87 backfired then quit???

[movin]

87 was cruising, backfired, then died as though the ignition was switched off. It will restart and idle but dies when placed under any load or throttle opened past idle. Any idea what to look for?

[nhromyak]

Sounds like a vacuum leak... Check intake head gaskets and tighten.

Also check all vacuum lines, especially to the fuel pressure regulator.

Good luck.

------------------
Nick Hromyak
'85 Carrera 7 & 9 Fuchs
Havin' Fun in Sacramento

[john walker's workshop]

the two most common items to fail are the DME relay and the head temperature sensor. check the three plastic plugs on the left side of the engine to make sure they're snapped on all the way. 2 black and a white one on the top. if the white plug only has one male terminal inside, it's the troublesome old style temp sensor.

[This message has been edited by john walker's workshop (edited 06-07-2001).]

[vjd3]

Not to post the same answer again and again but ... I suggest you check your throttle idle switch.

It works like this: The throttle idle switch tells the DME when the throttle is closed. The DME will cut off the fuel when you take your foot off the throttle as you decellerate, from about 3500 rpm down to 1200 or so, when it comes back on to allow you to idle. This is to save fuel and reduce emissions.

When the switch goes bad, the DME thinks the throttle is closed all the time. The car will idle normally, but giving it gas will make it bog down, backfire or die completely. If you can keep goosing the gas pedal and get lucky enough to push the rpms up over 3000 or so, and hold it there, the engine will accept throttle over 3000, but let it fall back below 3000 and you're stuck at idle again.

My former 88 Carrera did this intermittantly and it was a bear to diagnose because it wouldn't do it in front of the mechanic. A second shop diagnosed the problem immediately when I described the symptoms, put in the $65 switch (an hour of labor) and the car ran perfectly from then on.

Now, it *could* be the other things mentioned, but if you can get the car idling, bogging down and see if you can get the revs over 3000 and see how it behaves, my money's on the throttle switch.

Vic
88 Carrera

[movin]

Thanks for the help. I started with the DME relay, I had a spare, no effect. Next, I swapped the DME processer with a performance part I quit using because of poor gas mileage, bingo! that was it! I wonder how many DME units are claimed to be in need of replacement when this is the only problem. One thing more, does anyone know of a performance chip that delivers good gas mileage and performance? Maybe the best route is to tweek the DME unit via the tuning pot on the back and then adjust the air-meter adjustment screw about 9 to 10 turns out. Any comments?

[movin]

Well, I guess the problem returned. The car started 3 times after changing the chip, but when I tried to start it a 4th time to test drive it wouldn't start. Maybe there is something wrong with the DME. I am getting fuel during cranking at start-up but no spark. I working on the '911 Carrera Engine Starting Troubleshooting' check list today. Nice to know there is a place like this to go for help. By the way is there two ways of spelling Carrera, (Carerra)?

[Eric Coffey]

Tps (throttle position) sensor, head temp sensor, airflow sensor? just some ideas.

-Eric

[Eric Coffey]

Tps (throttle position) sensor, head temp sensor, airflow sensor? just some ideas.

-Eric

[Wayne 962]

Check the switch (backfiring is a rare occurance with these cars, and is symptomatic of this problem, like the early MFI cars). Also check for vacuum leaks (try spraying carb cleaner around the FI components (have a fire extinguisher on hand, in case you have open sparks!)

-Wayne

[movin]

OK, checked for vacuum leaks, found none, tightened hose clamps and manifold bolts anyway. Checked cylinder head temp. sensor, resist. ohms OK. Got the car started, seemed OK, idled and took throttle without a hitch. Check temp. sensor again at warm up, readings OK as temp. climbed. I'm still not confident it won't quit again. The symptom is to suddenly shut down while idling or cruising in gear, as though the ignition was swithched off. Attempts to restart yeild refusal to start. I got to wait till it cuts out again and then check voltage to the coil and spark from the coil during restart attempt. That should verify the ignition sys. is working. The reason I'm not looking at the throttle switch yet is I smell fuel during start-up attempts, so it's getting fuel and the backfire occured only once, when the symptom first started (shut-down). Just seems to be an ignition related problem.

[twin plugged targa]

Hey 'Movin'
Check out my old thread for some ideas.
http://www.pelicanparts.com/ultimate/Forum3/HTML/009484.html
Your sypmtoms sound very similar to mine?.
It would die when warmed up whatever revs.

I replaced DME relay, swapped for another DME, new Dist. cap, rotor and coil. Improved initially but she still died!.

It has been mentioned that it is the throttle switch but I could not even get it to fire once dead. Serious backfires to the point where I was scared I was going to lose the muffler!.
After 10 days or so of constant diagnosis and disheartning attempts, I had it towed to my local wrench who is currently working on it.
I spoke to him today, he said when it dies, he was getting bad voltage to the coil. You may wish to check this, however, when cold i was getting good voltage at the coil.

I beleive he is now looking at the flywheel sensors that were replaced by 'Vertex' 6 months ago (maybe badly?).
I will post an update as soon as my car is fixed.
By ready your post, I strongly beleive our symptoms and cause maybe related.
If you find something before me, maybe you could post something.
Hope this is of some help,
rgds Ben

[movin]

Thanks, I'm going to start it up again with a timing light on the 'coil to distributor' wire to check for signal output from the coil during warm up, hopefully it will quit again and I'll see if it's ignition related. Last time I started it up it sat there for 20 minutes, no symptoms, so I'll try again until I get it to quit. I also thought about a faulty flywheel sensor as a source of the problem, hope it's not, sounds expensive to repair. Got the throttle position switch too but will hold off installing it until I rule out the ignition system. I'll let you know what I find.

Originally posted by 86ragtop:
Hey 'Movin'
Check out my old thread for some ideas.
http://www.pelicanparts.com/ultimate/Forum3/HTML/009484.html
Your sypmtoms sound very similar to mine?.
It would die when warmed up whatever revs.

I replaced DME relay, swapped for another DME, new Dist. cap, rotor and coil. Improved initially but she still died!.

It has been mentioned that it is the throttle switch but I could not even get it to fire once dead. Serious backfires to the point where I was scared I was going to lose the muffler!.
After 10 days or so of constant diagnosis and disheartning attempts, I had it towed to my local wrench who is currently working on it.
I spoke to him today, he said when it dies, he was getting bad voltage to the coil. You may wish to check this, however, when cold i was getting good voltage at the coil.

I beleive he is now looking at the flywheel sensors that were replaced by 'Vertex' 6 months ago (maybe badly?).
I will post an update as soon as my car is fixed.
By ready your post, I strongly beleive our symptoms and cause maybe related.
If you find something before me, maybe you could post something.
Hope this is of some help,
rgds Ben

[twin plugged targa]

Heh movin,
I also had no problems warming up at standstill, ran up to half way mark on temp. gauge (30 mins). Did not want to overheat engine at standstill and so thought cured!.
Drove it about 5-6 miles and at a temp. cooler than at standstill she spluttered and died. on trying to restart she just backfired.
I have not heard from my wrench yet, but as soon as I do I will post the findings.
I fear my labor bill will NOT be cheap, but hope that in some way it can save other people (including yourself) a huge chunk of money!.
Good luck
rgds Ben