GE SPECTRA JGBP35 Gas oven

Solved a similar issue. Sounds like your glowbar igniter is shot and needs to be replaced. While the glowbar is glowing, it is not heating up sufficiently to release gas into the oven. The heat you feel in the oven is actually from the glowbar and not from ignited gas. Replace the glowbard. Here is what I recommended to someone else:

"Would be helpful to know brand and model. However, most gas ovens use a glowbar mechanism that regulates the amount of gas released into the oven. The glowbar also ignites the gas (and usually stays on all the time the oven is on). Often, the glowbar fails to heat up sufficiently and, as a result, doesn't allow the oven to release sufficient gas. If this happens, you may also smell small amounts of gas in the kitchen. The glowbar is hot enough to ignite the limited amount of gas being released into the oven. This is probably why the oven heats up but heats up very slowly. It's also possible that the heat being experienced in the oven is being generated from the glowbar itself without any gas being ignited. If this is the case however, it is unlikely that your oven to get very hot at all.

The way to test to see if they glowbar is failing is to test the amperage traveling to the glowbar when the oven is on. You can do this using a "clamp on meter" (purchased at any Home Depot or Lowes). Depending on the particular kind of glowbar you have, it should read above a certain amperage (in my case the reading was 2.7 amps and it should have been between 3.2 and 3.7 amps). I ordered a new glowbar from www.appliancepartspro.com and installed it myself (very easy). It fixed the problem. Here is a link that explains it pretty well (http://www.appliance411.com/faq/gas_range_ignition_systems.shtml#glow). Hope this helps."