Rough idle and hesitation at low speeds

Hey guys! I was looking for a FAQ or walk through for an issue like this, but wasn't able to find one. Does anyone know where I could find one? Or if another forum has one?

Basically I've got a 92 Custom Cruiser with the 305 that starts up and idles perfectly fine. 230k miles on him. Its only when I put it into gear and only sometimes does it cause a loss of RPM, hesitates, and stumbles ONLY when driving slowly in a neighborhood or in a parking lot.

If I add a little fuel the car feels like it wants to cut off unless I give it a lot. If I just tap the throttle, as soon as I let off the car will lose RPM, jiggle and sorta stumble trying to find the correct idle. But like I said, only when crusing at very slow speeds. On the highway he seems fine. No codes, or *12 using the paper clip method.

I've ordered a new EGR and ICV and will probably put in new plugs and wires while I'm at it. I was just curious if this sounded directly familiar to anyone, or if there was a thread with a sorta flow chart on what I should be checking.

I'll continue to search through the forums. Thanks for any help you guys can give!

http****://vid1280.photobucket.com/albums/a497/Only1Balto/20150224_134600_zps0sn1ys70.mp4


Video of whats going on.

Just did cap and rotors, no change.

Vacuum leak

Test or replace the throttle position sensor.

Thanks guys. I checked for vac leaks with the carb cleaner.

I'll look at testing the TPS.

My experience with a 92 OCC with a 305 that would act strangely, but not throw a code, was the small rubber hose between the fuel pump and output hose on the sender unit. I swapped out almost everything I could think of, until the only thing left was a fuel problem.

If you want to be able to check your fuel pressure, you can get a set of fuel lines from a 91-92 Fleetwood with an LO3/5 or a 93 Fleetwood. They both have Schrader valve ports on them.

If I were you, I would at least pull the fuel tank, and check the hose. It is a PITA job, but it is a lot cheaper than swapping out all of the sensors. BTW if it is not throwing a code, the part that causes the code is probably good. Fuel issues do not throw a code.

Just out of curiosity, how old is your fuel filter?

I know, I know....dont kill me.
Had a non-b body vehicle do this. Turned out to be the fuel filter.

Car has 220k, probably still on the stock fuel filter. I'll do those next. Thanks guys.

No codes.

Fred Kiehl wrote:

My experience with a 92 OCC with a 305 that would act strangely, but not throw a code, was the small rubber hose between the fuel pump and output hose on the sender unit. I swapped out almost everything I could think of, until the only thing left was a fuel problem.

If you want to be able to check your fuel pressure, you can get a set of fuel lines from a 91-92 Fleetwood with an LO3/5 or a 93 Fleetwood. They both have Schrader valve ports on them.

If I were you, I would at least pull the fuel tank, and check the hose. It is a PITA job, but it is a lot cheaper than swapping out all of the sensors. BTW if it is not throwing a code, the part that causes the code is probably good. Fuel issues do not throw a code.

I saw your post about the same subject on another thread. Have you seen the video I posted? Was your TBI acting the same way? I'm just looking for a sure step before I walk in that direction.

Fuel pump isn't as hard as it's made out to be on these cars.

That's my educated Internet guess, too.

I installed a new ICV and EGR. Started it up and let it run for 3-4 minutes. Then took it for a small test drive above 40 mph. No signs of low RPM's! I think I even got a little more pep out of him. I'll be looking at taking care of the fuel filter and pump next. Thanks guys!

I'll go down my checklist of things that I did, and what eventually fixed it.

About 6 months ago, I had a distributor put in (not something I could do in the time I had on the side of the road in front of my house). About two weeks after that, I had a low rpm when in gear, with the occasional stall. I chased the problem, replaced a few sensors, and a week would go by and the problem would come back. Replaced EGR, IAC, TPS (again, did one at fall wagon fest), even the Air Charge Temp Sensor. I'd get a week or so of the problem going away...only for it to come back.

So, I did what my father suggested some 6 months ago when the problem started. Checked the timing, only to find it out of whack. Since last Friday, I've had 0 issues with that problem, and I've noticed my MPG's are back to normal!

My original problem was an occasional massive drop in RPM when I put it in gear, with a very rare stall when under very light acceleration. (I found my fix reading through a similar problem on a truck forum).

On a side note, I've sent back my fuel pump and sock (I had to order through work, lol) as this fixed the problem.