Having an issue I hope someone can help me with.

Car: 89 GXL NA 5spd

Symptom: Will start up well, runs through the high RPM cycle, will then idle, runs for 3-4 minutes, and then just as it starts to warm up it just starts shutting down and can't be stopped (burping the throttle doesn't help). Can't start after that and the engine floods - after cool down and clean out of flood it will start fine and then do it again.

I just rebuilt the engine (2 used rotors, 2 new housings, and an Atkins rebuild kit) but this issue existed before I started the rebuild (was stored in my garage up to this point) as it would do the same thing when it was only running on the rear rotor (front spat a seal and scored the rotor and the housing, had no compression at all, and thus thus the rebuild).

I assumed this issue was part of not running on 1 rotor but it's still happening.

Note that when it does start now, the engine runs absolutely great - never ran better since I bought it.

Things I've checked:

1) Fuel - I seem to have lots of fuel coming from the filter and the filter is not very old

2) Air filter is almost brand new

3) I have a brand new set of plugs in it as I started it first after the rebuild with the old plugs that were in it and was saving the new ones for after it blew out all the Vaseline and crap from the rebuild.

Plugs are nice and clean when you pull them.

Note: also new ignition wires were installed as part of the rebuild.

4) verified that the plugs are firing from each coil before and after it shuts down

5) I haven't compression tested it yet but with the plugs out I'm getting a good compression "wooshing" from each rotor.

6) I tried restarting it right away by using a spray bottle with gas and spraying it in the intake as I turned it over. Doesn't go.

7) I tried compressed air injected into the intake as I turned it over. Doesn't go.

8) I put a brand new set of Bonez cats and an exhaust system so there seems to be lots of flow out the back and they shouldn't be plugged up. The manifold was also clean inside when I put it back on.

9) I put a brand new oxygen sensor on it as part of the rebuild.


I'm thinking that there's 1-2 sensors telling it to shutdown for safety or maybe the computer has gone a little screwy.

Has anybody seen this before and figured it out? Does anybody know what it is? Can you suggest what to try next?

Any help would be appreciated.

My email address is ghorner@xplornet.com if you want to email me directly.

Thanks

Grant

 

Update: Still haven't found the problem but I did do a compression test today.

Front Rotor:
Cold: 30 psi
After it quits: 32 psi

Rear Rotor
Cold: 32 psi
After it quits: 33 psi

(all numbers are approximate)

All bounces are completely even so it looks like my new apex seals are good.

I only checked one rotor for overall pressure (compression valve closed) and it only gave me just over 90 psi so that seems low but I'm hoping that's because it's never reached full operating temperature yet and hasn't been broken in yet.

I bought a clip on tester spark plug tonight so I'm going to test whether it's ignition or fuel shutting it down tomorrow.

Unfortunately I don't have a fuel pressure gauge to check the level of pressure before, during, and after for the injectors.

Any help, suggestions, or questions from anybody here would be greatly appreciated.


Thanks

Grant

 

Another Update:

Checked the spark yesterday while it was shutting down with a spark plug tool.

Looks like the ECU isn't shutting down the ignition (keeps sparking until it's dead) so this makes me think that it's basically flooding itself while running (too much fuel).

Anybody got any ideas?


Grant

 

I found out how to put the ECU into self-diagnoses and it's telling me there's an issue with the intake air temp sensor.

I have one on order and it's supposed to be in tomorrow.

We'll see if it solves my issue but I'm kinda thinking it probably won't.

Grant.

 

how is your timing?

do you have all 3 grounds?

your engine sound like low compression after rebuilt, but the problem u r experiencing is something else.

how is AFM and MAP sensor?

did u tested for vac leaks?

 

>how is your timing?

I can't keep it running long enough to to warm up and properly adjust the timing but it does run really well when it starts - better than it ever has.

I did mark on the CAS where the engine had been set before, lined up the marks on the CAS and the inside pulley when I put it back together so it does need to be checked but should be very close (especially since it runs so well for the 5 minutes).

>do you have all 3 grounds?

Yes - I broke the ground bolt off in the inner fender before I even started to take the motor out for the rebuild but I drilled it out, cleaned up the whole area, put a new bolt and washer on it, covered the inside with electrolytic grease, and covered the inside of the wheel well side with a protective coating to stop more corrosion.

I also had already replaced the ground wire between the transmission and the firewall as the previous owner had left the ground at the starter off so the original small wire melted eventually as it became the biggest ground for the starter. It's a lot heavier gauge now, has some good connectors, and has lots of electrolytic grease at both ends.

I also found the ground (this was before I needed to rebuild) that had been left off at the starter, cleaned it, put it back on, and covered everything with more grease so it has a good heavy ground again as it should.

>your engine sound like low compression after rebuilt, but the problem u r experiencing is something else.

Should be - I seem to have the right compression now and the issue actually existed before I started the rebuild. I was hoping the rebuild would fix it but no luck.

>how is AFM and MAP sensor?

How do I test them? I'll have to double-check the service manual but the Haynes manual says to leave it to the dealer (scary thought).

I did test the TPS today and found the narrow range is out of spec at 1.5K (should be 1K max). How would that affect running?

I wanted to test the coolant temp sensor at the back of the water pump housing but it's impossible to get the leads on the terminals of the connector since it's so close to the middle intake. I'll have to drain some coolant and remove it to verify.

>did u tested for vac leaks?

I have checked over all the vac lines during and after the rebuild - they are old but seem to be in good shape. I didn't find any cracks or loose fitting spots nor have I been able to find any leaks with a stethoscope when it's running.

I do have a fuel pressure tester gauge on order that also can be used to test vacuum so I plan to go through the engine when it arrives and check the pressure to see what it's doing when it quits.

Thanks a lot for the reply - I was thinking nobody had ever seen something like this before.

Grant

 

Found your post while searching for "oxygen sensor". My 93 FD is in the shop for the same symptoms...it just dies once it hits operating temperature. The diagnosis came back with a malfunctioning O2 sensor and water temperature sensor. It supposedly makes sense because the water temp sensor tells the ecu to decrease the fuel once it hits normal operating temperature. A malfunction here doesn't give the ecu this information, so the engine continues to run rich and subsequently kills the engine. Okay, I might have that backwards....but it made sense when they explained it to me. So you might want to check out the water temp sensor. Good luck.......

 

Another update:

I did some playing around, started it, pulled the water temp sensor right away (ECU should have gone into a limp home mode (adjusts the map to normal operating temperature)) and it did change how it was running a bit but still stalled after about 5 minutes total of running.

Looks like the water temp sensor isn't my issue.

Thanks for the info though Zoolander - much appreciated and glad to hear your FD is back up and running now. :oD

I played with it some again today and found that I can keep it running if I keep the engine over 2000 RPM (it runs great now since the rebuild). It seems to start to die somewhere around 1500 RPM or lower so it looks like it's definitely getting too much fuel and drowning itself.

My "assistant" (retired mechanic) and I sat and talked about what happened around the time this quitting issue started (before the rebuild).

Around that time, I tried to start the car one evening, the starter wouldn't role, and I was getting sparks around the ground wire from the firewall to the transmission bell housing.

I discovered the starter had been getting ground through it, it had melted off most of the insulation (it looked like it had been this way for quite a while) since it was too small to carry current for the starter, had burnt off, and this was all because someone previously working on the car had left the main engine ground off at the starter.

This means it was hunting for ground in other spots on the car also. I haven't found any burned ones yet but am wondering if this has somehow messed up the ECU.

It did run fine a couple of other times (just ran it, didn't actually drive anywhere) after I replaced the burnt ground and put the main ground back on at the starter.

Any comments or thoughts from anybody?

Maybe the ECU is activating the secondary injectors when it's not supposed to? Maybe messed up the fuel map and it's giving too heavy a fuel supply for under 1500 RPM in the normal operating temperature range?

I do have a used ECU on its way but it hasn't arrived yet so I'll try that when it arrives.


Thanks

Grant

 

you need to look for leaks with starting fluid.

but i dont think thats the reason why it's shutting off.


tps is ok, it's kinda higher cause it's not fully warmed up.



try this:


remove the bling cap from CAS (2 philips screws)

with main pulley at yellow mark verify the position of upper tooth

it should be pointing at the center or towards the bottom edge of the pickup.

ima try to find picture for you, or try to search, it's on this forum.


this is correct timing.

also, if you remove the little black tab, you should be able to see the tooth thru the little hole. should be in the lower portion when engine at yellow mark.