[tbucket101]

Has anyone, who has experienced an issue that turned out to be one of these ever have the truck BACKFIRE while acting up (cutting out while driving, stalling, and dying).....the damn backfire symptom has me puzzled as it "seams' that if it was a componet such as the ASD, then fuel would be shut off to the cylinders, therefore no excessive fuel would be dumped w/o a spark.....Ive heard that the CPS will cause these symptoms but have not red or heard of anyone having the backfire issue, and if it was the fuel pump, then would it stand to reason that if it is shutting the fuel supply, a backfire condition could not exit?.....or am I confused and dont have that corret thinking on what causes a backfire..ie, adequate fuel but a momentary laspe in spark

[John in MA]

An actual backfire is caused by timing issues or premature detonation.

You're grasping at straws. Go through this step-by-step. First run the codes and see what pops up. Then start measuring voltages and fuel pressure.

The CPS is a very likely cause. Common problem. And it relates to timing.

[greasefingers]

Yes a lean condition will cause the engine to back-fire. Figuring why is a different story. Pull the codes as John said.

Also what year, engine, and mileage???????????????????

Extracting Fault Codes:
Without ever starting the engine Turn the ignition switch ON, OFF, ON, OFF, ON and observe the CHECK ENGINE LIGHT. The CHECK ENGINE LIGHT should begin to flash a series of codes. The flashes will be separated by short and long pauses. The long pauses separate the "ones" and "tens" positions, and each code from the next. A code 55 will be displayed at the end of the test.

[John in MA]

Or if he has a later one the codes will be printed on the odometer readout.

[tbucket101]

Sorry, '98 GC, 4.0 auto, 110k.....CPS was changed today and nothing, still the issue, no codes are being flagged and at this point it is at a shop that "guarantees" they can solve this mystery....we will see.....

[Kcolg]

Mine just started this same issue over the weekend.

I went wheeling in Disney, and it kept acting like it was going to die, but never would.

On the way back home on the highway it would start to cut out again and I would loose power (no matter how much throttle I gave it it just started slowing down). Then is started backfiring while driving down the highway. I could hear it and feel it through the gas pedal.

Checked the codes and there were:

12 - ?
51 - ?
55 - end of codes

I know it is not related but no tranny codes either just the code 55.

Milage is 140,000

[tbucket101]

Sounds very familiar, will let you know what the shop says on mine.....

[Wheelin98TJ]

I'd say the most common cause of backfiring is an exhaust leak. This lets oxygen into the exhaust system and causes the explosion (backfire).

When does it usually backfire? During deceleration? Or is it more of a random occurrence?

A lean condition will also cause backfiring, so not getting enough fuel is definitely a possibility.

[tbucket101]

Well really the backfiring portion o fthe problem is probably just a symptom of the root cause as I have been experiencing the stalling/cutting out/dying issues w/o the truck backfiring but just recently this is an added little benefit to the problem......

[Wheelin98TJ]

You need to take a fuel pressure reading.

There is a schrader valve on the fuel rail. PSI should be 49.2 (+/- 5 PSI).

[Kcolg]

My backfire occurrs while accelerating.

Will see about getting the fuel pressure checked. If it is a fuel pressure issue, then would that for sure narrow it down to the fuel pump and or filter right?


tbucket101 any word on yours?

[greasefingers]

I believe I got my fuel pressure gage at Pepboys for $ 29. Just make sure it says Chrysler vehicles on the package. That way it will be the correct threads to screw on to the schrader valve at the fuel rail.

[WBowie]

Clogged fuel filter? Mine never backfired but I would lose power and it seemed like a bad fuel pump. Ended up being the sending unit in the tank and a clogged/old fuel filter.

[dino61]

I just had an intermittant fuel pump relay problem, with similar symptoms...swapped it with the intermittant wiper relay temporarily till I got a new fuel pump relay..

[Kcolg]

How did you discover that it was the relay that was bad. How did you test the relay? Just test for continuity?