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88 Honda Accord that revs

Hi everyone, I am asking for some advice on fixing a problem with my 88 Honda Accord. After starting it revs up between 2000 and 3000 RPMs for about 5-10 minutes and then drops down to a normal idle, after which it drives fine. It does it pretty much every time I start the car! I’m on Hawaii and it’s def an island car. Thanks!

What trim is it, DX, LX, or LX-i? That will tell us whether it’s fuel injected or carbureted.

I’m not sure what trim it is but the car is definitely carburated.

On MY 89 Accord which is also carb’d . . . I had this (and other) carb related problems for years . . . and I tried almost everything. I eventually changed the carb (about $250 I think) and never looked back . . . runs flawless, no carb problems since. Could be the choke . . it’s electric on the 89 (probably the 88 as well) and simply cleaning the contacts will fix it. The late 80’s Hondas had a lot of vacuum lines to the carb . . . by now they could be brittle and this could be the cause. Try switching on/of the AC when you get this condition . . . my Accord has a switch which raises the RPMs whenever the AC is engaged . . . could also be a dirty carb . . . try some Seafoam in the gastank . . .it really works well. There are a lot of little parts in the carb which could become stuck or gummed-up. I replaced the choke with a used part on mine once, but it only lasted awhile, probably because the part was as old as mine was anyway. If you DO decide to replace the carb, let me know and I’ll get you a part # and source. It was an easy fix, almost completely bolt-on. Good luck! Rocketman

Hello, that’s actually quite normal. Technical/Repair manual for this car specifies the fast idle to be around 2500 RPM. My 87 Accord will rev up in the same manner, but after a minute or so of driving, not right when I start it. The engine is designed to speed up until it reaches its operating temp. As long as it starts up and runs smoothly then I wouldn’t even worry about it. Also keep in mind you can offset the high engine rpm’s by hitting the throttle and they will gradually drop down when it gets closer to 195 degrees or so. Have fun.

ah, sorry. I missed in your O.P. you didn’t say cold engine, you said every time you start it. Not sure what to tell you then, but this is o.k. if it’s completely cold/first start of the day. Good luck.

In the 1970s and 1980s, it was common for carburetors to be set to run up to 2,000+ rpm at high idle. This was done to lower the emissions during idle…especially, during cold start. Many people complained about their car, or truck, running 35 mph, without touching the gas pedal. Federal law forbade setting the idle lower. A mechanic would tell the customer HOW the idle was adjusted, but, not adjust the idle, himself. Of course, this was, “hint, hint, nudge, nudge, wink, wink”!

I’ve owned my 89 Accord since new . . . August 1989 . . . and upon cold-start, 1500 rpm, drop to 1000, then to 750. Winter or Summer, always the same. The carb started to act-up at about 250,000, I tried everything to fix it. High idle (3000 upon start-up IS high, you should’ve heard it), low idle/stall, stumbling, etc. The only fix I came up with was a replacement carb . . . now the cold-start is about 1700 rpm, drops to about 1200, then to about 650, every time. Mileage now is about 450,000. If the OP didn’t have the high idle before, I think he is asking what to do about it now that the high idle has started. Maybe I’m wrong. I also agree that the problem goes away after 5-10 minutes, so why worry. One thing he could try is to use a hair dryer on the carb/choke/intake before starting for the day . . . to see if the choke and/or engine temp is causing the high idle. Setting the idle down however, won’t work because you’ll be adjusting it lower than the final (warmed-up) idle and it will stall. How about it OP? Does it do it only on cold-start? Rocketman

Thank you all for your responses! The car always revs on the initial start. If I drive it a short distance, like for five miles, and turn it off and run inside a store, it will rev high again when it’s restarted. This can go on for a while, if I am just running errands nearby. But, if I drive the car for a long distance, like for 30 minutes on the highway, then it revs less when it’s restarted (between 1000 and 2000). And it will go down right away if you give it a tap on the gas. The previous owner said he just let it warm up real well before driving it. It seems sort of funny to warm up your car in Hawaii, which is where I am! This ain’t North Dakota!

Hellokit hit it on the nose. If I put the car in gear when it’s reving it really strains the transmission, and you have to hold down the brake, otherwise it’ll pull away at 35 mph!

(FIXED! See the bottom, the problem is the TPS)

I have a 1988 Honda Civic LX, 1.5L engine, fuel injected, standard 5-speed transmission, 117,000 miles that has exactly this same issue: on cold start it revs up to about 2500 rpm in neutral (at stop lights and stop signs) for many minutes before settling down. I can sometimes bring down the idle speed after a cold start if I turn off the ignition and turn it on again: it starts up at 1500 RPM, but revs up to 2500 again until fully warm.

It’s been to four different mechanics including the dealer, who had it for a week and said they saw this same problem seven years ago but never found the answer.

Here’s what’s been done so far:

The engine sensors: CTS, TPS, TDC, IAT, all check normal. The IACV is working properly. Two mechanics suspected that the ECU was sending an incorrect signal to the IACV causing the high idle. I had an electrical specialist check out all the engine electrical signals.

Oxygen Sensor replaced, no change
Engine Coolant Temperature Sensor replaced, no change
ECU (the computer) replaced with an identical ECU, no change, original ECU re-installed
Idle Air Control Valve (IACV) replaced, no change
(There is no Fast Idle Thermal Valve (FITV) on this car: that would be another obvious thing to try.)

At this point, the next things I’m going to try are:

  1. Look for some sort of vacuum leak that only occurs when the engine is cold
  2. Try replacing the Throttle Position Switch (TPS). To do this, the whole throttle body needs to be replaced (the TPS is built in to the throttle body, so they have to be replaced together.)

Or does anyone else have any better ideas?

UPDATE 7/29/2008: The problem is the Throttle Position Sensor (TPS). The early (88-91) ECUs don’t always register that the TPS is bad, I pulled and found it was bad. How do you know it’s bad? Use a VOM, when it’s removed and out of the circuit, it should act like a 5K potentiometer (e.g. volume control) with smooth response throughout its entire range.

You can order an aftermarket TPS from here, so you don’t have to buy the whole $900 throttle body assembly from Honda:

Their product model is TPS-PRE-OM, it’s on this page for $79.99.

The TPS attachment to the throttle body is threaded, you have to file slots in the smooth bolt heads to unscrew. Replace those with Metric 8M bolts. When you attach the new TPS, set it with a VOM to .45V ± .05V. Everything should be fine.

I’m pretty sure your problem is the throttle position sensor (TPS), see my associated posting for a source for an aftermarket TPS. (Honda only offers a new throttle body with the TPS pre-attached and calibrated, which is very pricey.)