. But maybe that's not always the case?

[euro911]

Compression #s with engine warm, all plugs removed and throttle open:
110, 110, 130, 131

Robert, I haven't read the entire thread, so pardon me if this has already been addressed.

Which cylinders have the low compression #s. 1. ____ 2. ____ 3. ____ 4. ____

Have you performed a valve adjustment? If not, do so, then check compression again.

I had a hunting idle on the '71 (1.7L) when I first acquired the car. I replaced all the vacuum lines, adjusted points, set ignition timing, etc., but after adjusting the valves (right bank valves were too tight, not completely seating), the hunting stopped (IMG:style_emoticons/default/idea.gif)

(IMG:style_emoticons/default/popcorn[1].gif)

[rjames]

Compression #s with engine warm, all plugs removed and throttle open:
110, 110, 130, 131

Robert, I haven't read the entire thread, so pardon me if this has already been addressed.

Which cylinders have the low compression #s. 1. ____ 2. ____ 3. ____ 4. ____

Have you performed a valve adjustment? If not, do so, then check compression again.

I had a hunting idle on the '71 (1.7L) when I first acquired the car. I replaced all the vacuum lines, adjusted points, set ignition timing, etc., but after adjusting the valves (right bank valves were too tight, not completely seating), the hunting stopped (IMG:style_emoticons/default/idea.gif)

(IMG:style_emoticons/default/popcorn[1].gif)

No points lost for not reading through the whole thread. It's a lot to go through. I thought about starting a new post that starts off with everything I've tried, but then I'd have to re-read it myself. (IMG:style_emoticons/default/rolleyes.gif)

Valves have been adjusted.
Compression check on warm engine: cyls 1 & 2: 110, cyls 3 & 4: 131

[bzettner]

I'm on pins and needles! What is the latest on your intense diagnosis? I'm dealing with something similar and have read all of this thru a search and I'm listening to all of it. (IMG:style_emoticons/default/confused24.gif)