engine won’t rev, bogs down.

[interoz]

Hello!
I’m having an issue with a 94 Honda Civic DX that I obviously need help troubleshooting! I replaced the cylinder head yesterday because of lost compression. Prior to this, it ran good. After replacing the head, I buttoned everything back up and it started up and idled great. But it won’t rev up without bogging!

Symptoms:
Engine starts perfectly, idles great….press the gas more than 5-10% and it wants to bog down/ die. Very lightly press the gas and it will rev to about 3-4000 rpm. As soon as I let off the throttle, it eases back into a smooth idle again.

I have checked the following….
-TPS- adjusted and functioning.
-Vacuum- Cannot hear anything/ checked with carb cleaner/ checked with gauge at a couple different spots, holds 22 in hg at idle.
-Replaced fuel filter
– checked fuel regulator…good
– Fuel pressure…seems to be fine. I don’t have a pressure guage but it starts and will rev so I assume it’s good.
– checked crank timing…perfect.
– checked ignition timing…pretty close, set by ear. I need to pick up a timing light.
– checked MAP sensor
-Checked every connection….twice

I’ve got about 12 hours of looking at this engine…I’m out of ideas! HELP!

Thanks

Topic

[EricTheCarGuy]

As soon as I saw “I need to pick up a timing light” I didn’t have to read anymore. Engine timing is a percision enterprise, you don’t guess or do it by ‘ear’. Given your symptoms I would say that is a good place to start but MAKE SURE YOU FOLLOW THE SERVICE PROCEDURE FOR SETTING THE IGNITION TIMING if not it will not be set correctly and you may still have a problem and possible damage the engine as a result. Also I was not aware that the TPS was adjustable. In 15 years of working on Honda’s I’ve never seen a TPS problem that wasn’t caused by physical damage so I would put that back to where you started with it as if you don’t check it’s readings when doing your adjustement your doing it wrong. The same with the MAP sensor, haven’t seen any problems there that weren’t caused by someone else. Lastly given that you’ve just done a bunch of work on it a good thing to do is go back over your work to make sure everything is correct including the mechanical timing of the engine, check all your connectors and vacuum lines to make sure you put everything back where it was before you started. Good luck.

[interoz]

Yeah, you can buy just the TPS for a whole lot less($10-15) than the entire throttle body from honda. The only caveat is that you have to “clock” it. I’ve done it on a couple cars and see more and more often on other cars. You set it by measuring the voltage on the signal wire. Pretty easy actually…

I agree about the timing, I’ll pick up a light and check it. I’ll also check the cat as the car does have 180K miles on it! Thanks!

[jacobnbr1]

Cat converter and cam/crank timing come to mind. visually confirm timing belt is aligned correct and drop exhaust pipe down if you don’t have a back pressure gauge.

[Third Gear]

If all else fails check the injectors. On a particular 94 Accord that haunts me now and then – I did a number of things to it including replacing the head. It ran like garbage, couldn’t figure it out. Turns out the injectors went bad in the time it took me to remove the head, have it rebuilt, and put it back on. a donor rail with injectors from a junkyard car made it run like a new car. Strange, yet possible.

Check your compression NOW and do a leak down test to see if your head gasket was installed right. If you get bubbles in coolant or you’re losing a ton of air somewhere then the gasket wasn’t put on right.

Where both dowel pins present on the head? If not the head could be misaligned and the bolts probably were more difficult to torque without sqeaking.

[interoz]

Thanks for the response everyone…

I checked the ignition timing, it was off a tad but it is dead on now.
I also doublechecked the cranl/cam timing and it is still dead on.
I dropped the exhaust down and it made no effect. I took a look at the cat and it looked pretty good, no melting or clogged holes from what I could see.
I had no problems with the headgasket. Lined it up with the dowel pins, etc…
Did another compression test, 200+ across all cylinders.
I checked all the vacuum lines again…all good.

The car idles great, no hesitation starting…no hunting…I could probably balance a quarter on end on the valve cover it’s so smooth.

What am I missing?

[619DioFan]

First a question … you say the car idles smooth. what does the idle if you put it in gear ( is it an automatic ? ) if so put it in drive,brake on and let it idle, see how it responds. I would do a fuel pressure test.

[jacobnbr1]

I may have seen this before.A used engine was installed by the customer and now it sets a code 14 and will not rev up it goes into fuel cut.
First, verify the correct connector is connected to the Idle Air Control (IAC) valve. The wire colors should be Black/Yellow and Blue/Yellow. The wire colors on this vehicle were Black/Yellow and Red. That connector is for the purge solenoid.
Swap the connectors and code 14 is gone and the engine runs just fine.

[redfury]

IF everything worked great before you pulled the head, then there is most likely something you’ve overlooked. You could try disconnecting all the sensors except the TPS , O2 and MAF/MAP and see how it runs. The engine cold is going to run in open loop mode and will use default values to run the engine until those sensors come online. It’s needs to know how much air is entering the system in order to trim the fuel map. Maybe Eric can help out a little more with the technical side of it since I’m not that familiar with Imports in regards to this. Situations like this are where I love having OBD2 and a cheap scanner that can read live data. I can see if the sensors are doing what they are supposed to do.

Also, it might be a good idea to disconnect the battery and cycle the key a few times to discharge the computer and put it back into learning mode. Many times a repair can be made to a vehicle and not be effective until the computer is reset so it knows a faulty value has been corrected.

[jacobnbr1]

Did you find the problem?

[interoz]

Sorry for the delay, I kinda gave up for a bit ……

Jacob- I checked the IAC and Purge solenoid connections. They were correct, I couldn’t swap them if I tried becasue of the wire lengths.

69Diofan- I tested the fuel pressure and it was high, 71psi. I checked for pinched lines and didn’t anything so I replaced the fuel press reg. Pricey since it is now nla. The car is a manual so not really a way to check idle under load as you spoke of. It will drive though…as long as I don’t give it any gas.

Redfury- I disconnected the purge solenoid, IAC and the fast idle valve on the back of the intake. I also disconnected both sensors under the distributor. I didn’t see anything else to disconnect. Car started, idles a tad lower but smooth. Same thing, touch the gas and it bogs.

Not sure if this helps but…I noticed since the car has been sitting. It took quite a bit to start up. Almost like it lost fuel pressure. Maybe fuel pump beginning to fail?
Also also…I noticed if I disconncect the TPS, the idle does not lope. It should lope right?

Thanks again for the help…..

[jacobnbr1]

Did you see if it is setting any codes?

[dreamer2355]

Did you examine the wiring harness to make sure you didn’t accidently pinch any wires causing a short to ground or any other wiring issues?

[djdevon3]

Anyone thought of bad PCV or PCV valve? I throw that out there since a PCV valve is very easy to check.

[interoz]

-No codes coming up.
-Pcv valve would throw a code if it was bad. I’ll check it anyway, it can’t hurt at this point!
-I check the wiring harnesses, good idea.

I’ll report back! Thanks!

[380]

When your reving up the engine do u have the transmission in neutral or is it in gear.

[Author]

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