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YJ stalls under load Howell TBI 4.2 manual transmission

669 Views 15 Replies 6 Participants Last post by  MrTrash

Recently purchased a 1988 Jeep YJ 4.2 manual with a Howell TBI conversion stalls under load. California Version.

History of the Jeep is unknown but has a Howell TBI that looks almost new, almost like it was never run. The vacuum routing was a bit wonky when I got the Jeep. The MAP sensor was wired but not connected to the TBI. The distributor was not connected to the TBI and there was a cap over ”filter to atmosphere“ port on the TBI. the other sensors all had power when running. the electrical connects all appear to be sound.

I have been through the Howell install manual and all the connections appear correct. I checked as best I could for vacuum leaks with propane. I connected a gauge to the constant vac source on the TBI and it held pretty steady at 15/in hg. there is power to the MAP sensor and good power to the three fuses in the fuse box under the dashboard. I replaced the fuel filter as a precaution and fuel pressure is strong (I could not get a good reading). The jets have a good spray pattern. I added about 5 gals of fuel just in case the fuel was funky. Distributor is pointing to the number 1 cylinder at TDC. The timing is about 8 degrees.

the engine fires right up when cold and idles at about 950 rpm accordimg to the dash tach.

i haven’t been able to pull any codes from the OBD1 port or check if there is any issue with the fuel return.

any ideas for me? the problem is so bad that the jeep stalls every time I try to leave the driveway.

thanks in advance.
1 - 2 of 16 Posts

See post 4 on how to set your timing. You may have it retarded if you did not follow this procedure.

15 in hg vacuum at idle is low. retarded timing can cause that.

Using a fuel pressure gauge to verify your fuel pressure is a good idea.

Is your MAP sensor connected to intake or ported vacuum? It should be to intake vacuum.
But don't you have to ground pin A to B on the distributor to set the timing on a howell? It is common practice to have to do so on other GM TBI systems. It puts them into base timing mode. Also. vacuum advance has to be disconnected.

I cannot say for sure if this is needed on a howell, but would not be surprised.
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