Cuts out at 3000 rpm

[Harborman253]

My son has an 83 Prelude he just bought to fix up and drive. It idles fine, and will drive if you have your foot in it going thru the gears like a race car driver. However, it cuts out and acts like it is fuel starved if you try to cruise, or parked and hold it at 3000 rpm steady. We have cleaned the carbs, Seafoam, new filter, but I'm thinking it may be some sensor beings it falls so flat while holding it at 3000 exactly. Above or below 3000 its fine. Anybody have an idea? This my first time on here and would appreciate any help. Thanks.

[spiffyguido]

A bad throttle position sensor can cause trouble like that, but I'm not sure that the carbed Preludes are equipped with that sensor. Check on your throttle body for a black bodied two prong electrical sensor. If there is one, that could be the source of your troubles.

[Harborman253]

will check. Thanks for the quick reply.

[Harborman253]

My son checked online and says that it is not equiped with a throttle positoning sensor. Any other ideas?

[spiffyguido]

The throttle control valve?

Check the vacuum lines going to it for leaks. There is a testing procedure outlined on page 12-20 of the 1983 shop manual in our manuals section (see top of page).

Maybe your problem is there.

[Harborman253]

It is functioning and the vac line is good. Checking all the vacuum lines I can find, so far so good.

[spiffyguido]

Ok, that's good news I guess. Now I'm more confused though.

The carbs are fully mechanical, so there isn't any electronic wizardry that could be failing you there. If the throttle control valve is good, we have to start looking for other controls that meddle with the throttle. Choke, cruise control & automatic transmissions come to mind. To my knowledge, none of the carbed preludes had cruise control, so that's not an issue. The car will have a choke system, but you haven't indicated that this is only a problem when the car is hot or cold, so it's probably not the issue either. Does your car have an automatic transmission?

[Harborman253]

The choke wasn't working when he got it until we cleaned the carb, then it seemed to work.The original owner said it needed to be replaced, It does idle a bit high. Would the choke cause it to act goofey like this? , However after we cleaned the carbs it didn't seem to be an issue. Maybe we should look at this again?

[Harborman253]

Its a manual trans.

[spiffyguido]

I wouldn't rule out the choke, because it will alter fuel mixtures. However, I really doubt that you would see such problems consistently at 3000rpm.

This problem is becoming a difficult one. Because yours is a carbed engine, the fuel system is largely mechanical. We've already investigated many of the electrical components.

In your opening post, you mentioned that you thought this was a fuel problem. Is it possible that it could also be related to spark? Or does it really feel like the engine is leaning out?

[Harborman253]

We just went out and started it up, I was wrong the choke is not working at all. How difficult is that to replace and would that be a good place to start? I don't even know where the choke is on this thing yet. LOL. I'll look it up.

[spiffyguido]

The choke system is well documented in the service manual. Start with getting that resolved. It just might be the source of trouble.