Hello.


I have a 1995 Dodge Ram 1500 V8-360 5.9 Liter.


It has been working fine up until last week. I had just left, driving down the road and it started to falter, sputter and lose power above 2000 RPM. I brought it back and started to diagnose the problem.


The fuel pressure stays steady at 40 PSI, it doesn't change at all at idle or acceleration. There may be a fuel pressure regulator, I have not checked. All the components of the fuel system (filter, pump) are one unit in the tank and I have not replaced that yet, I am hoping I do not have to do that.


I just replaced the crankshaft position sensor because that is apparently a common problem, but it did not solve the issue.


Compression is consistent for all cylinders at about 115-125 PSI.


No oil in the throttle body, not likely a gasket issue, no burning (or at least not much) of oil. My levels are not changing.


No codes. It has an OBD 1 (not 2) - no codes present and no check engine light.


I have not pulled the injectors yet.

Pulled the connector to the O2 sensor on the catalytic converter, no change. I also "banged" on the catalytic converter - no noise potentially indicating it is not a problem with the catalytic converter.

The truck will idle at about 900-1000 and be fine for about 5 minutes until it warms up. OR if I try to increase the RPMs (even after just starting it) the engine will start to run very rough and start to stall above 2000 RPM.


I did have a similar problem a couple years ago when I was near empty and I barely had enough power to move forward. I limped to the gas station, filled it up and it was happy. I currently have 1/4 of a tank so I don't think it is the same problem, although I did add some seafoam to the tank. I also had a cylinder misfire on my newer Chrysler van that turned out to be a bad/clogged fuel injector, but that was only affecting one cylinder, this seems to be affecting all cylinders.


This post is similar to "225365-engine-runs-rough-at-2500rpm-and-starts-to-die-at-3000-rpm.html"


I would appreciate any suggestions on what to look at next. Thanks.

 

I would suspect the cat was clogged in any event. If you can, take that front O2 sensor right out of the cat, see if the truck runs any better.

 

You can still check codes, I had a 95 obd1….do the key dance trick then watch the check engine light, it will blink the code….example. It will flash check engine light 2 times, short pause then three times, that’s code 23, just look online what they are but I remember being able to pull codes up quickly online and that was 12 years ago when internet wasn’t as user friendly so to speak

 

40 psi is a little below spec but I think it wouldn't show as a problem until way up in the RPM range, if at all.

Does it smell like unburnt gas ? One of the quirks of the earlier second gen trucks is that the PCM and the instrument cluster use separate temperature sensors. A failed PCM temp sensor makes the engine run really rich. Would be easy to check with an OBD1 dial tool but I realize these are not easy to come by nowadays (pro level tools often still have OBD1 adapters).

 

Thanks for your replies.

Yes, I remember the key switch flashing of check engine light codes many decades ago! I used to do that on some 80's cars I had IN the 1980's.

But, I also happen to have an OBD1 adapter - no codes and no check engine light at all. Whatever it is isn't throwing a code, which is odd considering the issue.

DerTruck - No, I don't smell it running that rich and this vehicle DOES have a fuel pressure regulator so it would appear that is working since the pressure is not changing.

HeyYou - I'll see if I can get the sensor out (it has probably been there for decades) and see if there is any change.

I still wonder if it is as simple as bad gas or a clogged injector.

It would be nice if there was a definitive way to determine the problem without throwing unnecessary hardware at it.

Thanks.

 

Can your OBD1 tool show live data ? If so check coolant temp and the O2 sensor readings which might give some clues.

 

Unfortunately not DerTruck. I hooked it up and all it said was "No Codes" (or similar) there were no options at all.

Didn't get a chance to work on the truck today, it may not be until the weekend. But feel free to throw out any other ideas. Thanks.

 

It might not hurt to put some fuel system/injector cleaner into the gas tank.

 

Sorry for the great delay in responding but I did find the problem. As HeyYou suggested, I removed the cat O2 upstream sensor (located inside the cat) and the truck could breathe again and ran fine.

I removed the exhaust system, cut off the pipes from the cat and everything inside was busted. (Although when I banged on it, there was no rattling of broken pieces inside)

Unfortunately it is an expensive replacement so I will be purchasing a new cat for the truck shortly.

Strangely enough, the new cat's are half the size of the current cat. Everyone tells me this isn't a problem, but it seems to me there would be an air flow restriction due to the small size. We will find out soon enough.

Thanks for all the help!

 

For what its worth, I decided to upgrade to 3" exhaust (from the cat to the back) when my cat became old and worn out. The parts I used are as follows:

Dynomax UltraFlo Welded Muffler - 17233
Magnaflow Converter - 99047HM (dual 2" inlets, 3" outlet, front O2 sensor port)

I took these items to a local exhaust shop and they added the 3" straight pipe I needed, along with fabricating/bending a 3" tailpipe (plus adding an O2 bung in the 3" pipe behind the converter for the downstream O2 sensor) and welded everything up. The shop re-used my stock Y-pipe and welded it into the new converter. Truck feels powerful and the exhaust is tight and quiet.