91 vanagon struggles with low power

[ourv12]

My 91 Vanagon struggles to accelerate after it gets to operating temps. Ive noticed that if i drive it shortly after cold start up it has more power cause Im assuming its running richer during cold startup. Once it gets to normal operating temps its struggles to accelerate and it resembles it being starved of fuel like maybe running lean?? What would cause it to starve of fuel after it gets to operating temps? It starts just fine warm or cold and idles fine but driving under load is different story. Its had new fuel filter, plugs, o2 sensor fairly new, temp sensor is fairly new, injectors are good, cap and rotor, plug wires, and timing is slightly advanced. Any ideas what would cause it to run too lean?

[MarkWard]

It takes more fuel to accelerate than it does to rev the engine in neutral. First step would be to measure the fuel pressure. Fuel pressure may be fine on start up, but falls off as the pump warms up.

[Ahwahnee]

Other suspects might include a short to ground in the fat green O2 coax wire (would cause it to run rich but only after a few minutes) or a plugged catalytic converter.

What di the plugs look like?

[ourv12]

[ourv12]

[ourv12]

[quote="Ahwahnee"]Other suspects might include a short to ground in the fat green O2 coax wire (would cause it to run rich but only after a few minutes)

Is there a way to check the 02 coax wire with a ohm meter for a short to ground??

[MarkWard]

[ourv12]

[DanHoug]

take your voltmeter, ground the negative lead and slip the positive underneath the rubber boot of the O2 sensor connector in the engine bay. you'll be expecting values between 0-1vdc if your meter needs to be set on a range. you want the O2 sensor connected and the voltmeter on it.

with the engine warm, look for frequently varying values above and below 0.5v.... like once a second or so. that's the sign of a healthy O2 sensor and engine management changing the mixture as needed.

assuming a healthy O2 sensor (which can quickly and easily be contaminated by silicone from RTV sealant), a steady low value below 0.5v shows a lean condition. conversely, above 0.5 is indicating rich. generally, there are many ways that gets fooled up.
_________________
-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
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[MarkWard]

You didn’t mention you had checked the fuel pressure with a replacement pump. You still need to figure out if it’s compression, fuel, or spark.