When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I've got a 1999 f53 in a 32 foot holiday rambler class A that tries to run but seems to be over fueling, shaking and putting out black exhaust. We know its got spark, so what are the normal suspects I need to look for? I can't get any codes so I'm looking for a starting place. I have experienced a couple of short rough idle sessions and the idle going so low it almost died then would surge back up and down but seeming a bit low. It almost seemed that the IAC was doing its job, but unsure. I found a loose PCV hose under throttle assembly. That hose is loose where it connects to the PCV valve it seems but I've put my finger over it to plug it off and still won't start.
I got my rig towed home. I was able to start it and had to keep the revs over 3500 and it smoothed out slightly. If I reduced the revs it started to shake and run roughly. While I was running it it tried to rescan for fault codes and none were stored in the ecu. Then it was as if fuel were shut off and the engine died.
It's really hard so far to diagnose and I'm hoping this sounds familiar to someone. Maybe thoughts on some diagnostic tools to capture the suspect component?
For a vehicle that age all the vacuum lines/plastic fittings are suspect.
Vacuum leaks could be causing some of the surging.
Check all the vacuum hoses (and plastic fittings), particularly where they connect to the engine which subjects the hose to heat.
I would recommend changing them all to silicone and any plastic tees to brass.
Is there a fuel pressure test port on the fuel rail which looks like a tire valve?
If so, you can check the fuel pressure when the ignition switch is turned from OFF to RUN and again when it's running.
Low or fluctuating fuel pressure can cause erratic engine issues, Harbor Freight has a decent price for a basic fuel pressure tester.
The IAC controls all airflow into the engine at idle and when sticky or not working can cause issues while it tries to adjust the airflow.
There are no codes for a poorly working IAC, only catastrophic fail.
The PCV valve is specific to an engine and the amount of airflow thru it is figured into the engine controls so I'm not sure what plugging it off would do.
Check the air intake tube for gaps/cracks, particularly between the MAF and the throttle body.
Has the MAF been cleaned lately?
Rezvani's Latest Post-Apocalytic Monster Is a Ford F-150 Raptor Underneath
Slideshow: Called the Fortress, the 850-horsepower pickup combines Raptor underpinnings with military-inspired features, survival equipment, and a starting price of $285,000.
