Hey all, Got a big problem with my truck… I just completed a 700 mile trip over two days towing a 24ft boat in my 1998 1500 5.2L 4wd Ram.

I took it pretty easy with watching overheating and letting the truck rest every couple hours. At 300 miles into the trip some plug wires melted from being close to the header, luckily I had an extra set with me and also changed the cap & rotor, the plugs looked fine. Around the 500 mile mark, the fuel light turned on and I fueled up almost a full tank. After this my truck performance was pretty crappy.

Description at Idle: Smooth but erratic ticking and almost sounds like there is an exhaust leak.
After increasing the throttle: Bogs down and loses almost all power at high rpm (2500 to 3000rpm). Loud wooshing sound that wasn’t there prior.

After limping the truck and boat all the way home I proceeded to check the plugs/wires/cap and rotor again. All were fine. Plugs looked very good, no saturation however they almost looked as if it were running lean. Proceed to testing…

*Vacuum was pulling a steady 18psi at idle
*Checked the injectors by removing the electrical connectors, all responded the same by lagging about 50 rpm each.
*Visual check of the exhaust system for leaks, none found
*Changed timing chain/sprockets 3000 miles ago.
*Changed fuel pump 5000 miles ago.
Tomorrow I’ll do a compression test and pull the distributor to see if maybe its hosed…

Any input/help is greatly appreciated. Many many thanks in advance.

 

failure to rev up beyond 2500-3000 rpm sounds like a clogged cat.

to test - temporarily remove front O2 sensor to relieve pressure. if you see improvement, then it confirms the cat.

 

Also pour a bit of seafoam or oil in the intake while running and look for smoke in the engine compartment to find any exhaust leaks....
and not that its related to your issues but I hope you remembered to turn your overdrive off while towing...

 

Thanks guys, I'll check the cat and pour some seafoam after work. It is the original CAT, and that sounds like it is probably the issue. I'll respond tonight and tell what I found.

 

Seafoam is not going to fix it ! It's a 98. Plenum gasket is shot,along with the cat, o2 sensors, and plugs. Replacing them will fix it. And install a pcv valve from the dealer before you fire it up . While the intake is off, replace cap and rotor and plug wires. Route the plug wires in this manner. http://dodgeram.info/tsb/1998/18-48-98/18-48-98-v8.htm

 

did you even read my suggestion?
The seafoam is merely an easy safe way to tell if he has an exhaust leak in this case... the ticking he describes is a possible symptom of a leak and the seafoam will cause smoke to exit the leak and show itself...

 

Yes I did read. It aint gonna fix it .

 

Did you experience any backfiring?

 

Isnt it possible you just got some really, really bad gas?

 

Haha... Certainly seafoam will not fix it... Although I didnt get around to doing that.

No backfiring whatsoever

It IS possible that the gas was bad, and at the same station ive gotten bad gas there in the past, Im fairly certain its the CAT, NOT the Plenum (i'll explain)

So over the past 3000 miles i've lost a quart (need to replace my rear main which leaks slightly) Plus i towed a 9000lb boat for ~700 miles. The spark plugs looked great when i replaced them yesterday--These are good enough to rule out a blown Plenum.

The CAT is original and has 175k miles on it. Tonight I ran started the truck, let it idle for a minute and had my brother put his hand up on the exhaust tail pipe and revved it up until it bogged down at ~2500 rpm. He said he barely felt any pressure increase. We went to his 99 Jeep which also has a 318 and did the same which had MUCH MUCH more pressure...

I then pulled the upstream O2 sensor and ran the truck. I was able to rev up to ~4000 rpm.

Problem found.

Time for magnaflow?