Stumbling at 2600 RPM???

[PeteD]

My otherwise reliable and fun driving 75 1.8 with Dellortos has developed a stumble (kind like a skipping) at about 2600 (like when driving at 40mph in 4th). This is a cruising speed and it is kind irritating to say the least.

It does this cold or hot.

I have been through the whole ignition system (205AA dizzy, MSD 6200 ignition, MSD Blaster 2 coil, MSD wires, Bosch platinum plugs) and have not found anything. The fuel pressure in the driveway is constant. All jets in the carbs are clean. The fuel is fresh. The valves are freshly re-gapped. I'm running out of ideas. When I get back next weekend, I am going to hookup a fuel pressure gauge on a long hose and see if the fuel pressure varies while driving.

Other ideas? I could sure use a burst of brillance here.

Thanks!


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Pete Dubler
See my 914 at http://dublerfamily.com

[This message has been edited by PeteD (edited 06-22-2001).]

[bowlsby]

Don't know about the L-Jet cars, but what you describe is a classic problem with the throttle position switch on the D-Jet cars. The traces inside the switch wear out and cause a mid rpm stumble.

Cure: Replace switch.

OOPS I take it all back. I reread the post and see that you have carbs. I can't help you with those. Float stuck maybe?

[This message has been edited by bowlsby (edited 06-22-2001).]

[scotty914]

take your dizzy apart and clean it, my car ( 1.8 fi ) kind of did the same when it was driving but hard to tell when sitting and just revving, so as i was working on the car i cleaned it and it fixed that problem

scott

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scott thacher
75 1.8 running at last
75 under rust
(fine german rust)

[PeteD]

Scott,

I have a new cap, rotor, points, and condensor on the dizzy, so it is pretty clean. I will double check it though. No telling how much cottonwood cotton has gotten in there this terrible allergy year...

Other ideas???

Pete

[mejulihn]

Pete,
I have a similar problem with my 2.0 w/FI that I have been trying to diagnose for some time now without success. Please let us know if you find the cause of the "stumble". Mine is between 2800-3600 in all gears. Sometimes it is more noticable than others -- no idea why.

[kevinseven]

My '75 1.8 L-jet has the same deal. Cruising on the highway if I let the RPMs sit in the 2800 range I get stumbling. Sometimes it will lurch/stumble on me as I'm accelerating in lower gears -- seems to be as it moves through the 2800 zone.

I was thinking I botched something on my last tune up...dwell, timing, etc. Or I messed something up messing with my throttle switch. I'm planning on letting a professional look at it later this week.

kevin
atlanta, ga

[mejulihn]

Well, I think I solved my stumbling problem. I installed a new rebuilt distributor last night and the stumble is gone. My dizzy was badly worn and had a fair amount of wobble. The Haynes manual also suggests to check for a worn distributor for both a low rpm and high rpm "miss".