jtrask

Hello all:

I have just picked up a 1987 4.0L 4wd (little waggy w/ panels). Was taking it over to pick up vacuum hoses and the muffler exploded.

Any thoughts on why the muffler exploded would be helpful. I'd like to correct whatever caused it to blow before I have another one installed.

Thanks!
Jan

The Rooster

pictures? did the jeep back fire at all before this happened?

Carl48

Too rich fuel mixture...raw gasoline into hot muffler...kaboom.

jtrask

Yes, it did stumble and backfire. Here's a photo of the muffler.

If the fuel is running rich, how do I adjust it?

RTorrez1

I did have this happen to me in an old Dodge that I had a long time ago and it was due to it running to rich like Carl48 mentioned. It didn't back fire at all. But, after running for just a little bit it did explode.

89Laredo

Wow... I'd say its time for a tuneup

Omnipotent Octopus

I have never seen a muffler explode....pretty interesting.

89Laredo

used to happen with old carbed vehicles alot... Usually manuals, If they stalled it would still send fuel into the exhaust.

cpnwrench

muffleranatomy 101....... wow, never seen that!!!

check spark plugs for proper gap and for fouling, replace.


any codes you can retrieve?

O2 sensor?
MAP sensor?
TPS?

Clean the IAC.

87.....does it have an EGR valve? (diagram on firewall over brakebooster should define that, if its still there!)


vacuum lines all ok?


cpnwrench

jtrask

The EGR valve moves when I press it. Th EGR vacuum line was off. It's now reconnected.
New spark plugs (Champion Copper) as the old ones had carbon deposits.
Replaced the vacuum line that services the cabin air because that had a break. Replaced the vacuum that goes from the air cleaner to the CCV. The CCV needs to be replaced, but that is evidently a dealer part. It's clear though with no obstructions.

The Jeep is still backfiring. What do I need to check now?

Where is the IAC?

Thanks!

jtrask

Also ran seafoam through the injectors and dumped the rest in the gas tank.

89Laredo

When is the last time you did the oxygen sensor?

jtrask

Don't have a clue as I just got this last week. Is there a way to test the O2 sensor?

89Laredo

not really... Pry should get one, since renix wont tell you when its time, unlike OBD vehicles.
General consensus is that NTK is better than Bosch, and cheaper.

jtrask

I've just replaced the O2 sensor. It is running a little better, but still backfire when under load.

New MAP sensor, new O2 sensor, new plugs, cleaned IAC, cleaned throttle body, sprayed out TPS sensor when I was cleaning the throttle body. Not seeing cracks/breaks in the vacuum lines. PO put in new disty, cap and rotor. I think they mentioned that they also put in a cam sensor.

It's definitely running rich as evidenced by the carbon build up on all the plugs. When I press on the accelerator it bogs and backfires. It runs ok (but not great) when minimal pressure is on the accelerator. Seems to shift gears ok, but have not been able to get it past 2nd (auto trans).

The grounds are clean, and I'm running out of ideas. It seems like it's something in the adjustment area since all the plugs are equally carboned and there's no issue with cranking/idling.

Any thoughts or suggestions would be greatly appreciated as I want to get this running asap.

Thanks in advance!