92 civic vx 29mpg ??help?

[add|ct]

^This.

Try adjusting the idle speed with the IACV disconnected, then verifying its around 650-700 with it connected. The manual goes over several steps of fine-tuning the idle.

The more north you are, you'll want a slightly higher idle to help with cold starts, but anything over 1,000 after full temp is awkward. Sometimes my idle gets hung slightly with IACV issues and it doesn't settle to 650 until I rev the engine.

[IndyFetch]

Originally Posted by add|ct

^This.

Try adjusting the idle speed with the IACV disconnected, then verifying its around 650-700 with it connected. The manual goes over several steps of fine-tuning the idle.

The more north you are, you'll want a slightly higher idle to help with cold starts, but anything over 1,000 after full temp is awkward. Sometimes my idle gets hung slightly with IACV issues and it doesn't settle to 650 until I rev the engine.

Correct me if I'm wrong, but I think you can clean out the IACV with brake parts cleaner. Remove it and clean it out, and then re-install using the existing gasket, if applicable.

Is this correct?

[bowtieguy]

cleaned mine w/ carb cleaner and did re-install the same gasket.

[add|ct]

^Yes, and by disconnected I meant the wiring harness only(not removal for cleansing as far as setting the idle, you do that with it attached of course).

Just to clarify what I was saying, anyway.

I should pull it and give cleaning a whirl. I might replace the gasket this time. A mechanic did the servicing for me 2 years ago before I started getting more experience doing mechanic related work myself.

[amaterasu71]

Update... Well I got an o2 sensor and installed it.. here is what i have, the car does fine up to cruising speed, at 55 or 65 the motor starts to choke up losing power and feeling very doggy. the idle is where it should be but the rpms at 65 are 2600 and the shift light is on the whole time i have it in 5th gear? So im going to email the guy I bought it from and see if he changed the tranny but he told me averything else he replaced i would have thought he would have mentioned the tranny(ah optimism). ive changed iol, air filters next im going to check the plugs anything else? appreciate you guys opinions... ive looked over the postings about the tranny is there a way to look under neath and identify the tranny or do i have to look at timing and gears and such? thanks..

[add|ct]

I mean, what else would cause the RPMs to be that high? Wrong computer or transmission, aside from huge vacuum leak but you say the idle is fine. You should have an EGR system on the VX, that's for sure. Probably a new transmission, unless something else is keeping idle higher.

[theholycow]

With a manual transmission the only thing that can make cruising RPM higher is the wrong transmission, way wrong size tires, a slipping clutch, or a miscalibrated tachometer. Vacuum leak or wrong computer can't do that (unless the computer reports the wrong RPM to the tachometer, of course).

[add|ct]

^Okay, that's what I needed to hear. That's why my RPMs read higher(2,500 RPM @ 75 MPH instead of 2,400) is because my tires are larger than stock size(by 2.5%) and the speedometer reads slightly faster as well?

[theholycow]

No. Larger tires would make RPM lower at the same real speed and the speedometer would read slower. RPM would be the same at the miscalibrated speedometer's "same" speed.

Example:
10% oversized tires

Speedometer reads: 65mph
Actual speed: 71.5mph
RPM: Whatever RPM you would have seen when your speedometer read 65mph before the oversized tires.

Actual speed: 65mph
Speedometer reads: 59mph
RPM: Whatever RPM you would have seen when your speedometer read 59mph before the oversized tires.

Have you been calculating your 2.5% into your gaslog? Before you enter miles, multiply by 1.025.

[Kendaddy126]

I have a vx with a bad o2. I replaced the o2 and the thing started to choke out in lean burn. I need to clean the EGR ports... not easy... I can say that with my 02 disconnected I still get like 38.5 MPG... so I don't think it's only the 02. Sounds like you got the wrong gears or something going on. good luck... If the shift light works... bty... you don't have a CEL on... but why would it tell you to shift in 5th? Unless you have the world's first 6speed VX... Ha.. sorry, I amuse myself. If it studders under load at low RPM there is a good chance your egr valve or ports need to be cleaned/ replaced. Good luck!