UPDATED!: HELP! Lawnmower noise and what looks like backfire in the engine bay, Can someone help me figure out what may have happened? Options

[chrisdaun]

So 2 weekends ago I took the 914 out for a weekend drive. She was running great but on the way home the exhaust volume rose quickly and it started to sound like a loud lawnmower. I drove it 5 miles home and parked it till today.

She still starts and idles normal aside from the sound but when looking into the engine bay on the driver's side I noticed what looks like a backfire coming from a small hole just left of the air intake runner. I've attached a picture with an arrow pointing to the hole.

Anyone know what could be causing this?

Engine is a 2.0 fuel injected from a 74

Thanks in advance for any help or suggestions.

[reharvey]

That little hole in the head is for the EGR air injector. It goes right into the exhaust port above the exhaust valve and what was used to cap it off has come loose or failed in some way. All you need to do is find a way to cap it off again. Remember you're dealing with hot exhaust gasses under pressure. I capped mine with threaded metal plugs. If you can see threads in the hole you may be able to do the same. Good luck, Ray

[tod914]

x

[Dr Evil]

I used 10mm valve adjust screws to plug them. I know they are 10mm x fine pitch (I think it is 1.00).

[TheCabinetmaker]

head is from a75/76. Engine# will tell you what year the case is from.

[Tom]

Looks and sounds like it used to have the plug in there, so look around in the engine bay for what was closing the hole up before. Better check the others also. Two per side.
here is a pic of mine. First the front one, then rear.
Tom

[chrisdaun]

Thanks for the info guys. I seem to be missing all 4 of them. Is it normal not to have them in there? Did a gasket cover the hole and fail possibly?

As far as getting some bolts to plug the holes, I can get some 10mm fine thread like suggested above but is there a max length i shouldn't exceed?

Thanks again for all the replies! Your guys are super quick and helpful (IMG:style_emoticons/default/smile.gif)

[chrisdaun]

Looks and sounds like it used to have the plug in there, so look around in the engine bay for what was closing the hole up before. Better check the others also. Two per side.
here is a pic of mine. First the front one, then rear.
Tom

Any idea how long those bolts are and where the threads start in the head?
I stuck a 3" long 10mm bolt down the hole but never hit and threads.

[euro911]

Yes, you have either '75 or '76 heads.

I blew one of those out of a '75 head too. Had a big old flame shooting out at me.

Looking around in the engine bay, I found a 1" long set-screw looking stud with an Allen tip sitting on the left engine shelf.

I reinstalled it with a dab of Loctite, then did the same to the other three. The threads start quite a ways down in the hole, so I used a long Allen wrench to tighten it up.

There are a few ways to plug the ports ... sounds like maybe you also have Allen 'studs' plugging yours if you don't see bolt heads on the other three ports.

The pix Tom posted show what look to be brass(?) caps installed on the OEM air injection ports' screw in-fittings. Others have installed long bolts like you originally tried.

[chrisdaun]

Yes, you have either '75 or '76 heads.

I blew one of those out of a '75 head too. Had a big old flame shooting out at me.

Looking around in the engine bay, I found a 1" long set-screw looking stud with an Allen tip sitting on the left engine shelf.

I reinstalled it with a dab of Loctite, then did the same to the other three. The threads start quite a ways down in the hole, so I used a long Allen wrench to tighten it up.

There are a few ways to plug the ports ... sounds like maybe you also have Allen 'studs' plugging yours if you don't see bolt heads on the other three ports.

The pix Tom posted show what look to be brass(?) caps installed on the OEM air injection ports' screw in-fittings. Others have installed long bolts like you originally tried.

Well.... Bad news....
I got a longer bolt and threaded it in enough to plug the hole until I could order a valve adjustment screw like listed above. The other 3 holes still had the plugs in there and tight.

I started the car and it ran great like it used to. After about 15 minutes on the road the car started to hesitate and as i was pulling over white smoke poured out the tailpipe and the car died and would not restart.

Had the car towed home. Anyone want to buy a new project car?

[Cap'n Krusty]

That little hole in the head is for the EGR air injector. It goes right into the exhaust port above the exhaust valve and what was used to cap it off has come loose or failed in some way. All you need to do is find a way to cap it off again. Remember you're dealing with hot exhaust gasses under pressure. I capped mine with threaded metal plugs. If you can see threads in the hole you may be able to do the same. Good luck, Ray

The EGR and the Air Injection are 2 different systems. The holes shown are for the AIS, which uses a pump to force air into the exhaust ports, diluting the exhaust gasses. The EGR takes exhaust gasses and puts them into the intake, in this case the air cleaner (right above the throttle body).


The Cap'n

[euro911]

That sucks.

I was in no position to stop when I lost my 'plug' (night time in a really bad neighborhood), so I hobbled it home to find the problem the next day.

Even after I replaced the plug, it never ran right again. We ended up pulling the engine out and had a 2056 built up with new heads.

I still haven't taken the old heads apart to see what actually happened, but I think I drove it too far (about ten miles), sucked in a lot of cold air and it warped and exhaust valve (IMG:style_emoticons/default/confused24.gif)


Take the top end off to see what happened ... hopefully you only need a valve job (IMG:style_emoticons/default/confused24.gif)

[chrisdaun]

That sucks.

I was in no position to stop when I lost my 'plug' (night time in a really bad neighborhood), so I hobbled it home to find the problem the next day.

Even after I replaced the plug, it never ran right again. We ended up pulling the engine out and had a 2056 built up with new heads.

I still haven't taken the old heads apart to see what actually happened, but I think I drove it too far (about ten miles), sucked in a lot of cold air and it warped and exhaust valve (IMG:style_emoticons/default/confused24.gif)


Take the top end off to see what happened ... hopefully you only need a valve job (IMG:style_emoticons/default/confused24.gif)

No worries.

I'm serious about selling it though if you know anyone close to the East Bay Area.

Craigslist Ad:
http://sfbay.craigslist.org/eby/cto/3032554322.html

[chrisdaun]

Update: Yesterday I charged the battery and she fired right up! I changed the engine oil, drained and refilled the transmission with some fresh 80/90 GL5 gear oil and cleaned the battery terminals. Everything seemed to be fine so I took it for a drive but stayed close to home.

After about 15 minutes of driving around it started to sputter and hesitate and died just like before. It would crank over but not fire and there was a strong smell of gas from the tailpipe. I pushed it back into the garage and let it sit overnight and this morning it started but after some cranking and sputtering.

I'm guessing that after heating up something is causing the spark plugs not to fire and then the engine floods and needs to sit for the gas to evaporate out. Maybe the coil?

Any thoughts or ideas before I start buying parts? Pretty sure I can get the coil tested locally but not sure if that will test OK in a cold state.

Thanks in advance.

[TheCabinetmaker]

Yes, coils can break down when they get hot. Been stranded on the highway more than once from dead coils, and not just in 914's. any coil. They work fine till they get hot, then quit. Not saying this is your malfunction, but it is a symptom.

[SLITS]

1st ... I would ohm out the CHT ... pain in the ass to get to ... I say this because I bought a car with the CHT disconnected. I tried to start it and it wouldn't. Filled the exhaust with fuel. When I discovered the problem, I hooked it up and it fired off .. blew raw fuel out the exhaust pipe. When they go bad, it causes all sorts of problems.

2nd ... I would check the MPS. Had one go bad in Moab, UT. No start, shit piles of fuel in the exhaust. Had a spare, changed it and fired up and ran till I sold the car 2 years later.

3rd ... when it quits, check for spark. If none, look at the coil and condenser. When heated up, the coil can go bad.

That's the way I would proceed ........

[JeffBowlsby]

1st ... I would ohm out the CHT ... pain in the ass to get to ... I say this because I bought a car with the CHT disconnected. I tried to start it and it wouldn't. Filled the exhaust with fuel. When I discovered the problem, I hooked it up and it fired off .. blew raw fuel out the exhaust pipe. When they go bad, it causes all sorts of problems.

2nd ... I would check the MPS. Had one go bad in Moab, UT. No start, shit piles of fuel in the exhaust. Had a spare, changed it and fired up and ran till I sold the car 2 years later.

3rd ... when it quits, check for spark. If none, look at the coil and condenser. When heated up, the coil can go bad.

That's the way I would proceed ........

(IMG:style_emoticons/default/agree.gif) Sounds like a failing CHT or MPS. Will your MPS hold a vacuum?

[chrisdaun]

1st ... I would ohm out the CHT ... pain in the ass to get to ... I say this because I bought a car with the CHT disconnected. I tried to start it and it wouldn't. Filled the exhaust with fuel. When I discovered the problem, I hooked it up and it fired off .. blew raw fuel out the exhaust pipe. When they go bad, it causes all sorts of problems.

2nd ... I would check the MPS. Had one go bad in Moab, UT. No start, shit piles of fuel in the exhaust. Had a spare, changed it and fired up and ran till I sold the car 2 years later.

3rd ... when it quits, check for spark. If none, look at the coil and condenser. When heated up, the coil can go bad.

That's the way I would proceed ........

Thanks for the suggestions. I think I might rule out the coil because today when I started the car it fired right up but ran really rough. The idle is now really rough and when revving the engine even a little the car shakes. Its not longer drivable. I'll check the CHT and the MPS. Another suggestion was to see if the MPS holds a vacum. Is there an easy way to check that?

[euro911]

I use a Mighty-Vac



Start checking all the FI components. If you have D-jet FI, a good place for trouble-shooting info is Paul Anders' site Click Here

[somd914]

Your symptons are very similar to mine when the CHT harness wire was broken and making intermittent connection.

Check the resistance on the CHT on the CHT lead, then check it through the FI wiring harness at the ECU connector. Wiggle the wires when testing and see if the resistance changes.

My lead was broken on the harness side just before the CHT connector.