MH will not start

[txredfish1]

I own a 2004 Newmar Scottsdale on 2004 Workhorse 8.1L chassis.
At first the engine would start but moving up and down about 300 RPM until warmed up and then it ran OK. I took out and cleaned the mass input sensor (did not seem dirty) with the proper cleaner, checked air filter (looked OK). Went for a 60 mile drive, it did just fine. Next day, started engine, did the same, RPM up and down until warmed up. I then cleaned the throttle body, let it set for awhile. Tried to start, back fired a few times but would not start. It started one time, ran for about a minute died and then will not start. I checked a spark plug, it had gas on it and was fouled. I cleaned off the gas replaced back and tried to start, again I checked spark plug, same, a lot of gas on plug. A lot of spark from the coils. Checked fuel rail, plenty of fuel pressure. My mechanic came over, used his OBD II code checker. No error codes. Unhooked MAF sensor plug. Checked codes and still no codes. He thought that he should be getting some error codes. He thinks that the ECM is bad but not 100% sure. I checked ground wires, ECM plug wires. He said that temperature sensor, crank sensor and oxygen sensor was OK based on what he saw on his code checker. Any ideas?

[Stim]

How soon before it started acting up did you put gas in it?
Might be a water problem/bad fuel. ???

[mikim]

http://www.workhorseservice.com/services/engine-ventilation-cooling-kit/

Engine Ventilation Cooling Kit
Part #W8005026

This helps prolong the life of your exhaust manifolds and spark plug wires.
Includes new spark plug wires and shields for $199.50!

[crasster]

mikim wrote:
That model Workhorse chassis had problems with spark plug wires being burnt. They had a recall to put in a heat shield and additional air flow through the grill directing outside air directly onto the spark plug wires.

I agree, I would check and see if the sparks actually fire.

[Gjac]

Ed, I have a 1996 MH with a 454 TBI. The IAC is located on the RH lower side of the TBI. I had a lot of trouble with mine. It can be removed with 2 screws. Sometimes carbon will build up on the pindle and or the shaft that controls the pindle. Also check if the pindle is seating properly. You can clean and re install to see if that helps your rpm's.

[JimM68]

Theidle air control and throttle position sensor are both on the throttle body, and both are replaceble separately.

[txredfish1]

Matt,
I replaced the spark plug wires about 2 years ago (500 miles). I don't see or hear them arcing. About a month ago, when I was first having the problem, the engine was starting and running. But after started and running, the rpms would go up and down (about 300 rpm) until warm. Then OK. My mechanic placed a code reader on the engine at that time with no codes being set. Would this sound more like the TPS or IAC? Now engine just turns over and no starting and still no codes. Is the TPS located on side of throttle body? If located on side of throttle body, would I have to replace complete throttle body or just the sensor? Where is the IAC and TPS located? Thanks for the tips............

[Matt_Colie]

Txred,

On most vehicles, there are three things that go bad that may not set a MIL (code). Those are: the TPS (Throttle Position Sensor), the IAC (Idle Air Control) and Spark plug wires. The first two because the computer can't often tell the difference between a bad sensor and someone doing something that they shouldn't do. The wires only will show as a code if they cause a mis-fire and that can be difficult to detect without load on the engine.

So, inspect the plug wires first. If you need to replace them, hang on, they aren't cheap.

Matt

[mikim]

That model Workhorse chassis had problems with spark plug wires being burnt. They had a recall to put in a heat shield and additional air flow through the grill directing outside air directly onto the spark plug wires.

[enblethen]

Not sure what years have them, but there is a component called "Idle Air Control (IAC) valve" It sort of acts like a choke.
On my TBI injected engine, it is the base of the throttle body.