Backfire after spark plug wires replaced

[aznon1]

We had our spark plug wires replaced...with porcelain wires...but our motorhome is still backfiring, missing and loosing power when it shifts down for hills or when we ask it for more power. I have read thru 50 pages of problems on line. Our coach is in the fix-it shop today. Would a leak in the exhaust manifold cause those symptoms?

[aznon1]

We had our spark plug wires replaced...with porcelain wires...but our motorhome is still backfiring, missing and loosing power when it shifts down for hills or when we ask it for more power. I have read thru 50 pages of problems on line. Our coach is in the fix-it shop today. Would a leak in the exhaust manifold cause those symptoms?

[Richard 34A]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by aznon1:
We had our spark plug wires replaced...with porcelain wires...but our motorhome is still backfiring, missing and loosing power when it shifts down for hills or when we ask it for more power. I have read thru 50 pages of problems on line. Our coach is in the fix-it shop today. Would a leak in the exhaust manifold cause those symptoms? </div></BLOCKQUOTE>

It wouldn't be something as simple as a fuel filter or fuel pump, would it? (How many miles are on your MH?) Seems like a leak in the manifold could create those symptoms, and once had similar problems like that on a passenger car that turned out to be a plugged catalytic converter...

[DriVer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by aznon1:
... but our motorhome is still backfiring, missing and loosing power when it shifts down for hills or when we ask it for more power. </div></BLOCKQUOTE>If this type of condition is presenting itself, a service center equipped with a Tech II instrument would be your best resource to advise you what the problem is.

In my experience we have found that the TAC Module, which is a small electronics box lined with reflecting foil could be problematic. The box is located up and to the left of the brake pedal. This device controls the response from the gas pedal. A defective module will present in the manner you have described.

If this box is defective it will definitely show up on a scan. If you have a plugged fuel filter what will present itself would be an "O2" sensor problem as the engine would be starving for fuel.

I believe I can surmise that your motorhome isn't at a service center since I don't believe they would have replaced the wires with porcelain units unless they had ruled out any codes that would be present in your case given that the problem persists.

[aznon1]

We are actually at Midway Chevrolet in Phoenix. The spark plug wires were replaced in Medford Oregon on our trip back from Wash. state in September...the day before husband, Buz had a total cardiac arrest (and survived)! Midway Chev called and said the spark plug wires looked good...but suggested we replace the spark plugs, fuel filter and air filter. Our workhorse is an 03 with 23,000 miles on it. They replaced the fuel pump Dec 06 to fix the same back firing and loss of power when asking for extra gas....it didn't solve the problem. thanks for your suggestions

[TandW]

Check integrity of the mass air-flow sensor. Good luck!!

[DriVer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by T&W:
Check integrity of the mass air-flow sensor. Good luck!! </div></BLOCKQUOTE>Chief, Been there and done that! The MAF mostly caused a ping condition or that was my first hand experience with a MAF that had a major deformity in the screen. Unknown on my part if the MAF in a failed mode will cause backfiring.

[TandW]

Driver, when MAF fails into extreme lean condition engine will "cough" as throttle is opened. It sounds sort of like a backfire but rarely does in point of fact. Good luck!!

[Jeff H]

Sounds like you still have a burnt plug wire. Oregon to AZ. quite a drive.

[Steady Eddie]

The Coach is at the *right* place..Midway Chevrolet is a MD GM Truck Service Center. Reading the original post we do not know who the "they" are/were that replaced the fuel pump for a like problem in '06. "They" did not observe fuel rail pressure over time and driving conditions and were following the age-old rule of thumb: "If it pops, it's lean"..the new fuel pump did not fix it? It must have cured it for a time, as the Owners took delivery?? From the poster's comments it looks like Midway's Service Writer is a know-nothing. "Yeah, we'll throw an air filter element at it and maybe that fix your heavy wallet.." I had a Service Manager tell me once that I needed new front CV U-joint boots on my P32 Coach...
As DriVer has said, all these issues should be pointed out (found) with a Tech 2 Scan Tool. Did the rig (this time) ever throw a code?? Following the fuel path forward, it goes from the pump, through the gas filter, forward thru the fuel pressure regulator, into the fuel rail and on to each injector. Correct??

[kennersonf]

Has anyone thought it might be a crossed plug wire? That or a timing problem.

[Steady Eddie]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Fred K:
Has anyone thought it might be a crossed plug wire? That or a timing problem. </div></BLOCKQUOTE>
===========================
Fred--Thanks for the post.. ..the Poster said the rig was a 2003 Workhorse which has the coil-near-plug ignition system with no distributor. Each engine cylinder is supported by its' own coil pack, bolted the valve cover. The spark plug wires are individual to each and are only about 8 inches long. Both of the issues you brought up would be shown on a GM Tech 2 Scan Tool--if the Mr. Goodwrench knows how to use it. My gut feelings are that this is a case of getting a bit of a run around. I like to get one-on-one with Mr. Goodwrench and ask him a simple yes or no question.
"Are you an honest man?.." Yes or no. Look him right in the eye..works EVERY time and leaves the itchy Service Manager out of the equation..