Car stumbles/misses upon acceleration

[glhs571]

Hey all, my 88 csx-t is stumbling/missing constantly. It happens pretty much in all gears but its the worst in 1st gear. Spark plugs are within a year old (RN12YC's) changed the plug wires, cap, rotor and even distributor within the year as well. TPS and AIS should be good, I even put dielectric grease on all connections, vac lines are good (idles at 17ish). Cam and ignition timing checked out good. Fuel filter replaced August 2011, maybe time for a new one? Checked fuel pressure today. As turbovanman suggested in his write up the engine was cool and when I turned it on I got a reading of about 48 PSI, and after pulling the vac line the gauge bounced between 53-47 psi. I shut off the engine and the PSI held at around 53. The car currently has the stock coil it in, and I'm guessing its possibly a bad coil, FPR or maybe the fuel filter? Amy suggestions would be much appreciated. Thanks

[85boostbox]

When you changed plug wires did you do the coil wire as well? Does it clear up in higher RPMS? Does it miss at all idling? If so have you tried to get it diagnosed to a cylinder? And last but not least any codes?

[glhs571]

Yeah I changed the coil wire. It does clear up mostly during higher rpms....no I have not got it pinpointed to any one cylinder. Compression test will be next. I did check the plugs and they were slightly white. I also changed the fuel filter yesterday and it seems to run a bit better. I will check the codes tomorrow and report back. Thanks !

[glhs571]

Just checked the codes, 22 and 55. 22 is CTS, could be possible I got this when checking the timing the other day and had to unplug it?

[gears351]

Can you check it while driving? I had a similar problem and it turned out the fuel sock was bad - the pump checked fine at startup and pulling the vac line pressure would shoot to 55. Under load & boost pressure would drop from 55 to 20! causing stumbling, hesitation and actually toasted the motor. Tiny grains of grit got through the sock and were restricting flow at the pump screen.

[glhs571]

What's the fuel sock?

[glhs571]

TTT, anyone want to chime in here? Problem still exists, open to any suggestions at this point. The miss/stumble is getting worse at this point. Just swapped out the coil and FPR and it's still there. Pulled code 34 which is the speed control solenoid, not sure what exactly I'm looking for, minimopar.net says its near the battery? Anyone have any info on this? Thanks !

[gears351]

fuel sock is the pre-filter on the pump in the tank

[supercrackerbox]

Just checked the codes, 22 and 55. 22 is CTS, could be possible I got this when checking the timing the other day and had to unplug it?

Yes, you usually have to unplug the battery to clear the codes after setting timing. When you set the timing, was the timing mark on the flywheel pretty steady, or did it jump around a lot? I had a similar issue with my Charger recently, and the timing mark was all over the place. Turned out the shutter wheel was very loose on the distributor, and a new one took care of the issue.

[PunKid]

whats your plug gap and boost your running?

[glhs571]

.35 - 11ish psi. Problem is still there just getting worse at this point though.

[rampant150]

You really should check your fuel pressure on acceleration. A failing fuel pump will show those symptoms. To diagnose mine i needed to hook up a test gauge with a long hose to the fuel rail and take it for a drive with the gauge pinned under the windshield wiper.

[3Bar_Mopar]

Janky injector harness gave me similar problems....I cinched down a zip tie on the big harness plug to hold it together tight and it started to run fine again.

[glhs571]

Problem solved...it was the fuel pump....I had replaced it a few years ago (09) thinking it was in good condition still. Ended up getting a Walbro 255 from Cindy and wa-la no more missing or stumbling! Thanks everyone